AU2004100610B4 - Improvement in Means to Deliver Fuel to Engines - Google Patents

Description

-PAGE 1- PATENT DESCRIPTION AND SPECIFICATION CLAIM PATENT TITLE: IMPROVEMENTS IN MEANS TO DELIVER FUEL TO ENGINES Engines which run on a single fuel type are common with the petrol, diesel and LPG engines the most common. Spark ignition engines, which can run on alternative fuels, have been developed and the most common is the engine, which can run on petrol, natural gas or LPG.

The use of natural gas or LPG as a diesel engine fuel has to this time not been practical for a number of reasons.

For example, the difficulties encountered in controlling two fuels over a range of speeds and loads, in correct proportions, which will provide efficient operation with acceptable performance levels.

It has been found however, that a diesel engine will run very satisfactorily where diesel fuel is injected into a mixture of air and natural gas or LPG. This has the advantage that efficient operation, as a dual fuel engine is achievable at reasonable cost. There is an inherent simplicity in the system employed, which assures reliable operation. Softer and slower combustion characteristics of natural gas or LPG fuel result in lower noise levels, reduced stress and longer engine life.

The present invention has as its object the provision of apparatus whereby natural gas or LPG can be mixed in appropriate quantities with the air to be fed into the combustion chambers of a diesel engine. The air/gas mixture is compressed in the normal manner and on injection of diesel fuel combustion takes place with the combustion of the gas providing the majority of the combustion energy.

PAGE 2 The means for mixing the natural gas or LPG with the induction air comprises several elements. The first element is a mixer being an apparatus with a through bore for combustion air and a tangential entry for natural gas or LPG. This provides an intimate mixing of the air and the natural gas or

LPG.

The second element is a boost sensitive power valve, which is located, upstream in the natural gas or LPG delivery path from the first element and comprises a control valve for gas flow. The second element is designed for use in turbocharged engines. At low engine revolutions and heavy load turbo-charger operation is slow to meet engine demands and the second element of the apparatus overcomes this shortcoming by increasing the amount of gas in the combustion air stream.

The third element is a gas-throttling device. The purpose is to provide gas proportional to demand that is load on the engine. The element will supply gas to accommodate high load conditions and will reduce supply when the load decreases to give a 'lean' condition for cruising with associated economy of engine operation.

The several elements will now be described with reference to the drawings. It is to be understood that the first and third elements can be used without the second element.

The first element is shown in Figs. 1 to 3. In Fig. 1 there is shown a tubular body 1 of circular cross-section with an inlet end 2 and an outlet end 3. The body 1 has a near midlength circumferential outwardly extending enlargement 4 which provides a continuous internal channel in the body wall and PAGE 3 there is an inner sleeve 5 mounted in the body 1 to combine with the channel 4 to create a continuous circumferential chamber 6. The chamber 6 has an outlet, which is annular gap 7 which faces in the direction of air flow through the first element. Natural gas or LPG enters the chamber 6 through a tangential entry pipe 8 and as a result the discharge through the gap 7 into the airflow has a swirling motion which promotes mixing of the natural gas or LPG with the combustion air.

The second element is illustrated in Figs. 4 to 7, In Fig. 4, there is shown a gas inlet pipe 8 mounted in a valve block 9 and aligned with a gas delivery pipe 10 also mounted in the block 9. Mounted on the block 9 there is a valve assembly comprising a upwardly biased balance pin 11 where the bias is provided by a spring 12 adjustable as to pre-load by means of the threaded plug 13. Centrally mounted in the plug 13 there is a threaded stop member 14 which is engageable by the head 15 on the pin 11 to limit the "down" movement of the pin 11 and a valve member 16 in engagement with the pin 11.

The pin to valve engagement is provided by a collar 17 on the pin 11 in engagement with a recess 18 in the valve 16.

The upward movement of the valve member 16 under the influence of the spring 12 (acting through the pin 11) is limited by engagement of the back face of the valve member 16 with the counterbore shoulder 19 of a diaphragm mount 20 secured to the block 9.

Adjustable threaded into the mount 20 at 21 there is a spigot 27 of a diaphragm housing 22. The double pressure operated diaphragm 23-24 mounted in the housing 22 is connected to a spindle 25 slideable at 26 in the housing spigot 27 with the end of the spindle 25 engaged in the -PAGE 4counterbore 28 in the back of the valve 16. There is an inlet 29 to the diaphragm chamber so that turbocharger pressure can be introduced into the diaphragm chamber.

In the operation of a conventional turbocharged diesel engine, as the engine load increases there is an increase in air intake boost pressure. This results in a higher airflow to the engine corresponding to the speed of the turbocharger and there is an appropriate increase on the supply of diesel fuel to the engine.

In the operation of a gas/diesel engine as proposed, the supply of diesel fuel is limited and as engine demand increases gas is admitted in place of additional diesel fuel.

In the valve arrangement just described, when the engine is under load and engine speed is low, there will be low pressure and the valve 16 will be fully open resulting in an unrestricted flow of gas to the mixer described above. As the engine speeds up so will the turbo charger and there will be an increase in the demand for air through the mixer. There will be a corresponding increase in the boost from the turbo charger and this increased pressure is tapped and introduced through inlet 29 resulting in a closure to some degree of the valve 16. The result is a balance between the demand and supply of gas to the engine. Conversely, when the engine speed or load decreases the valve 16 will open due to lower turbocharger pressure acting on the diaphragms 23-24 and so the power/fuel balance will be substantially maintained over a wide range of speed load conditions.

The adjustment potential of the device is comprehensive with this threaded connection between 27 and 20 allowing adjustment of the total opening of the valve 16 to set the PAGE 5 power level of the engine for the high/low speed condition, where the turbocharger pressure is lowest.

Movement of the member 13 will vary the rate of closure of the valve 16 in response to turbocharger pressure increase.

The pre-load on the spring 12 will determine what turbocharger pressure will initiate the closure movement of the valve 16.

This adjustment sets the power level for the "middle" range of the engine power/speed conditions.

Adjustment of the member 14 determines the closure limit of the valve 16 as previously stated. The purpose of this adjustment is to establish the power level for high speed/load engine conditions. If the valve 16 were to close fully there would be an unacceptable power loss for high load/ speed conditions of the engine.

The third element of the apparatus is a throttle block for natural gas or LPG supply, as illustrated in Figs 8 9.

This device provides natural gas or LPG in proportion to demand determined by engine load.

The device comprises a housing 30, with inlet and outlet ports 33, and a rotary control bobbin type valve 31, which is connected to the operator's throttle control.

This valve comprises a 'flat' centre section, with two side ports machined through the body of the valve, each side of the centre valve (no.32).

The valve body has a central bore for gas flow, with two slots, 33 machined each side, on line with the cross bore which accommodates the bobbin valve.

-PAGE 6- The bobbin valve 31 can be rotated through 90' Fully closed, the blade of the valve is at 90' to the gas flow bore, and fully open, is parallel to the gas bore. In the fully closed position, the side ports 32 are at 90' to the machined slots 33 in the valve body, an in the fully open position, will be aligned with the slots.

In the operating sequence, at idle, the bobbin will be fully closed, and no gas will flow. As the engine speed is increased, the bobbin will be progressively opened, allowing an increasing flow of gas, as speed and power require. This allows a controlled amount of gas at all conditions except full loading.

The side ports will remain closed, until the throttle opening reaches approximately 70' (see 34). After 70' opening, the side ports 32 will align with the body slots 33, allowing gas to flow at a higher rate (see 35). This provides a higher flow of gas at times of full load. When the requirement for power is no longer needed, the throttle opening will be reduced, the side ports will close, returning the valve to economy cruising.

Claims (4)

1. A diesel engine induction manifold provided with a gas mixer having a cylindrical chamber with an inlet for induction air, an outlet for fuel gas/air mixture and a tangential gas inlet to promote mixing by swirling and a throttle located upstream of the gas inlet which throttle is under the engine operator's control.

2. A diesel engine induction manifold as claimed in Claim 1, wherein the throttle is a bobbin valve.

3. A diesel engine induction manifold as claimed in Claim 1 or 2, wherein the engine has a turbocharger and there is a diaphragm valve located between the throttle and the gas mixer which diaphragm valve responds to turbocharger pressure.

4. A diesel engine induction manifold as claimed in Claim 3, wherein the diaphragm valve moves against the pressure of a spring in order to vary the rate of closure of the valve in response to turbocharger pressure increase. A diesel engine with an induction manifold as claimed in any one of the preceding claims. COMS ID No: SBMI-03313300 Received by IP Australia: Time 12:28 Date 2006-04-13