ROTARY COMBUSTION CHAMBER ENGINE

Abstract: Slinding vane rotary combustion chamber engine. Vanes (12) are actuated by trunnions (13.1) running in lift (24.1) and retract cams (24.2). Volume between vanes (12), end plates (24) and rotor (11) varied by profile on stator (21) inside surface (21.1). Knock-free, low emission and complete combustion ensured at high compression ratio by suitable combustion chamber (11.1) geometry. Low volume quench zones enable high combustion efficiency. Seal lubrication in combustion zones made possible by local cooling and inter-seal flushing: the oil layer on the stator (21) inner surfaces (21.1) is constantly swept into oil exhaust passages in the vanes (12) thence to cool and cool oil constantly laid down on the stator inner surfaces (21.1). Vanes (12) themselves are oil cooled.

Description: ROTARY COMBUSTION CHAMBER ENGINE FIELD OF THE INVENTION The invention lies in the field of internal combustion engines, within the restricted field of rotary engines. BACKGROUND Early designs of rotary engines were suggested in the field of steam practice but even in the field of steam they did not replace reciprocating engines. In the field of internal combustion engines reciprocating engines achieved early dominance which they have never lost. Reciprocating piston engines presently dominate the transport market. However, this design is now mature. This results in improvements becoming smaller and less economic as they approach an asymtote or improvement in one criterion almost invariably involves deterioration in another. Briefly the problems are that emissions legislation forces fuel specifications with low lead fuel, forcing in turn an upper limit on octane number and hence constraints on spark ignition engine fuel economy by restricting compression ratios (consumption and specific cost). Securing a competitive power to weight ratio in compression ignition (diesel) engines, via turbo-charging, forces constraints on compression ratios (to reduce maximum combustion pressure), and fuel specification (lower limit on Cetane number), impairing economy (consumption and fuel cost). Only a tiny proportion of production of internal combustion engines is of rotary design and confined to the Wankel principle of a convex triangular rotor orbiting in an epitrochoidal stator. This invention relates to a rotary combustion chamber internal combustion engine producing shaft power. Modern trends, in most engine markets, demand nearly continual improvements in the following criteria: - economy (total cost), - compatibility (installation fit), - emissions (noxious gas; noise), and - wider fuel specifications (use poorer fuel without significant economy loss). The rotary engine concept promises useful improvements in all four of the above criteria, by virtue of inherent compactness and inherent knock resistance. However, the rotary engine concept introduces at least two major new problems as well: - oil film temperature (viscosity) problem - high pressure seal lubrication at near continuous flame temperatures in the stator combustion zone; and - quenching problem - combustion efficiency reduces as power cycle efficiency improves with compression ratio increase (larger fraction of fuel mixture in close proximity of cool stator wall not able to burn), caused by the epitrochoid (Wankel) geometry. OBJECTS OF THE INVENTION This invention aims at improvements in the criteria listed above (economy, compatibility, emissions, and wider fuel specifications, whilst easing the major rotary engine problems (oil film temperature; and quenching). SUMMARY OF THE INVENTION The implementation comprises positive displacement volume variation: fresh mixture or air is inducted (increasing volume over inlet port); compressed (decreasing volume over combustion chamber in rotor); confined to a hollow on the rotor during combustion, while the end gas is confined to a thin layer in immediate proximity of the cool stator, burned at near constant volume (good volume/area ratio possible; quench effect avoided in main combustion and exploited in end gas zone to avoid knocking); expanded (increasing volume over combustion chamber in rotor); and exhausted (decreasing volume over outlet port). It is possible to effect scavenging between exhaust and induction if pressurized air is available (e.g. turbo-charger bleed). By spreading cycle events around the stator circumference, the cooling problem can be reduced to local requirements (e g seal lubricant temperature in combustion zone) Fitting at least two cycles around the stator circumference, balances the combustion pressures on the rotor (relieves main bearings) and the rotor (vane) inertia forces It is a rotary machine implementation of one of the following engine cycles (depending on fuel choice mandated by engine application) Otto or spark ignition cycle, the Diesel or compression ignition cycle, or the Atkinson cycle (expansion ratio larger than compression ratio, ignition by spark or compression or otherwise put, the vane inlet stroke is lower than the vane expansion stroke ) Atkinson cycle (expansion ratio larger than compression ratio) can be achieved with an inlet stator profile lower than that of the expansion zone (fixed ratio difference) and/or by phase controlled inlet valves (variable ratio difference) The known advantages of this cycle are that higher thermal efficiency can be achieved by a higher expansion ratio while knocking can be controlled by a limited compression ratio The vane type rotary design used in this invention allows particular flexibility in achieving these desirable objectives Pre-ignition is also associated with high temperature but is caused by a glowing deposit or hot metal contacted by the unburnt mixture outside the quench zone and must be obviated by appropriate design features Better economy is achieved by first cost (compact geometry), fuel cost (lower consumption and higher specific power, possibly lower specific cost), maintenance cost (improved durability from wear resistant or thermal barrier coatings where required) Better compatibility is achieved by: compactness; power/weight ratio; low output shaft speed (low rotor speed from vane tip speed restrictions, depending also on rotor size and vane stroke - the seal linear speed is chosen to optimize friction loss); higher mean to maximum torque ratio (smaller, more frequent charges giving lesser torque ripple); lighter power plant installation (transmission, structure, suspension); inherent combustion pressure balance (two cycles over circumference); inherent inertia! force balance (profile symmetry, vane number); better load response (steady inlet and exhaust manifold flow rates, compact manifolding, lower rotor inertia and lower reflected inertia). Reduced harmful emissions are achieved :NOx (reduced residence time, lower (initial) combustion temperature - cool compression stator zone); improvements are also achieved in regard to noise (little mechanical shock and compact dimensions permit effective sound proof enclosure); CO2 (improved fuel economy) and CO (lean operation). Wider fuel specifications (use without significant economy loss) are permissible for volatile fuels by virtue of the method used to suppress knock. Less volatile fuels might require compression ignition (Diesel), alone or in combination with expansion ratio larger than compression ratio (fixed or variable ratio difference- to limit maximum combustion pressure) if high specific power is required. BRIEF DESCRIPTION OF DRAWINGS (A list of parts is given immediately before the claims). FIGURE 1 is a view of the principal parts of the engine on a section transverse to the engine axis. FIGURE 2 is an enlarged view of the vane actuating cams, trunnions and vane actuators on a section transverse to the engine axis. FIGURE 2A is an enlarged view of the tip area of the vanes, on a section transverse to the engine axis. FIGURE 3 is a view of the vane actuating cams and vane lifters on a section parallel to the engine axis, at one end of the engine. FIGURE 4 is an oblique view of a vane lifter and trunnion, with cam follower bearings in exploded view FIGURE 5 is an enlarged view of a vane on a section transverse to the engine FIGURE 6 is an enlarged view of a part of the vane on a section parallel to the engine axis FIGURE 7 is an enlarged view of a part of the vane on a section parallel to the engine axis, orthogonal to the section of figure 6 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring in particular to figure 1 , this invention is a new rotary internal combustion engine having combustion chambers 1 1 1 using sliding vanes 12 to separate successive charges and transmit combustion pressure forces to the rotor 1 1 Volumes between vanes 12 and rotor 1 1 are varied by profiles on stator 21 inside surface 21 1 , with axial closure from end plates 24 The combustion chambers thus rotate with the rotor and the, for example, cycloidal inner surfaces of the stator provide for the swept volume between each pair of vanes Other profiles than cycloidal can be used There are 16 combustion chambers separated by the same number of vanes Complete balancing of centripetal forces is therefore possible Dynamic balancing of the vanes and vane lifters and trunnions is possible although slight imbalances may arise due to uneven oil and other deposits Two inlet ports 55 at diametrically opposite positions of the stator and two exhaust ports 56 at diametrically opposite positions on the rotor provide for simultaneous cycles operating on opposite sides of the rotor and hence balanced gas forces on the rotor, minimizing loads on the bearings, this minimises average bearing losses, although combustion is inherently uneven form one cycle to the next Sixteen combustion chambers provide for relatively low torque ripple Smooth and silent operation is therefore attainable with this engine The axis of rotation 5 of the engine can be seen in the views of figures 1 and 2, being the axis of rotation of the rotor duπng operation Referring also to figures 2 and 3, rollers 13 2 and 13 3 running on lift cams 24 1 and return cams 24 2 respectively in end plates 24, are carried on trunnions 13 1 , which project from lifters 13 which actuate vanes 12 Referring to figure 2A, seals 15 1 , 15 2 and 15 3, can be spring, centripetal force and/or gas pressure actuated, to control leakage between adjoining chambers Seal lubrication is secured by controlling the temperature of oil residing on wear layer 21 1 (figure 2) Increased local cooling, by water cooling jackets 23 is provided The water jackets narrow in the combustion regions 23 1 to provide enhanced cooling rates here, particularly over zone e (figure 1 ) In principle, the possibility of air cooling can not be excluded, subject to certain constraints Oil flushing between seals 15 1 and 15 2 (low residence time to prevent oil carbonization) is required The important principle is to minimise residence time of the oil which is exposed to the flame temperatures A system of skimming off old oil from the inner surface of the stator and immediately behind laying a fresh layer of cooler oil is used The oil routing is explained more fully with reference also to figures 5, 6 and 7 below The seal oil, returning through the hollow vanes 12 also serves to cool the oil layer on the sides of vanes 12 The remaining seals at the end plates experience lower temperatures and/or lower speeds An alternative design approach is to use only two seals on each vane tip In both two seal and three seal designs, oil admission and oil draining are carried out between seal pairs, using axially spaced apertures located between them Special arrangements may be desirable for the interludes when the seals cross over the inlet and exhaust ports, for example, placing oil supply holes to pass over port bridges (not shown) Rotor surfaces subject to flame temperatures are covered with a thermal barrier coating 21 2 (fig 1 ) to reduce combustion heat loss and heat flow into rotor oil stream A thermal barrier exists due to the boundary layer of gases at the solid surface, which also reduces rotor surface temperatures Oil in front of the leading seal 15 1 , left on the stator inside surface, is laid down by lubrication of the trailing seal 15 3 This oil is collected in front of leading seal 15 1 , part of which passes under leading seal 15 1 to the cavity between 15 1 and 15 2 The remainder collects in front of leading seal 15 1 and is ejected by means of slot 1 1 6 into cavity 1 1 1 when rotor and stator approach closely (stations d and h) Depth of slot 1 1 6 is less than quench width Water cooling jackets 23 are shown, the cooling water enters at the inlet ports and circulates around the outer surfaces of the stator and exits at the exhaust ports In the region 23 1 , extending from the combustion region d to the region f, the water passages against the outer surfaces of the stator are narrowed This accelerates the cooling water, giving a higher heat transfer and rate of cooling, in these critical regions where the oil is exposed to flame temperatures Cyclic operation is as follows chambers a and b are in induction, c is starting compression, d is at (spark) ignition, e and f are in expansion, g and h are in exhaust/scavenge, after which the cycle is repeated The region 21 3 of the stator is of constant radius from the axis of rotation of the rotor This region is selected to be sufficient to confine the burning mixture to each combustion chamber d (the hollow 1 1 1 in rotor 1 1 ) and to confine the end gas to the very small clearances in close proximity to the cool stator wall 21 This arrangement allows completion of the combustion at constant volume, namely the volume of the combustion chambers This is relevant to another important aspect of the invention, namely that the combustion chambers 1 1 1 formed by the hollows in the rotor 1 1 are of small dimension so that the distance that the flame front has to travel upon ignition is small This means that burning can be completed before there is time for knocking to occur thus avoiding this problem At the same time, the clearances between the rotor outside diametral surface 1 1 3, between the combustion chambers, and the stator region 21 2 is small so that the quench crevice volumes are small, leading to high combustion efficiency (i e only a small volume of air-fuel left unburnt) The combustion chambers are shown in the views of figures 1 and 3 It can be seen in the view of figure 3 that the combustion chamber 1 1 1 does not extend across the full length of the engine The shape of this chamber in cross section parallel to the axis of rotation of the engine is a stretched semi-circular shape, or prolate semi circle The shape of this chamber in cross section transverse to the axis of the engine can be seen in the view of figure 1 , a semi-circular shape The combustion chamber can thus be described as having a "bath tub" shape, or a prolate hemi-spheroidal hollow shape This shape can be usefully used to match flame propagation, if the ignition is timed to occur at the center of the spherical shape The walls of each chamber where they meet the walls of the rotor which are very close to the inner surfaces of the stator are nearly orthogonal to the stator walls These features eliminate wedge shaped or other tapering spaces as the flame front approaches the limits of each combustion chamber which militates against any tendency to knocking, instead the flame front burns right to the limits of the chamber without knocking The regions 1 1 3 otherwise than at the combustion chambers attain very small clearances between the inner surfaces of the stator and the rotor surfaces, creating a squish effect which creates strong turbulence into the combustion chamber to facilitate good combustion, hence low unburnt fuel emission and contributing to high thermal efficiency, and knock free tolerance to high compression ratios using lower octane fuel (spark ignition) With the described geometry of the combustion chambers the time for complete burning of the mixture is so short that there is not enough time for knocking to develop Relatively high compression ratios become possible with the features of the invention described It is estimated that compression ratios of up to 12 5 1 will be practical Also, the residence time of the gases at high temperature will be low, leading to low NOx emissions Tangential force is generated by differential pressure over each vane 12, transmitted to lifters 13 at blade ends, converted to torque on collar 14 transmitted to output shaft 4 by mating splines 14 1 Referring to figure 4, the lifter 13 can be seen with integral trunnion 13.1 . Bearings 13.2 and 13.3 are seen "exploded" off the trunnion. Oil passages 13.41 and 13.42 allow passage of oil to the vanes and back along routes which will be described further below. Grooves 13.5 and 13.6 are provided for double seals with the end plates. Two lifters and trunnions are provided for each vane. Referring to figures 5, 6 and 7, vane construction is from suitably bent thin metal plate which are brazed or seam welded together in a strongly braced structure. This gives extreme lightness and rigidity as well as creating passages for oil flow. Figure 7 shows the triple lattice girder nature of the design. The structure also provides an oil passage 12.1 running parallel to the engine axis, which receives at its ends oil from the passages 13.41 and 13.42 in the lifters. Passage 12.1 communicates with a passage 12.2 running radially in the engine to lead the oil to the vane tips 12.3. Passage 12.2 is formed between two flat plates 12.1 1 which have a plate 12.12 formed to zig zag between the plates 12.1 1 in the manner of the braces in a lattice girder. The vane tips accommodate in this design three seals (not shown) in slits 12.4, 12.5 and 12.6. In operation the seal in slit 12.4 is a lagging seal, the seal in slit 12.5 is a middle seal and the seal in slit 12.6 is a leading seal. The oil in passage 12.2 passes through slotted holes 12.7 which are located between the seals 12.4/12.5 and 12.5/12.6, onto the inner surface 21 .1 of the stator. Thus cool oil is wiped onto the stator surface during rotation of the rotor, in operation. Staggered slotted holes 12.8 in the vane tip are located between the seals 12.4/12.5 and seals 12.5/12.6. As the seals moves over the inner surface 21 .1 of the stator, the hot oil on this surface is wiped off the surface and via the holes 12.8 which branch into passages 12.9 on either sides of the vane. Passages 12.9 on either side of the central passage 12. 2 are formed between the plates 12.1 1 and outer flat plates 12.13, with bent plates 12.14 zig zagging between them in the nature of braces or webs in a lattice girder. The oils then exits from the vane at holes 12.10. The oil then enters passages 1 1 .4 in the rotor which extend parallel to the engine axis, to the ends of the engine where the oil enters the sump or other arrangement, to an oil pump (not shown) with or without an oil cooler (not shown). The oil delivered by the oil pump passes to the main bearings 31 of the engine, thence via passages 14.6 to the passages 13.41 and 13.42 of the lifters. From here the circulation is repeated as described above. The oil circulation thus provides a vital cooling role, in accordance with the design of this invention. Only as an example, an engine constructed as shown in the drawings, viz. with 16 combustion chambers, having a rotor diameter of 158.75 mm, a length of 158.75 and running at approx. 1 800 r.p.m. would be able to generate a torque of about 269 Nm and a power output at that speed of 45.9 Kw. Such an engine could have an expansion ration of about 12: 1 and a total swept volume of 1 300 cc. Although air cooling of the stator outer surfaces is preferable form various points of view, water cooling may be used if necessary to provide sufficient control of oil temperatures on the inner surfaces of the stator. LIST OF PARTS SHOWN IN DRAWINGS 5 axis of rotation of the engine 1 1 rotor 11.1 combustion chambers 11.2 crevice between vane and rotor 11.2 11.3 outer circumferential surface 1 1 .4 rotor oil drain gallery 1 1 .5 rotor van slot 1 1 .6 slot on 1 1 .3 to permit gas/liquid to escape into 1 1 .1 during approach to max. compression or exhaust 12 vanes 12.1 oil passage along vane 12.2 oil passage up vane 12.3 vane tips 12.4 slit for seal 13.3 12.5 slit for seal 13.2 12.6 slit for seal 13.1 12.7 slotted holes for oil supply into inter seal cavity 12.8 slotted holes for oil return from inter seal cavity 12.9 vane passages down 12.10 oil return escape holes from vane 12.11 inner plates of vane 12.12 zig zag plates forming braces of vane 12.13 outer plates of vane 12.14 zig zag plates forming braces of vane 13 lifters 13.1 trunnions 13.2 roller bearings running on lift cams 13.3 roller bearings running on return cams 13.41 oil passages from collar 14 13.42 oil passages to vane 12.1 13.5 grooves for seals 13.6 grooves for seals 14 collar 14.1 splines 14.6 oil passages 15.1 vane seals, leading 15.2 vane seals, middle 15.3 vane seals, trailing 21 stator 21.1 stator inner surface/wear layer 21.2 thermal barrier on stator inner surface 23 water cooling jackets 23.1 restricted region of water jackets 24 end plates 24.1 lift cams 24.2 return cams 31 main bearings 55 inlet ports 56 exhaust ports

Claims: CLAIMS 1. A rotary internal combustion engine, which comprises a rotor rotatable in a stator, the rotor carrying vanes reciprocable in slots, the stator having an inner surface against which tips of the vanes slide during rotation, the inner surface having a profile which provides at least one cycle per revolution of induction, compression, ignition, expansion and exhaust, according to one selected from Otto, Diesel or Atkinson cycles, the stator having at least one each of an inlet port and an outlet port, characterized in that each vane is held between a vane lifter located at each end of the vane, which vane lifters each have a trunnion having cam followers running in lift and retract cams which are mounted in the stator. 2. A rotary internal combustion engine, as claimed in claim 1 , characterized in that the vanes have seals at their tips, in which an oil feed is provided into each vane, the oil issuing from the tip of each vane to provide oil flushing at the tips and wiping of the oil onto the inner surfaces of the stator, during rotation. 3. A rotary internal combustion engine, as claimed in claim 2, characterized in that three seals are provided at each vane tip, a leading seal, a middle seal and a lagging seal, in which oil feed channels and oil drainage channels are provided to spaces between the middle and lagging seal and to spaces between the middle seal and the leading seal, on each vane. . A rotary internal combustion engine, as claimed in claim 3, characterized in that each vane has a triple lattice girder structure formed in thin sheet metal, providing the oil feed channel in a central lattice girder structure between two flat plates with a bent plate zig zagging to form the braces in a lattice girder structure and the oil return passages are provided on either side of the central passage formed between two outer flat plates and the two flat plates of the feed channel with a bent plate zig zagging between them to form the braces in a lattice girder structure. 5. A rotary internal combustion engine, which comprises a rotor rotatable in a stator, the rotor carrying vanes reciprocable in slots, the stator having an inner surface against which tips of the vanes slide during rotation, the inner surface having a profile which provides at least one cycle per revolution of induction, compression, ignition, expansion and exhaust, according to one selected from Otto, Diesel or Atkinson cycles, the stator having at least one each of an inlet port and an outlet port, characterized in that the rotor has combustion chambers located between each pair of vanes, the chambers having a prolate hemi-spheroidal hollow shape and the rotor in regions of the rotor apart from the regions of the chambers having a small clearance from inner surfaces of the stator in regions of the stator in which combustion takes place.. 6. A rotary internal combustion engine, as claimed in claim 5, characterized in that each vane is held between a vane lifter at each end of the vane, which vane lifters each have a trunnion having cam followers running in lift and retract cams which are mounted in the stator. 7. A rotary internal combustion engine, as claimed in claim 6, characterized in that the vanes have oil seals at their tips, in which an oil feed is provided into each vane, the oil issuing from the tip of each vane to provide oil flushing at the tips and wiping of the oil onto the inner surfaces of the stator, during rotation. 8. A rotary internal combustion engine, as claimed in claim 7, characterized in that three seals are provided at each vane tip, a leading seal, a middle seal and a lagging seal, in which oil feed channels and oil drainage channels are provided to spaces between the middle and lagging seals and to spaces between the middle seal and the leading seal, on each vane. 9. A rotary internal combustion engine, as claimed in any one of claims 1 to 8, characterized in that the profile of the inner surfaces of the rotor is selected for complete combustion of the mixture to take place at constant volume.

Inventors: PRINSLOO GERHARD HEIN, PRINSLOO, GERHARD, HEIN
Applicants: PRINSLOO GERHARD HEIN, PRINSLOO, GERHARD, HEIN
Application year: 1999
Main classification: F02B53
IPC codes: F02B53, F02B55