Inventor:
Branko Krajnović
Ozaljska 36
10000 Zagreb, Croatia
branko.krajnovic@inet.hr
www.kra-car.com

Two-Process Rotary Internal Combustion Engine

1. FIELD OF THE INVENTION

This invention relates to the conversion of thermal energy into mechanical work in the internal combustion engines.

2. TECHNICAL PROBLEM

Poor utilization of fuel heat energy and too small amount of mechanical work gained.
All the known designs of the internal combustion engines are characterized by relatively poor fuel economy. The design of four-stroke internal combustion engine, which is presently most widely used, is based on an inefficient MECHANICAL and THERMAL concept.
Mechanical design in which the force line of action and moment arm length vary from the value of 0 at the top dead center (TDC) and ending again with 0 at the bottom dead center (BDC) may be considered as very unfavorable because of its inherent inability to fully utilize all of the pressure released by combustion.
In the contemporary reciprocating engines all the process phases are performed within the single volume, which may be considered as very unfavorable in regard to achievement of any higher efficiency of energy utilization.

The well-known theoretical process of maximum thermal efficiency (Carnot process) is distinguished by ideal sequence of changes of pressures and temperatures of a fluid. In the Carnot process, the working fluid RECEIVES heat during the expansion and REJECTS heat during the compression. By receiving heat during isothermal expansion when useful work is delivered, the internal energy of the working fluid obtained at the end of compression is being MAINTAINED in the Carnot process at T1=const.
In the contemporary reciprocating piston engines adding heat and increasing internal energy of the working fluid occurs during unfavorable period of time, when on account of mechanical design no work can be delivered. The work is mainly delivered during the adiabatic expansion when the internal energy of the working fluid is being DECREASED. That is one of the reasons that prevent the reciprocating engines to better perform thermally.
Since the internal combustion engines are heat engines in which thermal energy is converted into mechanical work it is imperative to utilize this heat to maximum extent.
However, with contemporary designs including Wankel rotary engine this is not the case.
Large amount of the heat released during fuel combustion is transferred to the walls surrounding the combustion volume. In case such part of the heat is immediately taken away by water by way of heat exchanger and dissipated to environment, as done in the contemporary engine designs, such heat is irretrievably lost. More heat is lost irretrievably by transfer of part of the heat from the system via large outer surfaces by radiation. If one adds up the heat of exhaust gases, which is being rejected directly and irretrievably into the environment, the fuel economy of the contemporary engines may be considered as very poor.
In present-day reciprocating internal combustion engines, approximately 35% of heat energy input is converted into useful work. The remaining energy, not to mention considerable mechanical losses, is mostly dissipated as heat losses: rejected in water, by radiation and in exhaust gases. These losses should be kept to the minimum and only then the fuel economy could be improved.

3. STATE OF AFFAIR

Shortcomings of the present-day reciprocating internal combustion engines
The performance of the reciprocating piston engine is limited by a great number of mechanical and thermal shortcomings due to its inherent design.
A big mechanical shortcoming is related to a need for the conversion of the piston linear motion into the crankshaft rotary motion accompanied by change of direction of force line of action. The fact is that when the pressure and temperature produced are at their highest, i.e. the working fluid internal energy is the greatest, the force line of action is almost perpendicular to the axis of rotation, and consequently useful work and torque generated are very small.
Change of volume (at a great change of piston speed) is obtained by movement of piston from TDC to BDC; the piston actually stopping in these points to change direction of movement, which induces annoying alternating acceleration causing non uniform operation.
Abrupt change of volume occurring at half revolution of the crankshaft is also unsatisfactory as regards obtaining any greater energy utilization. In addition to the shortened length of the force line of action (during expansion), the time required for performance of each stroke is also substantially shortened necessitating process to be performed at great speed.
The currently most widely used four-stroke engine delivers work over the path of 180° (1P) during crankshaft revolution of 720°. The specific nature of the mechanical process being performed in the cylinder, with the piston linked by connecting rod to the crankshaft so that up-and-down reciprocating motion of the piston can be converted into rotary motion, sets the geometry and size of the engine. For that reason greater arm of force and consequently greater torque cannot be obtained with small-size engines.
Arm of the force varies from 0 to a length amounting to maximum half of the piston stroke, this being the crankshaft radius. At the particular moment when the arm of force attained its maximum length the pressure has already dropped substantially due to expansion, and as the crankshaft turns the arm of force drops again to zero and the force line of action is directed to axis of rotation, which is the reason why in the reciprocating piston design prolonging expansion time would bring little or almost no gain.
On account of the working fluid reaching high temperature at the end of the compression stroke contemporary reciprocating engines are designed with relatively small compression ratios.
Low pressure produced by compression increases as the fuel burns at constant volume or with small increase of volume occurring at the end of combustion stroke. In Otto cycle, on account of compression ending with high temperature and relatively low pressure, the addition of heat by fuel burning results in increase of pressure, temperature and internal energy of the working fluid at the time when little change of volume occurs, i.e. at the time when NO USEFUL WORK IS DELIVERED. Heat released during combustion serves not only to increase the working fluid internal energy, but also to warm up relatively cold surrounding walls. Fuel burning commences before the end of the compression (about 300 before TDC and lasts about the same after TDC), and later commencement of burning (at the start of the expansion phase - after TDC) would be even more unfavorable due to too short expansion and heat losses on account of too high temperature and pressure of exhaust gases. In Diesel and Sabathe cycles the volume change during combustion is somewhat bigger and hence the results are better.
Taking into account this volume increase during combustion it would be necessary and worthwhile to have higher pressure at the start of combustion and accordingly higher compression ratio. Having in mind that air is compressed in these processes the maximum temperature at the end of compression is not limited. High temperature and pressure at the end of compression in these processes, due to too short duration of expansion and large masses of working fluid, results also in heat losses due to high pressure of exhaust gases, reducing thus substantially initial beneficial effects. The useful work is gained in these processes mainly on account of internal energy of the working fluid during adiabatic expansion, i.e. at the time of temperature drop of the working fluid and decrease of internal energy of the working fluid.
In the dead space unavoidable in such design, burnt gases left from the preceding cycle are trapped and the volumetric efficiency is decreased meaning that lesser mass of working fluid is being introduced into the process.
The engine of this type needs great number of valves (pressure drop!) operated by camshafts with associated mechanisms and springs resulting in friction losses and requiring certain work to be expended. The opening and closing of the valves are timed to extend periods of individual strokes. The most important expansion stroke, i.e. the stroke in which the work is delivered, is significantly shortened (exhaust valves are already opened after 130 - 135° of expansion), causing substantial part of the heat to escape with exhaust gases to environment in spite of burning starting already during compression. The loss of couple of bars of pressure at the beginning of exhaust is considered as favorable in respect of attaining as great speed of exhaust as possible. This points to the problem of lack of time since no loss can be considered favorable. However, on account of a given mechanical configuration (direction of force action and moment arm at the end of expansion are unfavorable again, amount of volume change is too small), the high temperature of burnt gases, which could maintain this couple of bars of pressure and produce some amount of useful work, is not utilized but it is rejected with discharge of exhaust gases to environment being in such fashion direct cause of high thermal losses.
Significant differences between the reciprocating internal combustion engine design and the rotary engine design are shown on page 1/14.

From the standpoint of heat efficiency the execution of the process events in a single volume can be considered as very unfavorable.

To attain better fuel economy and gain more useful work it would be beneficial to perform compression, as evidenced by the Carnot cycle, with INTENSIVE REMOVAL of heat from the working fluid during the first phase of compression. Such compression should take place within the compression volume the external walls of which should be INTENSIVELY COOLED FROM OUTSIDE. The compression shall occur at a slow enough rate (both over time and by slower volume change) so as to have sufficient time for removal of heat. By cooling working fluid during compression it would be possible to perform compression with higher compression ratios, which would result in higher pressure at the end of this compression with less energy input. In theoretical Carnot cycle the temperature of the working fluid at the end of isothermal compression is the same as the initial compression temperature (T2 = const.). To arrive at the required temperature in this process the adiabatic compression should occur, i.e. without any heat being removed from the working fluid during second phase of compression, however such compression cannot be carried out in the volume having intensively cooled surrounding walls.
Addition of heat to the working fluid by heat transfer from or through the cold surrounding walls is not feasible. Addition of heat to the working fluid by heat transfer from fuel burning in the volume surrounded by cold walls would not be beneficial due to the great energy losses because of heat transfer onto the surrounding walls during combustion.

It is apparent from above analysis that the best theoretical process with highest thermal efficiency, Carnot cycle, necessitates process to be performed in several volumes of various temperatures of surrounding walls.
It is the general intent to produce in heat engines as high pressure and temperature of working fluid as possible at the end of compression.
On account of the abrupt introduction of the working fluid into single-volume reciprocating engine and high velocity of working fluid flow during intake, intense transfer of heat from hot surrounding walls to the working fluid is taking place having as a result increase of temperature of working fluid at the intake phase already. Transfer of heat from hot surrounding walls to the working fluid is continued at the beginning of compression, resulting soon in high temperature of the fluid. In such fashion internal energy of working fluid is increased prior to any work being done on it, and consequently, for such compression more work needs to be expended.
During compression, temperature of the working fluid becomes higher than the temperature of surrounding walls, the direction of heat transfer is reversed and heat flows now from the fluid to the walls. Heat removal comes too late and at a too slow rate to enable compression to be effected at higher ratios. The compression occurs at a high mean exponent of polytropic compression, and on account of the working fluid high temperature attained prematurely, the compression ends with small compression ratio, resulting in low pressure at the end of compression.
It is possible to obtain high temperature at the end of compression by cooling the working fluid during compression, and by longer compression of working fluid up to higher compression ratios, which would result in higher pressure at the end of the compression. In the single-volume reciprocating design where the same volume is used for combustion as well, the temperature of the surrounding walls is too high so a satisfactory cooling of the working fluid during the compression is unattainable.
Having in view that in contemporary designs of internal combustion engines all the strokes are performed in the single volume, it is not possible to utilize advantages of heat accumulation in materials.
In the contemporary designs of internal combustion engines (where all the process strokes are performed in a single volume), optimal operating temperature is achieved in the surrounding walls. However, this results in a relatively low temperature of surrounding walls, and during each combustion stroke large part of the heat is given off to the surrounding walls, which are in turn cooled by water; in such a way the heat is transferred to the cooler and subsequently rejected to the environment.

Wankel rotary engine concept, regarding thermal considerations is similar to the reciprocating piston configuration since all the strokes occur in the single volume. The combustion and transfer of heat onto the rotor occurs against every rotor wall, making it impossible to attain desirable (cooler) thermal conditions for intake and compression. Rotor motion is planetary, compression ratios vary and are limited by design, problems exist with peripheral sealing, manufacturing is complex and costly, and fuel economy is somewhat less than with reciprocating design.
Poor fuel economy of present-day designs of internal combustion engines is a reason why in one cycle (most often 2 revolutions) only relatively small amount of useful work can be gained. On account of the small amount of work being gained in one revolution, the power can be obtained either by higher speed of revolution or increase of volume, both cases resulting in increased consumption of fuel and air, excessive pollution of environment accompanied by global warming of our planet.
The above review is an exercise undertaken to illustrate design weaknesses and shortcomings of reciprocating piston engines preventing more efficient performance of the process.
These shortcomings are the reasons of poor fuel economy of contemporary designs.
It is possible to remove such shortcomings by completely different design configuration.

4. OUTLINE OF THE BASICS OF INVENTION

(Due to complexity of the following matter, author proposes a second reading if necessary)
Improved energy efficiency in the internal combustion engines can be achieved as conceived by the author by:

4.a New heat process – (Krajnovic cycle)
4.b Heat accumulation in the system
4.c Utilizing accumulated heat in the system - (Carnot cycle)
4.d Mechanical design of internal combustion rotary engine,
which makes the above features feasible, distinguished by the following mechanical and thermal advantages:

1. No need for conversion of linear motion into rotary motion.
2. Change of volume occurs over 360° of shaft rotation.
3. DIRECTION of force line of action is ALWAYS IDEAL.
4. MOMENT ARM is almost always at its maximum.
5. Possibility of increasing engine power by increasing moment arm without increasing volume.
6. All the strokes are occurring AT THE SAME TIME.
7. Intake, exhaust and expansion are going on continuously over the whole 360°, while compression occurs over 260° of the shaft rotation
8. The design facilitates improved volumetric efficiency of filling.
9. The design allows substantially greater period of time for execution of each process event.
10. The engine operates without any need for valves and associated mechanisms.
11. The engine has exceptionally favorable ratio between mass and work delivered, i.e. enhanced power-to-mass ratio.
12. Rotary design is characterized by absence of negative inertial forces.
13. From the thermal aspect the design facilitates achievement of large compression ratios.
14. The design enables to reduce thermal radiation losses.
15. The design facilitates heat accumulation and its utilization.
16. The design facilitates better utilization of temperature and pressure of burnt gases.
17. Possibility of adapting manufacture to all applicable fuels.
18. Simplicity of design.
19. Quiet and smooth operation.

The rotary engine design is based on the well-known principle of operation: intake, compression, expansion and exhaust, but the THERMAL PROCESS IS PERFORMED in more efficient manner than in contemporary designs.
The essential difference of the new process proposed in relation to the known so far is that all the process events are carried out at the same time in a number of (expansion) volumes isolated from environment and between themselves which facilitates more favorable thermal control of the process. Intake and compression are taking place in ONE cylinder, whilst in the OTHER cylinder mounted on the same shaft undergoes fuel burning and heat accumulation during expansion.
Execution of thermal process in the system comprised of a number of (expansion) volumes isolated from the environment and between themselves facilitates REMOVAL of heat during compression and ADDITION of heat during expansion, the same as in Carnot cycle, which results in better energy efficiency and reduction of radiation losses. The heat retained in the walls surrounding cylinders can be utilized, or in other words, their temperature can be adapted to the needs of process execution. Large internal, suitably machined, round surfaces of ring and rotor, rotating together with the working fluid, slower changes of volume, in which the opposite walls are very close, as well as much longer available time represent beneficial factors for heat transfer. Great losses in present-day engines occur during fuel combustion because greater part of released heat is transferred to the relatively cold surrounding walls. The difference between the temperature of walls surrounding combustion volume and the maximum temperature of working fluid during the process should be as small as possible. Process maximum temperature can be decreased by providing larger air mass, with the material surrounding combustion volume being capable of withstanding as high operating temperature as possible. In this way total heat transfer from the working fluid to the walls during combustion will be lower.
For better energy efficiency to be attained it is necessary and desirable to have large compression ratios, meaning high pressure at the end of compression, implicating execution of process at very high pressures.
From the mechanical aspect, round, cylindrical structure represents the strongest possible design.

4. a New cycle (Author: Branko Krajnovic)

The most efficient practically feasible thermal process may be achieved by:
REMOVING part of the heat by reducing temperature of the working fluid during compression, thus decreasing internal energy of the working fluid at the time the work is done on it - which requires work input.
ADDITION of heat to working fluid during expansion, increasing its temperature, thereby INCREASING internal energy of working fluid at the end of compression at the time the work is done by it - hence the work is gained.
By addition of heat DURING EXPANSION the work is gained at the time when the internal energy of working fluid is being increased as well as at the time of being decreased. In comparison with the thermal processes which are currently most widely used, the process controlled in such a manner delivers, from the theoretical as well as from practical aspect, maximum work during single revolution. The value of this process, in addition to features outlined above, consists in a possibility to make use of Carnot cycle in the manner of and within realm of feasibility and simplicity.
It is impossible to execute in reality either adiabatic or isothermal theoretical processes. However such ideal processes are used as a standard of performance to compare actual processes accomplished in practice with ideal theoretical ones, and for theoretical comparison with other thermal processes.

Theoretical p-V diagram of Krajnovic cycle is depicted in Figure 1.
1 Start of process, T1 and p1 initial state of environment
1-2 Isothermal compression at T1 = constant.
2-3 Adiabatic compression
3-4 Isobaric forcing out of working fluid from the compression cylinder into the accumulating chamber at
p = constant
4-5 Isobaric passage of working fluid from the chamber into the expansion cylinder at p = constant.
5-6 Isochoric addition of heat at V = constant.
6-7 Isobaric addition of heat at p = constant.
7-8 Isothermal addition of heat at T = constant.
8-1 Adiabatic expansion.

THEORETICAL Ts diagrams of Otto, Carnot and Krajnovic cycles are depicted (for the purpose of comparison) simultaneously in Figure 5.

p-V diagram of practically feasible Krajnovic cycle is depicted in Figure 2.
Process starts at state 1 which is the initial state of environment. The process proceeds by compression of working fluid in the intake/compression cylinder, with REMOVAL OF PART of the heat from the working fluid during compression. At a set temperature and pressure the communication is established between the compression cylinder and the accumulation chamber. At the moment the communication is established the pressure in the compression cylinder is a little higher than the pressure in the accumulation chamber. During the next couple of degrees of revolutions the pressure is being equalized and the working fluid is forced into the accumulation chamber. By establishing communication at the exact predetermined moment the controlled mass of high pressure working fluid expands from the chamber into corresponding volume in the rotor bore of the combustion/accumulation expansion cylinder. Fast transition of working fluid lasts only a few degrees of shaft rotation (10-15° at very small pressure and temperature drop), after which the communication with the chamber is cut off, and the heat is ADDED to the working fluid by transfer of part of the heat from hot surrounding walls, thereby increasing its temperature and pressure in the isochoric process, PRIOR TO start of the combustion phase. Upon injection and auto-ignition of the fuel, the heat is added to the working fluid with COMBUSTION TEMPERATURE INCREMENT.
Fuel burning and heat addition occurs during expansion with gradual increase of volume. Upon completion of combustion, heat is added to the working fluid by taking off part of the heat from the surfaces which have absorbed part of the heat during combustion and which are rotating together with the working fluid. Part of the heat released by combustion is being ACCUMULATED in these walls. Expansion occurs with additional increase of expansion volume. Additional increase of expansion volume can be achieved by having greater size of expansion cylinder, but also by suitable addition of another expansion/exhaust volume, which enables to exploit any value of pressure.

1 Start of process, T1 and p1 initial state of environment
1-2 Compression with removal of the heat from the working fluid
2-3 Forcing out of the working fluid from the compression cylinder into the accumulation chamber
3-4 Expansion of the working fluid from the chamber into expansion cylinder
4-5 Addition of heat to the working fluid by transfer of heat from surrounding walls
5-6 Polytropic addition of heat to the working fluid by fuel burning
6-7 Addition of heat to the working fluid by taking off the heat from surrounding walls
7-1 Expansion of the working fluid.

4. b Accumulation of heat in the system

According to the proposal of the author, heat shall be ACCUMULATED in the SYSTEM and the accumulated heat subsequently UTILIZED.
At a particular number of revolutions by injecting and burning fuel the heat is ADDED to the WORKING FLUID and the SYSTEM in which the process takes place. Part of the heat released by combustion, this heat being inevitably transferred to the system walls surrounding combustion volume, needs to be ACCUMULATED in these WALLS. When the temperature of the accumulated heat in the SYSTEM walls, directly surrounding the working fluid during combustion, approaches the upper limit set by the material in respect of strength and endurance (in p-V diagrams hypothetically indicated as 1,0000 K) it is necessary to start removing this heat and UTILIZE IT IN THE PROCESS.
The heat is mostly accumulated in the walls surrounding rotor bore in which combustion takes place, peripheral part of the rotor mass and internal part of the outer ring which are in direct contact with the working fluid (Figure 18A page 10/14), and in part of the lateral walls surrounding working fluid during combustion. These surfaces are made out of a SPECIALLY SELECTED LAYER OF MATERIAL – PLATES.

A small part of the accumulated heat of the system can also be utilized during revolutions of the process with fuel burning by transfer of heat onto the working fluid PRIOR TO the beginning of the fuel burning, since the temperature of the working fluid at the end of compression is lower than the temperature of the surrounding walls in the combustion/accumulation cylinder.

4. c Utilization of accumulated heat in the system is achieved by Carnot process

The largest part of the accumulated heat is utilized when the temperature of the system approaches the upper limit set by the material in such a manner that at a certain number of revolution the injection and burning of fuel is interrupted. In this way further increase of temperature of the system is stopped. System is cooled by CIRCULATION OF THE AIR THROUGH THE SYSTEM. By REMOVING ACCUMULATED heat from the SYSTEM, heat is ADDED to the to the WORKING FLUID, maintaining in this fashion the internal energy during expansion attained at the end of compression.
Instead of cooling the system by water, removal of the heat from the system is done by air, meaning that during revolutions of system cooling, the fuel is NOT CONSUMED, and by utilization of the ACCUMULATED heat of the SYSTEM an amount of work is gained.

Theoretical pressure-volume diagram of possible application of Carnot cycle is shown in Figure 3.
1 Start of process, T1 and p1 = T5 and p5 in Figure 1.
State of the working fluid at this point is precisely defined in thermodynamic calculations by the following values: 'pressure and temperature of working fluid at the end of compression'. Pressure and temperature of working fluid at the end of compression are at their MAXIMUM during Carnot cycle.
1-2 Isobaric addition of accumulated heat at p = constant.
2-3 Isothermal expansion at T = constant
3-4 Adiabatic expansion
4-5 Identical to the process with combustion 1-2 Figure 1
5-6 Identical to the process with combustion 2-3 Figure 1
6-7 Identical to the process with combustion 3-4 Figure 1
7-1 Identical to the process with combustion 4-5 Figure 1

Practical pressure-volume diagram during revolutions of utilizing accumulated heat of the system in accordance with Carnot cycle is depicted in Figure 4.
No work could be gained in these revolutions without process involving injection and combustion of fuel (Figure 2), with part of the heat being accumulated in the system, so that the process of heat removal from the system starts at the point of change of process execution by not injecting and not burning the fuel (Figure 4, state 1).

1 Start of process, T1 and p1 = T4 and p4 in Figure 2
1-2 Addition of heat - by heat transfer with DV
2-3 Addition of heat - by heat transfer with DT
3-4 Expansion of working fluid
4-5 Identical to the process with combustion 1-2 Figure 2
5-6 Identical to the process with combustion 2-3 Figure 2
6-1 Identical to the process with combustion 3-4 Figure 2

Gain of work in these revolutions depends on air mass in the process, temperature of accumulated heat, pressure and temperature of air at the end of compression, as well as on heat transfer from the surrounding walls to the working fluid. In Carnot cycle heat is being utilized at the temperature limited by the endurance of materials used. In a real Carnot cycle heat is being removed from the material, some work is gained and the process returns to the point of 'state of working fluid at the end of compression'. From this point new revolution can be continued by another injection and combustion of the fuel.
In theoretical Otto process addition of heat to the working fluid occurs at constant volume. In theoretical Diesel process, it occurs at constant pressure. In Sabathe theoretical process the heat is partly added at constant volume and partly at constant pressure.
It is a well-known fact that in the real processes it is not so.
However, practical application of Carnot process in the way outlined above (as a real process) will not occur at the constant temperature but the energy efficiency will be at its practical maximum.
When the system in the range of combustion cools down to the set temperature (hypothetically 9000 K), the heat is added again to the working fluid and the system by injecting and burning of the fuel. In such an alternative manner it is possible in the SINGLE SYSTEM TO ADD HEAT TO WORKING FLUID over certain number of revolutions (1 or more) by fuel combustion, and over some other revolution by heat transfer, i.e. by utilizing accumulated heat of the system.

Application of the process in the engines at various modes of operation

In this engine, air is being compressed in the compression cylinder and forced into the chamber. The injection (and the auto-ignition) takes places directly in the expansion cylinder. By varying rate of injected fuel in relation to amount of air, the process temperatures vary, and consequently the temperatures of surrounding walls of the expansion cylinder. It is of paramount importance to utilize the heat introduced by fuel and accumulated in the expansion cylinder, which is well insulated and the heat could be carried away mostly by the working fluid (excepting minor losses due to heat transfer through the shaft, etc.).
Taking into account that the temperature of the walls is higher than the temperature of the walls in contemporary engines, the total heat transfer from the working fluid to surrounding walls during combustion will be lower, i.e. the same process peak temperature could be achieved with LESSER amount of fuel.
With stationary engines (power stations, gensets, etc.) operating in steady state mode of service, the process occurs by alternative execution of Krajnovic process (which delivers maximum work in one revolution) and Carnot process (which in the successive revolution delivers work by utilizing accumulated heat received in the preceding revolution). By controlling the proces in such a manner the most efficient thermal process may be achieved. With engines operating in steady state mode of service, the process may occur in continuous fashion utilizing THE SAME TEMPERATURE RANGE (using materials and lubricants of maximum allowable temperature) of the accumulated heat.
With engines operating in variable mode of service, the control of accumulated heat in material becomes more complex, but the possibilities of utilizing accumulated heat are more versatile. The values shown in the pV and Ts diagrams refer to the extreme mode of engine operation, with maximum speed of revolution attained. In actual engine service, the requirements in regard to such mode of operation occur very seldom, and as a consequence the process in 90% of time takes place at lower pressures and temperatures. By modifying pressure and temperature of the working fluid, the accumulated heat in material is being changed. In the event of no power requirement (neutral gear, no load operation, idling), fuel may be injected, not only in smaller amounts, but also at intervals of several revolutions. When decreasing speed of rotation, the engine operates with decreased rate of working fluid intake. In this way the engine operates at lower pressure and temperature at the end of compression, which should be maintained during expansion phase of the Carnot cycle, resulting in gain of work in cooling revolutions with the temperature of the accumulated heat in material becoming still lower. This enables fuel to be injected in each revolution, commencing at certain revolution limited by material allowable temperature (at vehicle starting, power requirements imposed), with the effect of gaining large work in each revolution as required. By carrying out tests and measuring heat transfer occurring in actual engine, it would be possible to determine increase of temperature in relation to fuel heat input in a single revolution. In the same manner, temperature drop in material could be determined following a cooling revolution. This is possible due to the fact that thermally insulated system is affected to negligible extent by external flow of surrounding air, regardless of the system moving or being at standstill. By controlling precisely the rate of fuel injection, based on power requirements, it would be possible to utilize efficiently the VARIABLE TEMPERATURE RANGE of accumulated heat in material.

Equalizing rotational torque

In the revolutions in which the fuel is injected and burned the work delivered is greater, the forces are larger, and the torque is higher than in the revolutions of system cooling. For improved balance of rotational torque TWO OR MORE SYSTEMS can be used on the same shaft. It is important to underline that in this way both methods of heat addition can take place SIMULTANEOUSLY. While in the first system the heat is ADDED (by injecting and burning fuel at appropriate revolution) in order to gain 'large amount of work', simultaneously in the other system on the same shaft the heat is being REMOVED (by not injecting fuel) and 'small amount of work' is gained, and so on in alternative fashion. In such a manner, the processes can be controlled in multi-system large-size engines, suitable for applications requiring exceptionally large power and torque (e.g. power plants, ship propulsion engines, trucks, buses, etc.). Equalization of rotational torque may be accomplished by incorporation of the flywheel. The subject design is characterized by exceptionally favourable ratio of 'active' mass (rotating mass) and 'passive' mass (stator), the masses of rotor and ring acting as a flywheel.

By controlling process in such a way it is possible to utilize more efficiently that part of the heat (energy), which is in contemporary designs rejected to the cooling water (about 25%).

By isolating system from the environment that part of the heat, which is wasted in current designs by radiation, could be utilized more efficiently (about 5%).

The system can be arranged with one expansion cylinder in which case the exhaust port shall be provided in it. Volume of the expansion cylinder can be greater in size than the volume of the intake/compression cylinder. Owing to the provision of exhaust port (in one or both side walls) the volume and time of expansion are reduced, and the combustion should start as soon as possible when the initial change of volume is being still slight. By using larger masses of the working fluid in the process (for the purpose of decreasing peak temperature of the process), or longer combustion time, the process may end, in spite of the larger expansion volume, with a loss of temperature and pressure at the beginning of the exhaust phase.
This pressure drop can be avoided by suitable addition of auxiliary expansion/exhaust cylinder, in which way combustion phase can start a bit later (the time and path of heat transfer is increased prior to combustion) when the volume has increased, and the combustion could last longer. Because of the need to transport the working fluid to this auxiliary expansion cylinder this variant is considered more complex, and for that reason the process embodiment will be described hereinafter as involving two expansion cylinders.
Isolation of a system is illustrated In Figure 7. Two expansion cylinders of identical volumes are shown isolated from the environment. The first expansion cylinder in which the combustion occurs is called combustion/accumulation cylinder, and the other one - expansion/exhaust cylinder.

1 Intake/compression cylinder
AK Accumulation chamber
2 Expansion cylinder of combustion/accumulation
3 Expansion/exhaust cylinder
4 Thermal and sound insulation of expansion cylinders from the environment
5 Shaft

Thermal conditions for execution of process events

Intake/compression cylinder IS EXPOSED TO EXCHANGE OF HEAT TO ENVIRONMENT and for this reason needs to be structurally separated and isolated from other parts of the engine. The cylinder walls may be air cooled by means of a blower, and in case of intensive cooling being required, the heat from the walls of this cylinder can be removed by water-cooling. The heat in the walls of this cylinder comes from the transfer of part of the heat from working fluid the temperature of which increases during compression, and has no origin in the fuel. This heat needs to be removed. For compression to take place an amount of work has to be expended, such work being gained simultaneously in the expansion cylinder, and this is done by utilizing fuel heat energy.
By maintaining temperature of surrounding walls of this cylinder at a low level, taking care to have slower volume change and lower velocity of working fluid during intake, the temperature of the working fluid at the end of intake, i.e. at the beginning of compression, will not be significantly increased in relation to the temperature of the environment and as a result the mass of working fluid admitted during intake will be greater.
Due to slower volume change during compression, occurring in the narrow space surrounded by large surfaces suitable for removal of heat, and much longer time of compression which takes place over longer path by rotation of shaft greater than 180°, mean exponent of the polytropic compression will be lower, and the compression may and shall last longer, whereby the necessary temperature is attained by high compression ratio. In this way, much higher pressure may be attained at the end of compression, i.e. at the beginning of combustion. To attain the most favorable exponents of the polytropic compression, this being the prime objective in obtaining excellent results from the subject design, the appropriate heat removal from the working fluid during compression should be achieved.
Since the design has not been tested yet, there exist no measured values of temperatures of heat accumulation and heat transfer. For the reason of identifying potential savings that could be made, it would be essential to determine the optimum temperature of the working fluid at the end of compression. In the event that the heat transfer in the rotor bore in the expansion cylinder is shown to be sufficiently intensive, as expected, it would be possible to complete compression phase in such a way that the temperature at the end of compression in the compression cylinder be slightly lower than customary.
The expansion cylinder of combustion/accumulation is structurally isolated from the environment thus preventing heat transfer by radiation, and it is also separated from the intake/compression cylinder. In this way heat conduction to intake/compression cylinder, which must be cooled, is also diminished. During engine operation the walls surrounding volume of rotor bore, and large round surfaces of rotor and outer ring in the combustion/accumulation cylinder will accumulate part of the heat released by combustion and become still hotter. The temperature of the accumulated heat in the material ought to be higher than the temperature of the working fluid at the end of compression.
In practical realization of this cylinder it would be preferable to use multi-layer materials of different thermal conductivity so as to enable the largest accumulation of heat to occur in the layer that is in contact with the working fluid and diminish heat conduction to other parts of structure. The walls surrounding volume of rotor bore in which combustion takes place could be made from the material capable of withstanding temperature higher than the temperature of accumulation.
Addition of heat to the working fluid PRIOR TO the beginning of the combustion and at the very moment of beginning of expansion will be achieved as soon as the system warms up. By such addition of heat, internal energy of the working fluid is further increased, but at the time when the working fluid begins to deliver work. Change of volume in the expansion cylinder at these degrees is very small. The heat is added to the working fluid in the hot volume of rotor bore in the expansion cylinder of combustion/accumulation. The walls of the rotor bore volume are exceptionally hot since burning of fuel takes place in this volume, and the temperature and pressure are additionally increased by heat transfer, and the surrounding walls and the walls of rotor bore volume shall be cooled to some extent. This part is the hottest part of the system, and transfer of heat in the bore can be accelerated by turbulence of the working fluid.
In such a way, part of the accumulated heat in the walls of the system can be utilized, requiring less work input.
On the left-hand side of Figure 6, indicated by the dashed line circle, the transfer of heat is shown flowing from the working fluid to the walls during combustion that takes place in the combustion/accumulation cylinder. This part of the heat is accumulated in the surrounding walls and can be utilized in a number of ways. Transfer of the heat from the walls to the working fluid is indicated on both diagrams by gray arrows.
On the right hand side of Figure 6, the transfer of heat is shown as existing in current reciprocating engines flowing from the working fluid to the walls and inversely. In current designs the heat that was removed is neither being accumulated nor used.
The heat accumulated in the combustion/accumulation cylinder may be utilized in a number of ways. Removal of the heat accumulated in the walls of this cylinder is possible by transfer (recovery) of heat from the walls to the working fluid, whereby:

1. heat is added to the working fluid prior to the beginning of combustion,
2. heat is not removed from the working fluid at the very beginning of combustion,
3. total heat transfer from the working fluid to the walls is reduced during combustion,
4. combustion process is accelerated,
5. on completion of combustion, part of the heat is returned to the working fluid,
6. heat is added to the working fluid at revolutions of cooling when no combustion is taking place.

Accumulated heat may be used partly in respect of less work input required, and partly in respect of more work gained.

Better fuel economy can be achieved by better utilization of the heat in spent combustion gases. In reciprocating piston engines this loss accounts for more than 30% of the total heat energy input.

The temperature of the burnt gases in reciprocating piston engines at the moment EO (exhaust opened) amounts to approximately 1200 K. High temperature of burnt gases may be utilized by employing an expansion process unlike the one that takes place in reciprocating piston engines. In reciprocating piston engines the direction of force and magnitude of moment arm at the end of expansion are too unfavorable to facilitate use of relatively low pressure.
In rotary engines, on the other hand, due to constant ideal direction of force and constant moment arm, it is possible, by enlarging expansion volume with suitable addition of an auxiliary expansion/exhaust volume, to achieve 'enlarged' and 'protracted' expansion phase, enabling utilization of temperature of spent gases and maximum exploitation of relatively low pressure for performing useful work.
The expansion/exhaust cylinder is located adjacent to the combustion/accumulation cylinder, and both of them together are isolated from the environment. Its purpose is to enlarge the expansion volume during expansion phase and prevent rejection of the heat of burnt gases from the combustion/accumulation cylinder directly to the environment. Such enlargement and prolongation of the expansion volume enables to add heat to the working fluid by later start of the combustion phase with larger volume increment. Round surfaces of rotor and ring are not exposed to friction and may be made from ceramic plates. Auxiliary expansion/exhaust cylinder is necessary also for the reason of enabling as great accumulation of heat as possible in the walls of combustion/accumulation cylinder, and thus retaining the heat in the system for longer period of time. In this way high temperature of the accumulated heat is concentrated on the smaller area enabling faster accumulation of heat.
Since the new design configuration still needs to be thermally tested, the test results may point to some other potential benefits too.
Auxiliary expansion/exhaust cylinder provides possibility of adjustment of the combustion/accumulation cylinder in respect of size and volume.
Communication with the auxiliary expansion/exhaust cylinder may be established at the most favourable moment.
In this design configuration the sizes and volumes of all the cylinders may vary individually.
In the figures that are part of this patent application the dimensions of all the cylinders are identical. They differ only in the volumes of the bore.
By turning the frame, the cylinders may be joined at the most opportune moments, and to achieve gradual enlarging of the volume the sliding impeller (5/3) shall be in its initial position.
In Figure 8, the manner of joining is shown of:
the expansion cylinder of combustion/accumulation (sliding impeller 5/2 at its 180° position), with the expansion cylinder of expansion/exhaust (sliding impeller 5/3 at its 0° position).
The sliding impellers coincide with each other, and the frames are turned and fixed at 180° position. The initial consideration is based on joining volumes at the indicated degrees.
In Figure 8a, the same volumes are shown in simplified form in respect to INCREMENT (volume increment depending on angle a is shown by shaded area). Such interpretation serves to illustrate more clearly joining of two expansion volumes.
Over the path indicated by s = 180° the expansion takes place simultaneously in two cylinders and due to constant ideal direction of force, constant moment arm, constant volume increment or constant area ('a') of two sliding impellers (5/2 and 5/3), the high temperature of burned gases will slow down pressure drop enabling any magnitude of pressure to be utilized for performing work.

4. d Mechanical design of the rotary internal combustion engine

The subject of the invention is design of rotary internal combustion engine having on the same shaft one intake/ compression cylinder and at least one, possibly two expansion cylinders (the latter embodiment being described hereinafter). In the intake/compression cylinder both intake and compression phases take place. Between the intake/compression cylinder and the combustion/accumulation cylinder the stationary accumulation chamber is located. In the first expansion cylinder the combustion takes place during expansion accompanied by accumulation of part of the heat. The other expansion cylinder is the auxiliary cylinder of expansion/exhaust. The events taking place in volumes of all the cylinders occur simultaneously.
In the stators of all the cylinders the following rotating coaxial members are located: rings, rotors and sliding impellers. Each cylinder is fitted with peripheral part of the frame (1) (Figures 9 and 10) in whose geometric center the peripheral ring (2) is located concentrically. Each cylinder is fitted with the rotor (3) which is eccentrically located in relation to the geometric center of the stator and the ring, and which is fixed to the shaft (4) located in its geometric center. Rotor and ring are positioned in such a way that they have contact all the time at one point (0), and they are connected radial by sliding impeller (5) which is inserted into rotor slot with its one side and into semi-circular recess in the ring with its other side (the latter forming a pivotal joint). In this way the sliding impeller enables forming two variable volumes in each cylinder, i.e. in respect to the direction of rotation - leading volume (A) and lagging volume (B). Each cylinder is comprised of lateral walls (9) concentrically positioned in relation to the peripheral frame with which they form confined volume in the stator. Lateral walls are fitted with bearings (10) carrying shaft (4), as well as intake port (6), exhaust port (12) or opening for passage of the working fluid (11). The contact point of the rotor and the ring (0) is denoted as 0° signifying initial degree of the sliding impeller rotation, and also 0° of the frame in relation to the rotating parts, and respectively of their mutual position in relation to other two frames. 0° of the first frame of the intake/compression cylinder and 0° of the second frame of the combustion/accumulation cylinder coincide with each other (Figure 18).
The third frame of the expansion/exhaust cylinder is turned and fixed at 1800 in relation to the frames of the previous two cylinders. If, for example, the sliding impeller in the first cylinder is in its initial position of 0° the sliding impeller in the second frame is turned by 180° being now in its 1800 position. The third sliding impeller coincides with the sliding impeller in the second cylinder because it is turned by 180° in relation to the sliding impeller in the first cylinder, but actually the third sliding impeller is at that moment in its 0° position because its frame is turned too by 180° (Figures 17 and 18).
During rotation the rotating parts fit tightly to the internal walls of the cylindrical frame and to the lateral walls of the frame, thus preventing leakage. To reduce peripheral friction of the ring with peripheral part of the frame the cylindrical rollers (8) are mounted in each of the corners of the peripheral frame supported by bearings in lateral walls.
The above listed components represent the main parts of each cylinder.
They are identical in all the cylinders, and any difference is in the bores, openings and channels for introducing working fluid.
These differences will be separately described, and visually shown in 3D as well.
In Figure 9 the sliding impeller is positioned at 180° so that volumes A and B could be seen.
In Figure 10 the position is shown in which the bore (7) in the rotor and segmental groove (11) in lateral wall coincide, the sliding impeller being in another position.
In Figure 11 the rotating parts of each cylinder are shown in 3-dimensional simplified form: ring (2), rotor (3) fixed to the shaft (4), sliding impeller (5) and peripheral rollers (8).

Flow of working fluid
The subject rotational design is characterized by absence of any valves, the flow of the working fluid through the system being enabled by bores in the rotor, segmental grooves in the rotor and segmental openings in the lateral walls. Until full flow is attained, the circular form of the bore enables favourable initial damping of all circulation. All bores, openings and grooves shall be adequately sized and smoothed so as to present as little resistance as possible to flow of the working fluid. The walls surrounding bores (most of all the partitions) shall be made of special material (ceramics).

Rotors
The bores (7) are drilled in the rotors at an appropriate angle leading from the lateral side to the peripheral side of the rotor (Figure 12). The purpose of the bores is to enable passage of working fluid from the front side of the rotor to lateral side or the other way around. By rotating rotor the communication is established or interrupted at the exact predetermined intervals with the segmental openings in the lateral walls (Figure 15) in which way the flow of the working fluid between the volumes is established or interrupted. All the bores, grooves and openings must be appropriately sized and smoothly machined so as to present as little resistance to the flow of working fluid as possible.
The differences among the bores in the rotors in regard to their purpose, configuration and location:
One bore (in the figures denoted as 1R - the first rotor) is provided in the rotor of the intake/compression cylinder, located on the leading side of the sliding impeller in direction of rotation (Figure 12). Upon forcing the working fluid into the chamber, some amount of the working fluid at high pressure will be left in this bore, which will expand, at the particular moment when the peripheral side of the bore during further rotation passes contact point 0 (Figures 9 and 10) and enters the intake side, into the intake volume on leading side of the sliding impeller and accelerate in this way the filling of the intake volume with increased mass of the working fluid and in controlled manner raise the initial pressure (Figure 16 f). This rotor is located between the lateral walls I and II.
Two bores (Figure 13) are provided in the rotor of the combustion/accumulation cylinder. In relation to direction of rotation, one bore is located on the leading side and the other on the lagging side of the sliding impeller. The bore located on the lagging side of the sliding impeller in the rotor of the combustion/accumulation cylinder (in the figures denoted as 2R/B - the second rotor, volume on the lagging side of the sliding impeller - B) is of a cylindrical form and it is drilled parallel to the rotor peripheral surface. The purpose of this parallel bore is to enable establishing communication at intervals between segmental volumes in the lateral walls III and IV. The volume of the cylindrical bore is connected with additional peripheral bore and joined together they form letter T (Figure 13/2). Rotor is positioned between lateral walls III and IV (Figure 15). At predetermined moment the communication is established between the bore 2R/B and the segmental opening in lateral wall III and working fluid expands into the bore 2R/B during initial degrees of expansion. The combustion takes place in the bore 2R/B the same as in the main combustion volume. The walls surrounding this bore shall be made from the material capable of withstanding high temperature of accumulation. Upon completion of the combustion, at predetermined moment during expansion the bore 2R/B coincides with the segmental opening IV/B in lateral wall IV, and the communication established with the bore 3R/B and working fluid expands into expansion/exhaust cylinder (Figure 17e).
The bore 2R/B located on the lagging side of the sliding impeller in the rotor of the combustion/accumulation cylinder connects the higher-pressure volumes by establishing communication with the bore located on the lagging side of the sliding impeller in the rotor of the expansion/exhaust cylinder during 180° of the shaft rotation. The purpose of the bore on the leading side of the sliding impeller in the combustion/accumulation cylinder (denoted in figures as 2R/A) is to establish the communication between the low-pressure volume with the bore on the leading side of the sliding impeller in the expansion/exhaust cylinder. The bore extends from the front side to the lateral side of the rotor in which the segmental groove is located (Figure 13). Segmental openings are made in specific places in the partition wall IV for connecting the volumes between these two cylinders. The partition wall is common for these two cylinders (Figures 15 and 18). Such configuration of the channel enables low pressure volumes in the cylinder to communicate over 360° of the shaft rotation ensuring continuous exhaust.
Two bores are also located in the expansion/exhaust cylinder.
The bore located on the lagging side of the sliding impeller (3R/B) in the rotor of the expansion/exhaust cylinder is of the same form as the bore 1R and it is shown in Figure 14. The purpose of this bore is to establish communication between the volumes for passage of the high-pressure working fluid with the combustion/accumulation cylinder. The peripheral bore (3R/A) on the leading side of the sliding impeller in the expansion/exhaust cylinder located at 1800 is permanently connected with the segmental groove in the rotor lateral side as shown in Figure 14, its purpose being to establish communication with the low pressure volume of exhaust gases. This communication by way of segmental groove in the lateral wall is established also over the whole 360° of the shaft rotation.

Lateral walls
Figure 15 shows lateral walls designated as I - V in the sequence of working fluid flow. Dashed lines indicate those volumes that are formed by rotors and rings along these walls. Walls I and II surround the compression volume. Intake ports (6) are provided in these walls. Segmental opening is made in the wall II through which the working fluid is being forced out into the accumulation chamber. This opening will be denoted hereinafter as (II). In Figure 15 the cylindrical accumulation chamber is shown visually between walls II and III. The walls III and IV surround expansion volume of combustion/accumulation. Segmental opening (III) is made in the wall III through which the working fluid expands from the chamber into the volume of the bore 2R/B in the rotor. The expansion/exhaust volume is formed between walls IV and V, the wall IV being the common wall and therefore larger than the other ones. Dashed lines in the wall IV indicate those volumes that are formed on both sides of the wall. Two segmental openings are made in the wall IV. The segmental opening for establishing communication with volume on the lagging side of the sliding impeller is denoted as IV/B and the segmental opening for establishing communication with volume on the leading side of the sliding impeller is denoted as IV/A. The wall V together with its peripheral frame is turned by 180° and provided with the exhaust port (12).

5. THE PROCESS

For better viewing the drawings showing geometric change of volume and flow of the working fluid through bores, grooves and openings in characteristic positions of the sliding impeller in all working volumes are maximally simplified. STATE OF THE WORKING FLUID in the said positions is shown in the INDICATOR DIAGRAMS in Figures 23 and 24 and described in THERMODYNAMIC COMPUTATIONS.

The process occurring in the intake/compression cylinder.
In Figure 16 the change of volume is shown in the intake/compression cylinder only. Since compression takes place in the accumulation chamber the other volumes are not shown here. In Figure 16 the intake ports (6) are shown coinciding one over the other the same as the segmental opening II in the lateral wall II (Figure 15) through which the working fluid is being forced into the accumulation chamber. The sliding impeller in the intake/compression cylinder (5/1) is turned by 180° relative to the sliding impellers (5/2 and 5/3) in the expansion cylinders (Figure 18).
In Figure 16a the sliding impeller (5/1) in the intake/compression cylinder is shown at its 90° position in the beginning of compression at the moment of INTAKE CLOSED (Figure 23-1). The sliding impeller starts compressing working fluid into volume (A) in front of it, and at the same time the working fluid for the new cycle is being drawn by the underpressure into volume (B) behind it through the intake ports (6) in lateral walls I and II during the whole 360° of the shaft rotation (Figures 16 a, b, c, d, e, f).
Utilizing inertia of the working fluid the intake takes place over the whole 360° of the shaft rotation (by rotation of the sliding impeller 5/1 from 90° to position 90°).
The compression of the working fluid lasts until predetermined temperature and pressure is reached at which moment the communication is established between the bore 1R in the compression rotor with the segmental opening in the lateral wall II. The accumulation chamber is mounted stationary on the other side of the lateral wall II (Figure 15) adjacent to the intake/compression cylinder. The beginning of the segmental opening in the lateral wall II can be set at the desired degree of rotation, meaning that the length of the segmental opening may be adapted as necessary. The moment of forcing the compressed working fluid into the accumulation chamber is shown in Figure 23-2. The pressure in the volume of the segmental opening in the lateral wall II, which is continuously connected with chamber volume, is, at the moment of connection with the bore 1R in rotor, the same as the pressure in the chamber (Figure 23-3) but slightly lower than in the bore 1R in the intake/compression rotor. In the next few degrees the pressures equalize, and the forcing of working fluid into the chamber is continued at the constant pressure and temperature. In Figure 23-4 the process state is shown when forcing of the working fluid into the chamber is completed and the communication between the bores interrupted. This communication must be interrupted before the peripheral trailing portion of the bore 1R passes contact point 0 so as to prevent establishment of communication between the high-pressure volume with the low-pressure intake volume.
The amount of the working fluid left in the bore 1R at the pressure of compression will expand into the intake side in front of the sliding impeller as soon as the peripheral trailing portion of the bore 1R passes contact point 0, in which way the initial mass and pressure of the working fluid will be increased by predetermined amount (Figure 16 f). At the moment when the sliding impeller in its 90° position passes the intake port again and closes introduction of the working fluid in front of it, the new revolution begins with compression action in the volume on the leading side of the sliding impeller and the intake action in the volume on the lagging side of the sliding impeller.
The accumulation chamber is necessary for several reasons. Filling of the volume of the bore 2R/B in the rotor of the combustion/accumulation cylinder occurs on establishment of communication with the chamber almost instantaneously by expansion of the working fluid into this volume because the working fluid in this chamber is under high pressure. By appropriately sizing the volume of this chamber only slight pressure drop ensues during filling. In order to reduce as much as possible conduction of heat through the walls from the part of the system which is accumulating heat, on to the intake/compression cylinder (which ought to be cooled from the outside), the most simple and efficacious way would be to move away the intake/compression cylinder which requires provision of separate accumulation chamber. The purpose of such accumulation chamber would be to store certain amount of working fluid under high pressure and temperature. The accumulation chamber will be in continuous communication with the segmental openings in the lateral walls II and III, consequently the volumes of these segmental openings need to be taken into account when calculating the volume of the chamber. The communication is established and broken at suitable predetermined intervals of time by establishing or breaking communication between the segmental openings and the bores in the rotors both of the compression cylinder and the expansion cylinder. The accumulation chamber is thermally insulated from the environment.

The process occurring in the combustion/accumulation cylinder.
In Figure 17 the positions of the segmental openings in the walls III and IV (Figure15) are shown concurrently. In the same way, the positions of the bores in both expansion rotors are shown concurrently as well as their positions at the moment of the communication being established between them. The frame of the expansion/exhaust cylinder is turned by 180° relative to the frames of the other two cylinders. Darker shading areas indicate volumes of higher pressure, and the lighter shading areas the lower pressure volumes.
In Figure 17a the sliding impeller (5/2) of the combustion/accumulation cylinder is in its “0” degrees position. At the same time the sliding impeller (5/3) in the expansion/exhaust frame is in its 180° position, because the sliding impellers coincide all the time. The bores positioned on the lagging side of the sliding impeller (2R/B and 3R/B) in the rotors coincide all the time too, and the communication between them is established by segmental opening IV/B in the lateral wall IV.
In Figure 17b the moment is shown of establishment of communication between the combustion bores 2R/B with segmental opening III in the lateral wall III. At the opportune moment, when the communication is established between the segmental opening in the lateral wall III and the bore 2R/B in the combustion/accumulation cylinder, the compressed high-pressure working fluid expands abruptly through the said segmental opening into the hot volume of the said bore 2R/B. The most opportune moment for establishing such communication between the chamber and the volume of the bore 2R/B in the combustion/accumulation cylinder is when the peripheral side of the bore 2R/B in the rotor is still a few degrees on the exhaust side, i.e. before the peripheral side of the bore passes the contact point (0). In such a way scavenging is enabled of the bore so that the spent combustion gases left from the preceding revolution may be forced out into the exhaust side (Figure 17b). In this way excellent volumetric efficiency is achieved. Filling of the bore 2R/B in the rotor of the combustion/accumulation cylinder is completed after several degrees of rotor revolution only (Figure 23-5), the communication being broken with the segmental opening in the lateral wall III and thereby with the chamber (Figure 17c). By breaking communication, the transfer of heat is enabled from the hot surrounding surfaces, in which way the temperature and pressure of the working fluid is increased during the beginning of expansion, at the time of very small change of volume, this pressure increase having no effect on pressure in the chamber. During first few degrees of expansion the fuel is being injected through the lateral wall or chamber into the bore 2R/B in the rotor, which bore represents main combustion volume. The injection may be carried out simultaneously with the filling of the bore with the working fluid or immediately after. The combustion begins either with auto-ignition or by firing spark plug (Figure 23-6). Figure 17d shows the expansion cylinder of combustion/accumulation during combustion - addition of heat (Figure 23-7). On completion of fuel burning, part of the heat from large surrounding surfaces which accumulated part of the heat during combustion, rotating together with the working fluid, is transferred back to the working fluid, and then at the opportune moment the communication is established with the expansion/exhaust cylinder and the enlarged expansion takes place (Figure 23-8).

The process occurring in the expansion/exhaust cylinder.
The partition wall IV between the two expansion cylinders is shared among them (Figure 15). At a predetermined moment, by connecting the bores and channels, communication is established between the high-pressure volumes behind the sliding impeller. The sketches in the Figure 17e illustrate joining of these volumes at the moment when the sliding impeller (5/2) in the combustion/accumulation cylinder is in its 180° position (Figure 17e). At this particular moment the sliding impeller (5/3) in the expansion/exhaust cylinder is in its '0' degree position because the frames are turned by 180° relative one to the other.

By turning the frame of the expansion/exhaust cylinder the joining of volumes may be carried out at some other moment, and the sliding impeller (5/3) in the expansion/exhaust cylinder shall be in its '0' degree position at the moment of joining so as to enable gradual increase of volume. In Figure 17e the moment is shown of establishment of communication between the bore 2R/B with segmental opening IV/B in the lateral wall through which the working fluid is introduced into the bore 3R/B in the rotor on the lagging side of the sliding impeller (5/3) in the expansion/exhaust cylinder, which is at that moment in its '0' degree position, so that the expansion takes places simultaneously in both expansion cylinders as shown by darker shading area in Figure 17f. At that particular moment new cycle begins in the combustion/accumulation cylinder of admitting the working fluid into the combustion volume 2R/B, the expansion continuing to take place in the expansion/exhaust cylinder up to the moment EO. The low-pressure volumes on the leading side of both sliding impellers are in permanent communication with the exhaust port during the whole 360° revolution. The exhaust port (12) in the lateral wall V (Figure 15) is indicated by dashed lines in Figures 17a and 17f only, however this port is always in the same position and for convenience it is not indicated in all the figures.
Figure 18 shows the volumes of three chambers, accumulation chamber, lateral walls and sliding impellers, the volumes being designated: Intake/compression cylinder (1), Accumulation chamber (AK), Expansion cylinder of combustion/accumulation (2) and Expansion/exhaust cylinder (3). The volumes of the segmental openings II and III are in permanent communication with the accumulation chamber AK and together they form the volume of accumulation chamber. At predetermined moments the segmental openings IV/A and IV/B in the lateral walls establish communication with the volumes of the bores in the rotors.
The sliding impellers (5/1, 5/2 and 5/3) are indicated by dashed lines in their respective positions.
All the sketches are shown in very simplified form with an intention to illustrate the basic idea of engine operation in a clear and simple manner. Many details have been left out which would otherwise make the schematics too complex and render them indistinct. The rotor widths in figures 10 and 18 differ. To simplify machining of slots in the rotors and to facilitate illustration and description of engine operation, the rotors are shown in the unfinished form. In reality, the rotors are wider than the sliding impellers, because an end plate is mounted onto the rotor sides prior to drilling the bore so as to seal the slot in the rotor thus preventing communication with segmental openings in the lateral walls. In Figure 19 the rotor is shown with the end plate mounted on its side, and with annular sealing grooves indicated in the end plate.

Sealing and lubrication of structure
On account of high temperature of material in the expansion cylinder, the lubrication presents a very complex task. Oil (or greases) cannot withstand high temperatures, and for that reason the number and size of surfaces requiring lubrication need to be held to a minimum. Owing to the effect of continuous speed of rotation of rotor, ring and impeller along the lateral walls, sealing can be achieved by CONTACTLESS labyrinth sealing action. This feature makes the subject design essentially different from the conventional reciprocating piston-type engine in regard to sealing. Inadequate sealing or friction result in comparably equal losses of input work or of work not gained, but contactless sealing renders use of lubricants unnecessary. In this way, the application of materials of high quality and strength, otherwise not distinguished by excellent sliding properties, is possible. Self-sealing action of 'the contact point' in the expansion cylinder, where the elongation is the greatest, can be achieved by exploiting the working fluid turbulence. This is made possible due to curved form of volume and suitably machined round surfaces of the rotor and the ring which are revolving in opposite direction (direction of pressure action in relation to contact point). Sealing of the contact point in the compression cylinder, due to low temperature of material and its small elongation, may be realized by contact of the rotor and the ring. Lateral sealing of the impeller may be carried out also by contactless labyrinth sealing action.
Lubrication and cooling of the impeller in the rotor slot may be carried out by drawing in or injection of small amount of oil dispersed in air into the slot volume under the impeller. During rotation from 0° to 180° the impeller comes out of the slot and as a result draws air and oil into the volume it left. Oil adheres to both surfaces (impeller surface and slot surface). The action of the impeller’s lower surface moving to periphery contributes to accumulation of oil over slot surface. Centrifugal force is also acting on oil deposited on the walls. Temperature of this slot surface shall be reduced by application in rotor of the multi-layer material, the rotor slot surfaces in contact with impeller surfaces being cooled by drawing in or injection of dispersion of cold air and oil in each revolution. During further rotation from 180°- 360°, with the impeller starting to return into the slot, the impeller is lubricated by oil deposited on slot surface. At the end of this motion (by suitable design of rotor lateral wall), small pressure is created in the slot in front of the impeller sufficient to force oil and air from the rotor center to periphery. By introducing oil into the central part of the engine, pushing out air and oil by combined action of impeller and centrifugal force the oil is circulated to the peripheral surfaces.
The lubrication of impeller 'crown' in the ring is carried out by suitable design of a groove made in the leading (cooler) edge of the impeller from bottom to the top. Such a solution should enable lubrication of the impeller in the cylinder, the surfaces of both impeller and the slot being cooled by introducing cold air and oil in the space under the impeller, and subsequently pushing out hot air to carry away heat up to the peripheral volumes. Oil is then circulated from the impeller 'crown' to the outer, peripheral surfaces of the ring for the purpose of lubricating peripheral rollers.

Thermodynamic computations

In Figure 20, the approximate magnitudes of pressure and temperatures are shown as attained at the end of compression in Otto cycle in contemporary internal combustion engines.
The upper curve in Figure 20 represents the temperature increment of compression process with mean exponent 1.35 up to the temperature of 800 K.
The curve at the bottom of Figure 20 represents the corresponding polytropic compression, with pressure of 28.4 bar being achieved at the end of compression.
The compression occurred over 180° of shaft rotation with the compression ratio of 11.8 : 1.
The approximate values of temperature and pressure at the end of the compression that could be achieved in the rotary configuration by removing part of the heat from the working fluid during compression.
In upper part of Figure 21 the temperature increment of compression process is shown with mean exponent 1.18 up to the temperature of 700 K.
The curve at the bottom of Figure 21 represents the corresponding polytropic compression, reaching pressure of 112.6 bar at this temperature. The compression occurred over 220° of shaft rotation at the compression ratio of 54.8 : 1.
The value of the mean exponent (1.18) was selected hypothetically. The testing and measurement of the real configuration will show what intensity of cooling of surrounding walls is necessary during compression to achieve high pressure and appropriate temperature at the end of the compression.
Figure 22 shows pV diagram derived from thermodynamic computation. In this computation the compression process was interrupted at lower compression ratio, lower pressures and lower temperature.
For that reason the computation was not based on the maximum possibilities, thus allowing possibility of deviation in achieving the values of the mean exponent.
(The above diagrams indicated DV only, i.e. mathematical variable, not the total volume.)
The accumulated pressure in the accumulation chamber is achieved at higher number of revolutions, and the dashed line bounded area shows accumulated compression work. In this pV diagram, the volumes of the two expansion cylinders are the same, but greater in size than the compression one. The purpose of this pV diagram is to illustrate these volumes. The surfaces under the thin line curves (depending on angle a) represent the compression volume, and the volume of two joined expansion cylinders respectively. Joining of these two volumes takes place at 180° of sliding impeller (5/2) position.

Figure 23 shows extended indicator diagram derived from the thermodynamic computation.
1. Commencement of compression (UZ) V = 424,37 cm3, p = 1,156 bar, T= 310 K , n=1,2, alpha 90° (Fig.16a)
2. Connecting compression volume and chamber, (p and T selected) (Fig.16d) compression volume:
V = 9,98 cm3, p = 107,17 bar, T= 675 K, alpha 300°
3. Accumulation chamber - state: V = 145 cm3, p = 95,19 bar, T= 657 K
4. End of compression and interruption of connection of compression volume with chamber: alpha 350°,
p = 99,78 bar, T= 675 K (Fig.16e). After approximately 180° of shaft rotation the connection is established between the chamber and the rotor bore in the expansion cylinder. The most favourable moment of establishing connection between the chamber and the expansion volume is described in the text (Fig.17b). Volume of bore in the expansion rotor is: V = 9,60 cm3,
5. State of the working fluid on completion of circulation of working fluid into the expansion volume and interruption of connection with the chamber (Fig.17c) p = 94,50 bar, T=658 K. From the start of circulation (with turbulence of working fluid) from the chamber into the expansion rotor bore, heat transfer is going on from hot surrounding walls to the working fluid. At the most favourable moment fuel is injected at high pressure.
6. Auto-ignition and start of fuel burning
7. p max = 238 bar, T max = 2890 K (Fig.17d)
8. Connection to additional expansion cylinder: p =19,6 bar, T=1885 K, alpha 180° (Fig.17e)
9. Exhaust open: p=1,1 bar

Figure 24 shows the temperature of working fluid during the process derived from thermodynamic computations.

Figure 25 shows the diagram of indicated work derived from the thermodynamic computations using the formula W=F*s.
The work of compression is negative, which has been taken into account in the computations. On this diagram it is depicted as positive work that needs to be expended.

Figure 26 depicts the diagram of expended and delivered work during a revolution with injection and burning of fuel, derived from the thermodynamic computations using the formula W=pDV+W.

Thermodynamic computations demonstrate that over one revolution the following can be gained from the fuel energy input in the volume of 400 cm3: work of app. 900 J, maximum torque of app. 500 Nm, mean torque during one revolution of app. 150 Nm. These results are achieved by filling cylinders with mass of 0.000472 kg of working fluid in one revolution. Combustion calculation was performed by VIBE method, based on Otto principle, with stoichiometric air to fuel ratio of 14.7 : 1, l = 1and (cv+cp)/2. Duration of combustion is 55° of shaft rotation.
At these values, and at a speed of rotation of 2,400 rpm the engine delivers approximately 36 kW (50 HP) of power.
Since the combustion takes place at the higher temperatures of the surrounding walls than with contemporary engines, the total heat transfer during combustion will be at the lower rate, and consequently, higher process peak temperature may be realized with the same fuel amount, or the same process peak temperature may be attained with lower fuel amount. Since the air is being compressed in this design, to achieve higher temperature greater mass of air should be provided.

The above calculations prove that by improved mechanical design, and improved process control much greater mechanical work could be obtained over the particular revolution with injection and burning of fuel. The unutilized part of the heat input in this revolution is being accumulated and subsequently used for generating an amount of work in the next revolution, thereby achieving much higher fuel economy.
In computing the work output, the amount of work was not taken into account delivered in the revolutions of system cooling when no fuel was being injected.
The positive inertial forces of the impeller were not taken into account too, the impeller at the moment of acceleration coming out of the slot and moving away from the axis center, and at the moment of deceleration entering the slot and moving back in direction of rotation center.

The fact shall be taken into account of the mechanical work accumulated in the flywheel. This accumulated work is used in conventional reciprocating piston engines over 540° of shaft rotation, folllowing 180° of expansion, for exhaust, intake, compression and so on in cyclical sequence.

Since all the process events in a rotary engine occur simultaneously and continuously, work is accumulated in the flywheel as a result of simultaneous action of all forces in all the volumes. Mechanical work accumulated in the flywheel may be used to perform intake, exhaust and compression with slowing down speed at the time of no power requirement, and by cooling of system through Carnot process the accumulated mechanical work and heat is utilized. In such a way fuel is consumed only in case of power requirement. Maintaining spinning reserve of the rotary structure in no load mode of service requires very small amount of fuel consumption.
Proposed rotary mechanical design renders needless: valves, camshafts, springs, pulleys, belts and other. The design provides for cooling the intake/compression cylinder ONLY, in which the process peak temperature is SUBSTANTIALLY LOWER than in cylinder of the single-volume reciprocating piston engines. Application of air cooling eliminates a need for cooling water pump. Lubrication is carried out by utilizing centrifugal force, without any need for continuous operation of the oil pump. Owing to less work expended for driving said facilities, and reduced friction losses of said facilities, higher mechanical efficiency may be achieved. (Contemporary reciprocating piston engines achieve em @ 0,75).
Supercharging may be attained by the structure itself (without additional facilities).
Kinetic energy of exhaust gases may be utilized for driving alternator.
The subject design of rotary engine may attain even higher mechanical efficiency (em @ 0,9). Exceptionally large rotational torque, to be attained by the subject design of rotary engine, would enable application of more simpler and lighter reduction gear.

The computations demonstrate that by controlling the thermal process as described above much greater work can be gained in the revolution of introducing and burning fuel. The unutilized part of the heat input in this revolution is being accumulated and subsequently used for generating an amount of work in one of the next revolutions. By applying proposed manner of heat utilization this engine may attain much higher thermal efficiency too (et @ 0,9). (The best contemporary reciprocating piston engines achieve et @ 0,50).
In this way exceptional results may be obtained as well as better utilization of fuel energy.
The total efficiency of conversion of heat into mechanical energy may amount to approximately 80%
(e @ 0,8).

By ingenuous utilization of thermal potential of materials, use of flow velocity and turbulence of working fluid, accurate distribution of accumulated heat and adequate introduction of fuel and oil, very good results could be expected practically right away. With further improvement of design and development of materials and lubricants, higher mechanical and thermal efficiency could be achieved, resulting in substantial increase of overall efficiency of conversion of thermal energy into mechanical work, with pollution and heating of the environment, and fuel consumption being substantially decreased.