Abstract
A six-phase thermodynamic cycle for a rotary internal combustion engine. The thermodynamic cycle comprising: Phase 1 (intake) air enters the central intake chamber and mixes with recirculated exhaust gas from phase 3; Phase 2 (low compression) the air and recirculated exhaust gas from phase 1 is compressed at a low compression ratio; Phase 3 (scavenge and recirculation) a portion of air and recirculated exhaust gas from phase 2 scavenges the combustion chamber and partially scavenges the expansion chamber; Phase 4 (high compression) the intake chamber separates to form a compression chamber and the residual combined exhaust gas and air from phase 2 is compressed at a high compression ratio into the combustion chamber; Phase 5 (power phase) an expansion chamber is formed, originating from the static combustion chamber and torque is produced to turn the output shaft; and Phase 6 (exhaust) exhaust gas from phase 5 is discharged.
Claims
1. A six-phase thermodynamic cycle for a rotary internal combustion engine with a double rotation centre, the engine comprising a housing with intersecting circular expansion and compression chambers, a dynamic central intake chamber and a combustion chamber at the top thereof; a power rotor; a following rotor; a rotating shaft; and a drive means, the six-phase thermodynamic cycle comprising: Phase 1 wherein in an intake phase, a volume of air enters the central intake chamber of the housing through a peripheral air intake port and mixes with recirculated exhaust gas from phase 3; Phase 2 wherein in a first compression phase, the volume of air and recirculated exhaust gas from phase 1 is compressed at a low compression ratio by the reducing volume of the dynamic intake chamber within the housing; Phase 3 wherein in a combined scavenge and exhaust gas recirculation phase, a portion of the volume of air and recirculated exhaust gas from phase 2 scavenges the static combustion chamber and partially scavenges the expansion chamber, the dynamic expansion chamber then merges with the dynamic central intake chamber recirculating the residual exhaust gas from phase 6 within the housing; Phase 4 wherein in a second compression phase, the dynamic intake chamber separates to form a dynamic compression chamber and the residual volume of combined exhaust gas and air from phase 2 is compressed at a high compression ratio into the static combustion chamber within the housing; Phase 5 wherein in a power phase, a dynamic expansion chamber is formed, originating from the static combustion chamber and torque is produced to turn the output shaft; and Phase 6 wherein in an exhaust phase, exhaust gas from phase 5 is discharged from the dynamic expansion chamber through a peripheral exhaust port in the housing.
2. The thermodynamic cycle according to claim 1, wherein phases 1, 2 and 3 of the six-phase thermodynamic cycle occur in succession.
3. The thermodynamic cycle according to claim 1, wherein phases 4, 5 and 6 of the six-phase thermodynamic cycle occur in succession.
4. The thermodynamic cycle according to claim 1, wherein during each phase of the thermodynamic cycle, at least a part of one other different phase of the cycle is also occurring simultaneously.
5. The thermodynamic cycle according to claim 4, wherein therefore, phases 1, 2 and 3 of the six-phase thermodynamic cycle occur simultaneously with at least a portion of one or more of phases 4, 5 and 6.
6. The thermodynamic cycle according to claim 1, wherein phase 1 (intake) occurs simultaneously with the majority of phase 4 (second compression).
7. The thermodynamic cycle according to claim 1, wherein phase 2 (first compression) occurs simultaneously with the majority of phase 5 (power).
8. The thermodynamic cycle according to claim 1, wherein phase 3 (scavenge and exhaust recirculation) occurs in very close proximity to phase 6 (exhaust).
9. The thermodynamic cycle according to claim 1, wherein when the central intake chamber achieves a maximum volume of air, the engine is at a rotation of top dead centre (TDC), or 0 degrees.
10. The thermodynamic cycle according to claim 1, wherein phase 1 occurs at a rotation of approximately between 260 degrees through to approximately 40 degrees.
11. The thermodynamic cycle according to claim 1, wherein phase 2 (first compression) occurs in a reducing volume of the dynamic central intake chamber of the housing.
12. The thermodynamic cycle according to claim 11, wherein compression is substantially created in a right hand side of the housing.
13. The thermodynamic cycle according to claim 1, wherein phase 2 comprises a relatively low compression ratio of approximately 2:1
14. The thermodynamic cycle according to claim 1, wherein phase 2 occurs at a rotation of approximately between 40 degrees through to approximately 180 degrees rotation.
15. The thermodynamic cycle according to claim 1, wherein phase 3 comprises a portion of the air and recirculated exhaust gas from phase 2 passing from a right hand side of the housing to a left hand side via a static combustion chamber at top dead centre.
16. The thermodynamic cycle according to claim 15, wherein phase 3 comprises the introduction of water to cool exhaust gasses in the expansion chamber.
17. The thermodynamic cycle according to claim 1, wherein in phase 3 the dynamic expansion chamber merges with the dynamic central intake chamber and the combined exhaust gas and air is drawn into the central intake chamber of the housing.
18. The thermodynamic cycle according to claim 1, wherein phase 3 occurs at a rotation of approximately between 180 degrees through to approximately 220 degrees rotation.
19. The thermodynamic cycle according to claim 1, wherein phase 4 (second compression) comprises the separation of the dynamic intake chamber to form a dynamic compression chamber within the housing.
20. The thermodynamic cycle according to claim 1, wherein the compression chamber is substantially created in a right hand side of the housing.
21. The thermodynamic cycle according to claim 1, wherein in phase 4, fuel is injected into the compression chamber (approximately 225 degree rotation).
22. The thermodynamic cycle according to claim 21, wherein during further compression in phase 4, the fuel is substantially vaporised.
23. The thermodynamic cycle according to claim 22, wherein during phase 4 a homogeneous charge mixture is created from the combined exhaust gas and air and vaporised fuel.
24. The thermodynamic cycle according to claim 1, wherein phase 4 (second compression) occurs at a rotation of approximately between 220 degrees through to approximately TDC/0 degrees rotation.
25. The thermodynamic cycle according to claim 1, wherein a static combustion chamber is located at top dead centre (TDC).
26. The thermodynamic cycle according to claim 1, wherein the combustion chamber contains a variable compression ratio mechanism.
27. The thermodynamic cycle according to claim 1, wherein in phase 5 (power), conditions in the combustion chamber comprise a homogenous charge and a high compression ratio.
28. The thermodynamic cycle according to claim 27, wherein the thermodynamic cycle utilizes homogenous charge compression ignition (HCCI) triggered by the heat of the following rotor arriving at top dead centre and controlled by the variable compression ratio mechanism.
29. The thermodynamic cycle according to claim 1, wherein the arrangement of the rotors transfers a high level of torque directly to the output shaft, immediately from top dead centre.
30. The thermodynamic cycle according to claim 1, wherein phase 5 occurs approximately between TDC/O degrees through to approximately 165 degrees rotation.
31. The thermodynamic cycle according to claim 1, wherein phase 6 occurs approximately between 165 degrees through to approximately 180 degrees rotation.
32. A rotary, internal combustion engine with a double rotation centre, comprising: a housing with intersecting circular expansion and compression orbits, defining respective dynamic expansion and compression chambers, a dynamic central intake chamber and a combustion chamber at the top thereof; a power rotor; a following rotor; a rotating shaft; and a drive means, characterised in that the power rotor and the following rotor being arranged in interlocking relationship with one another and seated on different rotational axes within the expansion orbit and the compression orbit respectively, wherein the power rotor is configured to rotate on the shaft, which turns said drive means and the following rotor is configured to rotate driven via a linkage with said drive means.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0061] For a better understanding of the invention, and to show how exemplary embodiments may be carried into effect, reference will now be made to the accompanying drawings in which:
[0062] FIG. 1 is a diagrammatic representation of a PRIOR ART 9-phase thermodynamic cycle of WO2014/083204;
[0063] FIG. 2 is a diagrammatic representation of a six-phase thermodynamic cycle of a preferred embodiment of the present invention;
[0064] FIG. 3 is an exploded perspective view of the engine according to a preferred embodiment of the invention;
[0065] FIG. 4 is a perspective view of a housing according to FIG. 3;
[0066] FIG. 5 is a perspective schematic internal view of a power rotor according to FIG. 3;
[0067] FIG. 6 is a perspective external view of a power rotor according to FIG. 3;
[0068] FIG. 7 is a perspective schematic view of a following rotor in a first rotation configuration according to FIG. 3;
[0069] FIG. 8 is a perspective schematic view of a following rotor in a second rotation configuration according to FIG. 3;
[0070] FIG. 9 is a perspective schematic internal view of a following rotor according to FIG. 3;
[0071] FIG. 10 is a perspective schematic end view of the assembled engine of FIG. 3 in a first top dead centre (TDC) phase of rotation;
[0072] FIG. 11 is a perspective schematic end view of the assembled engine of FIG. 3 in a second bottom dead centre (BDC) phase of rotation;
[0073] FIG. 12 is a cross-sectional side view of the engine of FIG. 3 showing the components of the engine;
[0074] FIG. 13 is a cross-sectional side view of the engine of FIG. 3 showing expansion and compression volumes;
[0075] FIG. 14 is a chart and table showing air cycle comparisons between PRIOR ART Otto engine, PRIOR ART Diesel engine and the present invention of FIG. 3;
[0076] FIG. 15 is a chart showing the estimated brake thermal efficiency of the engine of FIG. 3;
[0077] FIG. 16 is a chart showing the estimated low emission zone operation of the engine of FIG. 3;
[0078] FIG. 17 shows a schematic side view of the engine of FIG. 3 at TDC at the start of the power phase and end of the intake phase;
[0079] FIG. 18 shows a schematic side view of the engine of FIG. 3 at 90 degree rotation in the power phase and the start of the first compression phase;
[0080] FIG. 19 shows a schematic side view of the engine of FIG. 3 at 162 degree rotation during completion of the power phase and the nearing of the completion of the first compression phase;
[0081] FIG. 20 shows a schematic side view of the engine of FIG. 3 at 180 degree rotation during completion of the exhaust phase and start of the scavenge phase;
[0082] FIG. 21 shows a schematic side view of the engine of FIG. 3 at 225 degree rotation during the scavenge and EGR phase and start of the second compression phase;
[0083] FIG. 22 shows a schematic side view of the engine of FIG. 3 at 290 degree rotation in the intake phase and continuation of the second compression phase; and
[0084] FIG. 23 shows a schematic side view of the engine of FIG. 3 at 350 degree rotation nearing completion of the intake phase and the second compression phase.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0085] FIGS. 2 and 17 to 23 show a first embodiment of the invention, being a six-phase thermodynamic cycle for a rotary internal combustion engine 1 with a double rotation centre, the engine 1 comprising: a housing 10 with intersecting circular expansion A and compression B orbits, defining respective dynamic chambers, a dynamic central intake chamber and a static combustion chamber at the top thereof; a power rotor 20; a following rotor 30; a rotating shaft 40; and a drive means 50, the six-phase thermodynamic cycle comprising: [0086] Phase 1 wherein in an intake phase a volume of air enters the central intake chamber of the housing 10 through a peripheral air intake port 11 and mixes with recirculated exhaust gas from phase 3; [0087] Phase 2 wherein in a first compression phase, the volume of air and recirculated exhaust gas from phase 1 is compressed at a low compression ratio by the reducing volume of the intake chamber within the housing 10; [0088] Phase 3 wherein in a combined scavenge and exhaust gas recirculation phase, a portion of the volume of air and recirculated exhaust gas from phase 2 scavenges the combustion chamber and partially scavenges the expansion chamber, the expansion chamber then merges with the central intake chamber recirculating the residual exhaust gas from phase 6 within the housing 10; [0089] Phase 4 wherein in a second compression phase, the intake chamber separates to form a compression chamber and the residual volume of combined exhaust gas and air from phase 2 is compressed at a high compression ratio into the combustion chamber [0090] Phase 5 wherein in a power phase an expansion chamber is formed, originating from the combustion chamber and torque is produced to turn the output shaft 40; and [0091] Phase 6 wherein in an exhaust phase, exhaust gas from phase 5 is discharged from the expansion chamber through a peripheral exhaust port 12 in the housing 10.
[0092] FIGS. 3 to 13 show a rotary, internal combustion engine 1 with a double rotation centre according to an exemplary embodiment. As shown in FIG. 3, the rotary, internal combustion engine 1 has a double rotation centre A, B and comprises: a housing 10 with intersecting circular expansion A and compression B orbits, defining respective dynamic chambers, and a static combustion chamber at the top thereof; a power rotor 20; a following rotor 30; a rotating shaft 40; and a drive means 50, the power rotor 20 and the following rotor 30 being arranged in interlocking relationship with one another and seated on different rotational axes A, B, within the expansion orbit A and the compression orbit B respectively, wherein the power rotor 20 is configured to rotate on the shaft 40 which turns said drive means 50 and the following rotor 30 is configured to rotate driven via 2 linkages 37 with said drive means 50.
[0093] FIG. 3 shows an exploded view of the main components of the engine 1 of the present invention. In summary, the power rotor 20 and the following rotor 30 rotate inside the housing 10.
[0094] FIG. 4 shows the housing 10 made from aluminium and comprising a substantially annular shape defining a marginally elliptical chamber 13 therein. The chamber 13 is defined by two intersecting circles A, B with offset central axes of rotation A, B. The diameter of the left side A is greater than the diameter of the right side B of the chamber due to a greater diameter intersecting circle A, compared with the diameter of intersecting circle B. The housing 10 is water cooled by a water jacket (not exposed). The intake port 11 and the exhaust port 12 are provided through the housing 10 at a base thereof, but biased towards the side of the chamber 13 defined by circle A. Substantially opposite the ports 11, 12 at the top of the housing 10 and sitting approximately on the intersection of the two circles A, B, there is mounted a threaded cylindrical insert 14 with a glow plug 14a comprising a variable compression ratio mechanism to vary the compression volume within the combustion chamber. Mounted on opposite sides of the glow plug 14a again biased towards the top of the housing 10, is a fuel injection port 17 and a water injection port 18. The fuel injection port 17 enters the chamber 13 in circle B at an angle that delivers fuel injection close to the housing 10. Likewise, the water injection port 18 mirrors this arrangement in circle A.
[0095] As shown in FIGS. 12 and 13, the power rotor 20 substantially occupies the left side (roughly A) of the chamber 13 and the following rotor 30 substantially occupies the right side (roughly B) of the chamber 13, defining an approximately crescent shaped dynamic expansion chamber 120 and an approximately crescent shaped dynamic compression chamber 110 respectively.
[0096] As shown in FIGS. 5 and 6, the power rotor 20 comprises an aluminium outer body in two halves 21, 28, 29 of substantially semi-cylindrical form. A steel core 22 of substantially three-quarter cylindrical form and smaller diameter, extends from a flat side of the body 21. The flat side of the body 21 comprises a thrust plate 25. On one side of the core 22 and a trail plate 26 on the other side of the core 22. The core 22 also comprises flat face 23 slightly inclined to provide a slightly less than 90 degree angle with the thrust plate 25. A centrally located shaft bore 27 is provided through the core 22, which lies close to the flat face 23. The flat face 23 provides a toe on the core 22. Each of the body 21 and the core 22 comprise an aluminium cover 28, 29, whilst the thrust plate 25 is treated with a ferrous bonding thermal barrier coating.
[0097] As shown in FIGS. 7 and 8, the following rotor 30 is made up of a steel, substantially semi-annular body 31. The body 31 is hollow and comprises a rounded head 32 and a flat open tail 33. A pair of hollow bearing cylinders 34 is mounted, one either side of the body 31, the bearing cylinders 34 being mounted parallel with one another and on the same axis C as the body 31 such that approximately half of each bearing cylinder 34 is unattached or free. Each bearing cylinder 34 comprises a counterweight 35 mounted on the unattached/free half to counteract the weight of the body 31.
[0098] The following rotor 30 is assembled with a pair of inner side plates 38 each with bearings 39.
[0099] In addition to the power rotor 20, the following rotor 30 and side plates 38, the engine 1 further comprises two outer side plates 60, two inner shaft bearings 65, two drive bars 50 outside of the side plates 60, an outer casing 70 provided in two portions either side of the drive bars 50 and finally, two outer shaft bearings 75 provided either side of the outer casing 70.
[0100] FIGS. 10 and 11 show the combined rotating assembly of shaft 40, power rotor 20 and following rotor 30, (but not showing the following rotor counterweights 35, drive roller bearings 37 and drive bars 50 for ease). During assembly, the power rotor 20 and the following rotor 30 are seated together as shown in FIGS. 10 and 11, with the shaft 40 extending through the core 22 of the power rotor and through each bearing cylinder 34 of the following rotor 30. The shaft 40 is located on the axis A of the housing 10.
[0101] The following rotor bearing cylinders 34 extend through the outer side plates 60 such that the outer side plates 60 sit against the power rotor body 21. The drive roller bearings 37 of the following rotor 30 are positioned outside of the outer side plates 60 and seated within elongate slots 52 of the drive bars 50. The drive bars 50 are themselves seated on the drive shaft 40 via circular apertures 54 biased towards one end thereof outside of the inner shaft bearings 65. The inner side plate 38 of the following rotor 30 assembly fits around the shaft 40 and on the inside of the following rotor bearing cylinders 34. The outer casing 70 is seated on the shaft 40 to cover the entire working assembly including the main shaft bearings 75.
[0102] As shown in FIG. 9, the drive bars 50 are fixed to the shaft 40 and rotate in synchronisation with the power rotor 20. The following rotor 30 drive roller bearings 37 are seated within the drive bar slots 52 and therefore, the following rotor 30 is also turned in synchronisation with the power rotor 20. The position of the drive roller bearings 37 allows for the two rotors 20, 30 to have different centres of rotation A, B and different diameters of orbit. As the drive bars 50 rotate, the following rotor 30 drive roller bearings 37 travel linearly within the drive bar slots 52 with low friction, whilst the head 32 of the following rotor 30 maintains an accurate and consistent proximity to the power rotor 20 thrust plate 25. The following rotor counterweights 35, drive roller bearings 37 and drive bars 50 rotate outside of the outer side plates 60.
[0103] With this arrangement, both rotors are independently balanced.
[0104] FIG. 10 shows the relative rotor 20, 30 positions at top dead centre (000 degrees) and FIG. 11 shows the relative rotor 20, 30 positions at bottom dead centre (180 degrees). It can be seen that the shapes of the two rotors 20, 30 are inter-locking. A toe 24 of the power rotor 20 fits inside the shell-like cavity of the following rotor 30. The head 32 of the following rotor 30 sweeps linearly over the power rotor 20 thrust plate 25. A non-contact sealing between the following rotor head 32 and the power rotor thrust plate 25 is provided by both sealing surfaces comprising abradable thermal barrier coatings designed to wear sufficiently to expose a minimum clearance between the following rotor head 32 and the power rotor thrust plate 25. The inertial forces of the masses of the rotors 20, 30 mean that during combustion and expansion phases, the clearance between the following rotor head 32 and the power rotor thrust plate 25 is under compression, contributing to effective sealing. A small percentage of sealing losses are not detrimental since these losses contribute to the cycle's internal exhaust gas recirculation.
[0105] FIG. 12 shows a cross sectional view of the engine 1. The fuel injection mechanism 17 is directed into a dynamic compression volume 110. The water injection mechanism 18 is directed into a dynamic expansion volume 120. The variable compression ratio mechanism 14 and the water injection mechanism 18 are not strictly necessary for the basic performance of the engine 1.
[0106] FIG. 13 shows the crescent-shaped working expansion volume (left) 120 and the crescent-shaped working compression volume (right) 110 created by the interaction of the two rotors 20, 30 rotating within the housing 10. Since the diameter of the orbit of the power rotor 20 on the left side is greater than the diameter of the orbit of the following rotor 30 on the right side, the expansion volume 120 is greater than the compression volume 110, by approximately 32%. This over-expansion compared to the compression allows more pressure to be converted into mechanical work than in a traditional piston engine where the expansion volume and the compression volume are equal.
[0107] FIG. 14 shows a standard air cycle comparison between the thermodynamic cycles of PRIOR ART Otto, PRIOR ART Diesel and the engine of the present invention. The thermal efficiency of the engine 1 of the present invention can be theoretically proven using working compression (18) and expansion (22.8) ratios. The thermal efficiency of the thermodynamic cycle of the present invention is higher than that of either PRIOR ART cycles at 68.3%.
[0108] FIG. 15 shows an estimated >50% brake thermal efficiency of the engine 1 of the present invention, when the other key aspects of gas exchange efficiency, mechanical efficiency and combustion efficiency are taken into account.
[0109] FIG. 16 shows the estimated Euro 6/7 compliant low emission zone operation of the engine 1 of the present invention without after-treatment, because of low combustion temperatures <1,800 K (<1,500 degrees C.) due to the Homogenous Charge Compression Ignition (HCCI) strategy and internal cooled Exhaust Gas Recirculation (EGR).
[0110] The various phases of the thermodynamic cycle will now be described with reference to FIGS. 17 to 23. Due to the overlapping of phases 1-3 with phases 4-6, many of the phases occur simultaneously with one or more other phases and this can be seen clearly in FIG. 2.
[0111] For ease, the phases have been described in consecutive order, but beginning with phase 5 and ending with phase 1.
[0112] As shown in FIG. 17, top dead centre (TDC/000) is the start of a power phase (identified as phase 5 of the thermodynamic cycle). The fuel-air mixture is a homogenous charge due to the highly turbulent flow of the gas being fully compressed into the combustion chamber 140. The following rotor 30 retains a significant amount of heat from the combustion event and this thermal radiation is only delivered to the fuel-air mixture as the following rotor 30 arrives at TDC. The combination of the compression of the fuel-air mixture and the thermal radiation from the following rotor 30 provide accurate control of the homogenous charge compression ignition of the fuel air mixture. TDC is also the point of maximum volume of an intake phase 1 in the central intake chamber 130.
[0113] FIG. 18 shows rotation by 90 degrees, in which the power phase 5 is providing high pressure in the expansion chamber 120 on the left side of the housing 10 and is transferring torque directly to the shaft 40 via the power rotor 20. This direct mechanism is more efficient than a piston-connecting-rod-crankshaft arrangement and enables the delivery of high output torque immediately from TDC. This architecture delivers approximately three times higher torque compared to piston engines due to the leverage effect of the power rotor 20 acting directly on the shaft 40 and because the thermodynamic cycle delivers a power phase 5 in every revolution. During the power phase 5, the intake volume starts to be compressed in the first compression phase 2 on the right side compression chamber 110 of the housing 10. Both rotors 20, 30 utilise non-contact sealing with reduced friction compared to a piston engine. An outside circumferences of both rotors 20, 30 present very large sealing surfaces with minimal clearances with the housing 10. Sides of the rotors 20, 30 utilize labyrinth sealing grooves adjacent to the outer side plates 60. A small percentage of sealing losses (.sup.5%) are not detrimental since these losses contribute to the internal exhaust gas recirculation of the cycle.
[0114] FIG. 19 shows rotation to 162 degrees, by which time the power phase 5 is complete and the power rotor 20 is about to expose the exhaust port 12 to begin the exhaust phase 6. On the right side of the housing 10 in the compression chamber 110, the first compression phase 2 is also nearing completion. This phase 2 provides a relatively low compression ratio of about 2:1.
[0115] FIG. 20 shows rotation to 180 degrees, in which the exhaust phase 6 has completed and the pressure in the expansion chamber 120 has reduced to ambient. The tail 33 of the following rotor 30 exposes the combustion chamber 140 and the pressure from the first compression (phase 2) delivers a scavenge (part of phase 3) which clears and cools the combustion chamber 140 of residual exhaust.
[0116] FIG. 21 shows rotation to 225 degrees, where phase 3 provides a scavenge and exhaust gas recirculation (EGR) phase. Water is injected from injection port 18 into the expansion volume 120 which has the effect of cooling the exhaust gas and preventing the build-up of carbon deposits inside the engine 1. The cooled residual exhaust gas in the expansion chamber 120 is drawn into the central intake chamber 130 due to the low pressure induced by the expanding volume. This eliminates the need for an intake port on the outer side plate 60 of the engine 1. In parallel, the head 32 of the following rotor 30 engages with the housing 10 on the right side of the engine 1 to start the second working compression phase 4. At this point the direct fuel injection from fuel injector 17 into the compression volume 110 commences to allow sufficient time and space for full vaporisation of the fuel.
[0117] FIG. 22 shows rotation to 290 degrees, in which the low pressure of the expanding central intake volume 130 is drawing air into the engine 1 via the Intake port 11 in the intake phase 1. Air is not drawn into the engine 1 via the exhaust port 12 due to the momentum of the exhaust gas travelling in the exhaust pipe (not shown). In parallel, the second compression phase 4 continues in the compression chamber 110 on the right side of the housing 10, fully mixing the fuel and air to create a homogenous charge mixture.
[0118] By 350 degrees (FIG. 23) the intake phase 1 is nearing completion. This intake volume is almost three times the volume of the second working compression volume (phase 4) and contains approximately 20% cooled exhaust gas recirculation (EGR). The second compression phase 4 is also nearing completion. The relatively cool and high EGR percentage mixture is well prepared for homogenous charge compression ignition (HCCI), which delivers very rapid but low peak temperature combustion for maximum efficiency and minimum emissions. Since the combustion chamber 140 has no valves, a glow plug 14a) can be mounted into a threaded cylinder insert 14. By rotating the cylinder insert 14, the volume of the combustion chamber 140 can be altered and the compression ratio can be varied. This allows a high compression ratio to be used for low loads, maximising efficiency with a lean mixture, whilst for high loads with a richer mixture, the compression ratio can be reduced to avoid engine knocking and still maintain efficient and low emission HCCI operation.
[0119] The engine 1 of the present invention is mechanically simple and low cost to manufacture whilst being power dense (2 kW/kg, 145 kW/L). This makes it suitable as a range-extending ICE for PHEVs.
[0120] With the two inter-locking rotors (the power rotor 20 and the following rotor 30) being on different rotational axes A, B, exchange gases between the four dynamic chambers (intake 130, compression 110, combustion 140 and expansion 120) deliver low pumping losses.
[0121] The volume of the expansion chamber 120 is 32% greater than that of the compression chamber 110, providing an over-expansion which directly converts pressure to mechanical work with greater efficiency, over a much greater duration than a piston/connecting-rod/crankshaft architecture.
[0122] The homogenous charge compression ignition utilizes the heat absorbed by the following rotor 30 and is easily controllable via a simple variable compression ratio mechanism 14, 14a by adjusting the volume of the combustion chamber 140. This allows lean fuel-air mixtures and high compression ratios, but with low peak combustion temperatures and low NOx formation.
[0123] The non-contact sealing arrangement with abradable thermal barrier coatings is sufficient at speeds over 3,000 rpm and the perfectly balanced rotors 20, 30 can operate at up to 5,000 rpm without significant friction losses. The small percentage of sealing losses observed is acceptable since this merely contributes to the cycle's internal exhaust gas recirculation (EGR).
[0124] Water injection at port 18 maximises the power produced, cools the EGR and prevents carbon deposits building up inside the engine.
[0125] Although a preferred embodiment has been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention.
