GB1559847A

GB1559847A - Gas mixing devices

Info

Publication number: GB1559847A
Application number: GB49070/75A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-10-01
Filing date: 1976-10-01
Publication date: 1980-01-30

Description

(54) IMPROVEMENTS IN AND RELATING TO GAS MIXING DEVICES (71) We, FRANCIS LAMBERT ROBSON, a British subject of 3/114 Coates Avenue, Ovakei, Auckland, New Zealand, formerly of 131 Koutu Road, Rotorua, New Zealand, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to gas mixing devices. The invention is particularly, but not exclusively, applicable to such a device for efficiently mixing a fuel air mixture for an internal combustion engine.

It has been a disadvantage that a carburettor providing a fuel/air mixture for an internal combustion engine has tended to proportion rather than actually produce a homogeneous mixture of the fuel and air prior to its flowing to the combustion chamber of the engine through an inlet manifold. This substantial lack of homogeneous mixing of the fuel/air has tended to cause a considerable amount of unburnt fuel gases to appear in the exhaust emissions of the engine and also causes a buildup of carbon deposits in the combustion chamber and exhaust system of the engine.

Further, at the present time environmental controls relating to exhaust emissions are becoming more stringent and this is creating difficulties in designing internal combustion engines which meet these environmental controls.

An object of the invention is to enable a mixing device to be provided which provides improved fuel/air mixing.

The invention provides a gas mixing device for mixing gases flowing within a gas flow pipe comprising an apertured screen adapted to be mounted within such a pipe and comprising at least one step defined by a first, radially outer annular surface arranged to extend substantially orthogonally to the interior surface of the pipe when the device is mounted therein and a second, radially inner annular surface extending substantially orthogonally from the first surface, one or more apertures being provided in each of said surfaces such that in use gases flowing within the pipe and through said screen become mixed.

In order that the invention may be well understood, some embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 schematically shows the velocity components of gases flowing within a pipe; Figure 2 schematically shows the flow of a gas mixture through one of the apertures of a gas mixing device; Figure 3 schematically shows a gas mixing device; and Figure 4 schematically shows another gas mixing device.

The illustrated mixing devices are described with particular reference to the mixing of a fuel/air mixture for an internal combustion engine such as for example a reciprocating 4-stroke internal combustion engine operating on a petrol/air mixture.

It should be understood that the same devices are applicable wherever two or more gases are required to be efficiently mixed with one another.

Referring now to Figure 1, velocity of a gas flowing through a gas flow pipe 1 is schematically shown by the profile indicated by 2. It is clear that the velocity of the gas at the interior surface la of the pipe 1 is much lower than the velocity along the central axis of the pipe 1, being in accordance with gas flow phenomenon at high Reynolds numbers in the 60,000 to 100,000 range, and being due to the viscous drag of a boundary layer of gas at the interior surface la.

If the gas flowing through the pipe I of Figure 1 is a relatively loose mixture of gases and vapours of widely varying densities, then it can be shown that there is a tendency for the heavier gases or vapours to migrate to the boundary layer adjacent the interior surface la of the pipe 1 and when this occurs, it magnifies the tendency for the velocities to be much lower as the distance from the central axis of the pipe 1 increases.

The variation of the velocity of the gas across the pipe is utilized by the gas mixing device to create actual mixing currents.

Referring now to Figure 2, an aperture 4 of a mixing device is shown with the fuel/air mixture B passing therethrough.

On the downstream side of the gas flow further lateral currents of gas are shown entering the flow B and the velocity of all the gases are substantially constant. It should be noted that adjacent the downstream side of the wall 3 of the gas mixing device minute vortices C are created, which alter the velocity distribution within the pipe 1. Another factor which alter the velocity distribution within the pipe 1 is the action of localized jets passing through the apertures 4 parallel with the main flow B.

It has been discovered that minute vortices C have a short finite lifetime before decay and so, having expanded unwanted velocity components, they die out very quickly and do not cause any major disturbances as would be the case with larger vortices which would have relatively long lifetimes before decay. The diffusion of the gases from the apertures 4 of the device can be essentially completed in a distance of 10 to 20 aperture diameters beyond the surface 3 which distance, for example, may be not more than 10 millimetres.

Now referring to Figure 3, a pipe 1 is shown within which a fuel/air mixture D is caused to flow for example from the carburettor to the combustion chamber of an engine through an inlet manifold. The pipe can be provided within the inlet manifold of the engine or may be provided between the carburettor and the inlet manifold and be formed with suitable flanges at either end thereof which may be bolted at one end to the carburettor outlet and at the other end to the inlet manifold.

With reference to Figure 4, it is envisaged that the gas mixing device 5 could be mounted in the normal junction between the carburettor and inlet manifold and have an annular flange provided about an outer peripheral edge thereof formed to engage between the carburettor and inlet manifold flanges and would not therefore require a separate pipe to be bolted or otherwise secured therebetween.

Returning now to Figure 3, a gas mixing device 5 is mounted within the pipe 1 and is provided as a substantially circular coaxially stepped member for example stamped or pressed to shape and having a plurality of coaxial steps each of which is defined by a radially outer annular surface 7 which is substantially orthogonal to the interior surface la of the pipe 1, and a radially inner annular surface 8 extending substantially orthogonal from surface 7.

The gas mixing device 5 is formed in any suitable material such as for example metal, plastics and the like which is suitably resistant to gas deterioration and is provided with rows of apertures 6 in the surfaces 7, 8 of the steps of the device. Referring now to both Figure 2 and Figure 3 it will be seen that the device 5, upon gas mixture D flowing theretowards, said mixture D will flow through said apertures in the direction of arrows E and F through said apertures 6 which on a downstream side H of said device 5 creates substantial localized turbulence and results in efficient mixing of the gases or vapours with one another.

It is considered that the gas mixing device 5 may be secured within the pipe in any known manner, in particular, the peripheral edge 9 of the device may be made of such a size as to form an interference fit with internal surfaces la of said pipe 1 such that the gas mixing device may be pushed into the pipe and may lodge therewithin.

The total cross-sectional area of the apertures may be greater than the crosssectional area of the pipe 1 by from 25 to 50 per cent. This ensures that the mixing device 5 does not create undue restriction within the pipe 1 to reduce efficiency of the flow of the gas through the pipe. However, the ratio of the total cross-sectional area of the apertures 4 to the cross-sectional area of the pipe 1 may be reduced such that the total cross-sectional area of the apertures is at least equal to the crosssectional area of the pipe 1.

It will be appreciated that when the gas mixing device 5 as hereinbefore described is engaged within the pipe 1 all gas flowing through the pipe 1 must flow through the apertures 4 in said mixing device 5. Owing to the stepped configuration of the mixing device 5 and the positioning of apertures 4 therewithin, it will be appreciated that said apertures 4 in surfaces 7 and 8 will direct their localized jets of gas downstream thereof substantially orthogonally relative to one another and these jets of gas will interact with one onother to create mixing turbulence which results in efficient mixing of said gases downstream of the mixing device 5.

Now with reference to Figure 4 it is envisaged that the gas mixing device 5 may be formed of a gauze material having a suitable mesh size so as to match the velocity flow through the pipe 1. It is envisaged that the gauze material may be pressed into the stepped configuration and the gaps provided between the wires forming the mesh may provide the apertures 4 to operate as hereinbefore described with reference to Figures 2 and 3.

Thus there is provided a gas mixing device which is especially suitable to promote the efficient mixing of a fuel/air mixture for an internal combustion engine which provides for efficient combustion and also has the inherent advantage thereby of providing a substantially even distribution of fuel charge and therefore even power between the individual cylinders of the engine concerned, and thus provides for a much smoother power flow from the engine and enables a higher gear to be used at much lower engine speeds than would normally be possible.Further, the embodiments hereinbefore described may be used with an internal combustion engine as has been hereinbefore mentioned and thereby provide a substantial reduction in fuel consumption together with a much cleaner and pollution-free exhaust emission from the engine and a reduction in carbon deposits in the combustion chamber and exhaust system.

WHAT WE CLAIM IS: 1. A gas mixing device for mixing gases flowing within a gas flow pipe comprising an apertured screen adapted to be mounted within such a pipe and comprising at least one step defined by a first, radially outer annular surface arranged to extend substantially orthogonally to the interior surface of the pipe when the device is mounted therein and a second, radially inner annular surface extending substantially orthogonally from the first surface, one or more apertures being provided in each of said surfaces such that in use gases flowing within the pipe and through said screen become mixed.

2. A gas mixing device as claimed in claim 1, wherein the aperture screen is formed as a coaxially stepped perforated plate.

3. A gas mixing device as claimed in claim 1, wherein the apertured screen is formed from coaxially stepped gauze material.

4. A gas mixing device as claimed in any one of the preceding claims, wherein the apertures are arranged in the first and second surfaces such that they are aligned substantially orthogonally relative to one another.

5. A gas mixing device as claimed in any one of the preceding claims, mounted within a pipe such that all gas flowing through said pipe must pass through the apertures.

6. A gas mixing device as claimed in claim 5, wherein the pipe forms part of an inlet manifold of an internal combustion engine and the device is mounted downstream of a carburettor.

7. A gas mixing device as claimed in claim 5 or 6, wherein the total crosssectional area of the apertures at least equals the cross-sectional area of the pipe.

8. A gas mixing device as claimed in claim 5 or 6, wherein the sum of the crosssectional area of the apertures exceeds the cross-sectional area of the pipe by from 25 to 50 per cent.

9. A gas mixing device as claimed in any one of claims 5 to 8, wherein the device is mounted within the pipe such that an outer peripheral edge of the device forms an interference fit with an adjacent interior surface of the pipe.

10. A gas mixing device as claimed in any one of claims 5 to 8, wherein the device further comprises an annular flange engaged between respective annular flanges of two pipe ends at a junction thereof.

11. A gas mixing device substantially as herein described with reference to the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Now with reference to Figure 4 it is envisaged that the gas mixing device 5 may be formed of a gauze material having a suitable mesh size so as to match the velocity flow through the pipe 1. It is envisaged that the gauze material may be pressed into the stepped configuration and the gaps provided between the wires forming the mesh may provide the apertures 4 to operate as hereinbefore described with reference to Figures 2 and 3. Thus there is provided a gas mixing device which is especially suitable to promote the efficient mixing of a fuel/air mixture for an internal combustion engine which provides for efficient combustion and also has the inherent advantage thereby of providing a substantially even distribution of fuel charge and therefore even power between the individual cylinders of the engine concerned, and thus provides for a much smoother power flow from the engine and enables a higher gear to be used at much lower engine speeds than would normally be possible.Further, the embodiments hereinbefore described may be used with an internal combustion engine as has been hereinbefore mentioned and thereby provide a substantial reduction in fuel consumption together with a much cleaner and pollution-free exhaust emission from the engine and a reduction in carbon deposits in the combustion chamber and exhaust system. WHAT WE CLAIM IS:

1. A gas mixing device for mixing gases flowing within a gas flow pipe comprising an apertured screen adapted to be mounted within such a pipe and comprising at least one step defined by a first, radially outer annular surface arranged to extend substantially orthogonally to the interior surface of the pipe when the device is mounted therein and a second, radially inner annular surface extending substantially orthogonally from the first surface, one or more apertures being provided in each of said surfaces such that in use gases flowing within the pipe and through said screen become mixed.