GB2047337A

GB2047337A - Apparatus for producing fuel- air mixtures for internal combustion engines

Info

Publication number: GB2047337A
Application number: GB7925244A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-04-17
Filing date: 1979-07-19
Publication date: 1980-11-26
Also published as: DE2915416A1

Abstract

A low pressure injection nozzle 2 injects fuel into an air nozzle 3 into which combustion air is fed at 28 to produce a fuel air mixture characterised in that the diverging part of the air nozzle 3 includes at least two groups 34, 34' of slots or bores 4, 4' through one group 34' of which combustion air is supplied from low load to full load, the second group 34 supplying air only from an intermediate load to full load. The air flow is controlled by throttle valves 8, 10. Exhaust gas controlled by a valve 17 is recirculated. <IMAGE>

Description

SPECIFICATION Improvements in apparatus for producing fuelair mixture for I. C. E.

The invention relates to an apparatus for producing a fuel-air mixture for internal combustion engines formed by a fuel nozzle with low pressure injection which injects fuel jet into the area of venturi nozzle, for example, a lavell nozzle in which the combustion air is supplied and the fuel-air mixture is finely atomized.

Such a mixing apparatus is, for example, described in my German Specification 2645076.

The disclosure contents of this German Specification 2645076 is completely comprised by the present description in so far as it depends on the explanation of the present invention. By tests it has been shown that with a mixing apparatus according to the type described in German Specification 2645076 an optimum preparation in all driving ranges of the engine is not possible. With the experiments with a mixing apparatus according to German Specification 2645076 as a central injection in a four cylinder engine there resulted due to the oscillations in the suction pipe an accumulation of fuel in the lower area of the mixing chamber in particular at the diverging part of the air funnel. Although the preparation of the fuel-air mixture in the abovementioned mixing apparatus is superior to all other systems this preparation could still be improved.

Furthermore it has been proved that in the use of a controlled mixture formation apparatus as described with German Specification 2645076 a relatively large amount of space is taken up, because a plurality of double parts (two air tubes, two mixing chambers and so on) are required.

Furthermore the manufacturing and assembly costs are also increased.

The problem of the present invention is to develop an apparatus of the abovementioned type such that a controlled mixture formation apparatus with a substantially smaller number of parts and with the correspondingly reduced manufacturing and assembly costs is provided where by at the same time the preparation of the fuel-air mixture is improved in all load areas. In particular an undesired accumulation of non prepared fuel drplets at the diverging part of a venturi tube is avoided.

The invention is characterised in that a control mixture formation apparatus is provided in which in the diverging part of the air funnel at least two groups of slots or bores spatially separated from one another are disposed and that to the first group combustion air is fed to the lower area via the middle partial load area to the full load area and to the second group combustion air is fed to the partial load area to the full load area of the internal combustion engine.

The essential feature of the present invention is therefore the fact that with a single mixing chamber, a single fuel nozzle and a single air funnel a controlled mixture formation apparatus is provided for which previously according to the prior art always double parts were required.

According to the invention an apparatus for the production of a fuel-air mixture for internal combustion engines formed by a fuel nozzle with low pressure injection which injects the fuel jet in the region of an air nozzle, for example a lavall nozzle, into which the combustion air is fed and the fuel-air mixture is finely atomized, characterised in that a controlled mixture forming apparatus is produced in that in the diverging part of a venturi tube (3) at least two groups (34, 34') of slots or bores (4, 4') spatially separated from one another are arranged and that from the first group (34') combustion air is supplied to the lower over the middle partial load area to the full load area and the second group (34) combustion air is supplied to the middle partial load area to the full load area of the internal combustion engine.

The combustion air from the lower via the middle partial load area to the full load area is fed to the first group of slots or bores whilst to the second group of slots or bores additional combustion air is fed from the middle partial load area to the full load area of the internal combustion engine.

It is also essential that the combustion air for the lower via the middle partial load area te the full load area is divided into two currents the first current of which steam upwards to reach the mouth of the fuel nozzle and of the venturi tube in the mixture chamber and the second current in the diverging part of the venturi tube the first group of slots or bores. A partial preparation of the fuel-air mixture is effected therefore already due to the fact that stream upwards to the mouth of the fuel nozzle a first current of fuel is introduced into the mixing chamber which is then intimately mixed by the fuel jet of the fuel nozzle after which is arranged stream upwards of the venturi tube formed as a lavall nozzle.The second current of this combustion air is in the diverging part of the venturi tube introduced via the slots or bores into the mixing chamber and is intimately mixed there with the fuel-air mixture already prepared by the venturi tube.

A feature of the present invention is that the diverging part of the venturi tube is formed steplike whereby in each step a slot (or by way of substitution instead of the slot a row of bores arranged one behind the other) extending over the part of the periphery is extended. By the arrangement of steps with slots formed therebetween which extended partially over the periphery of the venturi tube sharp edges are produced which induce additional whirlings on the inner wall of the diverging part of the venturi tube.

Due to this air whirling an accumulation of fuel on the diverging part of the venturi tube is prevented.

Another embodiment of the present invention provides however a smooth non-stepped diverging part of the venturi tube; the previousiy described sharp edges are then omitted. By the arrangement of the slots or bores alone an accumulation of non prepared fuel drops in this area of the venturi tube is thus prevented.

The first group of slots or bores lead into a first air chamber of the apparatus which is in flow connection with a first air inlet; the second group of slots or bores leads into a second air chamber which is in flow connection with a second air inlet.

Via the first air inlet combustion air is fed from the lower via the middle partial lead area to the full load area whilst further combustion air is fed via the second air nlet to the middle partial load area to the full load arena. The control of the supply is effected via throt+le valves arranged respectively in the air inlets the first of which acts as a control mixture formation apparatus to the lower via the middle partial load area and remains open up to the full load area whilst the second mentioned throttle valve is opened from the middle partial load area and likewise remains open up to the full load area.

Additionally according to the invention it is arranged that in the diverging part of the venturi tube a portion of the exhaust gas from the internal combustion engine is introduced in certain load areas so that due to the thermal and dynamic energy of the exhaust gas an additional preparation of the fuel-air mixture is carried out.

The invention will be described with reference to the accompanying drawings:- Fig. 1 is a section through a mixing apparatus according to the invention; Fig. 2 shows a view of the mixing apparatus in the direction of the arrow 11 of Fig. 1; Fig. 3 shows a section on the line Ill-Ill of Fig.

1; Fig. 4 shows a section on the line IV--IV of Fig.

1; Fig. 5 shows a section of a second embodiment similar to Fig. 4 which shows the arrangement of bores instead of slots.; Fig. 6 shows a diagrammatic partial section through the diverging part of the venturi tube of the mixing apparatus according to Fig. 1.

The mixing apparatus contains a central mixing chamber 1. The fuel nozzle 2 discharges there into.

The fuel outlet end of the nozzle projects into the venturi tube 3. In the diverging part of the venturi tube air slots or bores 4, 4' are arranged which are in communication with air chambers 5 and 6 respectively. The air chamber 5 are located in the lower part of the mixing chamber 1 and is separated from the upper air chamber 6 (Fig. 4) by the walls 20.

The air chamber 6 is in communication with the connecting channel 14 by means of the passages 1 5 which connecting channel again is in communication via the opening 21 with the air inlet 9 in which the throttle valve 10 is located.

The air chamber 5 is in communication with the connecting channel 11 via the opening 13 which connecting channel is in communication with the air inlet 7 via the opening 22 in which the throttle valve 8 is disposed. An opening 12 is arranged between the connection channel 11 and the central space 1 9.

A further channel 1 6 is arranged for the supply of exhaust gas into the air chamber 5.

In the throttle valve 1 7 exhaust flows through the channel 1 6 into the chamber 5.

The manner of operation is as follows:- From the fuel nozzle 2 fuel finely atomized sprays into the venturi tube 3. The atomization of the fuel is effected at the fuel nozzle 2 as that part of the combustion air entering via the air inlet 7 with slightly opened throttle valve 8 is divided into two currents 28, 29 the current 28 of which stream upwards to the mouth of the fuel nozzle 2 in the central chamber 1 9. After the fuel nozzle 2 injects into the diverging part of the venturi tube 3 the current 28 of the combustion air is carried along and atomized the fuel.

The quantity of the fuel is controlled electrically or mechanically via known devices. The combustion air for idle running is preferably supplied at the outlet of the fuel nozzle 2 in the manner as described in German Specification 2645076. The content of the description of this German Specification 2645676 is thus to be included in the present description.

On entry into the partial load area of the engine the throttle valve 8 is opened and shortly after also the throttle valve 1 7. The combustion air for the partial load area of the engine flows on through the opening 12 into the central space 19 and also through the opening 13 into the air chamber 5. A part of the fuel flows around the fuel nozzle 2 and enters with acceieration through the narrowest part of the venturi tube 3 where it mixes intimately with the finely atomized fuel which is sprayed from the fuel nozzle 2.

The other part of the combustion air enters at high speed from the air chamber 5 through the slots 4' into the lower part of the enlarging area of the venturi 3. Thus falling fuel drops or fuel accumulating there are caused by oscillation, to mingle with very finely prepared combustion air and fed to the engine. It is essential that the first group 34' of slots or bores 4' associated with the lower to the middle partial load area up to the full load area is disposed in the lower part of the venturi 3 as shown in Fig. 4. Afterwards the control mixing formation apparatus is connected to the suction pipe of an internal combustion engine so that this has an inclination downwards in the direction of flow, the fuel which is already finely atomized by the fuel nozzle 2 and the combustion air of the current 28 inclines thereto to deposit on the lower part of the venturi 3. The slots 4' according to Fig. 4 or equivalent bores 4' according to Fig. 5 are arranged so that the fuel deposited is immediately taken along and is whirled and any accumulation of non prepared fuel is atomised.

Furthermore the length of the first group 34' of slots or bores 4' to be about 3040% and the length of the second group 34 of slots or bores 4 to about 6070% of the periphery of the venturi tube 3 at the relevant place of the slots or bores 4, 4'. This means that the effective flow cross section of the first group of slots or bores 4' is selected smaller by the said % rate than the cross section of the second group of slots or bores 4.

This is because in the lower or middle partial load area relatively little fuel is supplied and this fuel however is to be accelerated to a high speed.

The flow cross section of the first group of slots or bores is therefore selected small so that a relatively small quantity of fuel nevertheless emerges at high speed from the first group of slots or bores arranged at the bottom.

In the middle partial load area up to the full load area substantially more combustion air is supplied so that the top lying second group of slots or bores may have a larger flow cross section and nevertheless the combustion air still at extraordinarily high speed flows in through these slots or bores in the venturi tube. A special feature is that the slots or bores are arranged parallel and spaced apart from one another so that the combustion air currents emerging from the individual slots overlap and still mutually accelerate so that an additional preparation of the fuel-air mixture is effected.

Fig. 6 shows in diagrammatic form the procedure of the fuel preparation from the lower or middle partial load area.

The first current 28 of combustion air as hereinbefore described is introduced via the opening 12 into the central space 19 and is mixed in the direction of the arrow 25 with the fuel jet emerging from the fuel nozzle 2 in the direction of the arrow 25 which fuel jet is thus finely atomized.

At the diverging part of the venturi tube 3 are arranged the above described slots 4, 4' whereby from the lower or middle partial load area only one current 29 of combustion air is supplied via the slots or bores 4'. On the step-like formed edges of the diverging part of the venturi tube 3 are formed sharp edges 24 via which the full air mixture coming from the fuel nozzle 2 is whirled approximately in the direction of the arrow 26 and meets with the current 29 from the slots or bores 4'..An accumulation of fuel drops is thus prevented. Likewise it may obviously be arranged that instead of the step like formating of the diverging part the inner periphery of the venturi tube 3 it may be formed smooth.

The throttle valve 1 7 according to Fig. 1 allows hot exhaust gas into the lowermost part of the air chamber 5 which emerges through the lowermost slots 4' into the venturi tube 3. This hot exhaust gas also contributes thermally and dynamically to prepare fuel to be fed very finely divided to the engine.

The throttle valve 10 is opened only from the upper partial load up to full load. Thus the engine sucks additionally now also air through the slots 4 in the upper area of the Venturi tube 3.

The advantages of this mixture forming apparatus are as follows:- In the lower and middle partial load area in which the speed and quantity of the combustion air is still less this flows through only where it is used. This is at the outlet of the fuel nozzle 2 and in the lower part of the venturi tube 3 through the slots 4',. As the narrowest part of the venturi tube 3 allows through only about half of the combustion air compared with that required for full load there the air speed in the partial load area is already very great which effects a satisfactory preparation and mixing with the fuel.

At the same time combustion air flows through the slots or bores 4' and takes along fuel drops accumulating in this area, prepares the drops into the finest mist which mix with the air and are fed well prepared to the engine.

The same is effected by the exhaust gas lead back. The entry of the exhaust gases through the frontmost slot or bore 4' is therefore most advantageous because exactly in this area most fuel drops accumulate by falling out and by gas oscillations in the suction pipe. Therefore there a thermal and dynamic fuel preparation is of special importance. The outlet at this place through a larger slot is also effected symmetrically at both sides from the centre in that the exhaust comes in the same quantity into the individual cylinders which is necessary so that more exhaust gas can be supplied before with such cylinder ignition extinguishers result or poor combustion, thereby a greater deduction of the poisonous Nox formation is achieved.

With the supply of combustion air first in the upper partial load area through the slots or bores 4 is the advantage of a two stage mixture formation without two venturi tubes being necessary. Thus this register mixture formation is very compact simple and cheap.

The mixing apparatus is fixed with the mixture outlet side 23 to the suction pipe of an internal combustion engine most advantageously with an inclination downwards in the direction of flow.

Claims

1. An apparatus for the production of a fuel-air mixture for internal combustion engines formed by a fuel nozzle with low pressure injection which injects the fuel jet in the region of an air nozzle, for example, a Lavall nozzle, into which the combustion air is fed and the fuel-air mixture is finely atomized, characterised in that a controlled mixture forming apparatus is produced in that in the diverging part of a venturi tube (3) at least two groups (34, 34') of slots or bores (4, 4') spatially separated from one another are arranged and that from the first group (34') combustion air is supplied to the lower over the middle partial load area to the full load area and by the second group (34) combustion air is supplied to the middle partial load area to the full load area of the internal combustion engine.

2. An apparatus according to claim 1, characterised in that the combustion air for the middle partial load area to the full load area is divided into two currents (28, 29) the first current (23) of which arrives upstream of the mouth.of the fuel nozzle (2) and of the venturi tube (3) in the mixing chamber (1) and the second current (29) in the diverging part of the venturi tube (3) via the slots or bores (4').

3. An apparatus according to claims 1 or2, characterised in that in the diverging part of the venturi tube (3) groups (34 or 34') of slots or bore (4, 4') are disposed parallel to and spaced apart from one another the first group (34') of which at the outer periphery of the venturi tube (3) leads into a first air chamber (5) which is in flow connection with a first air inlet (7) and the second group (34) at the outer periphery of the venturi tube (3) leads into a second air chamber (6) which is in flow connection with a second air inlet (9).

4. An apparatus according to claim 1 or 2, characterised in that the first group (34') of slots or bores (4') associated with the lower or middle partial load area to the full load area is disposed at the lower part of the venturi tube (3) and the second group (34) of slots or bores (4) associated with the upper to the full load area is disposed at the upper part of the venturi tube (3).

5. An apparatus according to any one of the claims 1-4, characterised in that the length of the first group (34') of slots or bores (4') amounts to about 3040% and the length of the second group (34) of slots or bores (4) amounts to about 6070% of the periphery of the venturi tube (3) at the position of the slots or bores (4, 4') concerned.

6. An apparatus according to any one of the claims 1-5, characterised in that the length of the axis of the slots or bores (4, 4') are arranged at a small angle to the longitudinal middle axis of the venturi tube (3).

7. An apparatus according to any one of the claims 1-6, characterised in that the narrowest cross section of the venturi tube (3) is so small that only about 50% or less of the combustion air in respect of the requirement at full load can flow there through.

8. An apparatus according to claim 1, characterised in that an exhaust gas return through a channel (1 6) controlled by means of the throttle valve (17), rotary slide valves or other means is disposed at the lower part of the mixing chamber (1).

9. An apparatus according to claims 1 and 2, characterised in that an opening (18) connects the first air chamber (5) to the channel (16).

10. An apparatus according to claims, 1, 8 and 9, characterised in that the opening (18) is smaller than the cross section in the channel (16) with the throttle valve (1 7) fully opened.

11. An apparatus according to claims, 1, 8 and 9, characterised in that the opening (18) in the frontmost part of the air chamber (5) leads into the area of the front slots or bores (4').

12. An apparatus according to claim 1, characterised in that the lower slots or bores (4') are disposed symmetrically on both sides from the centre.

13. An apparatus according to claim 1, characterised in that by means of known iever control the throttle valves (8) and (16) open first and only after the middle partial load area is the throttle valve (10) opened.

14. An apparatus according to claim 1, characterised in that the mixing apparatus is connected to the mixture outlet side (23) on the suction pipe of an internal combustion engine.

15. An apparatus according to claims 1 and 14, characterised in that the mixing apparatus is so arranged that it is inclined downwards in the direction of flow.

16. An apparatus according to claim 1, characterised in that the lower slots or bores (4') are separated from the upper slots or bores (4) by a wall (20).

1 7. An apparatus for the production of a fuel air mixture for an internal combustion engine substantially as described with reference to the accompanying drawings.