GB2042076A - IC engine surface carburetting apparatus - Google Patents

Abstract

A container 24 for fuel 30 has an air inlet 33 and outlet 36 so that engine intake air is passed over the surface of the fuel 30 to entrain fuel vapour. The fuel level is maintained by a float controlled inlet valve (27). The fuel is heated by passing the water from the engine cooling system 15, 16, 17 through a heat exchanger 43 in thermal contact with the fuel, thereby maintaining the vapour pressure within the container. The fuel and vapour mixture may be delivered by a variable speed vane pump (60), Fig. 2 (not shown), to a throttle controlled primary air intake (66). <IMAGE>

Description

SPECIFICATION Caeburetting apparatus This invention relates to a carburettion system and has for its main object the reduction of the consumption of volatile liquid fuel in an internal combustion engine.

BACKGROUND OF THE INVENTION As fuel supplies dwindle, it becomes more and more essential to provide equipment which will enable an internal combustion engine to run on an extremely lean mixture. It is already recognised that under some circumstances an engine will run on a mixture of petrol vapour and air, which contains excess air instead of containing excess petrol, with respect to a stoichiometric mixture.

One of the problems which is associated with the extensive use of motor vehicles having petrol engines utilising conventional carburettion systems wherein petrol spray is mixed with incoming air, is that the products of combustion contain a large amount of contaminants, notably carbon monoxide and unburnt fuel. This is rendered necessary by the characteristic that petrol and air mixture burns better and more reliably if there is excess petrol. As a consequence however, there has been recognised a need for after burners and other anti-pollution equipment on internal combustion engines, and this results in consumption of still further quantities of fuel, or alternatively a loss of power.

The main object of this invention is to provide improvements whereby the consumption of volatile liquid fuel (for example gasoline) in an internal combustion engine will be reduced and yet which will result in an engine which functions satisfactorily over a wide range of petrol/air mixtures. A secondary object is to provide improvements whereby the need for anti-pollution equipment is reduced.

BRIEF SUMMARY OF THE INVENTION Briefly, in this invention, air is conducted through a conduit which contains volatile fuel in such intimate contact with the fuel that it entrains vapours, while the fuel is heated with waste heat of the engine to increase its vapour pressure and reduce the vapour pressure loss which would otherwise be encountered due to cooling of the liquid upon the evaporation associated with the vapour entrainment.

More specifically, the invention consists of container walls defining a container, a fuel inlet conduit opening into the container, a float arranged to sense liquid level in the container, a float valve in the fuel inlet conduit operatively coupled to the float for the maintaining of a liquid fuel level within the container, an engine air inlet conduit in fluid flow communication with the chamber and extending to the engine inlet such that upon operation of the engine, engine induction air is drawn through the conduit and it entrains said vapours, said container incorporating heat exchange means arranged to be heated by waste heat of the engine upon operation thereof.

The invention is distinguished over inventions such as that of Ericsson (Great Britain) 463,294, May 11, 1936, inter alia, in that the vapour pressure is maintained within limits by heating means, utilising the waste heat from the engine. This is of major importance, since the vapour pressure of most volatile liquid fuels is very dependant upon temperature. Still further, it is distinguished over prior art in that it is not essential for use to be made of what is herein termed a "conventional" carburettion system. That is, in some embodiments of the invention there is no nozzle over which air passes, causing liquid fuel to be entrained in the passage of air.

In any apparatus wherein there is a mixture of air and volatile fuel in a container, clearly there is a need for safety precautions to be taken. In the case of an internal combustion engine, the danger of explosion lies in.".back- firing" of the engine, and in one embodiment of this invention there is provided a non-return valve in the outlet conduit which extends frnm the container to the engine inlet. The nonreturn valve can conveniently be of such shape and so spring-loaded that it functions to quench any flame front moving towards the container from the engine at the same time as it closes the conduit.

in another embodiment of the invention the air outlet conduit between the container and the engine inlet comprises a pump which substantially closes the conduit against direct flow of flame fronts from the engine to the container.

It is desirable to maintain the size of the container as well as reasonably feasible because of cost and because of shortage of space in some installations, and while in some embodiments which are associated with smaller engines the air is caused to pass over the surface of liquid contained in the container, in other embodiments relating to somewhat larger engines, the air passes through the volatile liquid fuel contained in the container so as to entrain not only vapours but also particles of liquid fuel, but the quantity of liquid fuel entrained is modified by passing through baffles.

BRIEF DESCRIPTION OF THE DRAWINGS Two embodiments of the invention are described hereunder in some detail with reference to and are illustrated in the accompanying drawings in which: Figure 1 is a diagrammatic representation of a first embodiment which is useful on a small internal combustion engine, and Figure 2 is a similar diagrammatic represen tation of apparatus which is useful on a relatively large engine.

Referring first to the embodiment of Fig. 1, an engine is shown diagrammatically at 10 and is provided with an exhaust valve 11 and an inlet valve 1 2. The inlet valve forms part of the inlet of the engine which is generally designated 13, and which incorporates a manifold 14.

The engine is provided with a radiator 15, and a cooling pump 1 6 pumps engine coolant through a jacket surrounding the engine and through the radiator, use being made of a thermostat valve 1 7 to maintain water passing through that valve at a predetermined temperature which is the operating temperature of the engine (usually about 180OF).

So far as described heretofore, the engine is a usual type of engine commonly used in the art, and the invention herein is directed to the carburetting apparatus generally designated 20.

The carburetting apparatus 20 comprises an upper wall 21, a lower wall 22 and side walls 23 which define between them a container 24. The container 24 is provided with a fuel inlet conduit 26 having a float actuator valve 27 within the container space, the valve 27 being operated by a float 28 and float arm 29 in accordance with known art. This is effective in retaining a level of volatile liquid fuel 30 within a narrow range of tolerance.

The upper wall 21 is provided with a spring-loaded inlet valve 32 which, upon induction of air by the engine, opens an air inlet opening 33 by downward movement against a spring 34.

The upper wall 21 also has opening into it an air outlet conduit 36, and this passes into a throttle control zone 37 which incorporates a throttle butterfly valve 38, a safety gauze 39, and a further poppet valve 40, the arrangement being such that the gauze 39 and the poppet valve 40 perform the function of quenching and arresting any flame front travelling in a reverse direction and also closing off the air outlet conduit 36. The poppet valve 40 is convex in the upstream direction, so that it not only closes the air outlet conduit 36 upon backfire, it also quenches any flame front travelling in the reverse direction.

Upon operation, air is induced by the piston 42 of the engine 10 to pass the inlet valve 32, over the surface of the safety gauze 39.

This passage of air will entrain the vapours from the liquid fuel 30 cooling the fuel, and in order to compensate for such cooling, there is provided a heat exchange 43 in the form of a flat coil of tubing, the heat exchanger 43 receiving heated water from the thermostat valve 1 7 and returning it to the inlet of the pump 16. For average conditions in warm climates this will be found to meet all require ments, although under very cold conditions it will be necessary to provide further heating means for initial heating of the fuel 30.

In order to entrain a sufficient quantity of vapour in its passage over the fuel 30, there is provided a hinged baffle 45 within the container which deflects the air to pass over the surface of the fuel 30 at relatively high velocity. This of course is associated with relatively low pressure and ensures entrainment of quantities of vapour. By adjusting the location of the baffle 45, the quantity of volatile fuel entrained can be varied within wide limits, and indeed the air can be caused to so disturb the surface that particles of liquid fuel are entrained in addition to the vapour.

The embodiment of Fig. 2 is similar in many respects to that of Fig. 1 and similar parts bear similar designations. However instead of using the heat exchanger 43 which was a flat coil of tubing, the heat exchanger 50 comprises a lower jacket 51 and an upper jacket 52 respectively associated with but spaced from the lower wall 22 and upper wall 21 of the container 24 so that these walls themselves provide the heat exchange surfaces. Air is drawn through an air inlet tube 53 surmounted by a gauze sleeve 54, and the air is released beneath the surface level of the liquid fuel 30.The container also contains a fine mesh gauze 56 beneath the level of the fuel 30 but above the air inlet so that the air is caused to percolate through some of the fuel and thereby entrain a much greater proportion of liquid fuel along with the vapour than occurs in the first embodiment. This enables a much smaller container to be utilised. To prevent excessive quantities of liquid fuel from being carried into the engine, there are provided a plurality of baffles 57 within the container 24, and these baffles 57 are also associated with a layer of granular material designated 58.

The air outlet conduit 36 has included within it a sliding vane pump 60 which is driven by a variable speed electric motor 61, the speed of which is varied by a potentiometer 62. The air outlet conduit 36 also contains a butterfly restrictor valve 63 and this is coupled to the throttle butterfly valve 38 by means of a chain 64 (or a link) so that operating the throttle valve 38 will also give a corresponding control over the vapours and particles of droplets of liquid fuel passing upwardly through the air outlet conduit 36.

Once again use is made of a poppet valve 40 (although experience has indicated this is probably not necessary).

The throttle control zone 37 in the second embodiment is constituted by walls defining a vertical inlet tube 66 surmounted by an air cleaner and silencer 67, and most of the aspiration requirements of the engine 10 will be drawn downwardly by the piston 42 through the tube 66. At the time of writing this specification, there has been no instance of any "blow back" into the conduit 36 notwithstanding a large number of experiments, and this is thought to be due mostly to the sudden change of direction of the fue! vapours and droplets as they are entrained by the downwardly flowing air in the inlet tube 66. The pump 60 is a positive displacement pump and will give precise control over the quantity of vapour and liquid fuel withdrawn from the container 24.By simple adjustment means (lean to rich) the fuel consumption of the engine 10 can be reduced to the most suitable level for any given set of circumstances.

Consideration of both the above embodiments will indicate that the invention results in a simple mechanical means for control of engine fuel consumption, and it will be seen that the danger of discharge of unburnt fuel by the engine can be greatly reduced, and the proportion of partly burnt fuel evidenced by the presence of carbon monoxide can also be reduced to such an extent that in some instances anti-pollution equipment is not re quires.

However, it is not necessary to pass air over or through the liquid fuel in all instances, and if the fuel is heated to, say, about 70"C there is ample vapour pressure to cause vapour to be entrained in the air stream externally of the container. By utilising hot water from an engine cooling system, associated with a thermostat (as normally employed in such systems), the vapour pressure can be maintained within a useful range (about 4 psi to 10 psi), requiring no ancillary control means.

Claims (14)

1. Carburetting means for the mixing of volatile liquid fuel and air in the induction of an internal combustion engine, comprising: container walls defining a container, a fuel inlet conduit opening into the container, a float arranged to sense liquid level in the container, a float valve in the fuel inlet conduit operatively coupled to the float for the maintaining of a liquid fuel level with the container, an engine air inlet conduit in fluid flow communication with the chamber and extending to the engine inlet such that upon operation of the engine, engine induction air is drawn through the conduit and it entrains vapours of said fuel, said container incorporating heat exchange means arranged to be heated by waste heat of the engine upon operation thereof.

2. Carburetting apparatus for the mixing of volatile liquid fuel and air in the induction of an internal combustion engine, comprising: container walls defining a container, a fuel inlet conduit opening into the container, a float, arranged to sense liquid level in the container, a float valve in the fuel inlet conduit operatively coupled to the float for the maintaining of a liquid fuel level within the container, air inlet means and air outlet means extending through said walls, said air outlet means comprising an air outlet conduit extending to the engine inlet such that upon operation of the engine, engine induction air is drawn through the container and is placed into such intimate contact with the liquid fuel that it entrains vapours thereof, said container incorporating heat exchange means arranged to be heated by waste heat of the engine upon operation thereof.

3. Carburetting apparatus according to Claim 1 or Claim 2 wherein said heat exchange means comprises a heat exchanger having a heat exchange surface in contact with said liquid fuel within said container, and wherein said internal combustion engine is water cooled, said apparatus also including conduit means extending from the engine water cooling system to the heat exchanger and arranged to conduct water, heated by the engine, through said heat exchanger.

4. Carburetting apparatus according to Claim 3 wherein said heat exchanger comprises a heat exchanger conduit within the container and below said liquid level.

5. Carburetting apparatus according to Claim 3 wherein said heat exchanger comprises a jacket associated with and spaced from the lower wall of the container.

6. Carburetting apparatus for the mixing of volatile liquid fuel and air in the induction of an internal combustion engine having a water cooling circuit, comprising: container walls defining a container, a fuel inlet conduit extending through a said-wall and opening into the container, a float within the container, a float valve in the fuel inlet conduit so coupled to the float that it is operable to maintain a liquid fuel levet within the container, an air inlet opening in said container wall and an air outlet conduit opening at one end in a said container wall and at its other end at the engine inlet, a heat exchanger having a heat exchange surface within the container and beneath said liquid fuel level, and heat exchanger conduits extending to the water cooling circuit from the heat exchanger, so constructed and arranged that, upon operation of the engine, water from the water cooling circuit circulates through the heat exchanger and heats said liquid fuel in the container with waste heat, while engine ir;duc- tion air is drawn through said container in such intimate contact with said liquid fuel that it entrains vapours thereof.

7. Carburetting apparatus according to Claim 6 further comprising a non-return valve in said air outlet conduit.

8. Carburetting apparatus according to Claim 6 further comprising walls defining an inlet tube extending to the engine inlet, said air outlet conduit from the container entering through said walls and placing the air outlet conduit into fluid flow communication with the air inlet conduit.

9. Carburetting apparatus according to Claim 8 further comprising a throttle valve in the engine inlet tube, a restrictor valve in the air outlet conduit, and means coupling said valves to operate in unison for control of engine speed.

10. Carburetting apparatus according to Claim 6 further comprising a pump in said air outlet conduit incorporating means which at least partly close the conduit except on operation of the pump, and drive means coupled to the pump.

11. Carburetting apparatus according to Claim 10 wherein said drive means comprise an electric motor, and motor speed control means electrically coupled thereto.

1 2. Carburetting apparatus according to Claim 6 wherein said air inlet opening and air outlet opening in said container walls are both above said liquid fuel level, and further comprising a baffle also above said liquid level and arranged to confine air flow between those said openings to the proximity of said liquid level.

1 3. Carburetting apparatus according to Claim 1 2 further comprising baffle adjustment means operatively interconnecting the baffle and a wall of the container and operable to adjust the baffle position with respect to said liquid level.

14. Carburetting apparatus according to Claim 6 wherein said air inlet opening is below said liquid level and said air outlet opening is above said liquid level, such that air passing through the container is forced to pass upwardly through liquid fuel when contained therein.

1 5. Carburetting apparatus according to Claim 14 further comprising a plurality of baffles between said liquid level and said air outlet opening.

1 6. Carburetting apparatus according to Claim 14 further comprising a layer of granular material between said liquid level and said air outlet opening.

1 7. Carburetting apparatus substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawings.

1 8. Carburetting apparatus substantially as hereinbefore described with reference to and as illustrated in Fig. 2 of the accompany ing drawings.