GB2136050A - Petrol engine vaporised fuel system - Google Patents

Abstract

Petrol supplied by a pump (17, Fig. 1) is switched from a conventional carburettor (14) to a pipe 33 in a vaporiser 20 when the engine reaches its operating temperature. Petrol sprayed from the nozzle 34 is vaporised by heat from coils 30A, 30B containing engine exhaust gas or coolant or by an electric heating element. Unvaporised petrol is collected in a sump 29 containing a float valve 39 returning excess fuel to the supply tank. Air from a pipe 42 enters below the sump fuel level 40 and provides between 5 and 20% of the content of the vapour in the outlet pipe 21. A valve (22, Fig. 1) linked to the carburettor throttle valve 15 controls the flow of vapour to the engine intake downstream of the throttle valve. <IMAGE>

Description

SPECIFICATION Petrol engine fuel system This invention relates to the fuel system of a petrol engine; and to a fuelling device for use in such a system Petrol/air carburettors in petrol engines produce initially a mixture in which the petrol component consists principally of droplets. The efficiency of a petrol engine is disadvantageously affected by the presence of such droplets in a cylinder charge, due to incomplete burning of the fuel content of the charge.

An object of the present invention is to provide a petrol engine fuel system, and a fuelling device therefor, by which the disadvantage referred to above is obviated or mitigated.

According to one aspect of the present invention, there is provided a petrol engine having an induction conduit for fuel/air mixture, and air intake in communication with said conduit, a fuelling device adapted to produce petrol vapour, an outlet from said fuelling device being in communication with the induction conduit.

According to another aspect of the present invention, there is provided a fuelling device for producing petrol vapour, comprising a chamber, a petrol delivery head in the chamber for introducing a spray of petrol, heating means in the chamber for causing vaporization of petrol when the latter is introduced into the chamber, a drain for conducting petrol liquid from the chamber, and an outlet from the chamber for petrol vapour.

According to another aspect of the present invention, there is provided a method or system of fuelling a petrol engine, wherein petrol vapour with no more than 20% air is introduced into an induction conduit of the engine, and a main air intake to said induction conduit is separate from a source of said petrol vapour.

Preferably, to produce the petrol vapour, liquid petrol is sprayed continuously in a heated chamber having an outlet for said petrol vapour in communication with said induction conduit, liquid petrol is continually drained from said chamber and recirculated, and the level of liquid petrol at a lower part of said chamber is maintained at a predetermined level.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic representation of the layout of a petrol engine fuel system in accordance with the present invention; and Fig. 2 is a sectional elevation of a fuelling device in accordance with the present invention.

In Fig. 1, a petrol engine which is indicated generally by reference numeral 10 has an induction conduit in the form of an induction manifold 11, and an exhaust manifold 12. A main air intake 1 3 to the induction manifold 11 is associated with a conventional petrol/air carburettor 14 and a conventional throttle valve 15. A petrol reservoir or tank 16 feeds a petrol pump 17 from which petrol is delivered to the carburettor 14 by way of a change-over valve 18 the latter being thermally actuated by a heat sensor 19 mounted on the engine 10. The change-over valve 18 is adapted to divert petrol flow from the pump 17 from the carburettor 14 to a fuelling device 20 when the heat sensor 1 9 senses that the engine 10 has reached normal working temperature.Thus, with this arrangement, the change-over valve 18 constitutes a means of stopping dispensing of petrol liquid by the carburettor 14.

The fuelling device 20 consists of a close chamber the interior of which is in communication with the induction manifold 11 by way of a conduit 21 incorporating a flow control valve 22.

The throttle 1 5 and the control valve 22 are operable simulatenously as is indicated diagrammatically by the mechanical link 23. The fuelling device 23 incorporates a heating means described herebelow operable by heat exchange with exhaust gases through upstream and downstream connections 24 and 25 in the engine exhaust system.

The construction of the fuelling device 20 appears in detail in Fig. 2. A cylindrical casing 26 of the device 20 encloses a chamber 27. A flanged upper end of the casing 26 is closed by a cover or lid 28 having an outlet opening 29 in communication with an adjacent end of the conduit 21. The lower portion of the casing 26 has a sloping floor 26A and a central opening 28 in communication with a generally cylindrical sump 29. The chamber 27 is occupied principally by an open coiled heat exchange element consisting of mutually concentric outer and inner coils 30A and 30B which are interconnected to form a continuous conduit for conducting exhaust gases from the connection 24 to the connection 25. The assembly of the outer and inner coils is enclosed within a mesh screen 31.

On the main axis of the casing 26, the sump 29 carries a liquid petrol delivery head 32 which consists of a central pipe 33 having a jet 34 at the upper end thereof. The pipe 33 carries support arms 35 on which is mounted a shroud 36 of venturi configuration and having a top cap 37 of a fine mesh or wire gauze similar to that of the screen 31. The delivery head 32 lies within the inner coil 30B. The sump 29 also carries a drain pipe 38 for returning liquid petrol to the tank 16.

The pipe 38 is connected to a float valve 39 operable to maintain liquid petrol within the sump 29 at a predetermined level indicated by reference numeral 40. The sump 29 also carries an air inlet pipe 41 which is in communication with a multihold air delivery tube 42 within the sump 29 below the level 40.

Operation of the fuel system is as follows.

When the engine 10 is started from cold, the heat sensor 19 sets the change-over valve 18 to deliver petrol from the pump 17 to the carburettor 14. No liquid petrol is delivered to the fuelling device 20 at this stage. The engine is operated in a conventional manner being fuelled solely by the carburettor 1 4. While the engine is operating up to normal working temperature, hot exhaust gases flow through the heat exchange coils 30A and 308 within the chamber 27 of the fuelling device 20.

When the engine 10 reaches normal working temperature, by which time the chamber 27 will have been pre-heated, the heat sensor 1 9 effects actuation of the change-over valve 18 to stop delivery of petrol to the carburettor 14 and simultaneously to divert petrol flow to the delivery head 32 of the fuelling device 20. The carburettor 14 continues to fuel the engine for a short period of time while its conventional float chamber empties. Upon delivery of fuel to the delivery head 32, liquid petrol is sprayed from the nozzle 34 and thus wets the internal surfaces of the fuelling device 20. Petrol vapour is formed and surplus petrol liquid trickles down into the sump 29 where the predetermined level 40 is established by the float valve 39.In order to assist vapour formation, air flow is induced in the pipe 41 so that air bubbles continually disturb the liquid petrol lying in the sump 29. A supply of air to the pipe 41 may be obtained by an air intake (not shown) which may be situated at the front of a vehicle for ram effect air flow, or situated adjacent a cooling fan for induced airflow. The fuelling device 20 is dimensioned, and the components therein are disposed so that petrol vapour containing no more than 20% air (typically no more than about 5% air) is continuously available for extraction through the duct 21 which serves to supply the induction manifold 11 with virtually droplet-free fuel by which means the overall efficiency of the engine is improved.

In a modification of the fuel system described above, the fuelling device incorporates a heat exchange element adapted for connection to the engine cooling system from which a flow of heated coolant supplies the heat energy necessary for vaporization of the liquid petrol. In yet a further modification the heated exchange element is an electrical heating element.

In further modifications of the fuel system described above, the conduit 21 incorporates a heater for re-heating or superheating vapour en route from the fuelling device 20. Such re-heater or superheater may be constituted by a coiled conduit for vapour disposed within a chamber in communication with exhaust gases. A valve may be provided for operation selectively to vary the quantity of exhaust gas flow through the chamber.

The control valve 22 may be dispensed with and replaced by an automatic demand valve located nearer the induction manifold. The demand valve may incorporate a flow regulating device. The conduit 21 may merge at the air intake 13 with a vapour dispenser in the form of a tube formed to define an annular configuration and provided with a circular array of perforations or emission holes directed into the air intake. Upstream of the induction manifold, the conduit 21 may enter and leave a surge tank serving as an accumulator to cope with sudden heavier demand for fuel by the engine.

Claims (16)

1. A petrol engine having an induction conduit for fuel/air mixture, an air intake in communication with said conduit, a fuelling device adapted to produce petrol vapour, an outlet from said fuelling device being in communication with the induction conduit.

2. A petrol engine according to claim 1, wherein the fuelling device is adapted to produce petrol vapour at a temperature in the range of 100 degrees Farenheight to 1 30 degrees Farenheight.

3. A petrol engine according to claim 1 or 2, wherein the fuelling device is adapted to produce an air-and-petrol vapour mixture containing no more than 20% air.

4. A petrol engine according to any one of the preceding claims, including a carburettor arranged to dispense a combustible petrol-and-air mixture into the induction conduit, and a stopping means operable to stop the carburettor from dispensing petrol, whereby the engine is fuelled on starting by the said carburettor and subsequently by the said fuelling device.

5. A fuelling device for producing petrol vapour, comprising a chamber, a petrol delivery head in the chamber for introducing a spray of petrol, heating means in the chamber for causing vaporization of petrol when the latter is introduced into the chamber, a drain for conducting petrol liquid from the chamber, and an outlet from the chamber for petrol vapour.

6. A fuelling device according to claim 5, wherein the said drain has a valve and associated actuating means for maintaining a predetermined level of petrol liquid at a lower part of the chamber.

7. A fuelling device according to claim 6, wherein the said chamber lower part incorporates an air inlet conduit below said predetermined level whereby in operation air is bubbied through the petrol liquid.

8. A fuelling device according to any one of claims 5 to 7, wherein the petrol delivery head comprises a nozzle disposed within a shroud of venturi configuration.

9. A method or system of fuelling a petrol engine, wherein petrol vapour with no more than 20% air is introduced into an induction conduit of the engine.

1 0. The method claimed in claim 9, wherein the petrol vapour is introduced into the induction conduit at a point thereon other than at the main air intake.

11. The method claimed in claim 9, wherein the petrol vapour is introduced into the induction conduit by way of the main air intake thereto.

12. The method as claimed in claim 11, wherein the petrol vapour is introduced into the induction conduit by way of a tube formed to define an annular configuration and having a circular array of perforations or emission holes directed into the induction conduit.

13. The method claimed in any one of claims 9 to 12, wherein to produce the petrol vapour liquid petrol is sprayed continuously in a heated chamber having an outlet for said petrol vapour in communication with said induction conduit, Iqiuid petrol is continually drained from said chamber and recirculated, and the level of liquid petrol at a lower part of the chamber is maintained at a predetermined level.

14. The method as claimed in claim 13, wherein air is introduced into the chamber below said predetermined level.

1 5. The method claimed in claim 13, wherein the chamber is heated by means of heat exchange with exhaust from the engine.

16. A petrol engine fuel system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

1 7. A fuelling device substantially as hereinbefore described with reference to and as shown in Fig. 2 of the accompanying drawings.