WO1980000237A1

WO1980000237A1 - Vehicle braking and kinetic energy recovery system

Info

Publication number: WO1980000237A1
Application number: PCT/US1979/000518
Authority: WO
Inventors: F Lowther
Original assignee: Purification Sciences Inc
Priority date: 1978-07-20
Filing date: 1979-07-18
Publication date: 1980-02-21
Also published as: EP0016160A1

Abstract

A vehicle (10) with a rotary sliding vane engine (14) including a compressor (18), a combustion chamber (20), and a motor (22) in which the braking is done by connecting the rotor of the compressor (18) to a wheel (12) and braking rotation of the rotor by controlling the gas flow through the rotary sliding vane compressor (18), such as by varying the outlet to increase the pressure ratio. This eliminates the conventional friction brakes. The compressed air generated during braking is fed to a surge tank (28) for later use in operating the vehicle engine (14), thus recovering a portion of the kinetic energy of the vehicle (10). The rotary slide vane motor (22) can also be used as the brake by controlling the inlet thereto. The compressor (18) and motor (22) can be separate units or portions of one unitary rotary sliding vane device. The compressor brake and motor-brake can be used together or separately and as integral or separate parts of a rotary sliding vane engine (14) and also with other different types of engines.

Description

VEHICLE BRAKING AND KINETIC ENERGY RECOVERY SYSTEM

TECHNICAL FIELD

This invention relates to vehicles and in particular to a vehicle braking system which recovers a portion of the kinetic energy of the vehicle.

BACKGROUND OF THE PRIOR ART

The use of a vehicle motor for dynamic braking of a vehicle is known, and various attempts to recover the kinetic energy of a vehicle have been made. However, all such prior art suffers from many disadvantages. Regarding dynamic braking, a piston driven automobile, with a standard transmission, can supply braking action down to zero speed but such will "stall" the motor as zero speed is approached. Electric traction motors can not supply dynamic braking down to zero speed because the motor generator "gives up" at low speeds. A gas turbine can not supply any dynamic braking because no gas/rotor interaction occurs except at very high r.p.m.

Regarding the aspect of the present invention of recovering the kinetic energy of a vehicle, this has been discussed in the prior art, and attempts have been made such as using a flywheel in streetcars, etc, to either drive a generator and charge a battery, of to drive the vehicle through a clutch. Due to friction, a flywheel continuously loses its energy. However, all such prior art has so far been found commercially impractical, especially for the automobile.

BRIEF SUMMARY OF THE INVENTION

In a preferred embodiment of this invention, a vehicle employing a positive displacement Brayton cycle engine using a rotary sliding vane compressor and a rotary sliding vane motor, is braked by connecting the compressor rotor to a vehicle wheel and by braking the rotor by controlling the gas flow through the compressor (such as by variably increasing the pressure ratio in response to braking demand). The kinetic energy of the vehicle is recovered by feeding the compressed air generated during braking to a surge tank for later use in the engine. The compressor and motor can be separate units or they can be combined in a unitary device having a single stator and a single rotor with a compressor portion and a motor portion.

In another embodiment, the motor is used to do braking by variably closing off the inlet port; the kinetic energy can be recovered by having the braking motor evacuate a tank for later use. The motor can be used alone or in combination with a compressor-brake; in such case, the motor brake can be used also (on only) as the emergency brake.

The brake-compressor and the brake-motor can be separate from the vehicle engine, in which case they can be used in a vehicle having any type of engine.

It is an object of the present invention to provide a non-friction braking sys tem for a vehicle.0 It is another object of the present invention to recover the kinetic energy of a vehicle during braking as compressed gas stored for later use. It is a still further object of the present invention to use the engine as the brake system and to recover the kinetic energy in a form usable by the engine. It is another object of the present invention to provide a vehicle braking and kinetic energy recovery system in which differentials, gear boxes and conventional friction brakes are eliminated. It is another object of the present invention to recover the kinetic energy of a vehicle during braking and to brake a vehicle by controlling the gas flow through a rotary sliding vane device.

Parent applications serial No. 890,465; 908,155; and 920,445 filed March 27, 1973; May 22, 1978; and June 29, 1978 and entitled "GAS TURBINE SYSTEM", "GAS TURBINE SYSTEM", and "ENGINE SYSTEM", respectively, all by applicant, are hereby incorporated by reference in their entirety in this application.

BRIEF DESCRIPTION OF THE DRAWINGS understood by reference to the following detailed description thereof, when read in conjunction with the attached drawings, wherein like reference numerals refer to like elements and wherein;

Fig. 1 is a partly schematic, partly diagrammatic, view of a vehicle engine brake and kinetic energy recovery system according to one embodiment of the present invention;

Fig. 2 is a partly diagrammatic, partly crosssectional view of a compressor-brake according to one embodiment of the present invention; Fig. 3 is a partly diagrammatic, partly cross- sectional view of a unitary motor-compressor-brake unit according to one embodiment of the present invention;

Figs. 4 and 5 are diagrammatic views of a portion of the system of Fig. 1 showing variations in the arrangement of the compressed air surge tank 28 of Fig. 1;

Fig. 6 is a partly diagrammatic, partly schematic view of a vehicle having a rotary sliding vane engine employing the compressor-brake kinetic energy recovery system of the present invention; Fig. 7 is a partly schematic, partly diagrammatic, partly cross-sectional view of a compressor-brake illustrating certain aspects of the present invention;

Fig. 8 is a partly diagrammatic, partly schematic view of a rotary sliding vane engine having a compressor brake according to the present invention;

Fig. 9 is a diagrammatic side view of a rotary sliding vane compressor Illustrating certain aspects of this invention;

Fig. 10 is a partial side view of a rotary sliding vane compressor-brake of the present invention;

Fig. 11 is a partly diagrammatic, partly schematic side view of a rotary sliding vane compressor for use in describing certain aspects of the present invention;

Fig. 12 is a partial side view of a rotary sliding vane device useful in describing certain aspects of the present invention;

Fig. 13 is a partly diagrammatic, partly schematic view of a compressor-brake control system; Figs.14A and 14B are end and side views, respectively, of a rotary sliding vane device having a single tangent point with letters representing various of the parameters involved for use with respect to the detailed description;

Fig..15 is a partly diagrammatic, partly schematic view of a compressor-motor system employing the brake and energy recovery embodiments of the present invention; Fig. 16 is a diagram of an "energy tree" useful in visualizing certain aspects of thermal efficiency;

Fig. 17 is a diagram for illustrating various aspects of the present invention;

Figs. 18-22 are graphs illustrating various aspects of the present invention to be considered together with the detailed description set forth below;

Fig. 23 is a partly schematic, partly diagrammatic, view of a vehicle engine brake and kinetic energy recovery system according to one embodiment of the present invention; Fig. 24 is a partly diagrammatic, partly schematic side view of a rotary sliding vane motor-brake according to one embodiment of this invention; Fig. 25 is a partly schematic, partly diagrammatic, view of a vehicle engine brake and kinetic energy recovery system according to one embodiment of the present Invention; Fig. 2.6 is a partly diagrammatic, partly schematic view of a vehicle having a compressor-brake kinetic energ recovery system of the present invention.

Fig. 27 is a partly diagrammatic, partly schematic view of a closed cycle embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to the drawings, Fig. 1 shows one embodiment of the present invention including a vehicle 10, such as a car, having a wheel 12, an engine 14, and a brake pedal 16. The engine includes a compressor 18, a combustion chamber 20, and a motor 22 connected by a shaft 24 to the compressor 18. The compressor 18 is connected to the wheel 12 (such as by a shaft 26) for rotation therewith (it is the rotor of the compressor that is connected to the wheel 12). The engine 14 also includes a pressurized air surge tank 28 between the compressor and the combustion chamber.

The engine 14 is preferably a positive displacement, Brayton cycle, rotary sliding vane engine as described in copending application Serial No. 920,445, filed June 29, 1978 by applicant and entitled "ENGINE SYSTEM", the entire application of which is incorporated herein by reference. In operation, air is fed from ambient into the compressor 18, compressed air is then fed to the surge tank 28 and then to the combustion chamber 20 along with fuel, (as controlled by the accelerator, for example), where the mixture is burned, and the hot combustion gases are then fed to the rotary sliding vane motor 22. The exhaust from the motor 22 can be fed to ambient but is preferably heat exchanged (via heat exchanger 30) with the compressed air fed to the combustion chamber 20. The vehicle 10 can have any number of wheels, such as four and any number of engines 14, including one connected to both front (or both rear) wheels, or four engines (one for each of four wheels), etc. The rotor of the compressor 18 can be connected to the wheel 12 in any desired manner, either with or without the need for a shaft 26. The engine 14 can have any number of compressors and motors and combustion chamber, such as one motor and one combustion chamber and four compressors (one for each of four wheels).

Fig. 2 shows one preferred embodiment of compressor 18 including a stator 40, a rotor 42 rotatably mounted in the stator on the shaft 26, a plurality of sliding vanes 44, a gas inlet 46 and a gas outlet 48. The rotor and stator define therebetween a decreasing volume compression chamber 50. The compressor 18 includes means for controlling the gas flow therethrough, such as a movable shoe 52 connected to the brake pedal 16, such that the more the pedal is depressed to increase braking, the more the shoe 52 moves to the right in Fig. 2, thus covering up more of the gas outlet openings 54 and thus increasing the pressure ratio of the compressor 18. The shoe is shown on the outside of the stator for simplicity; it can also be located inside of the stator, and in fact, a wide variety of mechanical arrangements can be used in place of the shoe (as will be understood by those skilled in the art). The shoe can be connected to the brake pedal 16 with any one of a wide variety of mechanical, hydraulic, pneumatic or electrical linkages or couplings.

Fig. 3 shows another embodiment of the present invention in which both the compressor 18 and the motor 22 of Fig. 1 are portions of one unitary rotary sliding vane compressor-motor 50. The compressor-motor 50 includes a stator 52, a rotor 54 rotatably mounted in the stator on the shaft 26, a plurality of sliding vanes 56, a gas inlet 58, a compressed gas outlet 60, a hot compressed gas inlet 62, and an exhaust gas outlet 64. The rotor and stator define therebetween a decreasing volume compression chamber 66 (the compressor portion) and an increasing volume expansion chamber 68 (the motor portion). A movable shoe 70 is connected to the brake pedal 16 such that the more the brake pedal is depressed to increase braking, the more the shoe 52 moves to the left in Fig. 3, thus, covering up more of the gas outlet openings 72 and thus increasing the pressure ratio of the compressor portion of the compressor motor 50. The shoe 70 can be located inside the stator rather than outside as shown. The embodiment of Fig. 1 can employ, instead of a single tank 21, a pair of surge tanks 80 and 82 as shown in Fig. 4 connected in series, or alternatively the pair of surge tanks 80 and 82 can be connected in parallel as shown in Fig. 5 with or without an equalizing line 84 therebetween. The surge tanks can include pressure regulating and control means in the tanks themselves and/or a separate pressure regulator 86 as shown in Figs. 4 and 5. Fig. 6 shows another embodiment of the present invention including a vehicle 90 such as a car, having four wheels 91, 92, 93, 94, an engine 96, and a brake pedal 98. The engine includes a compressor-brake 100-103 (the rotor of each of which is connected to a respective one of the wheels 91-94) Air pressure lines 108-111 are connected from each of the compressors 100-103, respectively, to a first surge tank 112, from which air is fed to a second surge tank 114 and then to a combustion chamber 116 where the pressurized air is burned with fuel fed to the combustion chamber 116 by a fuel line 18. The products of combustion are then fed to motors 120 and 122. The exhaust gas from the motors 121 and 122 is fed via lines 124 and 126, respectively, to a heat exchanger 128 to heat the air fed to the combustion chamber 116. The motors 120 and 122 are connected to the compressor-brakes 102 and 103, respectively.

According to the present invention, the brake pedal 98 is mechanically connected to each of the compressor-brakes 100-103 in the manner shown, for example, in Figs. 2, such that the more the brake pedal 98 is depressed to increase braking, the more the pressure ratio of the compressors is increased, thus increasing the work done by the compressors and thus braking the compressor rotors and thus the wheels 91-94. The compressor-brakes 102 and 103 and the motors 120 and 122 can alternatively be as shown in Fig. 3, if desired.

During the braking operation of the vehicle 90, the gas compressed by the compressors 100-103 is fed via the compressed gas lines 108-111, respectively, to the first surge tank 112 for later use in operating the engine 96. During normal non-braking operation of the vehicle, if there is adequate supply of compressed air available (such as immediately following a hard braking operation), control means can be provided to sense such a supply and other control means can be provided to unload one or more of the compressors so that no work is required in turning the unloaded compressors. Means for unloading a rotary sliding vane are well-known, and include means (such as pneumatic means) for retracting the vanes.

The arrangement shown in Fig. 6 is only one of the many possible arrangements of the present invention. For example, the engine can include a motor for each wheel or for only one wheel or for any number of wheels. In addition, each motor can have its own individual combustion chamber 116 or there can be one combustion chamber for each pair of motors or four or more motors.

From the above discussion, it will be seen that the rotary sliding vane positive displacement device will supply dynamic braking down to zero speed. This is not true for electric traction motors since the motor/generator "gives up" at low speeds. A piston driven automobile with standard transmission will supply braking action down to zero speed but will "stall" the motor due to the gears, and it can not recover the energy in any useful form. The turbine, on the other hand, could use stored compressed air, but supplies no dynamic braking since no gas/rotor interaction occurs except at high R.P.M. Such limitations and problems in the prior art are overcome and solved by the present invention. The dynamic braking described above can recover the kinetic energy of the car in the form of compressed air and store it for future use. The fuel savings that result are particularly pronounced in stop and-go traffic. The present invention can be implemented in various ways, and according to the present invention, differentials, gear boxes, and conventional friction brakes can be eliminated. The present invention is preferably used with a positive displacement, Brayton cycle, rotary sliding vane engine to give, for the first time, a vehicle with an excellent energy management program. Consider a positive displacement, Brayton cycle, rotary sliding vane system with a 50 h.p. output at the shaft. The compressor required to supply the motor will be of the order of 20-30 h.p. However, consider the power levels during braking. A 4000 pound vehicle traveling at 60 miles per hour has about 880 horsepower seconds worth of kinetic energy. If braking is to occur in, for example, 10 seconds, then the compressor (acting as a brake) must absorb 88 h.p. or about 3 times its steady state load during the power phase. Several options are available in order to bring the power levels into a reasonable balance:

1. Make the compressor work harder during the brake period by increasing the compression ratio. This can be done by adding a variable geometry outlet port mechanically tied to the brake pedal. A simple schematic is shown in Fig. 7 including a compressor 190 comprising a stator 192, a rotor 194, a plurality of sliding vanes 196, inlet openings 198, and compressed gas outlet openings 200. The rotor is connected to a shaft 202 mechanically connected to a wheel of the vehicle. The rotor and stator define therebetween a decreasing volume compression chamber 204.

The compressor 190 includes a movable shoe 206 meachanically connected to a brake pedal 208 of the Vehicle, for controlling the minimum volume of the compression chamber 204 to control the pressure ratio of the compressor 190. As more intense braking is required, the movable shoe 206 moves upwardly in Fig. 7 and reduces the minimum volume in the chamber 204.

2. A similar option as In 1 above can be used to vary the inlet air ports 198 and thereby set the SCFM for the compressor 190. These options 1 and 2 provide a wide range of control. The pressure ratio and CFM can be set very low such that a near zero work or "windmilling" condition exists. At the other extreme, the inlet port (CFM) can be wide open and the outlet port choked off completely, so that the pressure ratio is set so high as to lock the wheel against any rotation. This is ideal from the brake viewpoint.

3. Hot gas can be routed through the compressor since for a given CFM and pressure ratio, the work of compression is a direct function of the gas temperature.

The first two of the above options are the most desirable at the present time. However, the hot motor exhaust gas can be "detoured" to the compressor, for example, from the heat exchanger during braking, to accomplish option number 3.

Fig. 8 shows another embodiment that has some advantages under certain conditions. Fig. 8 shows an engine 220 including a compressor 222 and a motor 224 connected to the compressor by a shaft 226. An air inlet line 228 feeds ambient air into the compressor 222 and a compressed gas line 230 feeds compressed gas from the compressor 222 to a surge tank 232 and then from the surge tank to a combustion chamber 234 where it is burned with fuel fed to the combustion chamber by fuel line 236. The hot gaseous combustion products are then fed to the motor 224 via the hot gas line 238 and the exhaust gas is fed to atmosphere by an exhaust line 240. An electric motor 242 is also connected to the shaft 226 and is connected to a battery 244 for starting the engine. As in the other embodiments described above, the compressor 222 is connected to a brake pedal 245 via a connection 246. In this case, a pressure control means 248 is connected to the mechanical connection 246 and it is also connected to the surge tank 232. The electric motor 242 (the starter device), must have enough power and torque to drive not only the compressor 222 but also the motor 224 and hence also the vehicle at low speed. As the engine 220 "catches", the driven shaft now overpowers the motor 242 which now acts like a generator and charges the battery 244. When more than one surge tank is included, then proper methods of regulation and balancing must be employed. For example, braking may call for storage of 300 psi air (20:1 pressure ratio) while the burner/motor operates at only 60 psi. In this case, an efficient pressure reducer between the tanks is required. Vents and pressure relief valves can be used (as will be understood by those skilled in the art) since it will be preferred, in some situations, to sacrifice some energy recovery in the interests of safety. The present invention can employ any one of a wide variety of drive arrangements, including various numbers of compressors, drive motors, and burners (or combustion chambers). Some of the possibilities are:

1. One expansion motor plus one burner and a compressor-brake for each wheel. This arrangement could drive two traction wheels via a differential.

2. Two expansion motors plus one burner and a compressor-brake for each wheel. These motors are on independent shafts each coupled to a drive wheel. The need for a differential is thus eliminated.

3. The same as 2 above except two burners are used one for each motor. In essence, this is two separate motors except for the tie in with the compressors, fuel pumps, brakes, energy recovery systems, etc. 4. One expansion motor for each drive wheel.

For example, a four wheeled vehicle would have four expansion motors. A multi-wheeled truck can have more than four expansion motors. Burners can come in any array: one burner per motor, one burner for all motors combined, one burner per two motors, etc.

5. One important aspect of this invention involves the fact that the expansion motor and brake compressor requirements can be distinct and independent. Thus, the traction configuration can involve one burner and one expansion motor to drive a four wheel vehicle, however, there may be one braking compressor for each wheel. 6. Various mechanical linkages and/or microprocessors (as are well-known to those skilled in the art) can be used to balance the fuel flows, hot gas, and other flows to multiple engines and/or combustors, and to balance the braking forces to all braking compressors.

The compressor-brake is preferably a rotary sliding vane device tied to a wheel or driven axle shaft and is preferably of the positive displacement type and serves two basic purposes: 1. Supplies compressed air to the fuel combustion system; the compressor may or may not be in conjunction with another compressor that is not tied to the driven shaft. 2. "Soaks up" kinetic energy as the vehicle is brought to a stop (or lower speed) and feeds the compressed air to a surge tank to store the energy as compressed air for future use by the vehicle power system.

It will be shown that these two functions present conflicting requirements to the compressor.

In the first place, the compressor must supply compressed air in the range of 30-100 psig and at about 2-10 SCFM per horsepower of output shaft power to the combustion system. The R.P.M. of the compressor is (direct drive) dependent upon vehicle speed. The output pressure is relatively independent of R.P.M. but the amount of air delivered (SCFM) depends directly upon R.P.M. It is desirable to store the compressor output in a surge tank intermediate to the combustion process. The power level of the compressor in the "powered" mode of operation is of the order of 1/4 to 3/4 of the shaft output. Thus, a 40 h.p. useful shaft output will require a compressor capable of delivering from 10 to 30 h.p. depending upon conditions of the time.

An unloading mechanism at the compressor inlet port can be used in order to reduce the compressor work, at a fixed speed, under certain conditions. Consider for example, the acceleration process just after coming to a stop (city traffic). In this case, the "braking" surge tank may be full and it is desirable to run the combustor on this air. The shaft R.P.M. will be high during this period and yet it is desirable that no energy be expended in the compressor since an adequate compressed air supply is on hand. The answer here, of course, is an unloader, such as an arrangement that allows the vanes to rotate and not do any work. Such unloaders are standard practice today, mostly for the purpose of safety. The same compressor described above preferably serves as the active element in the brake system (a separate brake-compressor can alternatively be used). There are two distinct functions to be performed by the compressor in the braking mode: 1. Upon demand supply braking action to the vehicle. The braking action takes the form of resistance to motion. This is a rotary compressor characteristic when the outline is choked off.

2. Convert the kinetic energy of the vehicle to thermal and pressure energy in compressed and stored air.

Analysis shows that the compressor peak power Is greater, during the braking period than during the power period. Consider the following typical case:

Shaft output, Net 50 h.p.

Compressor 20 h.p.

Kinetic Energy of vehicle 14.7 h.p.-min. 4,000 pounds, 60 m.p.h.

Thus, if 12 seconds is allowed to bring the vehicle from 60 m.p.h. to a complete stop, the compressor must work at a level of 73 h.p. or about 4 times its normal work load. This represents no problem but it does influence vane thickness, variable port geometry, and other design parameters,

As set forth above, various ways can be devised to make the compressor work harder during the braking period, including the three options of: 1. Increase the compressor outlet pressure. This makes the compressor work harder for a given R.P.M. and gas flow rate (CFM).

2. Increase the compressor CFM for a fixed outlet pressure and R.P.M.

3. Increase the compressor inlet gas temperature. It is desired that the compressor-brake pressure ratio be mechanically adjustable similar to the choke on a present day automobile. Fig. 9 is a diagram showing the geometry in a rotary vane compressor 250.

The compressor 250 includes a stator 252, a rotor 254 having a plurality of sliding vanes 256, air inlet openings 258 and compressed air outlet 260. The rotor 254 is connected to a wheel such as by means of a shaft 262. The volumetric ratio will be proportional to the ratio of the areas A₁ and A₂ shown shaded in Fig. 9. The pressure ratio is proportional to the area ratio raised to the specific heat ratio, which is about 1.4 for air. Thus, an area ratio A₁/A₂ = 2:1 would yield a pressure ratio of 2^1.4 or 2.6:1. The physical reason is that the compression is nearly adiabatic which results in a heated gas that further adds to the pressure. Note in Fig. 9 that the "smallest" volume area A₂ can be reduced (to create a higher pressure ratio) by reducing the size of the outlet port and/or by increasing the number of vanes. Preferably, the outlet port aperture is mechanically variable.

Fig. 10 is a partial view of the compressor Fig. 9 and shows one way for accomplishing this. Fig. 10 shows a mechanical linkage 270 for moving a sliding member or shoe 272 that varies (reduces or increases) the size and location of the outlet port 260 and hence modulates the area A₂. Adequate precautions are taken to assure smooth contact between the vane and aperture components. Additionally, the shoe 272 is in the high pressure area and the problem of high pressure gas leaks in and around the linkage must be recognized. The shoe 272 in g. can be on the inside of the stator 252 rather than on the outside as shown. Many methods of aperture control are available (linear as well as rotary) as will be understood by those skilled in the art.

The CFM rating of the compressor depends upon the area A₁ in Fig. 9, the R.P.M., and the number of vanes. One way to supply the necessary variable CFM (at a given R.P.M.) is to vary the inlet port such that no compression occurs until the area A₁ has been reduced by rotation. The dashed lines in Fig. 9 mean that those areas are open to ambient.

Fig. 11 indicates the geometry of the compression chamber if more of the stator is open to ambient. The uncompressed area, A₁ of Fig. 9, now becomes A₁ of Fig. 11. Figs. 9 and 11 show this basic aspect.

Fig. 12 illustrates how the inlet openings can be controlled and varied. Fig. 12 shows a compressor 280 having a stator 282 with a plurality of openings 284, and a rotor 286 with a plurality of sliding vanes 288. The compressor 280 includes a movable shoe 290 for controlling and varying the relative geometry of the inlet openings 284. The problem of leakage in Fig. 12 is not severe since the shoe is at the low pressure region. Note, however, that variations in the input aperture will modulate both the pressure ratio and, the CFM delivered.

Unloading, that is, allowing the compressor to do zero work at full R.P.M., can also be practically accomplished by retracting the vanes mechanically, hydraulically, or pneumatically, such as by pneumatic unloader means 249 in Fig. 11. Such devices for forcing the vanes in or out on demand are known and therefore need not be described in detail here; any of such devices can be used here. Thus, by fully both refracting the vanes, the pressure and flow can be reduced to zero at full R.P.M.

Additionally, it can be desirable to fully close the outlet line and/or the inlet line to supply positive locking action that corresponds to today's emergency brake. An overall control scheme is shown in Fig. 13. Fig. 13 shows a compressor-brake 300 having a stator 302, a rotor 304 connected to a wheel, a plurality of sliding vanes 306, a compression chamber 308, air inlet openings 310, air outlet openings 312, a shoe 314 controll the inlet openings 310, and a shoe 316 controlling the outlet openings 312. The condition of a surge tank 318 can control and adjust the (air inlet CFM) control through a pressure controller 320. The condition of the brake 16 can adjust one or both of the inlet and outlet openings 310 and 312, because braking can call for maximum work out of the compressor (i.e. maximum CFM and maximum pres sure) The linkages are such that braking overpowers the surge tank control on the inlet aperture. Another useful control logic can be used. This logic will provide that during normal operation (power to vehicle), the surge tank 320 is judged by the logic to be full when the pressure reaches, say, 70 psig. However, during braking, the tank 320 can take on additional air until the pressure rises to, say, 200 psig. In this way, there is always adequate reserve to accommodate the compressed air available from braking.

Figs. 14A and 14B show a compressor-brake having certain labeled dimensions. The preferred values for those dimensions and other parameters are, for one embodiment of the present invention: Length (L) 12 inch Stator Radius (R₁) 6 inch Maximum Vane Extension (∈ ) 2 inch Maximum R.P.M. 1146

Gas Inlet Temperature 70°F Gas Outlet Temperature (Max. ) 800°F Nominal Power 30 h. p.

Air Delivery at Max. R.P.M. 250 SCFM Nominal Pressure Ratio 4: 1

Vane Thickness 3/ 8 inch Number of Vanes 8

Mechanical Control

Delivery 0-250 SCFM at 1146 R.P.M.

Pressure Ratio 4:1 to 16:1 Max. Moment of Inertia 1000 lb. ft.²

Fig. 15 shows an engine system 350 according to another embodiment of the present invention including a single, unitary, positive displacement compressor-motor 352 (the circle represents a rotary sliding vane compressor motor according to the present invention, such as shown in Fig. 3). The compressor-motor 352 has an air inlet 354, a compressed air outlet 356, a line 358 for feeding compressed air to a compressed air or surge tank 360, a line 362 for feeding compressed air from the surge tank 360 to a regulating valve 364 from which the compressed air is fed to a combustion chamber 366, where it is burned with fuel fed to the combustion chamber 366 through a fuel line 368 and a regulating valve 370. The hot combustion gases are fed solely from the combustion chamber 366 through a gas line 372 to a hot gas inlet 374 of the compressor motor 352. The exhaust gas is fed from an exhaust port 376 and exhaust line 378 to ambient. The term "solely" means that gas from the combustion chamber can not flow backward toward the source of compressed air. The valve 364 can include a check valve or one way valve. A throttle control 380 is connected to each of the regulating valves.

The surge tank 360 is always charged up and can supply a sudden surge for acceleration and/or start-up purposes, in addition to supplying the gas required for burning during normal steady operation.

The engine system 350 also includes a brake pedal 382 connected to a shoe 384 for causing braking the rotor of the compressor-motor 352 and therefore of the wheel to which the rotor is connected, with the compressed air produced during braking going to the surge tank 360 as described above. ^: Some seemingly impossible efficiencies result when a portion of the vehicle kinetic energy is recovered via dynamic braking. In order to fully understand this process, a review of the basic energy relationships will be useful:

1. The engine thermal efficiency is a measure of the portion of the chemical energy in the fuel that is successfully converted to useful shaft output. The major portion of the chemical energy not successfully converted ends up as heat in the exhaust. This is true for a turbine type engine as well as for a gasoline piston engine. For example, Vincent in "Supercharging the Piston Engine" on page 194 gives the following budget for a gasoline engine: Heat to Brake h.p. (useful) 24-30%

Heat to Coolant 10-12%

Heat to Oil 1.5%

Heat to Miscellaneous 1%

Heat to Exhaust 58-60% 2. The miles/gallon are calculated on the basis of engine thermal efficiency. Vehicle kinetic energy is just another loss that ends up as heat in the brake lining.

3. The situation changes with energy recovery. Efficiency must be calculated differently, otherwise values greater than 1 will occur. This effect is shown by example The following serves to illustrate item 3 above Consider the simple budget.

Waste Heat 0.1 Btu

Shaft Output 1.0 Btu Total Yield From Fuel 1.1 Btu

The efficiency of this engine for its very brief cycle is

1.0/1.1 = 90.9%.

Now, apply energy recovery to the same basic engine: Waste Heat 0.1 Btu

Shaft Output 1.0 Btu

Total Yield From Fuel 1.1 Btu Now, the shaft output is broken down:

Vehicle K.E. 0.9 Btu

Friction Losses 0.1 Btu

Shaft Output 1.0 Btu Assume 90% of the kinetic energy is recoverable. This is fully equivalent to a fuel reduction and can be used during the next burn phase. The efficiency for this case, by the same definition is

Fig. 22 is a graph showing thermal efficiency with recovery vs. the fraction of kinetic energy recovered, for several values of thermal efficiency. This clearly shows the inadequacy of the thermal efficiency definition. The process may be more clearly visualized with the help of the energy tree of Fig. 16.

An exact analytical expression for the energy efficiency is derived below.

Referring now to Fig. 17, the equivalent efficiency with energy recovery, is calculated below. Define:

Equation 5 expresses the equivalent new thermal efficiency with the understanding of the previous discussions that Y7 can be greater than 1. In order to remedy this, a new form of efficiency must be defined that considers only losses (heat and friction) and fuel energy. That is, the classical thermal efficiency includes, and treats, kinetic energy as a loss. The more appropriate thermal efficiency must exclude the recoverable kinetic energy. The net result is that the actual amount of fuel burned will need to satisfy only the heat in the exhaust and friction losses. The dynamic braking/energy recovery system of the present Invention can be carried out with a wide variety of methods and apparatuses, as will be clearly understood by those skilled in the art. The central concept is to convert vehicle kinetic energy into compressed gas (potential energy) for later use. It is important to note that energy in the form of compressed gas can be utilized in many, different ways in the system. The recovered kinetic energy of braking can be used to compress the working gas in a closed system. In fact, as shown in Fig. 27, it can be advantageous to have a braking compressor 500, a surge tank 504, and inlet and outlet lines physically placed in a sealed container 502 such that the braking energy is captured by compressing an already highly compressed gas into the tank 504. Suitable valves506 and 508 such as one-way can be employed as will be understood by those skilled in the art. This can provide a smaller size engine, lower R.P.M., etc. It can be desirable to gear up (or down) the braking compressor relative to the wheel or drive axle.

One preferred embodiment is for the traction motor to be a two tangent point device as in Fig. 24 described below. One half of the motor is essentially free-wheeling (no compression or expansion) with half of the rotor and vanes exposed to ambient for cooling purposes. It is desirable in some embodiments to have variable inlet and outlet port geometry, such that during braking, this "free-wheeling" portion of the motor can be put to work and supply dynamic braking and stored compressed gas. In fact, an "intermittent cool" cycle analogous to the intermittent burn cycle (described in copending application serial No. 890,465) can be applied to this second "free-wheeling" side of the motor. That is, continuous cooling may not be required. Every minute (or so), the second half of the motor can be made to compress gas and hence reduce the load on the other compressors.

Efficient dynamic braking requires the compress to work as hard as possible. One way to do this is to fe hot gas to the compressor during this period. That is, compressor work is proportional to inlet gas temperature. Thus , it can be desirable to burn fuel in the engine duri braking just to supply hot gas to the compressor. In thi as in the other cases, it is desirable that the compresse gas storage tanks be heat insulated in order to conserve the valuable heat content in the compressed gas.

Another aspect of this invention is the use of the traction motor during braking also. Thus, braking action can be achieved by having the motor act as a "vacuum" pump during braking. Useful work can be accomplished by evacuating a tank. This can be accomplished, for example by a series of valves connecting the combustor, motor, and surge tank(s).

In addition, it may be desirable to supplement the energy storage system by other means. For example, a compressor not tied to the driven axle can be used and can be purposely given a large rotational mass to act as a flywheel. The same can be said for the motor shaft if a suitable clutch is provided. Electrical capacitors can be supplied to "soak up" additional kinetic energy. A rough estimate of the energy storage capacity of the compressed air tank is presented in Fig. 18 and merely represents the classical equation stating the work required to pump a gas into a tank.

automotile drag data, taken from "Mark's Mechanical Engineers Handbook" and presented in Fig. 19 can be expressed:

It is of interest to calculate, approximately, the ratio of friction losses to K.E. for a constant speed vehicle neglecting effects during the accelerating and braking phase. The previous equations combine to give:

Fig. 22 was discussed above.

Fig. 23 shows a vehicle having an engine and brake system similar to that shown in Fig. 1 with the exception that instead of having the brake 16 coupled to the compressor, the brake is connected to the motor 22 for braking the wheel 12 (the rotor of the motor 22 being connected to the wheel 12 for rotation therewith). In this embodiment, the more that the pressure on the pedal 16 is increased, the more gas flow to the inlet opening to the motor 22 is decreased.

Fig. 24 is a cross-sectional view of a motor brake

400 having a stator 402, a rotor 404 having a plurality of sliding vanes 406, with the stator and rotor meeting at two tangent points and defining therebetween a motor or expansion chamber 408. The motor brake 400 includes a hot, compressed gas inlet 410 and an expanded exhaust gas outlet 412. The rotor is connected to a shaft 414. As will be seen in Fig. 24, about half of the motor brake 400 is "open" thus, cooling of the vanes 406 occur each half revolution to the openings 416 in the open half of the stator. Fans, blowers, compressors, water sprayers, etc. can be used as an aid to cooling in the vanes 406 in Fig. 24. When the brake pedal 16 in Figs. 23 and 24 is depressed, it can operate a valve 418 in the hot compressed gas line 420 which valve can open or close the line 420 and can connect the the inlet opening 410 to a tank 422 whereby the braking force of the motor serves to evacuate the tank 422 for storing the kinetic energy of the vehicle in the form of the evacuated tank 422 for later use in the engine 14.

Fig. 25 shows another embodiment of the present invention similar to Figs. 1 and 23 wherein the braking employs a combination of a compressor-brake and a motor brake in the same system. In this system, the motor brake can also (or solely) be operated as the hand or emergency brake by simply closing off the gas inlet thereto. Fig. 26 shows a vehicle 460 according to another embodiment of the invention. The vehicle 460 includes an engine 464, a transmission 466, a drive shaft 468, a differential 470 and rear drive axles 472. In this embodiment, the engine 464 can be of any desired type. The vehicle 460 includes a brake pedal 473 connected to a compressor-brake 474, the rotor of which is connected respectively to one each of the wheels of the vehicle. The compressor-brakes are connected to a surge tank 476 for storing, for later use, the compressed air generated by the compressor brakes 474 during braking.

Alternatively, the compressor-brake 474 can be a motor-brake, or a combination, unitary compressor motor-brake, as discussed above.

Fig. 27 was discussed above.

In one embodiment of this invention as applied to an automobile, when the driver lifts his foot off of the accelerator and before applying pressure to the brake pedal, a free wheeling condition exists in which the engine does not do any braking. There is zero fuel flow and zero compressed air flow from the surge tank to the combustion chamber, the compressor is unloaded and the motor is also unloaded and/or the motor inlet and outlet are open to ambient (by suitable valves when there is no demand from the accelerator). Alternatively, the compressor can continue to compress air and feed It to the surge tank, for example, a pressure regulator can unload the compressor during coasting when the surge tank supply reaches a desired value. While the preferred embodiments described above employ rotary sliding vane devices, other known positive displacement devices can be used in the present invention either as part of the engine or separate from the vehicle engine as is the case with the rotary sliding vane device Further, while thepreferred embodiment is in a Brayton cycle engine, other types can be used. The present invention has primarily been described above with reference to open cycle engine systems, however, the present invention can also be used in closed cycle engine systems Further, a rotary sliding vane motor can be run backwards as a compressor to accomplish the dynamic braking, this embodimen would be more expensive because of the need for a clutch and possibly gears.

The invention has been described in detail with particular reference to the preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinafter and as defined in the appended claims.

Claims

CLAIMS.

the steps of:

(a) powering said vehicle with an engine including a compressor for compressing a gas, a combustion chamber for receiving said compressed gas and burning fuel to heat said compressed gas, and a motor for converting hot compressed gas into rotation of a shaft, and at least one of said compressor and motor being a rotary sliding vane device including a rotor connected to a wheel of said vehicle for rotation therewith; and

(b) braking said vehicle by braking said rotor and therefore said wheel.

2. The method according to claim 1 wherein said device includes a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, a gas inlet in fluid communication with said chamber, a gas outlet in fluid communication with said chamber, said rotor having a plurality of sliding vanes thereon, and wherein said braking step comprises variably controlling the flow of gas through said rotary sliding vane device.

3. The method according to claim 2 wherein said device is said compressor, wherein said stator and rotor define therebetween a compression chamber having a decreasing volume in the direction of rotation of said rotor, said gas inlet being in fluid communication with a larger volume portion of said compression chamber, and said gas outlet being in fluid communication with a smaller volume portion of said compression chamber, and wherein said controlling step comprises controlling the flow of gas through said compressor.

4. The method according to claim 3 wherein said controlling step comprises varying the pressure ratio of said compressor.

5. The method according to claim 3 wherein said controlling step comprises increasing the pressure ratio of said compressor.

6. The method according to claim 5 wherein said controlling step comprises, varying the location of said gas outlet.

7. The method according to claim 5 wherein said compressor controlling step comprises controlling the relative geometry of the compressor inlet and outlet.

8. The method according to claim 4 including the step of unloading said compressor during at least some non-braking operations thereof.

9. The method according to claim 4 wherein said controlling step comprises controlling the total quantity of gas flow through said compressor.

10. The method according to claim 9 including controlling the location of the said gas inlet to said compressor.

11. The method according to claim 3 including the step of feeding compressed gas produced by said compressor during braking thereof to a surge tank for future use in said motor, thus recivering at least a portion of the kinetic energy of said vehicle during braking and thus also relieving the amount of work required, of said compressor during non-braking operation.

12. The method according to claim 11 including feeding gas from said surge tank to at least one of said combustion chamber and said motor.

13. The method according to claim 2 wherein said device is the motor, wherein said stator and rotor define therebetween a motor chamber having a decreasing volume in the direction of rotation of said rotor, said gas inlet being in fluid communication with a smaller volume portion of said motor chamber, and said gas outlet being in fluid communication with a larger volume portion of said motor chamber, and wherein said controlling step comprises controlling the flow of gas through said motor.

14. The method according to claim 13 wherein said controlling step comprises controlling the area of said gas inlet.

15. The method according to claim 14 wherein said controlling step comprises variably controlling the area of said gas inlet.

16. The method according to claim 14 wherein said controlling step comprises closing said gas inlet.

17. The method according to claim 2 wherein both of said compressor and motor are rotary sliding vane devices and wherein said braking step comprises braking the rotor of both of said compressor and said motor.

18. The method according to claim 1 including the step of operating said engine with a substantially constant pressure Brayton cycle.

19. The method according to claim 1 including operating said engine with an intermittent burn cycle including a burn phase and a cool phase.

20. The method according to claim 19 including the step of operating said engine with a substantially constant pressure Brayton cycle.

21. A method for braking, a vehicle having at least one wheel comprising the steps of:

(a) providing said vehicle with a rotary sliding vane compressor including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining therebetween a compression chamber of decreasing volume, a gas inlet in fluid communication with a larger volume portion of said compression chamber, and a gas outlet in fluid communication with a smaller volume portion of said compression chamber, said rotor also having a plurality of sliding vanes thereon; and

(b) braking said vehicle by braking rotation of said rotor.

22. The method according to claim 21 wherein said braking step comprises variably controlling the pressure ratio of said compression chamber.

23. The method according to claim 22 wherein said step of variably controlling the pressure ratio comprises varying the location of the said compressor gas outlet.

24. The method according to claim 22 including opening said gas inlet and outlet to ambient atmosphere.

25. The method according to claim 24 including the step of unloading said compressor during at least some non-braking operations of said vehicle.

26. The method according to claim 25wherein said step of unloading said compressor comprises unloading said compressor during all non-braking operations thereof.

27. The method according to claim 21 wherein said braking step comprises controlling the quantity of gas flowing through said compressor.

28. The method according to claim 21 including the step of feeding compressed gas generated by said compressor during braking to a surge tank.

29. The method according to claim 21 wherein said stator and rotor also define therebetween a separate expansion chamber of increasing volume, a gas inlet in fluid communication with a small volume portion of a set expansion chamber and a gas outlet in fluid com munication with a larger volume portion of said expansion chamber and including the step of controlling the size of said gas inlet to said expansion chamber for further braking said vehicle.

30. A method for braking a vehicle having at least one wheel comprising the steps of:

(a) providing said vehicle with a rotary sliding vane device including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining therebetween an expansion chamber of increasing volume, a gas inlet in fluid communication with a smaller volume portion of said compression chamber, and a gas outlet in fluid communication with a larger volume portion of said expansion chamber, said rotor also having a plurality of sliding vanes thereon; and (b) braking said vehicle by braking rotation of said rotor.

31. The method according to claim 30 wherein said braking step comprises controlling the flow of gas through said device.

32. The method according to claim 31 wherein said controlling step comprises controlling the area of said gas inlet.

33. The method according to claim 31 wherein said controlling step comprises variably controlling the area of said gas inlet.

34. The method according to claim 31 wherein said controlling step comprises closing said gas inlet.

35. Apparatus comprising: (a) a vehicle having at least one wheel;

(b) an engine connected to said vehicle for powering said vehicle and including a compressor for compressing gas, a combustion chamber for receiving said compressed gas and means for burning fuel therein for heating said gas, and a motor, at least one of said compressor and motor being a rotary sliding vane device including a rotor connected to a wheel of said vehicle, and

(c) means for braking said vehicle including means for braking said rotor and therefore said wheel.

36. The apparatus according to claim 35 wherein said device includes a stator enclosing a chamber , said, rotor being mounted in said chamber and connected to said wheel for rotation therewith, a gas inlet in fluid communication with said chamber, a gas outlet in fluid communication with said chamber, and said rotor having a, plurality of sliding vanes thereon, and wherein said braking means includes means for controlling the flow of gas through said device.

37. The apparatus according to claim 36 wherein said device is said compressor and wherein said controlling means includes means for controlling the flow of gas through said compressor.

38. The apparatus according to claim 37 wherein said controlling means includes means for varying the pressure ratio of said compressor.

39. The apparatus according to claim 38 wherein said controlling means includes means for increasing the pressure ratio of said compressor.

40. The apparatus according to claim 38 wherein said controlling means includes means for varying the location of said gas outlet.

41. The apparatus according to claim 38 wherein said controlling means includes means for controlling the quantity of air flow through said compressor.

42. The apparatus according to claim 41 wherein said controlling means includes means for controlling the location of said gas inlet.

43. The apparatus according to claim 36 including a surge tank and including a gas line for feeding compressed gas generated by said compressor during the braking rotation thereof to said surge tank, thus recovering at least some of the kinetic energy of said vehicle.

44. The apparatus according to claim 43 including means for feeding gas from said surge tank to at least one of said combustion chamber and said motor.

45. The apparatus according to claim 36 wherein said device is said motor and wherein said controlling means comprises means for controlling the flow of gas through said motor.

46. The apparatus according to claim 45 wherein said controlling means comprises means for controlling the area of said gas inlet.

47. The apparatus according to claim 46 wherein said controlling means comprises means for variably controlling the area of said gas inlet.

48. The apparatus according to claim 46 wherein said controlling means includes means for closing said gas inlet.

49. The apparatus according to claim 35 including means for unloading said device.

50. The apparatus according to claim 35 wherein both of said compressor and motor are rotary sliding vane devices.

51. The apparatus according to claim 50 wherein said braking means includes means connected, to the rotor of said compressor.

52. The apparatus according to claim 51 wherein said controlling means includes means for varying the pressure ratio of said compressor.

53. The apparatus according to claim 52 including means for closing said gas inlet.

54. The apparatus according to claim 35 including means for operating said engine with a substantially constant pressure Brayton cycle.

55. The apparatus according to claim 35 including means for operating said engine with an intermittent burn cycle including a burn phase and a cool phase.

56. The apparatus according to claim 55 including means for operating said engine with a substantially constant pressure Brayton cycle.

57. Apparatus for braking a vehicle comprising:

(a) a vehicle including a wheel;

(b) a rotary sliding vane compressor, said compressor including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining therebetween a compression chamber of decreasing volume, a gas inlet in fluid communication with a a larger volume portion of said compression chamber and a gas outlet in fluid communication with a smaller volume portion of said compression chamber, said rotor having a plurality of sliding vanes thereon; and (c) means for braking rotation of said rotor for braking rotation of said wheel and therefore of said vehicle.

58. The apparatus according to claim 57 wherein said braking means comprises means for variably controlling the pressure ratio of said compression chamber.

59. The apparatus according to claim 58 including means for varying the location of said gas outlet.

60. The apparatus according to claim 58 wherein said gas inlet is an air inlet and Including means for opening said air inlet to ambient during braking.

61. The apparatus according to claim 60 including means for unloading said compressor during at least some non-braking operations of said vehicle.

62. The apparatus according to claim 61 wherein said unloading means comprises means for unloading said compressor during all non-braking operations thereof.

63. The apparatus according to claim 57 wherein said braking means comprises means for controlling the quantity of gas flowing through said compressor.

64. The apparatus according to claim 57 including a surge tank and a gas line from said εas outlet to said surge tank for feeding compressed gas generated by said compressor during braking to said surge tank.

65. The apparatus according to claim 57 wherein said stator and rotor also define therebetween a separate expansion chamber of increasing volume, a gas inlet influid communication with a smaller volume portion of said expansion chamber and a gas outlet in fluid communication with a larger volume portion of said expansion chamber, and means for controlling the size of said gas inlet to said expansion chamber.

66. The apparatus according to claim 57 wherein said compressor is connected in a closed loop system including the compressor inlet line and outlet line and a surge tank connected to said outlet line for feeding gas compressed by said compressor during braking, to said surge tank.

67. The apparatus according to claim 66 including a sealed container enclosing said compressor, surge tank, inlet line and outlet line, and wherein said closed loop system Includes valve means for maintaining the compressed gas in the surge tank.

63. Apparatus for braking a vehicle comprising:

(a) a vehicle including a wheel;

(b) a rotary sliding vane motor, said motor including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining therebetween an expansion chamber of increasing volume, a gas inlet in fluid communication with a smaller volume portion of said compression chamber and a gas outlet in fluid communication with a larger volume portion of said chamber, said rotor having a plurality of sliding vanes thereon; and

(c) means for braking rotation of said rotor for braking rotation of said wheel and therefore of said vehicle.

69. The apparatus according to claim 68 wherein said braking means comprises means for controlling the flow of gas through said device.

70. The apparatus according to claim 69 wherein said controlling means comprises means for controlling the area of said gas inlet.

71. The apparatus according to claim 70 wherein said controlling means comprises means for variably controlling the area of said gas inlet.

72. The apparatus according to claim 70 wherein said controlling means includes means for closing said gas inlet, thus braking said shaft because further rotation of the rotor would tend to create a vacuum in the chamber adjacent said inlet.

73. The apparatus according to claim 69 including means for unloading said device.

74. A rotary sliding vane motor, said motor including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining therebetween an expansion chamber of increasing volume, a gas inlet port in fluid communication with a smaller volume portion of said compression chamber and a gas outlet port in fluid communication with a larger volume portion of said chamber, said rotor having a plurality of sliding vanes thereon, and means for varying the port geometry.

75. An apparatus according to claim 74 wherein said varying means comprises means for varying the pressure ratio of said motor.

76. A rotary sliding vane compressor, said compressor including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining therebetween a compression chamber of decreasing volume, a gas inlet port in fluid communication with a larger volume portion of said compression chamber and a gas outlet port in fluid communication with a smaller volume portion of said compression chamber, said rotor having a plurality of sliding vanes thereon, and means for varying the port geometry.

77. The apparatus according to claim 76 wherein said varying means comprises means for controlling the outlet port geometry.

78. The apparatus according to claim 76 wherein said varying means comprises means for varying the pressure ratio of said compressor.

79. A rotary sliding vane motor, said compressor including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining there between a compression chamber of decreasing volume, a gas inlet port in fluid communication with a larger volume portion of said compression chamber and a gas outlet port in fluid communication with a smaller volume portion of sliding vanes thereon, an means or controlling the pressure ratio of said motor.

80. A rotary sliding vane compressor, said compressor including a stator enclosing a chamber, a rotor mounted in said chamber and connected to said wheel for rotation therewith, said stator and rotor defining therebetween a compression chamber of decreasing volume, a gas inlet port in fluid communication with a larger volume portion of said compression chamber and a gas outlet port in fluid communication with a smaller volume portion of said compression chamber, said rotor having a plurality of sliding vanes thereon, and means for controlling the pressure ratio of said compressor.