WO1991006757A1

WO1991006757A1 - Fuel delivery system for an internal combustion engine

Info

Publication number: WO1991006757A1
Application number: PCT/AU1990/000514
Authority: WO
Inventors: Russell Philip Lutherborrow
Original assignee: Vaportec Industries Pty. Ltd.
Priority date: 1989-10-25
Filing date: 1990-10-25
Publication date: 1991-05-16

Abstract

A fuel vaporization unit (10) for delivering fuel vapor and air to an induction passage of an internal combustion engine, the unit (10) including a vacuum chamber (11) having air inlets (12, 13, 14) for transport air, the transport air being a proportion of the total air required for combustion, a fuel inlet (17) through which fuel can be delivered to the chamber (11), a fuel vapor outlet (15) through which fuel vapor and transport air can be delivered downstream to the induction passage, a heater means (32) for delivering heat to the chamber (11) to promote vaporization of fuel within the chamber (11) such that under the influence of negative pressure downstream of the chamber (11) transport air is drawn through the chamber (11) along with fuel vapor in order to deliver a mixture of air and fuel vapor through the fuel vapor outlet (15) downstream to the induction passage.

Description

FUEL DELIVERY SYSTEM FOR AN INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

THIS INVENTION relates to a fuel delivery system for an internal combustion engine and in particular to a fuel vaporization unit which utilises the vacuum created in the intake manifold of the internal combustion engine in order to assist vaporization of the fuel.

BACKGROUND ART

An air-fuel mixture is normally delivered to the intake manifold of the internal combustion engine via a carburettor. The carburettor atomizes the fuel as a fine spray mist and during the engine decompression stroke, the vacuum created in the manifold draws air through an air filter thus drawing the fuel mist and air as a mixture into the cylinder, the fuel is burnt and the combustion products are exhausted after which the process is repeated.

In an engine in which fuel metering is effected by means of a single carburettor, the fuel mixture to all the cylinders should be the same but it is difficult to divide the charge equally between the cylinders. When several carburettors are provided, on the other hand, difficulty arises in balancing the mixture strength to all the cylinders. A still further problem with the use of carburettors is that fuel is present in the intake manifold.

A fuel injection system has the advantage that a metering of the fuel is performed separately from the metering of the air supply to the cylinders. Thus the mixture strengths for the cylinders may be adjusted individually permitting more accurate control. Furthermore, the intake manifold design is simplified and the manifold is dry, which avoids the various problems caused by fuel in the manifold which tends to be deposited on the walls of the manifold and disturbs the mixture strength under transient conditions. The chief disadvantage of fuel injection, however, is the complexity, which is reflected in the cost and in reliability.

Another problem with conventional carburettor and fuel injection systems is that the air fuel mixture is not intimately combined when in the cylinder and this results in an incomplete hydrocarbon burn, giving low engine performance and higher exhaust emission levels than are desirable or would be achieved if a cleaner burn could be effected.

It has been proposed to completely vaporize fuel and deliver a fuel vapor to the induction manifold. However, fuel delivery systems employing vaporizers have, to date, failed to vaporize the heavier fuel fractions and as the vaporization process is relatively slow, difficulties have been encountered not only in the vaporization process but also the supply of vapor under high fuel demand situations.

OUTLINE OF THE INVENTION It is an object of the present invention to overcome or alleviate at least to some degree the aforementioned problems associated with the prior art. In one aspect, the invention resides broadly in a fuel vaporization unit for delivering fuel vapor and air to an induction passage of an internal combustion engine, the unit including a vacuum chamber having an air inlet for transport air, a fuel inlet through which fuel can be delivered to the chamber, a fuel vapor outlet through which fuel vapor and transport air can be delivered downstream to the induction passage, a heater means for delivering heat to the chamber to promote vaporization of fuel within the chamber such that under the influence of negative pressure downstream of the chamber transport air is drawn through the chamber along with fuel vapor in order to deliver a mixture of air and fuel vapor through the fuel vapor outlet downstream to the induction passage of the internal combustion engine. In another aspect, the present invention resides in a fuel delivery system for delivering a mixture of fuel vapor and air to the induction passage of an internal combustion engine, the system comprising a fuel vaporization unit and a blower means downstream of the vaporization unit and upstream of the induction passage, the vaporization unit including a vacuum chamber having an air inlet for transport air, a fuel inlet through which fuel can be delivered to the chamber, a fuel vapor outlet through which fuel vapor and transport air can be delivered downstream to the induction passage via the blower means, and a heater means for delivering heat to the chamber to promote vaporization of fuel within the chamber, the blower means being operable in response to demand for fuel to increase the negative pressure within the vacuum chamber thereby causing an increase in vapor production. The term transport air is used herein to refer to a proportion of the total air required for combustion. In other words, in order to burn the fuel vapor leaving the vacuum chamber, additional air is added to the mixture downstream of the vacuum chamber. Typically, the transport air represents about 5% of the total air required for combustion.

In the specification upstream and downstream refers to the direction of flow of transport air through the vacuum chamber from the air inlet to the fuel vapor outlet. A quantity of fuel diffusing or vapor adsorbing material an be located within the chamber to assist diffusion and vaporization of fuel.

The chamber preferably includes a film forming surface adjacent the fuel inlet so that fuel entering the chamber flows as a thin film over the film forming surface in order to assist vaporization of fuel within the chamber.

The fuel inlet is preferably located adjacent the downstream end of the chamber, and the film forming surface is preferably an internal wall spaced from the inner wall of the chamber and forming a skirt extending along the chamber to enclose the fuel vapor outlet and the quantity of fuel vapor adsorbing material, such that the film of fuel can flow to a point adjacent the upstream end of the fuel vapor adsorbing material. A return conduit can be provided adjacent the upstream end of the adsorbing material so any fuel in the liquid state can be recycled to the fuel inlet.

The chamber preferably includes a fuel reservoir upstream of the fuel vapor adsorbing material and a heater adjacent the reservoir so that heat can be applied to the reservoir to provide a surge of vapor within the chamber. Advantageously, the reservoir is spaced from the fuel vapor adsorbing material by an apertured wall. In one embodiment, the film of fuel can flow beyond the fuel vapor adsorbing material and into the chamber reservoir. Advantageously, a return line is provide between the chamber fuel reservoir and a main fuel reservoir. Fuel is preferably delivered to the chamber along a fuel line so that the main reservoir, fuel line, fuel inlet, film forming surface, chamber reservoir and return line form a closed circuit. Preferably fuel is circulated through the circuit by a fuel pump in the fuel line. As the action of the negative pressure in the vacuum chamber can cause very low temperatures, water vapor in the air can freeze, it is preferable to preheat the fuel and to this end, an electrical resistance heater is employed in the circuit, preferably the heater is located in heat transfer relation with the fuel line in order to maintain the inlet fuel at a predetermined temperature. The temperature of fuel in the fuel line can be maintained between 0°C and 100°C but preferably 0°C and 60°C with an optimum at approximately 45°C.

The fuel vapor outlet preferably includes a bowl for collecting condensate which might accumulate in the chamber while the engine is not running. The condensate accumulated in the bowl can be used when starting the engine in order to provide a rich mixture for starting purposes.

The fuel diffuser or fuel vapor adsorbing material can be any suitable fuel diffuser or vapor adsorber, such as activated charcoal, or any suitable foam which has a high surface area to volume ratio represented by voids in the foam ranging in size from .05mm to 1.8mm, with a preferred size of from .1mm to 1.00mm. Advantageously, the fuel vapor adsorbing material is contained in a canister having an upstream end wall and a downstream end wall and an adjoining side wall. The canister is preferably located beneath the skirt of the film forming surface, so that the skirt extends partially along the side wall of the canister. The end walls of the canister are preferably perforated to allow passage of air and vapor through the canister while perforations in the side wall can be employed it is preferred to limit the perforations in the side wall to a region adjacent the upstream end of the canister. Where foam is employed inside the canister the density of the foam can be readily altered by compressing the foam prior to placing the foam inside the canister.

The air inlet can be located at any position upstream of the fuel vapor adsorbing material. Alternatively, a plurality of spaced air inlets can be employed.

Advantageously, some of the air inlets are located upstream of the chamber reservoir so that air is drawn through the fuel in the chamber reservoir. The air can be delivered to the chamber under high pressure, although lower pressure air can be employed, or alternatively ambient air can be employed. The blower can be any form of blower including centrifugal pumps or rotary vacuum pumps and so forth that can be controlled in response to demand for fuel and the blower is therefore preferably slavishly driven in concert with the engine drive shaft suitably rated to maintain an elevated vapor pressure throughout the speed range of the engine. With this arrangement demand, under say acceleration conditions, would effect negative pressure through the vacuum chamber, which would increase the velocity, evaporation rate of vapor, due to the small amount of transport air involved and vapor holding capacity of the transport air. Advantageously, the whole system downstream from the blower is airtight - capable of pressure application to the induction passage.

The additional air required for complete combustion can be provided by connecting the fuel delivery system in parallel with the air intake of a conventional carburettor while using the present system for delivery of fuel. BRIEF DESCRIPTION OF THE DRAWING In order that the invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawing Figure 1 which is a schematic drawing illustrating one preferred embodiment of the invention.

METHOD OF PERFORMANCE Referring to the drawing, there is illustrated a delivery system employing a fuel vaporization unit 10, for delivering fuel vapor and air to an induction passage of an internal combustion engine (not shown), the unit includes a vacuum chamber 11 having three air inlets 12, 13 and 14, a fuel vapor outlet in the form of an inverted frusto-conical bowl 15 through which fuel vapor can be delivered to the induction passage, and a quantity of fuel vapor adsorbing material 16, inside the chamber between the air inlets 12 and 13 and 14 and the fuel vapor outlet 15. Fuel is delivered to the chamber through a fuel inlet 17, so fuel delivered to the chamber can be adsorbed into the fuel vapor adsorbing material, and under the influence of negative pressure in the induction passage or by virtue of blower 33, air is drawn through the fuel adsorbing material, and fuel vapor is desorbed from the fuel adsorbing material in order to deliver a mixture of air and fuel vapor through the fuel vapor outlet to the induction passage.

In the illustrated embodiment, the chamber includes a film forming surface in the form of a dome 18 and a depending skirt 19 contiguous with the dome 18, so that fuel flowing out of the inlet 17 flows as a thin film over the dome and down the skirt onto the side wall 20 of a canister 21 in which the fuel vapor adsorbing material is housed. As the fuel flows over the film forming surface it will be continuously subjected to a vacuum by virtue of the application of the vaporization unit to a multi-cylinder internal combustion engine, and much of the fuel will be vaporized before it reaches the upstream end of the canister 21. Any excess fuel will be partially absorbed into the lower region of the fuel adsorbing material, and once this portion is saturated any additional fuel will flow through the perforated plate 22 separating the canister 21 from the chamber fuel reservoir 23 and thereafter flow into the chamber fuel reservoir 23. Fuel is delivered to the chamber 11 from a main fuel reservoir 24 via a fuel line 25, and a return line 26 enables circulation 'of fuel between the chamber reservoir and the main reservoir 24 as a closed circuit. A fuel pump 35 is employed to circulate the fuel. It is preferable to preheat the fuel prior to delivering the fuel to the chamber, and to this end an electrical resistance heater 27 is employed in the fuel line. Fuel is supplied to the main fuel reservoir 22 from the vehicle's main petrol tank along line 28. Air is normally delivered to the chamber under low pressure from a low pressure air funnel 29 but in some circumstances it may be desirable to provide air under pressure, and accordingly a blower 30 is employed and can be activated at any stage to, for example, assist starting the engine. In order to provide additional fuel vapor for acceleration purposes the chamber includes a recess such that the recess is surrounded by the chamber reservoir 23 as an annular reservoir of fuel. An electrical resistance heater 32 is moveable into or out of the recess 31 in order to deliver an intense burst of heat to the fuel within the reservoir 22 such that vapor can be boiled off, thus supplying additional vapor to the interior of the canister and thereby providing a greater amount of vapor to the induction passage of the internal combustion engine, thus providing more fuel for acceleration. The movement of the heater 32 can be controlled by any desired means such as a solenoid, by compressed air or by a mechanical linkage to the vehicle accelerator pedal.

Acceleration can be further assisted by employing the blower 33 between the fuel vapor line 34 and the induction passage of the internal combustion engine such that the negative pressure within the chamber can be increased therefore causing a greater amount of vapor to be produced.

In use, fuel is continuously circulated through the fuel circuit defined by reservoirs 23 and 24, fuel line 25, fuel pump 35, fuel line 26 and the vacuum chamber 11. Fuel entering the chamber 11 at the fuel inlet 18 is immediately subjected to negative pressure arising from the multi- cylinder internal combustion engine to which the vapor line 34 is connected. The fuel flows as a thin film over the film forming surfaces 18, 19 and 20, and as the thin film of fuel is being subjected to negative pressure vaporization occurs over the relatively large surface area. Liquid fuel is absorbed into the fuel vapor adsorbing material through the end wall 36 and perforations 37 to partially saturate the fuel vapor adsorbing material contained within canister 21. While air is being drawn into the chamber through air inlets 12, 13 and 14, the air mixed with the fuel vapor stored in the fuel vapor adsorbing material is drawn through the canister 21, and through apertures 38 in the end wall 39 of canister 21, whereafter the fuel vapor and air mixture passes out of the canister through the fuel vapor outlet 15 to the induction passage of the internal combustion engine. Thus, vaporization is controllably achieved under the influence of vacuum and heat while a minimum amount of air is introduced into the vacuum chamber for transportation of the vapor. Thus, under high demand conditions, the vaporization unit can respond to supply vapor as required for most normal operating conditions of the internc.1 combustion engine to which the fuel delivery system is connected.

Other features illustrated in the drawing include i temperature sensor 40 which indicates the normal operating temperature of the chamber at say 50°C-60°C and an air pressure gauge 41 which indicates the normal operating pressure which typically ranges from 15 inches of mercury to 23 inches of mercury. Whilst the above has been give l by way of illustrative example of the present invention, many variations and modifications will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as claimed in the appended claims.

Claims

1. A f el vaporization unit for delivering fuel vapor and air to an induction passage of an internal combustion engine, the unit including a vacuum chamber having an air inlet for transport air, the transport air being a proportion of the total air required for combustion, a fuel inlet through which fuel can be delivered to the chamber, a fuel vapor outlet through which fuel vapor and transport air can be delivered downstream to the induction passage, a heater means for delivering heat to the chamber to promote vaporization of fuel within the chamber such that under the influence of negative pressure downstream of the chamber transport air is drawn through the chamber along with fuel vapor in order to deliver a mixture of air and fuel vapor through the fuel vapor outlet downstream to the induction passage.

2. A fuel delivery system for delivering a mixture of fuel vapor and air to the induction passage of an internal combustion engine, the system comprising a fuel vaporization unit and a blower means downstream of the vaporization unit and upstream of the induction passage, the vaporization unit including a vacuum chamber having an air inlet for transport air, the transport air being a proportion of the total air required for combustion, a fuel inlet through which fuel can be delivered to the chamber, a fuel vapor outlet through which fuel vapor and transport air can be delivered downstream to the induction passage via the blower means, and a heater means for delivering heat to the chamber to promote vaporization of fuel within the chamber, the blower means being operable in response to demand for fuel to increase the negative pressure within the vacuum chamber thereby causing an increase in vapor production.

3. A fuel vaporization unit according to claim 1 where the vacuum chamber includes a surface adjacent the inlet so that fuel flows over the surface as a film of fuel to promote vaporization.

4. A fuel vaporization unit according to claim 3 wherein the surface is in the form of a dome and a depending skirt contiguous with the dome so that fuel flowing out of the inlet flows as a thin film over the outside of the dome and down the skirt, a fuel diffusing or adsorbing material beneath the dome to assist diffusion of fuel and to promote vaporization.

5. A fuel vaporization unit according to any one of claims 1, 3 or 4 including a fuel circuit for circulating fuel from an upstream end of the chamber to a downstream end of the chamber.

6. A f el delivery system according to claim 2 wherein the vacuum chamber includes a surface adjacent the inlet so that fuel flows over the surface as a film of fuel to promote vaporization.

7. A fuel delivery system according to claim 6 wherein the surface is in the form of a dome and a depending shirt contiguous with the dome so that fuel flowing out of the inlet flows as a film over the outside of the dome and down the skirt, a fuel diffusing or adsorbing material beneath the dome to assist diffusion of fuel and to promote vaporization.

8. A fuel delivering system according to any one of claims 2, 6 or 7 having a fuel circuit for circulating fuel from an upstream end of the vacuum chamber to a downstream end of the chamber.