GB2060765A

GB2060765A - Adding fluids in fuel-air mixture intake passages

Info

Publication number: GB2060765A
Application number: GB7929664A
Authority: GB
Original assignee: Chester R A
Current assignee: Chester R A
Priority date: 1979-08-24
Filing date: 1979-08-24
Publication date: 1981-05-07

Abstract

An annular jet of air (or vapour or gas) is drawn in through an annular slit 21 from a gallery 14 in a device clamped between the mating flanges 2 and 5 of a carburettor 1 and inlet manifold 6 of an internal combustion engine. The gallery is supplied through a connection 19. The device is formed by two plate like members 8, 9 and defines a construction to draw in the jet which reatomises fuel which collects on the walls of the induction passage and also helps to create a mixing vortex. <IMAGE>

Description

SPECIFICATION Improvements in induction systems for fuel-air mixtures This invention relates to improvements in induction systems for fuel-air mixtures.

In accordance with the present invention, an induction system through which a fuel-air mixture passes in use, includes a narrow, elongaged inlet for introducing a jet of vapour or gas through the inner wall surface of the passage. Preferably, the passage has a constriction adjacent the inlet to reduce the static pressure adjacent the inlet and thereby draw in the vapour or gas.

Preferably, the inlet is elongated in a plane transverse to the flow direction in the passage.

Where the induction system includes the wellknown butterfly type of throttle valve, the passage immediately downstream of the throttle valve may include two such inlets on opposite sides of the passage adjacent the two regions of maximum flow which occur when the throttle is nearly closed. In most cases however it is preferred that the inlet extends around the full circumference of the passage in a plane transverse to the flow directions through the passage.

In practice, the inlet and constriction may be formed in a device which is inserted between the mating flanges of a carburettor and innduction manifold of an internal combustion engine. Such a device then has a central aperture through which.

the fuel-air mixture passes in use, a narrow slit formed in the wall of the central aperture and means for supplying vapour or gas (such as air) through the slit. These supplying means may comprise a gallery formed in the device and surrounding the slit, the gallery being connected to a source of vapour or gas, such as the ambient atmosphere, preferably through a filter. Where the internal combustion engine has a crank case breather connection to the manifold, it is particularly convenient to use this connection to supply the gallery.

Preferably, the surfaces on each side of the slit are convexly curved as seen in axial section.

Advantageously, the most constricted portion of the constriction is downstream of the slit.

The invention will now be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is an axial sectional view through the lower part of a carburettor and the upper part of an inlet manifold of an internal combustion engine, and Figures 2 and 3 are views of the mating faces of the two halves of the device incorporated between the carburettor and manifold in Figure 1.

Figure 1 shows the lower portion 1 and mounting flange 2 of a conventional downdraught carburettor having a butterfly-type throttle valve disc 3 mounted on a transverse throttle spindle 4. The carburettor is mounted on the top flange 5 of the inlet manifold 6 of the internal combustion engine by means of studs or bolts 7.

The normal packing member which is conventionally inserted between the carburettor and manifold is replaced by the device formed by upper and lower plate-like portions 8 and 9 formed as die-castings in a zinc-based alloy. The upper portion 8 has a central aperture 10 of internal diameter approximately equal to the internal diameter of the manifold portion 6. The lower portion 9 has a central aperture 11 of internal diameter smaller than the aperture 10 so as to define a constriction. Each of the mating faces of the upper and lower portions 8 and 9 is formed with an annular groove 12, 13 of semicircular section so as to define a toroidal gallery 14 (Fig.1) when the two portions are assembled together.Further, each portion 8, 9 has a spigot extension 15, 16, each of which is formed with a straight groove 17, 1 8 leading into the grooves 12 and 1 3 so as to provide an inlet connection 1 9 for supplying air, gas or vapour into the gallery 14.

The mating surfaces of the upper and lower portions 8 and 9 are slightly spaced from each other in the regions immediately on the inside of the grooves 12 and 1 3 so that in the assembled state, a narrow slit 21 is left leading from the gallery 14 into the central apertures 10, 1 This slit is typically 0.07 to 0.15 mm wide (measured in the axial direction of the inlet manifold 6) and as a result its total cross-sectional flow area is approximately equal to that of a typical breathertype connection between the crank case and inlet manifold.

As can be seen in Fig.1 , the upper edge of each aperture 10, 11 is radiused at 22 and 23.

In operation, air (or gas or vapour) is drawn in through the narrow slit 21 from the gallery 14 and forms a radially inwardly directed jet which extends around the whole circumference of the inlet passage and impinges on the mixture passing through it to create a vortex action to help mixing of the fuel and air components of the mixture.

Further, any fuel which has settled out on the internal wall surface 24 of the carburettor will tend to be re-atomised by the jet as the fuel attempts to cross the gap 21. Settling out of "condensation" of fuel is particularly likely to occur at small throttle openings adjacent the two narrow crescent shaped gaps 25 and 26 through which all the mixture passes at small throttle openings. As a result, the device according to the invention has yielded in one test fuel economies of more than 20% while greatly improving smoothness and "tractability" at low engine speeds and throttle openings.

In modified embodiments of the invention, the gap 21 is adjusted and/or created by placing appropriate shims around the outside of the grooves 12 and 13, or around the clearance holes 27 for the boolts or studs 7.

1. An induction system through which a fuel-air mixture passes in use, wherein the system includes a narrow, elongated inlet for introducing a jet of vapour or gas through the inner wall

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in induction systems for fuel-air mixtures This invention relates to improvements in induction systems for fuel-air mixtures. In accordance with the present invention, an induction system through which a fuel-air mixture passes in use, includes a narrow, elongaged inlet for introducing a jet of vapour or gas through the inner wall surface of the passage. Preferably, the passage has a constriction adjacent the inlet to reduce the static pressure adjacent the inlet and thereby draw in the vapour or gas. Preferably, the inlet is elongated in a plane transverse to the flow direction in the passage. Where the induction system includes the wellknown butterfly type of throttle valve, the passage immediately downstream of the throttle valve may include two such inlets on opposite sides of the passage adjacent the two regions of maximum flow which occur when the throttle is nearly closed. In most cases however it is preferred that the inlet extends around the full circumference of the passage in a plane transverse to the flow directions through the passage. In practice, the inlet and constriction may be formed in a device which is inserted between the mating flanges of a carburettor and innduction manifold of an internal combustion engine. Such a device then has a central aperture through which. the fuel-air mixture passes in use, a narrow slit formed in the wall of the central aperture and means for supplying vapour or gas (such as air) through the slit. These supplying means may comprise a gallery formed in the device and surrounding the slit, the gallery being connected to a source of vapour or gas, such as the ambient atmosphere, preferably through a filter. Where the internal combustion engine has a crank case breather connection to the manifold, it is particularly convenient to use this connection to supply the gallery. Preferably, the surfaces on each side of the slit are convexly curved as seen in axial section. Advantageously, the most constricted portion of the constriction is downstream of the slit. The invention will now be further described by way of example with reference to the accompanying drawings, in which: Figure 1 is an axial sectional view through the lower part of a carburettor and the upper part of an inlet manifold of an internal combustion engine, and Figures 2 and 3 are views of the mating faces of the two halves of the device incorporated between the carburettor and manifold in Figure 1. Figure 1 shows the lower portion 1 and mounting flange 2 of a conventional downdraught carburettor having a butterfly-type throttle valve disc 3 mounted on a transverse throttle spindle 4. The carburettor is mounted on the top flange 5 of the inlet manifold 6 of the internal combustion engine by means of studs or bolts 7. The normal packing member which is conventionally inserted between the carburettor and manifold is replaced by the device formed by upper and lower plate-like portions 8 and 9 formed as die-castings in a zinc-based alloy. The upper portion 8 has a central aperture 10 of internal diameter approximately equal to the internal diameter of the manifold portion 6. The lower portion 9 has a central aperture 11 of internal diameter smaller than the aperture 10 so as to define a constriction. Each of the mating faces of the upper and lower portions 8 and 9 is formed with an annular groove 12, 13 of semicircular section so as to define a toroidal gallery 14 (Fig.1) when the two portions are assembled together.Further, each portion 8, 9 has a spigot extension 15, 16, each of which is formed with a straight groove 17, 1 8 leading into the grooves 12 and 1 3 so as to provide an inlet connection 1 9 for supplying air, gas or vapour into the gallery 14. The mating surfaces of the upper and lower portions 8 and 9 are slightly spaced from each other in the regions immediately on the inside of the grooves 12 and 1 3 so that in the assembled state, a narrow slit 21 is left leading from the gallery 14 into the central apertures 10, 1 This slit is typically 0.07 to 0.15 mm wide (measured in the axial direction of the inlet manifold 6) and as a result its total cross-sectional flow area is approximately equal to that of a typical breathertype connection between the crank case and inlet manifold. As can be seen in Fig.1 , the upper edge of each aperture 10, 11 is radiused at 22 and 23. In operation, air (or gas or vapour) is drawn in through the narrow slit 21 from the gallery 14 and forms a radially inwardly directed jet which extends around the whole circumference of the inlet passage and impinges on the mixture passing through it to create a vortex action to help mixing of the fuel and air components of the mixture. Further, any fuel which has settled out on the internal wall surface 24 of the carburettor will tend to be re-atomised by the jet as the fuel attempts to cross the gap 21. Settling out of "condensation" of fuel is particularly likely to occur at small throttle openings adjacent the two narrow crescent shaped gaps 25 and 26 through which all the mixture passes at small throttle openings. As a result, the device according to the invention has yielded in one test fuel economies of more than 20% while greatly improving smoothness and "tractability" at low engine speeds and throttle openings. In modified embodiments of the invention, the gap 21 is adjusted and/or created by placing appropriate shims around the outside of the grooves 12 and 13, or around the clearance holes 27 for the boolts or studs 7. CLAIMS

1. An induction system through which a fuel-air mixture passes in use, wherein the system includes a narrow, elongated inlet for introducing a jet of vapour or gas through the inner wall surface of the passage.

2. An induction system according to claim 1 wherein the passage has a constriction adjacent the inlet to reduce the static pressure adjacent the inlet and thereby draw in the vapour or gas.

3. An induction system according to claim 1 or 2 wherein the inlet is elongated in a plane transverse to the flow direction in the passage.

4. An induction system according to any of claims 1 to 3 and a butterfly throttle valve, the passage immediately downstream of the throttle valve including two said inlets on opposite sides of the passage adjacent the two regions of maximum flow which occur when the throttle is neariy closed.

5. An induction system according to any of claims 1 to 3 wherein the inlet extends around the full circumference of the passage in a plane transverse to the flow directions through the passage.

6. An induction system according to any of the preceding claims, the inlet and constriction are formed in 3 device which is inserted between the mating flanges or a carburettor and induction manifold of an internal combustion engine.

7. An induction system according to claim 6 and including a gallery formed in the device and surrounding a slit forming the said inlet, the gallery being connected to a source of vapour or gas, such as the ambient atmosphere, preferably through a filter.

8. An induction system according to claim 7 for an internal combustion enginer having a crank case breather connection to the manifold, wherein the breather connection is used to supply the gallery.

9. An induction system according to any of the preceding claims wherein the surfaces on each side of the inlet are convexly curved as seen in axial section.

1 0. An induction system according to any of the preceding claims wherein the most constricted portion of the constriction is immediately downstream of the inlet.

1 A device for insertion in an induction system for fuel-air mixture in an internal combustion engine, comprising a body having a passageway therethrough for fuel-air mixture, at least part of the passage being of reduced crosssectional area, a slit extending circumferentially around the wall of the passage, and a gallery for supplying vapour gas or air to the slit.

12. A device according to claim 10, wherein the body is formed in two portions with a division plane coinciding with the slit.

13. A device substantially as hereinbefore described with reference to the accompanying drawings.