GB2085072A - Atomising I.C. engine intake mixture - Google Patents

Abstract

A plurality of annular members 27, 38 and 41 are spaced relative one to another and adapted to be located in a manifold of the engine so that the surfaces of the members are located in the fastest moving portion of the mixture stream, the arrangement being such that the surfaces extend substantially parallel to flow lines of the mixture stream moving adjacent thereto so that movement of the stream relative to said surfaces causes components of the stream to move uniformally without substantially increasing the pressure drop in the passageway. The annular members (54, 55, 56), Figs. 10 and 11 (not shown), may comprise cylindrical walls with outwardly flaring downstream end portions and be spring mounted to vibrate in response to the mixture flow. <IMAGE>

Description

SPECIFICATION Internal combustion engines This invention relates to internal combustion engines and particularly to a device for forming droplets from a stream of fuel/air mixture flowing in an inlet passageway of such an engine to effect reduction of liquid fuel consumption therein.

A study of internal combustion engines involving the application of theoretical and experimental work in two phase flows made over a period of time and tested on a number of different processes as revealed that the flow of fuel droplets in an airstream passing along an inlet manifold to cylinders of an engine interchange continuously between internal surfaces of the manifold and the airstream. The characteristics of the fuel droplet population thereby change as the flow passes longitudinally of the manifold, the droplets increasingly becoming representative of those produced by entrainment from the manifold walls rather than those produced by carburettor action.The study has indicated that the mean droplet size decreases with the square of velocity over a liquid film surface and that, for optimum combustion, the droplets in a cylinder should be below a size set by the time available in the expansion stroke of that particular cylinder. Thus large droplets are obtained by relatively slow moving airstreams, such as those moving adjacent the inner surfaces of the manifold, and will not result in optimum combustion.

If, therefore, additional droplet making surfaces are located in the fastest moving part of the airstream, in contrast to the slower moving parts adjacent inner surfaces of the manifold, the number of droplets below the predetermined size for optimum combustion will be increased.

However, in general, placing surfaces in flow streams increases pressure drop thereby causing decrease of power output of the engine.

It is desirable, therefore, to provide droplet making surfaces in the fastest moving part of the airstream without increasing the pressure drop in the manifold by any significant amount.

It is also, desirable to provide a device for producing liquid fuel consumption in an internal combustion engine which is inexpensive to manufacture.

According to the present invention, there is provided a device for forming droplets from a stream of fuel/air mixture flowing in an inlet passageway of an internal combustion engine comprising: a plurality of surfaces for location in said stream, and means for locating said surfaces in the fastest moving portion of said stream, the arrangement being such that said surfaces extend substantially parallel to flow lines of said stream moving adjacent thereto so that movement of said stream relative to said surfaces causes components of said stream to move uniformally without substantially increasing pressure drop in the passageway.

In this manner, as the flow lines sweep along the surfaces, a small amount of kinetic energy of the stream is lost in forming a thin liquid film on the surfaces thereby creating additional droplets in the fastest moving portion of the stream.

However, there is no significant increase in pressure drop in the passageway because form drag is reduced to a minimum due to the selected disposition of the surfaces relative to the direction of flow of the stream.

The said surfaces may be disposed in spaced relation relative one to another so that each said surface is located in a component of said stream not previously encountered by another said surface during movement of said stream.

The said surfaces may be disposed relative one to another at varying angles to a longitudinal axis of the device.

The said angles may decrease progressively in a downward direction of said device.

The said surfaces may comprise a plurality of annular members.

The dimension of each said surface in the direction of said stream preferably is not in excess of 4 mm.

Each said surface may extend in the direction of said stream and may comprise in cross section a first component and a second component extending at an angle to the first component, the second component being gradually contiguous with the first component so as to inhibit creation of re-entrant stream.

The space defined by a second component of each said surface and a second component of an adjacent surface may decrease in the direction of flow of said stream.

The said surfaces may be carried on a carrier and the carrier may be supported resiliently by a support member.

- A trailing edge of each said surface may be serrated.

Following is a description, by way of example only and with reference to the accompanying drawings, of one method of carrying the invention into effect.

In the drawings: FIGURE 1 is a diagrammatic representation of a manifold of an internal combustion engine showing direction of flow of gas streams therein during operation of the engine, FIGURE 2 is a diagrammatic cross section of a device in accordance with the present invention, FIGURE 3 is a plan view in the direction Ill-Ill of Figure 2, FIGURE 4 is a perspective view of one embodiment of a device in accordance with the present invention, FIGURE 5 is a plan view from above of the embodiment shown in Figure 4, FIGURE 6 is an elevation of the device shown in Figures 4 and 5, FIGURE 7 is a plan view from below of the device shown in Figures 4, 5 and 6, FIGURE 8 is a graphical representation of a comparison of tests carried out on a motor vehicle, the tests indicating fuel consumption of the engine of the vehicle driven so as to make regular stops, the comparison being between the engine when and when not provided with the device, FIGURE 9 is a graphical representation similar to Figure 8 indicating relative performances of the engine when the vehicle is driven at a steady speed, FIGURE 10 is a plan view from above of another embodiment of a device in accordance with the present invention, and FIGURE 11 is a cross section on the line Xl-1 1 of Figure 10.

Referring now to Figures 1 to 3 of the accompanying drawings, there is shown in Figure 1 a portion of a manifold 10 of an internal combustion engine, the manifold 10 comprising a first portion 11 and second portions 12 and 13 extending at right angles to the first portion 11 and in opposite directions one from another, the second portions 12, 13 being in communication one with another and with the first portion 11. The first portion 11 extends downstream from a carburetter (not shown), the second portion 1 2 provides an inlet to a cylinder, for convenience referred to as a 'right-hand cylinder', of the engine and the second portion 1 3 provides an inlet to another cylinder, for convenience referred to as a 'left-hand cylinder', of the engine.The arrowed chain lines shown in Figure 1 are mean flow lines of a gas stream passing from the carburetter through the first portion 11 and the second portion 12 to the right-hand cylinder when the piston of the right-hand cylinder is effecting an induction stroke. The references A and B indicate expending turbulent regions and the reference C indicates a stagnation area.

Referring now to Figures 2 and 3 of the drawings, there is shown a diagrammatic representation of a device for location at the junction of the first portion 11 and the second portions 12 and 1 3 comprising annular frustoconicular surfaces 14, 1 5 and 16 connected together by means of vanes, one of which is shown at 17 in Figure 2. The frusto-conicular surfaces 14, 1 5 and 1 6 are arranged so that the progressive increase in diameter of each of the surfaces extends in a downward direction of the first portion 11 of the manifold 10.The location of the surfaces 14, 1 5 and 1 6 relative to the vanes 1 7 and relative one to another and the angles of the surfaces relative to a longitudinal axis of the first portion 11 of the manifold 10 are arranged to conform with the direction of flow of fuel/air mixture flowing through the manifold 10 in accordance with the chain lines indicated in Figure 1, assuming that the flow is similar if the left-hand cylinder, or any other cylinders, are effecting an induction stroke.The inner edge portion of the vanes are located to be approximately parallel with an outer stream of the main flow of the fuel/air mixture, as indicated by the line a, b, c, d in Figure 2 representing the outer stream of the main flow of the mixture when the right-hand cylinder is effecting an induction stroke.

Referring now to Figures 4 to 7 of the accompanying drawings, there is shown an embodiment of a device 1 8 incorporating the features illustrated in Figures 2 and 3. The device thus comprises a plate 1 9 having three apertures 20, 21 and 22 the centres of which are located on a common axis of the plate 1 9, the central aperture 21 being larger than the apertures 20 and 22 and the apertures 20 and 22 being of equai diameter. The central aperture is contiguous with a downwardly inwardly tapered flange 23 having an inner surface 24 and an outer surface 25. Secured to the outer surface 25 of the flange 23 are four downwardly extending spacer members 26 located symmetrically about the axis extending through the centres of the apertures 20, 21 and 22.The lower end portions of the spacers 26 are secured to an outer circumferential surface 28 of an upperfrusto-conicular annular member 27 having an inner circumferential surface 29. The inner surface 29 of the upper annular member 27 has secured thereto four downwardly extending vanes 30, 31, 32 and 33 extending radially outwardly from a central longitudinal axis extending through a centre of the aperture 21 at right angles to the plane of the plate 19 and the vanes being located symmetrically relative to the longitudinal axis passing through the centres of the apertures 20, 21 and 22. Each of the vanes 30 to 33 has an outer longitudinal edge 34, an inner longitudinal edge 35 and opposite side faces 36 and 37.A lower end portion of each of the vanes 30 to 33 is secured to an outer circumferential surface 39 of a lower frusto-conicular annular member 38 having an inner circumferential surface 40. The inner longitudinal edges 35 of the vanes 30 to 33 are provided with notches (not shown) in which are received an intermediate frusto-conicular annular member 41 having an outer circumferential surface 42 and inner circumferential surface 43.

The device 1 8 is located on a seat (not shown) of a manifold (not shown) for receiving a carburetter (not shown), the seat having upstanding pins (not shown) which locate the apertures 20, 22 of the device 1 8 whereby the device engages the seat with the annular members 27, 38 and 41 being located on a central longitudinal axis of a portion of the manifold extending from the carburetter and depending into a chamber (not shown) where branches of the manifold communicating with cylinders of an engine communicate one with another.

In use, the inner surface 24 of the flange 23 guides the flow of fuel/air mixture passing into the manifold from the carburetter downwardly of the device 1 8 to form a central longitudinal core extending through the device 1 8. The fuel/air mixture is drawn over the surfaces of the annular members 27, 38 and 41 but form drag is reduced to a minimum because the spacing of the annular members 27, 38 and 41 relative one to another and the angle of the inner and-outer surfaces of the annular members relative to a central longitudinal axis extending through the annular members is arranged in accordance with the mean flow lines, as shown in Figure 1.The passage of the fuel/air mixture relative to the inner and outer surfaces of the annular members 27, 38 and 41 and relative to the side faces 36, 37 of the vanes 30 to 33 causes a thin liquid film of the fuel to be deposited on the surfaces. The velocity of the mixture causes the film to be pulled off the surfaces as a sheet which finally breaks up into droplets. Since the surfaces are located in the fastest moving portion of the stream, the diameters of the droplets are sufficiently small to ensure optimum combustion in cylinders of the engine.In Figure 8 of the accompanying drawings there is shown two graphs showing representations of measurements made of the fuel consumption in litres per 100 km of an engine of a motor vehicle plotted against the number of stops per mile made by the vehicle the graphs being represented at X and Y, graph X representing performance of the engine after having been tuned and provided with the device shown in Figures 4 to 7 of the accompanying drawings and graph Y representing performance of the engine when untuned and when not provided with the device.

In Figure 9 similar graphs are shown at V and W, the graphs representing measured fuel consumption of the engine of the vehicle when driven at steady speed, graph V being performance of the engine when provided with the device shown in Figures 4 to 7 of the accompanying drawings and graph W being performance of the engine when not provided with the device.

It will be appreciated that the graphs represented in Figures 8 and 9 of the drawings indicate that 12-1 5% saving in city traffic and 9% at steady speeds from 50-1 20 kph result when a tuned engine of a vehicle is provided with a device as shown Figures 4 to 7 of the drawings.

The components of the device may be fabricated from sheet metal and welded together to form the device. The stamping and welding operations do not require a high degree of skill and, since the materials are relatively inexpensive, the device embodies the desirable characteristics of ease and in expensiveness of fabrication.

Furthermore, since the device in accordance with the present invention, when provided in an operating internal combustion engine, reduces means and maximum droplet sizes at or just before the division of the manifolds, the device will beneficially effect metering over and above its effect on combustion efficiency. Additionally, the spray making surfaces enhance metering by allowing droplets to deposit in one direction and be re-entrained in another direction. These characteristics are important in satisfying the fuel/air metering, or controlled distribution, requirement that (1) the flow is continually reversing direction in the manifold; (2) the droplets direction of flow will always lag behind the air flow direction changes and (3) the smaller the droplets, the more closely they follow the air flow.

It will be appreciated that the surfaces of the device 18 located in the stream of fuel/air mixture will contribute to beneficial droplet formation for two reasons. In the first instance the surfaces are located in the fastest moving part of the airstream and in the second instance, as the stream passes over the surfaces, a thin liquid film is deposited on the surfaces which film is pulled off as a sheet and subsequently breaks up into droplets of small diameter. The minimum length of the surfaces in the direction of flow for forming droplets of the required maximum size by entrainment from the film is of the order of 4 mm and such minimum surface length in the flow direction maximizes the available surface edge so that both droplet forming modes, i.e. fast air stream and thin liquid film, are optimised together.

Referring now to Figures 10 and 11 of the accompanying drawings, there is shown a modified device 45 which is similar to device 18 except that the device 45 comprises a first component 46 and second component 47. The first component 46 comprises a plate 48, similar to the plate 1 9 of the device 18, having a central aperture 49. Depending from the plate 48 at 0%, 90%, 180% and 360% locations circumferentially of the central aperture 49 are brackets 50, 51, 52 and 53. The second component 47 comprises three cylindrical members 54, 55 and 56 each having outward downwardly swaged lower end portions.The diameter of the cylindrical member 54 is larger than the diameter of the cylindrical member 55 and the diameter of the cylindrical member 55 is larger than the diameter of the cylindrical member 56. The surfaces of the swaged portions of each of the cylindrical members 54, 55 and 56 contiguous with the circumferential surfaces of the remaining portions of the cylindrical members extend gradually over a transition radius indicated at R. The angle of the swaged portion of each cylindrical member 54, 55 and 56 relative to the unswaged portion thereof increases progressively in relation to the diameters of the cylindrical members 54, 55 and 56.The cylindrical members 54, 55 and 56 are connected in spaced relation by means of four ribs 57, each rib being located equi-distant an adjacent rib, so that the central longitudinal axis of the cylindrical members 54, 55 and 56 are coaxial with a longitudinal axis extending through a centre of the aperture 49 and parallel to the brackets 50 to 53.

The cylindrical member 54 has four upwardly extending projections 58, 59, 60 and 61 each located equi-distant from an adjacent one of the projections 58 to 61. Each projection 58 to 61 is provided with a contiguous radially outwardly extending flange 62. A pair of flanges 62 are each received in a corresponding slot (not shown) of a corresponding one of the brackets 50 to 53 and the remaining pair of flanges 62 are each adapted to be resiliently connected to a corresponding one of the remaining brackets 50 to 53 by resilient means 63 such as a guide pin and coaxial helical spring.

The device 45 is located in a manifold of an internal combustion engine in similar manner to the device 1 8 and, during operation of the engine, fuel/air mixture is drawn through the manifold and passes over the surfaces of the cylindrical members 54, 55 and 56. The gradual change of angle from the main portion of each of the cylindrical members 54, 55 and 56 to the outwardly downwardly swaged parts thereof causes gradual change of the angle of direction of flow of the mixture and modifies the stream lines thereof thereby causing deflection of the flow towards respective manifold ports of the engine.

Droplets directly colliding with the swaged parts of the cylindrical members 54, 55 and 56 will form a thin layer of liquid on those parts and the gradual transition from the main portion of each of the cylindrical members 54, 55 and 56 to the outwardly downwardly swaged parts thereof prevents creation of a re-entrant jet and guides the flow towards the periphery, in the direction of flow, of the swaged parts. The circumferential surfaces of the main portion of each of the cylindrical members 54, 55 and 56 acts as a prefilm formation surface of big droplets and finer droplets are formed therefrom as the fuel/air mixture flows along the surfaces of the swaged parts.This occurs because the volume swept out by the mixture in passing between a swaged part of one of the cylindrical members 54, 55 and 56 and a swaged part of an adjacent one of the cylindrical members decreases in the direction of movement of the mixture, due to the varying angles of the swaged parts, resulting in an increase in the velocity of the air in the mixture being proportionally increased relative to the fuel film as the mixture passes between adjacent swaged parts. This 'air blast' effect assists the process of formation of finer drops at the outer edges of the swaged parts.

The outer edges of each of the swaged parts may be serrated so as to increase the effective circumferential length of the outer edge of each swaged part.

The spring loading provided by the resilient means 63 provides the capacity for the second component 47 to vibrate relative to the first component 46 under the effect of a pulsating air flow due to periodic opening and closing of the intake valves of the engine. However, the effect of the resilient means 63 is to constrain vibrations of the second component 47 relative to the first component 46 and, in consequence, displacement of the second component 47 relative to the first component 46 in the direction of the central longitudinal axis extending through the cylindrical members 54, 55 and 56.

It will be appreciated that, in providing for vibration of the second component 47 relative to the first component 46, the device 45 is provided with the capacity to absorb stresses which the device is subjected to during operation of the engine. However, the capacity of the device 45 to vibrate is such that, during vibration of the second component 47 relative to the first component 46, there is a resultant shattering effect on the impacting and depositing droplets which results in the process of fine spray formation being enhanced.

Claims (10)

1. A device for forming droplets from a stream of fuel/air mixture flowing in an inlet passageway of an internal combustion engine comprising: a plurality of surfaces for location in said stream, and means for locating said surfaces in the fastest moving portion of said stream, the arrangement being such that said surfaces extend substantially parallel to flow lines of said stream moving adjacent thereto so that movement of said stream relative to said surfaces causes components of said stream to move uniformly without substantially increasing pressure drop in the passageway.

2. A device as claimed in claim 1 wherein said surfaces are disposed in spaced relation one to another so that each said surface is located in a component of said stream not previously encountered by another said surface during movement of said stream.

3. A device as claimed in claim 2 wherein the said surfaces are disposed relative one to another at varying angles to a longitudinal axis of the device.

4. A device as claimed in claim 3 wherein the said angles decrease progressively in a downward direction of said device.

5. A device as claimed in any one of the preceding claims wherein the said surfaces comprise a plurality of annular members.

6. A device as claimed in any one of the preceding claims wherein the dimension of each said surface in the direction of said stream is not in excess of 4 mm.

7. A device as claimed in any one of the preceding claims wherein each said surface extends in the direction of said stream and comprises in cross section a first component and a second component extending at an angle to the first component, the second component being gradually contiguous with the first component so as to inhibit creation of re-entrant stream.

8. A device as claimed in claim 8 wherein a space defined by a second component of each said surface and a second component of an adjacent surface decreases in the direction of flow of said stream.

9. A device as claimed in claim 8 or claim 9 wherein the said surfaces are carried on a carrier and the carrier is supported resiliently by a support member.

10. A device as claimed in any one of the preceding claims wherein a trailing edge of each said surface is serrated.

1 1. A device for forming droplets from a stream of fuel/air mixture flowing in an inlet passageway of an internal combustion engine substantially as hereinbefore described and as illustrated in the accompanying drawings.