Combustion – Combustion bursts or flare-ups in pulses or serial pattern
Reexamination Certificate
1999-02-26
2001-10-16
Clarke, Sara (Department: 3743)
Combustion
Combustion bursts or flare-ups in pulses or serial pattern
C431S001000, C431S006000, C431S074000, C431S079000, C431S258000
Reexamination Certificate
active
06302682
ABSTRACT:
TECHNICAL FIELD
This invention relates to use of laser technology for hydrocarbon fuel combustion.
BACKGROUND ART
Natural gas burning power sources such as gas turbine electrical power generating plants are operated with as lean fuel/air mixtures as practical in order to reduce the production of NO
x
emissions. Conventional pilot light flames which burn rich fuel/air mixtures and electrical spark plugs have been used for initiating and stabilizing flames in gas burning turbines. However, when lean fuel mixtures are used, the use of a pilot light with a richer fuel/air mixture is necessitated to stabilize the flame because otherwise, at fuel/air composition mixtures near the flammability limit, the combustion process becomes so unstable that the flame cannot be sustained. The richer burn of the pilot flame itself produces a higher flame temperature which contributes significantly to the over-all production of NO
X
.
Therefore, a method which does not contribute to NO
x
pollutant emissions is needed by the power generation industry to stabilize the ultra-lean combustion of fuels.
An object of this invention is to provide an apparatus for laser ignition of hydrocarbon fuels.
It is an object of this invention to provide a method for stabilization of hydrocarbon fuel combustion flames.
It is another object of this invention to provide a method for cleaner combustion of hydrocarbon fuels.
It is a further object of this invention to provide a method of initiating hydrocarbon fuel combustion without contact of the initiator with the burning fuel.
It is yet another object of this invention to provide a method of initiating hydrocarbon fuel combustion that reduces interference with the flow dynamics in the combustion chamber.
Another object of this invention is to provide a means for directing a laser initiating spark into any selected location within a fuel vapor cloud.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. The claims are intended to cover all changes and modifications within the spirit and scope thereof.
DISCLOSURE OF INVENTION
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, there has been invented a method comprising use of a laser-induced spark to initiate and stabilize fuel combustion in applications such as gas turbine electrical power generating engines and jet turbine engines where it is desired to burn lean fuel/air mixtures which produce lower amounts of NO
X
.
More specifically, a laser spark is generated by focusing laser light to a sufficiently tight laser spot within the fuel to cause the ionization of air and fuel into a plasma. Repeated pulses of high peak power or a dual pulse format of alternating short duration high peak power and long duration low peak power pulses can be used.
The laser may be operated in an intermittent maimer with the laser being fired only when incipient extinction of fuel combustion is detected by using a feedback control unit.
REFERENCES:
patent: 3473879 (1969-10-01), Berberich
patent: 4302933 (1981-12-01), Smith
patent: 4434753 (1984-03-01), Mukainakano et al.
patent: 4702808 (1987-10-01), Lemelson
patent: 4852529 (1989-08-01), Vowles
patent: 5497612 (1996-03-01), Few et al.
patent: 5588299 (1996-12-01), DeFreitas
patent: 5829962 (1998-11-01), Drasek et al.
patent: 5876195 (1999-03-01), Early
Early James W.
Thomas Matthew E.
Clarke Sara
Gemma Morrison Bennett
The Regents of the University of California
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