WO1997047872A1

WO1997047872A1 - Gaseous fuel injection system

Info

Publication number: WO1997047872A1
Application number: PCT/AU1996/000349
Authority: WO
Inventors: William Michael Lynch
Original assignee: William Michael Lynch
Priority date: 1996-06-07
Filing date: 1996-06-07
Publication date: 1997-12-18
Also published as: AU5888196A

Abstract

A fuel injection method and apparatus, suitable for use with an internal combustion engine operated on LPG, has a reservoir (1) for LPG with an outlet (9) connected via a pump (3) and a non-return valve (5) to a heating chamber (6), which is preferably heated by hot air or hot water, and then via a gas pressure regulator (12) to an injector (10). The apparatus operates such that LPG is pumped by the pump (3) through the non-return valve (5) to the heating chamber (6), where the LPG is heated to allow gaseous LPG to be transmitted to the injector (10) once a predetermined pressure set on the regulator (12) has been reached, whereupon the injector (10) injects the LPG into the crankcase, transfer ports, carburettor or cylinders of the internal combustion engine. The internal combustion engine may be a two-stroke engine, and lubricant may be injected into the engine along with the gaseous LPG using lubricant injection means that are arranged to adjust the amount of lubricant in accordance with engine speed, preferably by drawing the lubricant into the fuel flow by use of the venturi effect.

Description

GASEOUS FUEL INJECTION SYSTEM

This invention relates to an apparatus for injecting vaporised liquefied gas fuel into an internal combustion engine.

Various apparatus have been used for the delivery of fuel into the combustion chambers of internal combustion engines, but most of these relate to fuels which are liquid at normal ambient operating conditions. With such fuels, either a carburettor or a fuel injection system is used. Particular problems arise, however, when the fuel is gaseous at normal temperatures and atmospheric pressures, but is stored in liquid form under pressure. One common form of such fuel is liquefied petroleum gas (LPG). However, there are other equivalent fuels such as hydrogen, propane and liquefied natural gas (LNG), and it is to be understood that throughout this description and claims, a reference to LPG or liquefied petroleum gas should be taken to include a reference to such an equivalent fuel, and to any other volatile gas or substance adapted to be used as a fuel for an internal combustion engine, which is gaseous at normal temperature and pressure, but which is stored in liquid form under pressure.

The efficient delivery of LPG-type fuels to such engines can be difficult. The usual method involves mixing the gaseous fuel and air before introducing this mixture to the engine.

It is an object of the present invention to provide a fuel injection apparatus for internal combustion engines operated on LPG, which overcomes some of the problems of prior art devices or at least provides an alternative apparatus.

The invention provides a fuel injection apparatus adapted to be fitted to an internal combustion engine operated on LPG, said apparatus including a reservoir for LPG, said reservoir having an outlet connected via a pump and a non-return valve to a heating chamber and then via a gas pressure regulator to an injector, wherein, in operation, LPG is pumped by said pump through said non-return valve to said heating chamber, which heating chamber is adapted to heat said LPG to allow gaseous LPG to be transmitted to said injector once a predetermined pressure set on said regulator has been reached, whereupon said injector injects said gaseous LPG into the crankcase, transfer ports, carburettor or cylinders of said internal combustion engine.

Preferably, said injector is actuated by combustion pressure from the engine or by a sensor responsive to engine speed, thereby ensuring delivery of fuel is regulated according to engine speed.

Preferably, said heating chamber is heated by hot water or hot air. The injector may be arranged to feed the gaseous LPG continuously or in any other manner as required by the particular type of engine and/or the fuel feed thereto.

When the engine is a two-stroke engine, lubricant must be injected into the engine along with the gaseous LPG.

Preferably, in order that the amount of lubricant injected is commensurable with the amount required by the engine speed - the higher the engine speed, the greater the amount of lubricant required - means are provided for automatically adjusting lubricant feed.

At higher engine speed the fuel flow is faster so the rate of fuel flow to the engine may be used to regulate lubricant injection rate by drawing the lubricant into the fuel flow by use of the venturi effect.

In a preferred arrangement, the lubricant injecting means includes a constriction in a feed pipe for introducing the LPG to the engine, or in a by-pass stream drawn off from the feed pipe, said constriction forming a venturi, closely adjacent to which is at least one feed point for lubricant such that the reduction in pressure at the feed point or points caused by passage of gaseous LPG through the venturi sucks lubricant from a reservoir into the fuel stream in an amount dependent on the rate of fuel flow and on the engine speed.

In order that the lubricant feed rate may be controlled over a wide range and to ensure adequate lubrication at all engine speeds without over- lubrication at low speed, there are preferably provided at least two feed points fed by feed pipes of small diameter rather than a single feed point fed by a larger diameter feed pipe. At least two feed points can preferably be switched from operational to non-operational by engine speed controlled means for example, engine speed controlled valves.

Thus, at idling and low engine speeds a first feed point, which may conveniently be termed a "low speed" feed point may be operational with the flow of lubricant therefrom being controlled both by the rate of flow of fuel through the venturi and by valve means, for example, needle valve means in the feed pipe connecting the feed point to the lubricant reservoir. As fuel flow and consequently the engine speed is increased, the valve in the lubricant feed pipe may be opened further until the feed pipe is wholly unobstructed and operating at its maximum capacity. At this point, a valve in a second lubricant feed pipe connecting a second "high speed" feed point to the lubricant reservoir may be opened to allow the introduction of further lubrication into the fuel stream. At maximum engine speed both fuel pipes may be opened to their fullest extent and delivering lubricant at the limit of their carrying capacity.

The presence of engine speed controlled valves in the lubricant feed pipes provides for fine control of lubricant addition through the entire engine speed range. The valves on the lubricant feed pipes are preferably computer controlled.

When there are two or more feed points, the lower speed lubricant feed point is preferably located near the wall of the fuel pipe and the high speed lubricant feed point is located centrally of the pipe.

The constriction forming the venturi may be created by a valve member in the fuel pipe which is operated in response to the engine speed or which itself controls engine speed.

The valve may, for example, comprise a speed controller, for example a throttle operated by the accelerator pedal or other throttle control. Where the valve is separate from the speed controller, it is preferably a rotary valve or a needle valve and this may be so whether the valve is present in the main fuel feed pipe or in a by-pass flow pipe. such a valve member is preferably controlled by computer to adjust fuel flow through the venturi.

The invention also provides a method of lubricating a two-stroke LPG engine wherein lubricating oil is introduced into a vaporised LPG stream and wherein the quantity of lubricating oil introduced is increased as the rate of flow of fuel to the engine increases, wherein the introduction of lubricating oil is controlled by the action of a venturi in the fuel pipe which draws lubricant from a lubricating oil reservoir in response to the reduction in pressure resulting from passage of fuel through the venturi.

The two-stroke engine lubricating arrangement can also be used with two- stroke engines other than LPG two-stroke engines and may for example comprise a unit for insertion into the fuel pipe of, for example, a two- stroke petrol or diesel engine.

Thus, the invention also provides a lubricant feed system for a two- stroke engine comprising a chamber that can be inserted into the fuel line of an engine, said chamber forming or enclosing a venturi through which the fuel passes and, downstream of said venturi, at least one lubricant feed point connected to a lubricant reservoir such that passage of fuel through the venturi draws lubricant from the reservoir to be entrained in the fuel an amount dependent on the ratio of fuel flow. The construction of the lubricant feed apparatus may be generally as described hereinbefore.

Embodiments of the invention will be described in detail hereinafter, with reference to the accompanying drawings, in which:

Fig. 1 shows in schematic form an embodiment of a fuel injection system for an LPG-operated internal combustion engine in accordance with the present invention; and

Fig. 2 shows in schematic form an embodiment of a lubricating system in accordance with the present invention.

Referring firstly to Fig. 1, a pressurised fuel reservoir (1) is shown containing liquefied petroleum gas (LPG). The pressure within the reservoir (1) is typically 826.8 kPa (120 psi). Fuel is pumped from the reservoir (1) via a centrifugal pump (3) from reservoir outlet (4) to a heating chamber (6) via a non-return valve (5).

The heating chamber (6) has an inlet (7) and an outlet (8) to allow heated water to heat fuel line (9) within the heating chamber (6). Fuel line (9) is connected to an injector (10) via gas pressure regulator (12). A sensor (11), responsive to engine speed, activates the injector (10).

In operation, when using propane gas, the pressure regulator (12) is set to approximately 500 kPa when ambient temperature is approximately 10°C. The injector typically injects 10 cm³ to 20 cm³ of gas per stroke when the engine is operating at 6,000 rpm. Lubrication for the engine is provided in the case of two-stroke engines by oil injection and in the case of two-stroke engines by oil injection and in the case of four-stroke engines by provision of a wet sump.

Turning to Fig, 2, the lubricant injecting apparatus (21) consists of a section of the feed pipe (22) in which are located a low speed lubricant feed point (23) and a high speed lubricant feed point (24). Gaseous fuel enters the pipe section (22) at (25) and leaves at (26). A rotary valve (27) is controlled by a computer (28).

The low speed feed point (23) is located near the wall of the pipe section (22) and the high speed feed point (24) is located in the central region of the fuel stream. Feed points (23) are fed by lubricant feed tubes (32) and (33), respectively. Feed points (23) and (24) and lubricant feed tubes (32) and (33) have a bore size in the range 50 to 100 micron and the ends (32) and (33) at feed points (23) and (24) are angled at 45° to the direction of gaseous fuel flow.

The rotary valve (27) restricts the diameter of the feed pipe (22) upstream of the lubricant feed points (23) and (24) and provides a venturi which draws lubricant from the reservoir (29) to feed points (23) and/or (24) at a flow rate dependent on the pressure drop provided by the venturi .

Further control of lubricating oil flow is achieved by needle valves (30) and/or (31) located in tubes (32) and (33) respectively, near the low and high speed feed points (13) and (14). The needle valves (30), (31) may also be controlled by computer (28).

The lubricant injecting apparatus (21) may be located in the fuel or fuel/air stream at any location where there is a suitable flow before the fuel enters the combustion chamber of the engine.

In operation, at low speeds oil emerges from the low speed fuel point (23) and is introduced into the fuel/air stream in atomised form. Valve (30) is gradually opened as more and more oil is required. When or before, the maximum capacity of the low speed lubricant feed (23) has been reached and further lubricant is required, the valve (31) is opened, gradually actuating the high speed feed point (24), thereby increasing the amount of lubrication to the engine. With the high speed feed point (24) operating, the low speed feed may be adjusted so that both feed points (23) and (24) are feeding lubricant at the same or substantially the same rate.

In this specification and claims, the terms lubricant, lubricating oil or oil include oil diluted with diluents that includes liquid fuels. Indeed, the reduction in viscosity achieved by such dilution may ne advantageous is aiding atomisation.

Needle valves (30, 31) are adjusted to regulate the amount of oil being injected into the fuel or fuel/air stream over the speed range of the engine by controlling whether the lubricant enters from one or other or both fuels points (23, 24). However, other adjusting means may be used to regulate this flow.

The claims form part of the disclosure of this specification.

Claims

1. A fuel injection apparatus adapted to be fitted to an internal combustion engine operated on LPG, said apparatus including a reservoir (1) for LPG, said reservoir (1) having an outlet (9) connected via a pump (3) and a non-return valve (5) to a heating chamber (6) and then via a gas pressure regulator (12) to an injector (10), wherein, in operation, LPG is pumped by said pump (3) through said non-return valve (5) to said heating chamber (6), which heating chamber (6) is adapted to heat said LPG to allow gaseous LPG to be transmitted to said injector (10) once a predetermined pressure set on said regulator (12) has been reached, whereupon said injector (10) injects said gaseous LPG into the crankcase, transfer ports, carburettor or cylinders of said internal combustion engine.

2. Apparatus according to claim 1, wherein said injector (10) is actuated by combustion pressure from the engine or by a sensor (11) responsive to engine speed.

3. Apparatus according to claim 1 or claim 2, wherein said heating chamber is heated by hot water or hot air.

4. Apparatus according to any one of claims 1 to 3, wherein the engine is a two-stroke engine and lubricant is injected into the engine along with the gaseous LPG using lubricant injection means that are arranged to adjust the amount of lubricant in accordance with engine speed.

5. Apparatus according to claim 4, wherein the lubricant injection means operates by drawing the lubricant into the fuel flow by use of the venturi effect.

6. Apparatus according to claim 5, wherein said lubricant injection means includes a constriction in a feed pipe (25) for introducing the LPG to the engine, or in a by-pass stream drawn off from the feed pipe, said constriction forming a venturi, closely adjacent to which is at least one feed point (23, 24) for lubricant such that the reduction in pressure at the feed point or points (23, 24) caused by passage of gaseous LPG through the venturi sucks lubricant from a reservoir (29) into the fuel stream in an amount dependent on the rate of fuel flow and on the engine speed.

7. Apparatus according to claim 6, wherein at least two feed points (23, 24) include a lower speed lubricant feed point (23) located near the wall of said fuel pipe (25) and a higher speed lubricant feed point (24) located centrally of the pipe (25).

8. Apparatus according to claim 6 or claim 7, wherein said constriction forming said venturi is created by a valve member (27) in the fuel pipe (25) which is operated in response to the engine speed or which itself controls engine speed.

9. Apparatus according to claim 8, wherein the valve comprises a rotary valve (27) or a needle valve , which is preferably controlled by computer (28), to adjust fuel flow through the venturi.

10. A method of lubricating a two-stroke LPG engine wherein lubricating oil is introduced into a vaporised LPG stream and wherein the quantity of lubricating oil introduced is increased as the rate of flow of fuel to the engine increases, wherein the introduction of lubricating oil is controlled by the action of a venturi in the fuel pipe which draws lubricant from a lubricating oil reservoir in response to the reduction in pressure resulting from passage of fuel through the venturi.

11. A lubricant feed system for a two-stroke engine, comprising a chamber (25) that can be inserted into the fuel line of an engine, said chamber (25) forming or enclosing a venturi through which the fuel passes and, downstream of said venturi, at least one lubricant feed point (23,24) connected to a lubricant reservoir (29) such that passage of fuel through the venturi draws lubricant from the reservoir (29) to be entrained in the fuel an amount dependent on the ratio of fuel flow.

12. A method of providing fuel to an internal combustion engine operated on LPG, including the steps of pumping said LPG from an outlet (9) of an LPG reservoir (1) via a non-return valve (5) to a heating chamber (6) and then via a gas pressure regulator (12) to an injector (10), such that said heating chamber (6) heats said LPG to allow gaseous LPG to be transmitted to said injector (10) once a predetermined pressure set on said regulator (12) has been reached, whereupon the gaseous LPG is injected by said injector (10).