Fluid sprinkling – spraying – and diffusing – Combining of separately supplied fluids – Liquid flow induces atmospheric air
Patent
1989-12-15
1991-10-29
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Combining of separately supplied fluids
Liquid flow induces atmospheric air
239589, 431 9, F23D 1462, F23D 1448, F23D 1404, B01F 302
Patent
active
050608673
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to the control of the motion of a gaseous, liquid or mixed-phase fluid jet emanating from a nozzle. The invention is concerned in particular aspects with enhancing or controlling the rate of mixing of the jet with its surroundings, and in other aspects with controlling the direction in which the jet leaves its forming nozzle. A particularly useful application of the invention is to mixing nozzles, burners or combustors which burn gaseous, liquid or particulate solid fuels, where it is necessary for a fuel-rich stream of fluid or particles to be mixed as efficiently as possible with an oxidizing fluid prior to combustion. The invention is however directed generally to mixing of fluids and is not confined to applications which involve a combustion process.
In a particular configuration the invention allows control of the vector direction in which a jet exits a nozzle, and hence may be used to control the direction of the thrust force exerted on the body from which the jet emanates. The feature may also be employed to direct a jet in a particular direction for any other purpose.
BACKGROUND ART
Heat energy can be derived from "renewable" natural sources and from non-renewable fuels. Currently the most usual fuels used in industry and for electricity generation are coal, oil, natural and manufactured gas. The convenience of oil and natural gas will ensure they remain preferred fuels until limitations on their availability, locally or globally, cause their prices to rise to uneconomic levels. Reserves of coal are very much greater and it is likely that coal will meet a substantial portion of energy needs, especially for electricity generation, well into the future. The burning of pulverised coal in nozzle-type burners is presently the preferred method of combustion in furnaces and boiler installations. It is predicted that this preference will continue for all but the lowest grades of coal, for which grades fluidised beds, oil/coal slurries or some form of pre-treatment may be preferred.
Gasification of the coal is a recognised form of pre-treatment. The viability of using lower grade coals, via a gasification process, as an energy source for power generation and heating could be increased if an inherently stable gas burner, which is tolerant of wide variations in the quality of the gas supplied to it, could be developed.
One usual constraint in the design and operation of prior combustion nozzles for gaseous fuels is that the mass flow rate of the fuel through a nozzle of given size is restricted by the rate at which the nozzle jet velocity decays through mixing to that of the flame propagation velocity in the mixture. For a flame to exist this condition must occur at a mixture strength within the combustible range for the particular fuel and oxidant. If the flow rate through the nozzle is high, such that the condition occurs far from the exit plane of the nozzle where the intensity and scale of the turbulent velocity fluctuations are both large, the flame front may fluctuate beyond the lean limit for combustion of the mixture resulting in extinction of the flame. Hence, if the spreading rate and mixing of the fluid jet emanating from the nozzle can be greatly enhanced, the flame front will be more stable and will be positioned closer to the nozzle. In a similar manner, improvements in the mixing process for the combustion of particulate fuel (for example, pulverised coal) which is entrained in a gas stream can lead to more effective control over the particle residence times required for drying, preheating, release of volatiles, combustion of the particles and the control of undesirable emission products such as oxides of sulphur and nitrogen.
Swirl burners, bluff-body flow expanders or flame-holders and so-called slot-burners are among the devices which have been used to enhance mixing of the fuel jet with its surroundings to overcome, or delay, the type of combustion instability described in the preceding paragraph, at the cost of increased pressure loss th
REFERENCES:
patent: 2098455 (1937-11-01), Lattner
patent: 3876362 (1975-04-01), Hirose
patent: 3954382 (1976-05-01), Hirose
patent: 4127332 (1978-11-01), Thiruvengadam et al.
"Fluid Amplifiers" by Joseph M. Kirshner, pp. 118-125, McGraw-Hill Book Co. .COPYRGT.1966.
Luxton Russell E.
Nathan Graham J.
Kashnikow Andres
Luminis Pty. Ltd.
Merritt Karen B.
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