WO1993008398A1

WO1993008398A1 - Fuel delivery system

Info

Publication number: WO1993008398A1
Application number: PCT/AU1992/000542
Authority: WO
Inventors: Leigh William Sharples
Original assignee: Gasresearch Australia Pty. Ltd.
Priority date: 1991-10-16
Filing date: 1992-10-12
Publication date: 1993-04-29
Also published as: MX9205965A; AU675208B2; AU2760792A; TW228560B

Abstract

A carburettor (1) for low-pressure gaseous fuel (11) comprising: a hollow body (2) having a through bore, a venturi (3) in said through bore, a throttle valve (4) downstream of said venturi (3), a jet (9) positioned in the venturi (3), said jet (9) connected to a gaseous fuel supply (11), a flow control valve (15) interposed between said jet (9) and said fuel supply (11), said control valve (15) being operatively connected to the throttle valve (4) such that movement of the throttle valve (4) causes translation of a valve element (26) in a gas port whereby the area of the port is varied to regulate the flow of gaseous fuel (11) to the jet (9) in direct proportion to movement of the throttle valve (4).

Description

FUEL DELIVERY SYSTEM FIELD:

The present invention relates to the field of fuel delivery systems, particularly for internal combustion engines. In particular, the present invention deals with a system for providing a fuel and air gaseous mixture ready for combustion.

BACKGROUND ART:

In order to reduce fuel costs, many internal combustion engines particularly those used in automotive vehicles, have been adapted to run on gaseous fuels, such as CNG or LPG fuels, rather than more expensive liquid fuels, such as petrol or diesel. The engines are 'converted' to gaseous operation, usually by the addition of a regulator vaporiser, mixer and manifold(s). These components serve to convert the high pressure gaseous fuel stored in onboard fuel tanks to a lower pressure fuel which, when mixed with air, provides a fuel/air mixture ready for combustion by the engine.

A difficulty with existing converted engines is that a significant reduction in power output of the engine is noticed after the engine is converted to run LPG or CNG fuels. This is often due to poor fuel/air mixtures being fed to the engine. Fuel is thus not combusted under optimum conditions. Also, the ratio of fuel to air in the mixture which is combusted by the engine is determined external of the engine carburettor or fuel injection system, where liquid fuels are usually mixed. Accordingly, little, if any, control of fuel/air ratios throughout the entire operating range of the engine is undertaken.

Prior art systems utilise manifold vacuum to control a diaphragm which regulates flow of gaseous fuel. Accordingly, when the engine is started, a vacuum must be created in the engine before the diaphragm allows fuel flow into the engine. This results in relatively lengthy engine cranking times. Restrictive hoses and connectors are used between the diaphragm and engine manifold in order to gain greater vacuum, and thus more responsive diaphragm control.

However, when the engine is running at relatively high speed, the restrictive hoses serve to reduce the amount of fuel flowing to the engine. Furthermore, as the speed of the engine increases, the manifold vacuum decreased, which in turn serves to increase the richness of the fuel flow to the engine. A reduction in performance and economy is thus noticeable.

Poor engine performance may also be attributable to poor mixing or ratios of the fuel and air. In some known arrangements, the gaseous fuel is allowed to dribble down the inside surface of the carburettor venturi. The fuel remains in close proximity to the /0839

carburettor walls, and does not mix adequately with the air passing through the carburettor venturi.

Furthermore, not an insignificant amount of fuel is wasted when the engine is de- accelerating as diaphragm control systems are relatively slow to reduce fuel air mixture passing to a deacceierating engine. A danger of fuel leakage may also occur when the engine has been switched off. Gaseous fuel which is present in the conversion equipment may be allowed to bleed through the engine and out the engine exhaust uncombusted. OBJECT:

An object of the present invention is to provide a fuel delivery system which alleviates at least one disadvantage of the prior art.

A further object of the present invention is to provide a fuel delivery system which enables satisfactory control of fuel and air ratios throughout the entire operating range of the engine.

A still further object of the present invention is to provide a fuel delivery system which may be calibrated for each particular engine it is fitted to.

Yet another object of the present invention is to provide a fuel delivery system which enables an engine to consume substantially less fuel than existing gaseous fuel systems, and/or alleviate the reduction in power output of the engine due to the conversion to gaseous fuels. SUMMARY OF INVENTION:

The present invention provides a stream of combustible gaseous fuel material directly into an air stream path in relatively close proximity to the engine. In this way, the present invention in one form provides the gaseous fuel material directly to and for mix in a carburettor arrangement; the fuel material being mixed in the carburettor with air to an appropriate fuel/air mixture for combustion by the engine.

The present invention also provides a carburettor adapted to mix air and a gaseous fuel in order to provide a combustible fuel/air mixture, said carburettor comprising : a hollow main body portion through which a stream of air is adapted to enter at one end; and a jet having an open end located in said air stream, wherein: in operation, said fuel/air mixture is provided by feeding said gaseous fuel directly into said air stream via said jet.

The present invention also provides a valve for regulating the supply of a low pressure gaseous fuel, said valve comprising: an inlet coupled to a source of low pressure gaseous fuel; an outlet adapted to provide a predetermined amount of gaseous fuel to an external device; a valve member adapted to cooperate with a valve seat to regulate the flow of gaseous fuel to said outlet; and a projection extending from said valve member into the flow path of said low pressure gaseous fuel, said projection being contoured to provide said predetermined amount of gaseous fuel.

The present invention is predicated on the discovery that air velocity through the carburettor can draw in and mix gaseous fuel rather than manifold vacuum. A venturi provides, in one form, a preferred arrangement for gaseous fuel/air mixing.

Furthermore, it has been surprisingly found that by jetting the low pressure gaseous fuel directly into the air flow path through a venturi-type device, such as a carburettor, substantial enhancement in power output of the engine is achieved. Mixture of fuel and air is thus enhanced. Surprisingly, it has also been found that a significant economy is achievable in the amount of fuel consumed by utilising a valve arrangement to regulate the amount of low pressure gaseous fuel delivered to the engine. Preferably, the valve arrangement is a needle and seat arrangement. Control of the air-fuel ratio throughout the entire operating range of the engine can also be achieved by contouring a projection in the valve to a desired outer configuration, which therefore controls the amount of gaseous fuel passing through the valve.

The present invention also provides a valve for regulating the supply of a low pressure gaseous fuel to an engine for combustion, said valve being operably coupled to a butterfly valve of a carburettor fitted to said engine. It has also been surprisingly found that by controlling operation of the gaseous fuel valve in conjunction with operation of the carburettor butterfly valve, a significant improvement in fuel economy is achieved through the reduction in the amount of unburnt gases passing through the engine and out to exhaust.

The configuration of the valve of the present invention further enables the valve to be located in relatively close proximity to the carburettor fitted to an engine. This close fitment further reduces drag forces on the flow of gaseous fuel to the carburettor.

The present invention provides a carburettor adapted to mix a gaseous fuel and air in order to provide a combustible fuel/air mix, said carburettor comprising : fuel inlet means adapted to provide gaseous fuel into an air stream, said inlet means being further adapted to regulate the amount of fuel passing into said air stream in accordance with the velocity of said air stream.

The present invention also provides a fuel delivery system comprising in combination the carburettor and the valve described above.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, wherein :

Figure 1 shows, in combination, the carburettor and valve of the present invention at an engine idle setting; Figure 2 shows the combination set for initial engine acceleration;

Figure 3 shows the combination at a setting for higher engine RPM; Figure 3A shows an enlarged view of a component part of the valve of the present invention;

Figure 4 shows torque and horse-power output from an engine fitted with the system of the present invention.

Figure 5 shows comparison torque curves of an engine; Figure 6 shows a preferred form of venturi diffuser; Figure 7 shows a preferred jet positioning in the venturi; Figure 8 shows modifications relating to the structure of the carburettor and valve system disclosed in Figures 1, 2 and 3;

Figure 9 relates to a modification of Figure 7; and

Figures 10A and 10B show an air pass valve for use in conjunction with the present invention.

Like numerals in the drawings denote like component parts of the present invention.

In general, the Figures show a preferred form of the present invention in which the carburettor 1 has a hollow main body portion 2, which includes a venturi 3 at one end of the body portion 2.

At the other end of the carburettor 1 , there is provided a butterfly valve 4, which serves to control the flow of gaseous fuel/air mixture to the engine for combustion. The butterfly valve 4 pivots about shaft 5. Gear 6 is also coupled to shaft 5. In an automobile, the accelerator pedal (not shown) is usually coupled via a cable mechanism to shaft 5. Acceleration and deceleration of the engine is controlled by movement of the butterfly valve 4. Operatively coupled to the gear 6 is a rack 18 which serves to proportionately control movement of fuel valve 15. Fuel valve 15 serves to regulate the flow of gaseous fuel 11 into jet 9 for mixture with incoming air flow 8.

A bypass fuel path is provided by pilot line 12 and idle port 10 for fuel and air channel 10A. When the engine is off, fuel valve 15 is closed, thus preventing fuel 11 flowing into jet 9. Furthermore, butterfly valve 4 is closed.

Figure 1 shows the system of the present invention set for the engine to run at idle speed. The butterfly valve 4 at an idle position, closes off the air flow 8 passing to the engine via the butterfly valve 4. The flow of air 8 at the idle position of valve 4 is considered too low to draw fuel from jet 9 and fuel valve 15 is closed. Accordingly, an alternate path is provided to allow for gaseous fuel to enter the engine, comprising an idle port 10 which serves as a junction of fuel line 12 and air channel 10A. Air and fuel is mixed in the idle port proximate the junction of line 12 and channel 10A. .Low pressure gaseous fuel 11 is derived from an onboard gaseous fuel tank (not shown) and passes via a converter to port 11 and also pilot line 12, to the idle port 10.

Figure 1 shows the path of air flow 8 via channel 10A, fuel flow via line 12 and the flow of fuel/air mixture. The carburettor may contact the engine intake manifold directly or contact an intermediate passage.

An idle adjustment screw 14 provides an adjustment of the amount of fuel flow and hence the fuel/air ratio at low r.p.m. of the engine.

A fuel valve of the present invention provides a means by which the amount of gaseous fuel can be regulated and controlled over the entire operating range of the engine in order to optimise the fuel/air ratio of the combustible mixture entering the engine.

Fuel valve 15 serves to regulate the flow of gaseous fuel' 11 by means of valve _ member 16 and seat 17. As shown in Figure 1 , the valve member 16 abuts seat 17 and therefore no fuel is allowed to flow into jet 9. Fuel for engine idling only flows via pilot line 12.

Figure 2 shows operation of the fuel delivery system of the present invention as the butterfly valve 4 is moved to a slightly open position so as to accelerate the engine from idle to low speed (just above idle speed).

The flow of idle fuel/air mixture via idle port 10, including fuel flow via line 12 and air flow via channel 10A continues only as long as there is enough vacuum at port 10.

As shown in Figure 2, as the accelerator is depressed, the valve 4 is moved to beyond progression port 20. The vacuum at the progression port 20 opens valve 21 and provides more fuel 11 into the air flow passing by one opening created by movement of butterfly valve 4, at point 13 in addition to the fuel mixture emanating from idle port 10. As the engine speed increases from idle, this additional fuel supplied to port 20 is required to maintain the correct air/fuel mixture.

A port valve 21 comprising pressure sensitive needle and seat valve 22 senses the increased air flow 13 and opens to allow additional fuel into the carburettor, which fuel is mixed with the passing air 13 for combustion by the engine.

The fuel valve 15 also includes a resilient mechanism 19 which serves to further control the operation of member 16 and the flow of fuel 11 , thus at this time, valve 15 remains closed so that no fuel 11 passes through jet 9. The gear 6 coupled to shaft 5 rotates as the butterfly valve 4 is opened. The gear

6 moves rack 18 which in turn serves to move valve plunger 24 outwardly relative to valve body 25.

The resilient mechanism 19 serves to delay the flow of gaseous fuel into jet 9 at idle or low engine speeds. Figure 3 illustrates a further step in the acceleration of the engine from low to higher speed. The resilient mechanism 19 serves to bias valve member 16 against seat 17 to close valve 15 when the butterfly valve 4 is at idle or low speed positions. However, as the butterfly valve 4 is opened and gear 6 moves rack 18 further outwardly, the plunger 24 moves to engage the top 27 of projection 26 and move the projection 26 further outwardly and move valve member 16 away from seat 17 to open valve 15 and permit fuel 11 to flow into jet 9. The velocity of air flow 8 via venturi diffuser 7 is sufficient to draw fuel through jet 9 and enable mixing of air and fuel within region 28 in venturi 7.

It is important to directly or operatively couple the regulation of gas supply, for example by a needle/seat arrangement, to engine r.p.m., in order to obtain metering of gas flow to air flow (into engine) throughout the engine's rev. range. The coupling can be achieved in many ways, by lever, cable, other known mechanisms or rack and gear as herein preferred. The metering of gas to air flow enables precise ratios of fuel/air to be obtained and optimised for each particular engine. The further jet 9 is placed into venturi air flow 8, the -greater the draw past jet

9, the more fuel is sucked into the air flow to create a fuel mixture for combustion.

Figure 7 shows a preferred positioning of jet 9 in venturi diffuser 7. The upper figure shows a view looking down into venturi 3. The ratio of -area occupied by jet 9 to the area available for air to pass by jet 9 is 1 to 3, preferably 1.8 to 2.2, and most preferably 2.0. That is, the jet occupies an area of between 1 to 3 times more than the area available for air.

The lower figure shows in cross-section, an end view of jet 9. Preferably the ratio of area occupied by jet 9 to the air area is 0.5 to 2, preferably 1.1 to 1.3. Referring to Figure 3, as the butterfly valve 4 is opened further for higher engine speed, valve 15 is proportionately opened to allow more fuel into the venturi diffuser for mixing with air to form a combustible air/fuel mixture. The projection 26 may be tapered or stepped to provide a larger orifice for fuel flow through valve 15.

In order to obtain correct or optimum ratios of fuel and air throughout engine operating range, projection 26 can be contoured and shaped to a predetermined configuration. Thus a narrowing of projection 26 will enable more fuel 11 to flow into jet 9 for higher engine r.p.m. or richer air/fuel mixtures. The converse also applies.

Figure 3A shows an enlarged view of projection 26. The amount of fuel drawn in via jet 9 depends on engine speed and air flow through venturi 7 past jet 9 due to reduced pressure and the size of the orifice in valve 15 between valve 16 and seat 17. The size of the orifice in valve 15 may be increased for higher engine speed, or richer fuel mixtures, by tapering or stepping the diameter of projection 26. As the valve member 16 is moved further outward, more space is created between valve member 16 and seat 17. The size of this space determines the amount of fuel 11 entering jet 9. The amount of fuel 11 entering jet 9 is also determined inversely by the volume occupied by projection 26 in the opening defined by seat 17. Thus, if the projection 26 is contoured in its outer shape, more or less fuel 11 can pass by seat 17 and enter jet 9. This is particularly so when the valve member 16 is moved outwardly beyond end 29 of jet 9.

Accordingly, at an end 30 of projection 26, there is provided a narrowing as an example embodiment. In operation, when end 30 is moved so as to sit near seat 17, a larger gap for fuel 11 to flow through into jet 9 is provided between end 30 and seat 17.

It is anticipated that the projection 26 is to be contoured on its surface in such a way, for each make and size of engine, so as to provide optimum fuel/air ratio of combustible mixture entering an engine throughout the engine's operating range. When the driver of the automobile lifts their foot from the accelerator pedal this serves to return butterfly valve 4 to its idle position and close valve 15 and the engine then decelerates as shown in Figure 1. The closure of valve 15 reduces significantly the flow of fuel 11 into jet 9, and hence the quantity of unburnt gas passing to exhaust. It has also been found that if seat 17 is formed as a projection into the path of the flow of fuel 11, more accurate control of fuel flow into jet 9 can be achieved. A turbulent flow is created in fuel flow proximate seat 17.

Furthermore, it has been found that the shape or configuration of the venturi diffuser 7 serves to enhance the performance of the fuel delivery system of the present invention.

Figure 6 shows a preferred form of diffuser 7. The solid shape is a most preferred form, whereas the shapes denoted by dotted lines have been found to work less efficiently. The solid shape has a slight taper on its internal surface. Figure 4 shows graphically horsepower (HP) and torque (FTID) output of a 3.8 litre V6 GMH engine using the fuel delivery system of the present invention.

Figure 5 shows an approximate comparison of torque output of a 3.8 litre V6 GMH engine running on various fuels. At 3000 r.p.m. a prior art LPG conversion unit branded

IMPCO 225 produces 68 horsepower (HP). The engine running on petrol fuel injection produces 91 HP, whereas using the fuel delivery system of the present invention, the engine running on LPG fuel produces 105 HP.

Modifications relating to the invention disclosed above will now be described. With regard to Figure 8, the body 2 is shown with relatively parallel walls. That is, the thickening shown at the venturi end of the carburettor body has been found not to be essential, in one form of the invention.

Furthermore, the valve 21 as disclosed above may be deleted, however the port 20 still remains. idle adjustment screw 14 has been moved to channel 10A. It has been found that the function of the idle adjustment is more effective if placed in the air flow path rather than the fuel flow path. Furthermore, it has been found that the adjustment screw, if placed in the fuel path, is not an accurate method of regulation of idle adjustment. The gas flow in path 12 has been found to be too small to affect accurate regulation.

It has also been found that, in general, with regard to the present invention, the aiπfuel ratio should be of the order of 10:1 to 20:1 dependent on the engine, and preferably 13:1 for most l.C. engines on the market today. It has been found that there are a number of ways in which the aϊπfuel ratio can be effected. The ratio is determined by the proportions of the area occupied by the venturi air, the diffuser, the jet and the size and/or contour of projection, an example of which is shown in Figures 3A and 7.

The present invention is also applicable to many various gaseous fuels including methane, LPG and CNG. With regard to Figure 9, it has been found not to be necessary to provide three legs holding the venturi 3 in place. Furthermore, the jet or spud may extend through the one leg as shown in dotted lines. The end of the jet at which the gas flow from which the gas flow is emitted may terminate anywhere within the inner area of the venturi (shown in dotted lines). Preferably the end of the spud is terminated at an angle travelling from its upper most tip down to the bore of the venturi. The area, in plan view, of the angled end of the spud has relevance in determining ainfuel ratio. The greater the angle of the spud end, the more area occupied by the spud in the venturi, therefore more fuel may be introduced into the air flowing through the venturi. Figures 10A and 10B show an air pass valve which may be used in conjunction with the present invention although is equally applicable to petrol or other fueled engines. Figure 10A shows the valve in a closed position and Figure 10B shows the valve in an open (pass) position.

The valve may be placed in connection with the manifold (to engine in Figure 2), gas input (11) or high/low pressure fuel converter.

The purpose of the valve is to reduce fuel consumption in conditions of deceleration of the engine. In Figure 2, when the butterfly 4 is closed, high manifold vacuum causes fuel to flow via bypass circuit 10 and 12. The valve as disclosed, in such conditions, will open to an air pass position and allow air to pass through the fuel delivery system and thus provide air rather than fuel into the manifold of the engine in response to a condition of high manifold vacuum. The quantity and timing of air must be regulated in order to avoid the engine stalling and this can be set in accordance with the fuel/air requirements of each engine type.

Under conditions of high vacuum, piston 100 is drawn down.^* The amount of piston movement is dependent on the amount of vacuum and piston size. The example shows a piston of preferably 20 mm diameter and ports 101, 102 of 4 mm diameter. Springs 103 and 104 also serve to regulate the amount of piston movement. Spring 103 also serves to return or bias piston 100 towards a 'home' (closed) position under reduced or nil manifold vacuum.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A fuel delivery system for use with internal combustion engines, and adapted to deliver relatively low pressure gaseous fuel for combustion by said engine, said system comprising a venturi arrangement through which an air stream is adapted to pass; a jet having one end positioned in said air stream, the gaseous fuel passing for mixture through said jet and directly into said air stream.

2. A device for providing fuel/air mixture to an internal combustion engine, the fuel being a relatively low pressure gaseous fuel, said device being arranged to provide the gaseous fuel directly into an air stream for mixture with the air stream.

3. A device as claimed in Claim 2, wherein the fuel is provided directly into the air stream via a jet.

4. A device as claimed in Claim 3, wherein the fuel is LPG or CNG.

5. A valve for regulating the supply of a low pressure gaseous fuel to an IC engine for combustion, said valve being operatively coupled to means for regulating engine r.p.m. in order to meter fuel flow to air flow as required by the engine.

6. Avatve adapted to regulate the supply of a relatively low pressure gaseous fuel to an IC engine for combustion, said valve comprising a needle and seat valve arrangement.

7. A valve as claimed in Claim 5 or 6, further comprising a projection extending into the flow path of the fuel, said projection being contoured to supply a predetermined amount of fuel through said valve.

8. A valve adapted to operatively communicate with a manifold of an IC engine, the valve having an input part and an output port through which gaseous material may pass to the manifold, said valve further comprising a control port adapted to sense vacuum pressure; wherein under conditions of relatively low vacuum pressure, the valve substantially prevents passage of the gaseous material; and under conditions of relatively high vacuum pressure, the valve substantially allows passage of the gaseous material.

9. A valve as claimed in Claim 8, wherein piston means is provided in association with the control port to prevent or allow passage of the gaseous material, the piston means further having biasing means adapted to define or limit the extent of movement of said piston means.

10. A valve(s) as hereinbefore described.

1 1. A device or system for providing fuel/air mixture as hereinbefore described.