GB2036868A

GB2036868A - Atomising I.C. Engine Fuel by Mixing with Exhaust Gas

Info

Publication number: GB2036868A
Application number: GB7942351A
Authority: GB
Original assignee: Rover Co Ltd
Current assignee: Rover Co Ltd
Priority date: 1978-12-07
Filing date: 1979-12-07
Publication date: 1980-07-02

Abstract

Exhaust gas from pipe 14 is conveyed by pipe 24 through valve 25 and introduced tangentially into chamber 18. Metering valve 22 regulates the amount of fuel which issues from orifices 23. Inclined valves 21 swirl the mixture as it emerges into air intake pipe 15. Valve 25 is electrically actuated and is responsive to exhaust gas temperature, engine speed and inlet manifold pressure. When the engine is idling or at full power valve 25 turns so that air is supplied from pipe 28 to chamber 18. In a constant vacuum carburettor, gas from valve 25 is supplied to the fuel jet adjacent the needle-controlled fuel outlet orifice. <IMAGE>

Description

SPECIFICATION Improvements relating to Internal Combustion Engines This invention relates to internal combustion engines, and in particular to engines which employ exhaust gas recirculation.

Engines are known in which a portion of the exhaust gases is returned to the intake air or airfuel mixture in order to reduce the emission of unwanted pollutants. It is also known to mix a small quantity of atmospheric air with the fuel so that the fuel is broken into small droplets and is thereafter more easily thoroughly mixed with the bulk of the intake air to promote even distribution of the fuel to a plurality of cylinders.

The present invention provides an internal combustion engine including means for producing an air-fuel mixture for combustion and means for recirculating exhaust gases, wherein the arrangement is such that exhuast gases are introduced to fuel before said fuel is introduced to intake air to form said air-fuel mixture.

Embodiments of the invention will now be described with reference to the accompanying drawings: Figure 1 shows schematically an internal combustion engine in accordance with the invention provided with a fuel sprayer; and Figure 2 shows a carburettor for another embodiment of the invention.

Figure 1 shows an engine block and cylinder head assembly 11, having four cylinders each fed by a respective branch of an inlet manifold 1 2.

Exhaust gases are carried away by a four-branch exhaust manifold 13 which is connected to an exhaust pipe 14.

Intake passages to the engine, are continued upstream of the inlet manifold 12 as a single inlet passage 1 5 which contains a butterfly-type throttle valve 1 6. Immediately downstream of the throttle valve 1 6 is a means for producing the airfuel mixture intended for combustion in the engine.

Atmospheric air which flows from the inlet 17 of inlet passage 1 5 past valve 1 6 is supplied with fuel by a fuel sprayer 1 8 located in the wall of the inlet passage.

Fuel sprayer 1 8 consists of coaxial circular section tubes 19 and 20 the annular space between which connects with the inlet passage 1 5 by way of a swirler 21, consisting of a set of substantially radially extending vanes each inclined with respect to radial planes of the tubes.

Fuel such as gasolene is passed along tube 19, under the control of a metering valve 22, to apertures 23 from which it is sprayed into the annular space between the tubes 19 and 20. A conduit 24 conducts a small proportion (up to 10%) of the exhaust gases from the exhaust pipe 14 to the annular space between the tubes by way of a valve 25 and a flow regulator 26, which latter may be a variable sized constriction. The exhaust gases pass into the annular space in the sprayer 1 8 by way of an annular jacket extending around tube 20 and a plurality of apertures 27 in the wall of tube 20.

Flow through apertures 27 is almost tangential to the wall of tube 20 which results in a vortex forming in the annular space. Fuel sprayed from apertures 23 is swept into the vortex formed by the exhaust gases and then out into the inlet passage 1 5 by way of the swirler 21 which increases the swirl of the exhaust gases and ensures intimate mixing of the fuel and exhaust gases before the fuel is introduced into the inlet passage 1 5.

Mixing of the fuel with the swirling exhaust gases ensures that the sprayed fuel is atomised, and moreover, owing to the temperature of the exhaust gases, that the fuel is to some extent vapourised. The swirl of the exhaust gases ensures that the exhaust gas/fuel mixture is thoroughly mixed with the intake air so that even distribution of fuel is provided between the four cylinders of the engine. This provides that the mixture strength may be accurately set for each cylinder to obtain the desired combustion process in all cylinders. The presence of exhaust gases in the mixture is used to decrease the formation of oxides of nitrogen during the combustion process.

Under some circumstances the presence of exhaust gases in the air-fuel mixture for combustion is not required, for example at idle when gas flow is limited to the minimum that will sustain combustion and at full throttle when maximum oxygen intake is required for maximum power. Under these circumstances the recirculation of exhaust gases is ceased by actuation of electrically operated valve 25. To maintain atomisation of the fuel, the valve is operable to connect the sprayer with a conduit 28 containing air instead of with conduit 24.The actuation of valve 25 is automatically controlled by an electronic control unit responsive to signals indicative of engine running condition; in the present instance the signals are obtained by monitoring exhaust gas temperature, engine speed and depression in the inlet passage 1 5. The introduction of exhaust gases rather than atmospheric air to the fuel sprayer in the illustrated example is preferred because due to their temperature the exhaust gases can provide vapourisation of the fuel in addition to atomisation, and moreover because the exhaust gases tend to be at higher pressure than atmospheric and as a result a more powerful vortex is obtained for atomisation of the fuel.

It will be appreciated that the invention has wider application than in the illustrated embodiment. For example the form of the fuel sprayer may be varied considerably, even to the extent that the fuel could be introduced to the exhaust gases in the inlet passage 1 5 if the air flow were arrranged to be stratified so that the fuel was substantially surrounded by exhaust gases as it entered the inlet passage for the purposes of atomisation.

More significantly, the invention could be applied to engines not employing a fuel sprayer, for example carburetter fed engines, in which the exhaust gases could for example be fed into the fuel prior to or immediately upon its emergence from the jet tube.

Figure 2 shows a constant depression carburettor which could be used in place of the sprayer 1 8. The carburettor consists of a passage 31 through which intake air passes to the engine, a throttle butterfly valve 32, a jet tube 33 for delivering fuel to the intake air. Fuel flow is metered by a needle 34 in the jet tube and moveable with a piston 35 the height of which varies with air flow rate. Recirculated exhaust gas (or air) from valve 25 is fed to the jet through a conduit 36 so that it is introduced to the fuel before the fuel is introduced to the intake air.

Claims

1. An internal combustion engine including means for producing an air-fuel mixture for combustion, means for recirculating exhaust gases to the engine inlet, and means for introducing at least some of said exhaust gases to fuel before said fuel is introduced to intake air to form said air-fuel mixture.

2. An engine as claimed in claim 1, including means for shutting off the supply of recirculating exhaust gases.

3. An engine as claimed in claim 2, including means for introducing air to said fuel before the fuel is introduced to the intake air to form the airfuel mixture.

4. An engine as claimed in claim 2 or 3, including means for controlling said valve in rsponse to electrical signals indicative of engine running condition.

5. An engine as claimed in any preceding claim, including means for regulating the flow of recirculating gas.

6. An engine as claimed in any preceding claim, wherein said means for producing an airfuel mixture comprises a carburettor having a fuel jet, and wherein exhaust gases are passed into said fuel prior to the emergence of the fuel from the jet into the intake air.

7. An engine as claimed in any one of claims 1 to 4, wherein said means for producing an air-fuel mixture comprises a fuel sprayer.

8. An engine as claimed in claim 7, wherein said fuel sprayer produces a vortex of recirculating exhaust gas and sprays fuel into said vortex.

9. An engine as claimed in claim 7 or 8, wherein said fuel sprayer includes a swirler.

10. An internal combustion engine substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.