Gas and liquid contact apparatus – Contact devices – Porous mass
Patent
1990-02-06
1991-03-05
Miles, Tim
Gas and liquid contact apparatus
Contact devices
Porous mass
261 96, 261 97, B01F 304
Patent
active
049975986
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to a vaporising device and in particular relates to a device useful in evaporating liquid into gaseous streams for example liquid fuels into an air stream.
BACKGROUND OF INVENTION
In internal combustion engines, turbines, liquid fuel fired furnaces, and the like, liquid fuel is mixed with an oxidising gas stream, for example an air stream. In a conventional fuel/air mixing device such as a carburettor the fuel discharges from a jet or metering bar in a stream which is torn apart into ligaments which progressively break up and contract into droplets of various sizes. During this process vaporisation takes place and the droplets progressively reduce in size the finest vaporising completely. Ideally, all of the liquid droplets would be vaporised and uniformly distributed in the air stream by the time they reach the combustion zone or combustion chamber.
In practice, especially under the varying conditions which internal combustion engines in particular are subjected to, some of the droplets are incompletely vaporised and this has adverse effects on both fuel economy and the cleanliness of the exhaust gases. In most conventional devices such as carburettors complete vaporisation only occurs at some part throttle conditions. Furthermore vaporisation occurs at a substantial distance away from the point of fuel discharge which distance varies with variable fuel demands of the engine. Fuel vaporasation is improved with forced fuel injection systems where the fuel injection nozzle functions to mechanically atomise the fuel at the tip exposed to the air stream. Fuel injection has several advantages over conventional carburettors but suffers from the disadvantages of high manufacturing costs and additional complexity requiring more sophisticated servicing.
The invention seeks to provide a form of vaporising device improved in the above respects.
SUMMARY OF INVENTION
According to the present invention there is provided a vaporising device which comprises a nozzle located in a gaseous stream such that a small portion of the stream passes through the nozzle, the nozzle comprising a wall of porous material being a sintered metal through which the liquid to be vapourised percolates from one side thereof into the gas stream through the nozzle and wherein the surface of the sintered metal is selectively closed by machined portions of the surface thereof.
The porous material is a sintered metal, in particular brass, bronze, cupro-nickel or the like. Conveniently, the wall will be cylindrical in configuration and the gas stream may flow over the cylinder, in which case the liquid will be supplied internally of the cylinder, or may flow through the cylinder, in which case the liquid will be supplied externally of the cylinder.
The primary use of the device of the invention is envisaged to be in mixing hydrocarbon fuels with an air stream, for use in for example an internal combustion engine, and the terms `fuel` and `air stream` will be used hereafter but it will be appreciated that the device of the invention is useful wherever a liquid is to be evaporated in to a gas stream.
In a preferred form of manufacturing a device in accordance with the invention the applicants have utilised a property of sintered non-ferrous metals hitherto regarded as a disadvantage. A sintered metal tube or cylinder, for example of a type available for use in filtration systems, cannot normally be machined since machining of the sintered metal surface causes the porous porosity of the surface to be lost since the physical cutting action of the machine tool causes the spherical grains of the sintered material to flatten and close the interstices. Thus, by selectively machining portions of a cylinder of sintered material the surface area can be varied at will. Thus, as will be described more fully heriafter, the flow characteristics of a cylinder of sintered material can be altered to provide a nozzle having the necessary fuel delivery characteristics for a particular end use.
FIGURES IN THE DRAWINGS
REFERENCES:
patent: 1857565 (1932-05-01), Pahl et al.
patent: 2149460 (1939-03-01), Muller
patent: 3352545 (1967-11-01), Denine
patent: 4486362 (1984-12-01), Forster et al.
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