GB2303883A

GB2303883A - Gas engine

Info

Publication number: GB2303883A
Application number: GB9515883A
Authority: GB
Inventors: John Osborne
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-08-03
Filing date: 1995-08-03
Publication date: 1997-03-05
Anticipated expiration: 2015-08-03
Also published as: GB2303883B; GB9515883D0

Abstract

A gas engine installation comprises storage means associated with the engine for holding compressed gas, means for supplying the compressed gas to the engine, conversion means for deriving work from potential energy stored in the compressed gas and optionally (a) means for recycling the exhaust gas after the work cycle to a compressor for return to the storage means, and/or (b) means for drawing in ambient air for compression in a compressor in communication with the storage means. The engine may take the form of a reciprocating piston or rotary device and preferably the compressed gas used is air.

Description

A Gas Engine This invention relates to a gas engine and more particularly an engine which is powered by compressed air.

Working on the principles that the internal combustion engine has literally reached its peak in both performance and economy and has been found to produce toxic or harmful emissions (by-products of the combustion process), a new and better power source must be found.

The combustion engine has evolved well but still falls short of new goals set almost annually, mainly in the emissions area. In several countries there have been new laws introduced which state that vehicles must produce no harmful or toxic emissions. For example the state of California in the United States of America has introduced such a law. Some large car manufacturers already claim that they are producing cars which do not produce such emissions. In fact some companies even manufacture vehicles which produce a better air quality than that which is initially drawn in. However this claim is only true of inner city areas which already have vast pollution problems. The fact remains that by-products of the combustion process are still emitted and it is almost impossible to have zero emissions when the vehicle fuel utilised is based on hydrocarbon.

It would be possible to use nuclear power as an alternative but due to a totally unacceptable public image this would not really be a viable project. Furthermore, disposal of the spent fuel would be very difficult given the number of vehicles currently driven on the roads and accidents or leakage would also be a problem. However, apart from producing steam and low level radiation it would not produce any other toxic emissions.

Electric vehicles have never really been feasible or practical and they also produce harmful emissions, all be it not directly, but a vehicle which is to be charged nightly or every seventy miles by utilising a national grid domestic power supply is going to create extra demand which will force power stations to work overtime and necessitate more power stations to be constructed, all of which will produce harmful emissions of some sort or another.

The aim of the present invention is to provide an engine which overcomes or mitigates the aforesaid disadvantages by using compressed air as a fuel source.

According to the present invention there is provided a gas engine comprising storage means associated with the engine for holding a compressed gas, means for supplying the compressed gas to the engine, conversion means for deriving work from potential energy stored in the compressed gas in the engine and optionally (a) means for recycling the exhaust gas after the work cycle to a gas recompression means for return to the storage means, and/or (b) means for drawing in ambient air for compression in a gas compression means in gas communication with the storage means.

The device may advantageously be used as a prime mover in motor vehicles, fixed or mobile power plants, surface vessels, submarines, fixed or rotary wing aircraft etc.

Preferably air may be used as the working fluid.

The conversion means may comprise apparatus of the type known as an expander, the function of which is to admit a working fluid from a high pressure region, expand it with the object of producing work and deliver it to a low pressure region. The expander may take the form of a reciprocating piston device in any configuration i.e. in line, vee, radial, free piston etc, or a rotary device in any configuration i.e. epitrochoidal (Wankel) type, fixed vane etc.

Preferably also the conversion means produces mechanical energy in the form of at least one rotating shaft.

The recycling means may take the form of one or more axial, centrifugal, reciprocating, sliding vane, helical screw or Roots compressor. The compression means may be single or multi stage, single or double acting.

The recycling means may be driven either directly by the device, or, for example, from within or at the output of a gearbox connected to the device or from the motion of any vehicle in which the device is used as a prime mover i.e from wheels, drive shafts etc.

The storage means may take the form of a pressure vessel with at least one outlet to supply the conversion means with compressed working fluid and at least one inlet to receive working fluid compressed by the compression means.

Preferably the storage means may also be provided with means to remove moisture from the working fluid.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which are shown: Figure 1A - 1C. A sectional view of a reciprocating piston engine in accordance with the present invention, Figure 2A - 2C. A sectional view of a rotary engine in accordance with the present invention, Figure 3. A sectional view of a rotary vane and chamber arrangement in accordance with the present invent ion, Figure 4. A representation of an automobile engine showing possible locations for working fluid compressors, and Figure 5. A cut-away view of a reciprocating piston engine showing possible drive points for working fluid compressors.

Referring to Figures 1A to 1C there is shown a reciprocating piston engine 5 comprising a piston 10, a cylinder 15, a connecting rod 20, a crank 25 to convert the linear motion of the piston to rotational motion, an inlet port 30 and inlet valve 35 and an exhaust port 40 and exhaust valve 45. The engine 5 may comprise any number of cylinders in a multitude of arrangements, i.e. in line, vee, radial, free piston etc.

The engine 5 operates on the principal that very highly compressed air is used to push a piston 10 down a cylinder 15 rather than the usual fuel/air charge being ignited. The engine may therefore be described as an expander, the function of which is to admit a working fluid from a high pressure region, expand it with the object of producing work and deliver it to a low pressure region. As low level heat & expansion take place it is possible to construct the engine 5 from composite material such as plastics. It is also possible to use oval pistons, as opposed to conventional round pistons to increase surface area. Piston rings may also be substituted for rubber seals. With a dry sump and force feed lubrication system the engine can operate upside down or on its side depending upon the application. The engine may be used in a variety of applications including motor vehicles, fixed or mobile power plants, surface vessels, submarines, fixed or rotary wing aircraft etc.

Keeping the moisture out of the compressed air system in the form of condensate will be addressed in the following way. Air storage tanks (not shown), three of which are proposed, may be fitted with automatic drain valves which operate regularly, either by one of the main line compressors going into a temporary idle condition, due to its respective storage tank being fully charged, or by the provision of an electronic solenoid and a control unit carrying out a predetermined programme. One or more "Air Dryers" may be fitted to the induction line to reduce to a minimum the condensate entering the system. An electrical heater may also be fitted to the air intake for damp applications, but will not be necessary for all climates.

Once the air is compressed and stored it must be distributed to the cylinder(s) 15, this can be done either mechanically or electronically. A mechanical distributor operating on much the same principal as those found in a spark ignition engines, whereby two lobes line up and a spark is allowed to pass across, may be used. For the present invention however two ports line up, one containing the compressed air charge at round 300 p.s.i.

and the other at a considerably lower pressure but above that of atmospheric pressure, taken as 14.7 p.s.i. at sea level. The compressed air then passes down a length of pipe to the cylinder 15, opens a non return (inlet) valve 35 from its seat and enters the cylinder 15, striking the piston at top dead centre (T.D.C) or thereabout (Figure 1B). The piston 10 is thus caused to move down the cylinder 15. When the pressure in the cylinder 15 and the delivery pipe becomes balanced the non return valve 35 shall rest back on its seat.

Before the piston 10 reaches bottom dead centre (B.D.C.) the exhaust valve 45 opens (Figure 1C), venting the cylinder 15 to atmospheric pressure. There is no need to scavenge the cylinder 15 as no charge is burned and no form of combustion has taken place. As soon as the piston 10 is at T.D.C. again the process can repeat itself. The exhaust valve 45 may be a standard poppet valve with a seat and a spring of a required strength to ensure that the valve 45 is closed quickly and remains shut until acted upon by a cam to re open it.

A second mechanical method of delivery utilises a manifold at storage tank pressure or a series of delivery pipes corresponding to the number of cylinders that the unit possess. A cam opens the inlet valve, for example a poppet valve with spring, on the inlet side and compressed air enters at storage tank pressure in the same manner as above at T.D.C. for the same effect.

The electronic method is similar to those described above with a manifold or series of delivery pipes but instead of the compressed air entering through the inlet valve it enters through a form of injector controlled by a solenoid. The solenoid is energised and the injector allows compressed air to enter directly into a cylinder at a point when its corresponding piston is know to be at T.D.C. The compressed air again pushes the piston down to B.D.C. Thus creating mechanical motion and power.

Injection times may be worked out in crank angle degrees and degrees of rotation.

A flywheel is still utilised to smooth out the power strokes and carry the engine over non power strokes. It also provides a power take off point (P.T.O.). Starting is achieved by a toothed gear on the flywheel and an electrical starter motor (when necessary).

Referring now to Figures 2A to 2C there is shown a rotary engine 50 comprising a casing 55, a central shaft 60, a trihedral rotor 65 provided with seals 70 at its vertices, an atmospheric air inlet port 75, an outlet port 80 and inlet pipes 85 to convey compressed air to the engine from the storage tanks (not shown).

Compressed air is introduced through the inlet pipes 85 and into a chamber 90 defined between the casing 55 and the trihedral rotor 65. The expansion of the compressed air within the chamber 90 causes the trihedral rotor 65 to rotate about the central shaft 60. The rotation of the trihedral rotor 65 causes air to be drawn into the engine 50 through the atmospheric inlet port 75 and compressed between the rotor 65 and the casing 55. Air compressed thus may be vented to atmosphere or passed to further compressors prior to being used to replenish the storage tanks.

It is considered that rotary engine design (as opposed to a reciprocating engine) is superior as the motion at the pistons and cylinders is already rotatory and therefore there is no need to convert it. Also it is thought that wear in the rotor tips 70 may no be as large a problem as it is with the petrol counterpart, as compressed air can be lost to the atmosphere without expensive side effects to the environment, and running costs, so long as performance is not sacrificed.

Figure 3. shows an alternative arrangement of a rotary engine in accordance with the present invention comprising a substantially circular chamber 95, a rotor 100, an inlet port 105 and an outlet port 110. The rotor 100 further comprises a plurality of vanes 115 disposed about a shaft 120 which is free to rotate within the chamber 95. Compressed air enters the chamber 95 via the inlet port 105 and causes the rotor 100 to rotate. The compressed air then passes to the outlet port 110 from where it may be vented to atmosphere or recompressed and passed to the storage tanks. A plurality of such engines may be provided about a common shaft to provided the required power output for a given task.

Also a battery back up and a small compressor may be provided in case of the entire contents of the storage tanks being dumped to atmosphere, and starting is therefore impossible. A pipe to "quick charge" the system shall also be provided to assist in road side and garage maintenance (where compressed air is available).

A safety system will be incorporated in vehicles whereby in the event of accident or collision the contents of the tanks shall be dumped to atmosphere. In the event of a vehicular accident the compressed air may also be channelled up to the passenger compartment to inflate airbags, thus there is no need for explosives, and to operate other safety features. It will also be possible to inflate tyres at the road side by means of a air line take off from the storage tanks at an accessible position.

It will also be possible to operate brakes, suspension etc. where desired and necessary from the stored compressed air system.

The invention described herein uses air as a catalyst for mechanical motion, but once the air has been expelled it has been dried and filtered and is therefore cleaner than when it was induced to the engine.

The possibilities for an engine which can instantly produce its own fuel, i.e. compressed air are endless from a economy and environmental view point. For example a road side generator used to control a temporary set of traffic lights can now run unhindered and continuously without a normal hydrocarbon fuel being burned for the entire duration of the lighting period required. This therefore increases flexibility of the operation and reduces cost in and also continually cleans the environment the whole time that the unit is in operation.

This principal can be adapted for 2 or 3 stroke cycles on reciprocating engines, but it is considered that a two stroke will be more appropriate as it will further increase power output which is considerably less than that of an equivalent capacity petrol or diesel engine.

At least some of the mechanical energy generated by the engine may be used to compress air which in turn may be used to power the engine. Figures 4. and 5. show possible sites on a reciprocating piston engine 125 from where compressors may be driven. These include the timing belt 130 and pulleys 135, flywheel 140, gearbox 145 and drive shafts 150. The type of compressor used depends on a number of factors including required output, available space and power input to name but a few.

In applications where engine power is limited, i.e. by engine size and capacity, an alternative drive for the compressors may be utilised either instead of or as well as an engine drive such as a drive from the road wheels on an automotive application.

this is also the proposed P.T.O. (power take off) point for the generators (dynamo/alternator) on an electric vehicle.

The purpose of the compressor is to charge the air storage tanks with compressed air and to keep them charged. The compressor may be driven from a variety of different places, one of which may be a direct drive from the engine itself. It may also be necessary to gear the compressor drives so that they run at a speed twice or greater than the engine speed so as to have the ability to create the large amounts of air required without any short fall in the supply. Engine drive may be taken from a shaft or a gear from the timing case gear or pulleys. The compressors may be either air or water cooled and lubricated by the engines own lubrication system. The compressor may either be single or twin cylinders axial, centrifuged, sliding vane etc (to assist in air production where required) and will have either built in or remote unloading mechanisms.A governor valve should ideally be fitted to reduce compressor "on-load" or working time. This is achieved by causing the compressor to "cut-out" or "Idle" when system pressure has been attained, conversely when the system pressure drops the governor valve will cause the compressor charging to be re-established. A safety valve may be incorporated to prevent the system from over pressurising due to failure in any part of the compressed air system, this valve is fitted to either the cylinder head of the compressor or the compressor discharge line.

Air reservoirs are designed to store the compressed air. They are generally made of sheet steel and have a burst pressure of about eight time the safety valve setting. Steel bosses are welded onto the reservoirs to accept pipe connections and such components as drain taps and valves, low pressure indicator switches etc.

To avoid damage to engine components condensation must be removed from the working fluid. Air dryers are by far the most effective way or removing water from the air. The air dryers firstly acts like a condenser or wet tank but allow still saturated air to pass through a highly absorbent "dessicant bed". This can reduce the water content of air by up to 90%. A small proportion or dry clean air is occasionally allowed to pass through the dessicant bed to dry or regenerate the dessicant charge. Water is expelled from the air dryer through an automatic drain valve on receiving a signal from the governor valve.

It is also possible to utilise the compressed air to push down the piston and then to transfer it's energy (or reverse it) to opposite side of the piston, or use the compressed air to create a vacuum so as the piston is then sucked up in the bore. Thus a two cylinder engine can have the same amount of power stokes and power output as a four cylinder. By forcing the compressed air through a series of chambers or Venturi it will be possible to increase air flow, and speed so as the compressed air is considerable more potent by the time that it reaches the piston.

The power of air cannot be brought into question when it is considered the devastation that tornado's, and other such phenomenon can have. It is on this principal that the C.A.

engine has it's foundation. Once the compressed air is on tap, the ability to create mechanical motion becomes strong, but this is only half the battle, some means must be sought to speed up the air flow so as to maximise the air charge. If this were not possible to do then to get any form of potent performance from the unit, the air pressure would need to raised to unacceptable proportions. To speed up the air flow the tornado principals have been adopted yet again, also when it is considered that a ballet dancers arms move in, her centrifugal force is concentrated inward, and so her speed is greatly increased. Thus the reason for the need to force the compressed air down a series of Venturi, or chambers to increase the air flow to the proportions needed to create reasonable performance and economy.

The principal of using the vehicles driving wheels, along with the drive pulleys from the power unit itself, can also be applied to electric vehicles, whereby constant charging is required.

Generators can take a direct drive from the driveshafts or wheels, or power unit. This would mean that the whole time that the vehicle is in operation it is being charged (simply by being driven), the only limitation to this are the amount of wheels available for use, or the size and location of the generators plus the distance driven, and the time used.

The embodiments of the invention described hereinbefore given by was of example only, and are not meant to limit its scope in any way.

Claims

1. A gas engine comprising storage means associated with the engine for holding a compressed gas, means for supplying the compressed gas to the engine, conversion means for deriving work from potential energy stored in the compressed gas in the engine and optionally (a) means for recycling the exhaust gas after the work cycle to a gas recompression means for return to the storage means, and/or (b) means for drawing in ambient air for compression in a gas compression means in gas communication with the storage means.

2. A gas engine as claimed in claim 1 adapted for use as a prime mover in a motor vehicle, fixed or mobile power plant, surface vessel, submarine, fixed or rotary wing aircraft.

3. A gas engine as claimed in claim 1 or claim 2 wherein air is used as the working fluid.

4. A gas engine as claimed in any preceding claim wherein the conversion means comprise apparatus of the type known as an expander, the function of which is to admit a working fluid from a high pressure region, expand it with the object of producing work and deliver it to a low pressure region.

5. A gas engine as claimed in claim 4 wherein the expander takes the form of a reciprocating piston device.

6. A gas engine as claimed in claim 4 wherein the expander takes the form of a rotary device.

7. A gas engine as claimed in claim 5 or claim 6 wherein the conversion means produces mechanical energy in the form of at least one rotating shaft.

8. A gas engine as claimed in any preceding claim wherein the recycling means take the form of one or more axial, centrifugal, reciprocating, sliding vane, helical screw or Roots compressors.

9. A gas engine as claimed in any preceding claim wherein the recycling means are driven either directly by the engine, or from within or at the output of a gearbox connected to the engine or from the motion of a vehicle in which the engine is used as a prime mover.

10. A gas engine as claimed in any preceding claim wherein the storage means take the form of a pressure vessel with at least one outlet to supply the conversion means with compressed working fluid and at least one inlet to receive working fluid compressed by the compression means.

11. A gas engine as claimed in claim 10 wherein the storage means are provided with means to remove moisture from the working fluid.

12. A gas engine substantially as hereinbefore described with reference to and as shown in Figs 1A to lC; or Figs 2A to 2C, or Fig 3 of the accompanying drawings.