WO1998010172A2

WO1998010172A2 - Vaned rotary engine with regenerative preheating

Info

Publication number: WO1998010172A2
Application number: PCT/GR1997/000034
Authority: WO
Inventors: Eleftherios Meletis; Demos P. Georgiou
Original assignee: Eleftherios Meletis; Georgiou Demos P
Priority date: 1996-09-06
Filing date: 1997-09-08
Publication date: 1998-03-12
Also published as: WO1998010172A3; PL328818A1; JP2001505273A; IL124315A0; EA199800439A1; EP0865565A3; BR9706705A; GR1002755B; CA2236573A1; EP0865565A2; AU4027597A

Abstract

A vaned rotary engine with a cylindrical (circular cross section) stator (1) and a multilobed rotor (2) having the same axis with the cylinder. The rotor is keyed to a shaft (3), supported on the baseplate (11) through the bearings (14). The rotor lobe tips (17 and 18) provide a sufficient blocking of the combustion chamber (12) to allow for a (nearly) constant combustion process. This chamber is embedded in the stator wall and the fuel is injected into it through the injection nozzle (8). The four volumes needed for the thermodynamic processes, i.e. the inlet (21), the compression (13), the expansion (20) and the exhaust (19), are formed by the two cavities formed between the stator inner surface and the rotor outer one with the help of three diaphragms. The first diaphragm (9) separates the inlet-exhaust volumes and is continually in touch with the rotor surface. The other two are positioned very close to the combustion chamber, one in front (7) and the other behind it (6), as the rotor rotates. The back diaphragm is initially in contact with the rotor surface while the other is recessed. When the pressures in the compression and the expansion volumes are nearly equal, the two diaphragms exchange position, by lowering the front one and withdrawing the back one. This exchange leads to a mixing of a part of the flue gasses with the air, thus acting as a regenerative preheating mechanism for the air.

Description

VANED ROTARY ENGINE WITH REGENERATIVE PREHEATING BACKGROUND OF THE INVENTION The present invention relates generally to the concept of vaned rotary thermal engines . The operation of the present engine is based on a thermodynamic cycle that is a modification of the well known OTTO cycle. This modification is based on a mixing between a portion of the flue gasses and the compressed air , at a pressure well above the inlet one , so that the air is preheated internally and reaches a much higher temperature (when compared to the simple OTTO cycle) at the end of the compression stroke. This, in turn permits the compression ignition to be possible.

The implementation of the OTTO and the DIESEL thermodynamic cycles has been attempted by various mechanisms. The most well known is the reciprocating piston one. Other mechanisms are based on the epitrochoidal shape of the cylinder (with the Wankel engine being the best well known application) and the moving vanes in a statically and dynamicaly balanced rotor concept. The last concept has not produced so far any comercially developed engine but there have been proposed a number of different engine inventions based on this idea. The vaned rotary engine concept, in general, considers a balanced rotor inside a circular cross section cylinder. The cavities formed between the inner surface of the cylinder and the outer surface of the rotor create the volumes required for the implementation of the thermodynamic processes of a given cycle. The variation of the volumes , as the rotor turns, is achieved by positioning a number of radially moving vanes in the periphery of the cylinder. These vanes separate each cavity into two or more parts. The various ideas proposed so far on this general concept differ on the number of vanes, on the position of the combustion chamber, on the route of the flue gasses and the atmospheric air, on the sealing of the cavity volumes, etc. Patents that have been issued in the past for inventions implementing the concept of the vaned rotary engine include : (i) USA patents No 631815 (1899) , 1354189 (1920), 1616333 (1927), 2409141 (1946) , 2762346 (1956), 3280804 (1966) , 3467070 (1969), 3797464(1974), 383723 (1974) (ii) Japan patent No JP-A-56126601 (iii) German patennt No DE 3426853 Al (iv) French patent No 2406072 (v) WPO patent No 1480985 . All these inventions implement a version of the vaned rotary engine concept and attempt to realize the OTTO or/and the DIESEL cycles.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a vaned rotary engine that achieves a constant volume combustion following a compression ignition. The engine is formed by an outer cylinder with circular cross section and an inner rotor with a number of lobes having the same axis of 0 rotation as the cylinder. The spacing between the inner surface of the cylinder and the outer surface of the rotor forms a number of cavities, equal in number to the number of the lobes. The minimum requirement is for two lobes, but the dynamic balancing of the rotor demands four lobes. Dynamic balancing, otherwise, may be achieved in a multicylinder engine. yt- The basic description of the engine will be given for the two lobe rotor, since the other configurations simply reduce the arc formed by two consequtive cavities , ail other positions aranged in proportion. The two cavities formed in the two lobed rotor cover all 360 degrees of the arc in the inner surface of the cylinder cross section. The four volumes 20 needed for the implementation of the thermodynamic cycle (namely inlet - compression - combustion and expansion - exhaust) coexist at any moment within the two cavities. This is achieved with the help of three vane diaphragms . These diaphragms are positioned on the periphery of the cylinder cross section (and along its entire length) and their tip follows the 25 outer surface of the rotor after proper activation by a camshaft mechanism or electrically or by any other means). Only two diaphragms are doing this at any moment. One is the diaphragm that separates the inlet - exhaust volumes and the other is near the combustion chamber. This chamber (for the two lobes rotor configuration) is positioned at an arc of 180 degrees 30 away from the (neihbouring) inlet - exhaust oppenings and is embedded inside the wall of the cylinder. On the two sides of this chamber are positioned two diaphragms. As the rotor rotates (clockwise) the diaphragm on the right of the chamber is called the "front" diaphragm, while the one on the left is called the " back" diaphragm. Only one of these two diaphragms is touching the rotor surface at any moment, initially the

"back" one and the the "front" one. The two diaphragms exchange roles at a given angular position of the rotor, when the "back" diaphragm is lifted (towards its cavity inside the wall of the cylinder) and the "front" one is lowered towards the rotor surface. This takes place after the flue gasses have been expanded partially in the expansion volume and the new atmospheric air has been compressed partially in the compression volume and when the pressures in the two volumes are nearly equal. By this process a part of the flue gasses is being trapted in the new enlarged compression volume and mixes out with the air resulting in a temperature rise for the air. The continuation of the compression process leads to a very high temperature for the new mixture of gasses, when they have been forced to enter the combustion chamber. This temperature allows for a very fast fuel evaporation and combustion witout the need for any external ignition assistance.

The constant volume combustion here is achieved by blocking the exit of the combustion chamber by forming a lobe shape so that it has a constant radius equal to that of the cylinder cross section for an arc sufficient for the completion of the combustion process. End plates and proper sealing mechanisms block the axial leakage from any of the four volumes.

The geometry of the rotor surface apart from the two arcs mentioned above is designed in order to provide the necessary volumes and a smooth acceleration for the diaphragms.

OUTLINE OF THE DRAWINGS

Figure 1 presents the ideal version of the thermodynamic cycle of the engine. Figure 2a and 2b present axial and transverse cross sections of the engine. Figure 3 is a transverse cross section that describes phase 1. Figures 4 to 7 describe respectivelly the phases 2 to 5.

THE IDEAL THERMODYNAMIC CYCLE The ideal version of the thermodynamic cycle of the proposed engine is illustrated in Figure 1, in the P-V axes. The first process is the isentropic compression from the point 100 to the point 101. At this point (and before the compression is finished) the "back" diaphragm is lifted and the "front" one is lowered. This leads to a mixing of the expanding flue gasses with the compressed air, so that their corresponding point on the P-V diagram to be at the point 102. The compression volume, now, becomes larger (when compared to that at the point 101), since the exchange of the two diaphragms leads to a transfer of a portion of the expansion volume into compression one. The isentropic compression then proceeds, till to the point 103. At this point the fuel is introduced into the combustion chamber and a constand volume combustion process is realized, up to the point 104. From the point 104 till the point 105 the flue gasses expand isentropicaily. At this point the exchange of the diaphragms takes place (and while the compression and expansion volume pressures are nearly the same), so that the expansion volume is reduced, since a part of it is transfered to the compression volume. The resulting state of the flue gasses is the point 106. Then, the expansion process continues up to the point 107. At the point 107 the exhaust oppening is oppened, so that the flue gasses are expanded in the atmosphere to the point 108. The processes then continue to the exhaust one, till the point 110, which is an isobaric process. The entire cycle is completed for a rotor shaft turning of an arc half that between an inlet oppenning and a neihbouring exhaust one. In the configuration described in detail here this is 180 degrees, since the arc between the two opennings is 360 degrees. For the more realistic four lobe rotor (which is statically and dynamically balanced) the corresponding arcs are 90 and 180 degrees respectivelly.

DESRIPTION OF THE INVENTION

The description of the proposed invention will be made with the help of the two sections illustrated in the figures 2a and 2b.

The cylindrical (circular cross section) stator (1) supports the diaphragm (9) between the inlet (5) and the exhaust (4) opennings and the diaphragms in front (7) and behind (6) the combustion chamber (12), which in turn is embedded inside the wall of the stator. The stator wall, in addition includes cooling fluid cavities (10) as well any supporting subsystem needed for the operation of the engine (cooling, lubrication, control, fuel etc). The rotor (3) posses the same axis with the stator and is keyed to the power shaft (2), which in turn is supported by the corresponding bearings (14) on the baseplate support (11). The endplates (15) with the corresponding seals (16) safeguard against any axial leakage. The fuel is injected into the combustion chamber(12) through an injection nozzle (8).

The lobe geometry takes two basic requirements into consideration : (i) For an arc sufficient to block the exit of the combustion chamber, its radius is constant and (nearly) equal to that of the stator inner surface (ii) the rest must exploit the available space in order to maximize the volume in each cavity, but its surface must be smooth, so that the accelerations imposed on the diaphragms in touch with the rotor surface are not extreme. The two lobe rotor, then, has two lobe tips, (17) and (18), positioned at an arc of 180 degrees. The centers of these two tips form the major axis of the rotor. The initial position of the rotor (when the turning angle is equal to zero), is taken that for which the major axis passes through the center of the combustion chamber (12) and the diaphragm (9) between the two opennings. PHASE 1 (Figure 3) The combustion chamber is blocked by the tip of the rotor lobe (17), while the same happens for the two opennings (4) and (5) by the opposite lobe tip (18). The fuel is injected into the chamber through the injection nozzle (8) and burns with the air-flue gass mixture at constant volume (at least as long as the tip 17 blocks the chamber exit). The diaphragms (9) and (6) are in touch with the rotor surface. PHASE 2 (Figure 4)

The rotor (3) turns clockwise, the expansion volume (19) increases and the pressure of the flue gasses coming out of the combustionn chamber is reduced. The flue gasses fromm the p[revious cycle, in the exhaust volume (20) exit through the exhaust openning (4), when this is uncovered by the movement of the lobe tip (18) and while the separating diaphragm (9) moves inwards, in order to be in touch with the rotor surface. The "back" diaphragm (6) is also moving, while the "front" one stays within its resses inside the stator wall. The compression volume (13) decreases, so that the pressure of the new air increases. PHASE 3 (Figure 5)

The rotation of the rotor leads to the uncoverring of the inlet openning (5) from the lobe tip (18) and the formation of the inlet volume (21) PHASE 4 (Figure 6)

When the pressures in the compression volume (13) and the expansion volume (20) arc nearly equal, the "back" diaphragm (6) is lifted from the surface of the rotor and the "front" diaphragm (7) (which had started moving inwards some time before) comes into contact with the rotor surface. In this exchange, part of the expansion volume joins the compression volume and the trapped flue gasses mix out with the atmospheric air in the original compression volume. The reduced ammount of flue gasses in the (smaller) expansion volume continues to expand. PHASE 5 (Figure 7) The rotor completes an arc of 180 degrees. The lobe tips (17) and (18) exchange positions. The inlet volume (21) becomes the compression (13) one, while the expansion volume (20) becomes theexhaust one (19). The compressed flue gas mixture has been enclosed within the combustion chamber volume. The rotor is ready to proceed to the next cycle.

Claims

CLAIMS 1. A vaned rotary engine with a cylindrical (circular cross section ) stator (1), enclosing a rotor (3) keyed to a shaft (2) and possessing the same axis with the stator cylinder. The Shaft is supperted in the support baseplate (11) through the bearings (14). Endplates (15) and the relevant seals (16) safeguard against the axial leakge. The rotor surface forms two lobe tips ( 17 and 18), at 180 degrees apart. The purpose of these tips is to provide a closure of the combustion chamber (12) exit while the combustion process lasts, so that a (nearly) constant volume combustion can be achieved. The combustion chamber (12) is embedded inside the stator wall and the fuel is injected into it through the injection nozzle. The stator includes also all the supporting subsystems needed for the operation of the engine (e.g fuel, coolant, control, etc). The two cavities formed between the stator inner surface and the rotor outer one are separated with the help of three stator wall supported diaphragms into four parts, the four volumes of the engine, i.e the inlet (21) , the compression (13), the expansion (20) and the exhaust

( 19) volumes. One diaphragm (9) separates the inlet from the exhaust volumes, so that it does not allow the air entering through the inlet openning (5) to mix with the exhausting flue gasses through the exhaust openning (4). In the two lobe rotor this diaphragm is positioned at an arc of 180 degrees with respect to the combustion chamber. The other two diaphragms are positioned before (6) and after (7) the combustion chamber (12), as close to that as possible. Only one of them is in contact to the rotor surface at any moment. The "back" diaphragm (6) is activated first, but when the pressures in the compression volume (13) and the expansion

(20) one are nearly equal this is lifted and the "front" diaphragm (7) is lowered. This exchange leads to a mixing between a part of the flue gasses and the compressed air that acts as an internal regenerative preheating of the air.

2. The number of the lobes can increase in any number possible , so that the above described processes are realised in the arc that corresponds between two neihbouring inlet-exhaust opennings.

3. The engine cylindrical stator may be split into a number of stators with the rotors inside each rotated to the others in order to achieve dynamic balance.

4. The supercharging as employed in the existing reciprocating engines may be employed here as well.