NZ192034A - System for supplying lpg/cng to diesel engines - Google Patents

Description

1 920 Patents Form No. 5 PATENTS ACT 1953 COMPLETE SPECIFICATION After Provisional Number 192034 Dated: 5 November 19 79 "GASEOUS FUEL SYSTEM FOR DIESEL FUELLED ENGINES" I, HARVEY MARSHALL REID, of 11 Wakefield Street, Lower Hutt, New Zealand, a British subject and New Zealand citizen, hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: 1 92C This invention relates to fuel systems for combustion engines and more particularly relates to fuel systems for compression ignition or diesel engines and the adaption of such engines to run on diesel fuel and/or gaseous fuel such as liquid petroleum gas (LPG) or compressed natural gas (CNG).

A diesel engine is normally provided with a liquid fuel injection system and for conversion to run on diesel fuel or a combination of diesel fuel and LPG or CNG the engine is provided with a gas fuel supply source and the LPG or CNG is induced via a pressure reducing and flow control valve or regulator and a venturi inlet into the cylinders of the diesel engine via an air inlet manifold.

The present invention more specifically relates to diesel engines with LPG conversions however as will become apparent from the ensuing description, the invention will also have application to CNG conversions for vehicles.

LPG will not normally burn efficiently in diesel engines if the ratio of LPG to diesel fuel is incorrect as, due to the nature of the liquid fuel injection equipment and engine characteristics, there is a comparatively low injection of diesel fuel into an engines combustion chamber at low engine revolutions.

In some situations where diesel engined vehicles are involved in stop/start running and hill starts, it 's necessary or desirable that the engines run on pure 192034 or almost pure diesel fuel at lower engine revolutions; and it is particularly desirable that vehicles which are fitted with automatic transmissions start on pure diesel, and for general running have a fuel system which can vary the ratio of diesel to gas when this is necessary.

The present invention is provided with one object improving or regulating engine performance at lower engine revolutions in engines converted to operate on dual fuel (liquid diesel and LPG or CNG) .

Further objects and advantages of the present invention will become apparent from the ensuing description.

According to a first aspect of the present invention for an internal combustion engine of the compression ignition or diesel kind having a liquid fuel injection system, there is provided a means for operating said engine on liquid fuel and/or on a mixture of gaseous and liquid fuels comprising flow control and pressure reducing valve means arranged for coupling to a supply source of gaseous fuel, a venturi inlet for the gaseous fuel arranged for connection to an air inlet manifold for the engine and for connection to said valve means, and control apparatus actuable according to the speed of the engine to control operation of the valve means to prevent or restrict gaseous fuel flow at low engine revolutions and permit and/or vary the flow of the gaseous fuel into the inlet manifold between low and high engine revolutions; said control apparatus including a speed switch arranged for connection to the engine to detect the engine speed, and a solenoid device electrically connected to and actuable by the speed switch for controlling the flow of liquid diesel fuel from a fuel injector pump to fuel injectors of the engine fuel injection system. 192G34 According to a second aspect of the present invention there is provided a method of controlling the supply of liquified or pressurised gaseous fuel to the fuel induction system of an internal combustion engine designed to operate on liquid fuel, comprising the fitting and employment of control apparatus controlling gas flow to the fuel induction system wherein operation of the control apparatus is determined by the speed of the engine; said control apparatus further controlling the amount of liquid fuel delivered to the engine.

The present invention will now be described by way of example with reference to the accompanying drawings in which:- FIGURES 1A, IB and 1C are illustrations in graph form showing fuel intakes and comparing these with a range of engine speeds for a normal diesel engine, that is an engine normally fuelled or designed to be fuelled by liquid diesel fuel only. Figure 1A showing relative diesel fuel intake in an engine converted in accordance with the present invention for dual diesel fuel/ LPG operation; Figure IB showing relative LPG intake in an engine converted in accordance with the present invention for dual diesel fuel/LPG operation; and in Figure 1C the upper graph line indicates normal diesel fuel usage with conversion of the engine to dual fuel operation, and the lower graph line indicates an example of diesel fuel usage when cut back to normal delivery with gas. 4 OCT 1984 192034 FIGURE 2 is a diagrammatic drawing showing a diesel/LPG system in accordance with the present invention.

It is to be appreciated that a conventional 5 diesel engine will not normally run purely on LPG, and LPG conversions for diesel engines are designed such that a converted engine will run on a mixture of LPG and diesel; and it has been found that the ratio of diesel to LPG for best overall engine performance of 10 the LPG is approximately 2/3 diesel to 1/3 LPG. With reference to figures 1A, IB and 1C these proportions can be at approximately 2000 RPM for an engine.

In Figure 1A the curve represents a typical volume of diesel fuel consumed at the indicated engine 15 revolutions in a converted engine, in figure IB the curve represents LPG consumption in a converted engine, and as can be seen from the graphs on figure 1C for an engine without an LPG conversion in accordance with the present invention the proportion of diesel injected 20 into the combustion chambers of the engine decreases ✓ at lower engine speeds such that engine performance is adversely affected.

Figure 2 of the drawings is a diagrammatic plan view of a typical diesel engine with LPG conversion 25 apparatus in accordance with the invention. In the drawing a diesel engine indicated by arrow 1 is fitted with a conventional injector pump 2 which injects liquid diesel fuel via supply lines 3 and injectors 4 19203 to the combustion chambers of the engine 1. The engine 1 is provided with a supplementary LPG conversion apparatus by which LPG fuel is supplied from a supply reservoir 5 and associated pressure reducing and flow control valve unit or regulator 6 to the engine combustion chamber via supply lines 7, 8 and a venturi unit 9 coupled to the air inlet manifold 10 of the engine. The supply of LPG to the engine cylinders is controlled by a further valve 11 which operates automatically when the engine is running. The further valve 11 operates automatically in direct relationship to a control rod (not shown) of the injector pump 2.

A system as afore-described works satisfactorily at higher engine speeds but not so effectively at low engine speeds. Accordingly, in addition to the basic conversion apparatus afore-described there is provided a speed switch 12 (such as an electric, electronic, mechanical or electro-mechanical speed switch) connected to the engine and which detects the engine speeds and is capable of effecting electric switching operations, and a solenoid unit 13 is electrically connected thereto and arranged to be operable in relation to a control unit or link 2a controlling the supply of liquid diesel fuel from the injector pump 2 to the injectors 4. In accordance with this invention the speed switch 12 and the solenoid unit 13 provide automatic switching to full diesel usage at low engine resolutions P such operation being effected by the 192034 control unit or link 2a of the injector pump 2. When higher engine revolutions are reached the speed switch 12 will activate the solenoid unit 13 which in turn automatically and simultaneously operates the control 5 unit or link 2a to cut-off diesel fuel to approximately 2/3 (or such other prescribed amount) of normal fuel volume whilst the LPG supply valve 6 is turned fully on, and the engine thereafter will run on a ratio of approximately 2/3 diesel and 1/3 LPG fuel (or such 10 other prescribed ratio) as is indicated by line C in figure 1A. The vertical line C joining the upper and lower curves of the graph shows the effect of the speed switch 12 activating the solenoid unit 13 at approximately 100 0 engine revolutions per minute.

In applying the invention to a CNG conversion system the aforegoing principles can be adopted or in an alternative arrangement the CNG can be passed from the valve or regulator unit 6 via a butterfly throttle valve (not shown) to the venturi 9 (the 20 butterfly throttle valve taking the place of further valve 11), and the throttle linkage can be set up to to operate both the injection pump 2 throttle lever and the butterfly operating lever so that the engine can operate on a combination of diesel fuel and CNG 25 at all throttle openings. The speed switch 12 can be arranged to actuate an electric solenoid unit fitted or connected to valve 6 or the throttle butterfly valve to cut off gas flow when the engine reaches the 192034 governed speed of the injector pump to prevent excess unburnable gas flowing into the engine on engine revolutions increasing above the limit of the injector pump.

Injector pumps for fuel injection systems do vary in construction and operation and some constructions e.g. rotary pumps and those having hydraulic governors, are not provided with control rods with which a sensor or further valve 11 can be 10 associated. Accordingly it is envisaged that the sensor or further valve 11 can be dispensed with and CNG flow can be prevented, restricted and/or varied by an electric solenoid unit associated with the control valve or regulator 6 and electrically coupled 15 to the speed switch 12 or solenoid unit 13 e.g. by connection 14.

In any or all of the variations described the solenoid unit or units can be provided with damper means to smooth operation of the actuated parts and 2 0 engine running.

Thus, an LPG conversion in accordance with the present invention overcomes the serious disadvantage of power loss which, occurs when a diesel engine is run on diesel fuel and LPG at low engine revolutions 25 because of injection pump "drop-off", and which power loss is particularly noticeable at starting.

In a CNG conversion in accordance with the present invention, and when the reduced diesel fuel 192034 setting is constant, the arrangement provides that the CNG is prevented from flowing when there is no or insufficient diesel fuel.to ignite such as may occur on engine over-run and when the vehicle is descending 5 hills. Both conversions in accordance with the invention provide for more efficient use of LPG and CNG fuels.

Some preferred, aspects of the present invention have been described and illustrated by way of example only, and it will be appreciated that modifications and 10 additions thereto may be made without departing from th.e scope of the appended claims.

Claims (13)

192034 WHAT I CLAIM IS:

1. For an internal combustion engine of the compression ignition or diesel kind having a liquid fuel injection system, a means for operating said engine on liquid fuel and/or on a mixture of gaseous and liquid fuels comprising flow control and pressure reducing valve means arranged for coupling to a supply source of gaseous fuel, a venturi inlet for the gaseous fuel arranged for connection to an air inlet manifold for the engine and for connection to said valve means, and control apparatus actuable according to the speed of the engine to control operation of the valve means to prevent or restrict gaseous fuel flow at low engine revolutions and permit and/or vary the flow of the gaseous fuel into the inlet manifold between low and high engine revolutions; said control apparatus including a speed switch arranged for connection to the engine to detect the engine speed, and a solenoid device electrically connected to and actuable by the speed switch for controlling the flow of liquid diesel fuel from a fuel injector pump to fuel injectors of the engine fuel injection system.

2. A means as claimed in claim 1 wherein said control apparatus includes a sensor device for controlling the flow of gaseous fuel between the valve means and the venturi, said sensor device being actuable by or in accord with a control rod of an injector pump of the engine fuel injection system.

3. A means as claimed in claim 1 wherein an electric solenoid device is incorporated in or associated with, so as to be capable of actuating, a gas flow control, valve of the valve means I -10- > ■■ h ' i /. L ii ^o4 192034

4. A means as claimed in any one of the preceding claims wherein for normal engine running the gaseous fuel flow and liquid fuel flow are arranged to be regulated by the control apparatus to provide a fuel mixture in a prescribed ratio of diesel fuel and gaseous fuel to the engine combustion chamber(s), and for low engine revolutions gaseous fuel flow is arranged so that it can be prevented or restricted by said control apparatus.

5. A means as claimed in any one of the preceding claims wherein the valve means and control apparatus are arranged and constructed for operation in the delivery of liquified petroleum gas (LPG) from the supply source.

6. A means as claimed in any one of claims 1 to 4 inclusive wherein the valve means and control apparatus are arranged and constructed for operating in the delivery of compressed natural gas (CNG) from the supply source.

7. A means as claimed in claim 6 wherein a butterfly throttle valve is provided for controlling flow of the CNG to the venturi inlet, said butterfly valve being actuable by control mechanism for the liquid fuel injection system.

8. A means for operating an internal compression ignition or diesel engine on a mixture of gaseous fuel and liquid fuel and for controlling the flow of said fuels substantially as hereinbefore described with reference to the accompanying drawings. -11- 1T2C54

9. A vehicle having an engine incorporating the means according to any one. of the preceding claims.

10. A method of controlling the supply of liquified or pressurised gaseous fuel to the fuel induction system of an internal combustion engine designed to operate on liquid fuel, comprising the fitting and employment of control apparatus controlling gas flow to the fuel induction system wherein operation of the control apparatus is determined by the speed of the engine; said control apparatus further controlling the amount of liquid fuel delivered to the engine.

11. A method as claimed in claim 10 wherein said control apparatus includes a regulator valve controlling gas flow, an electric solenoid device for operating the regulator valve, and a speed switch connected to the engine to detect engine speed and electrically coupled to the solenoid to effect operation thereof at prescribed engine revolutions.

12. A method as claimed in claim 10 or claim 11 wherein the gaseous fuel is compressed natural gas and flow of the compressed natural gas to the venturi inlet is controlled by a butterfly throttle valve.

13. A method as claimed in claim 10 or claim 11 and employing the means according to any one of claims 1 to 8 inclusive. HARVEY MARSHALL REID, By His Authorised Attorneys, JOHN A. REMMINGTON & ASSOCIATES -12