 Radiative
Ignition of Gas-Turbine Combustors
The replacement of spark-plug ignitors with laser ignition systems in
gas-turbine and other combustors has been the objective of this work. This
multi-year contract effort, which was concluded during this reporting period,
began as an industry/university partnership between URI/CLA and AVCO/Lycoming.
During the lifetime of this contract, as part of the major realignments that
have occurred within the national defense arena, AVCO/Lycoming was purchased and
became Textron/Lycoming which was later purchased by Allied Signal. Throughout
these transitions, UTSI/CLA performed the research and proof-of-principle
experiments that demonstrated the significant advantages of laser ignition.
Included in these advantages are the opportunities for redesign of gas-turbine
combustors to obtain lighter weight, lower- temperature materials and (2) the
ability to achieve high-altitude relight following jet engine flame-out.
Several
significant advances were achieved during this past year.
A fast camera operated at nominally 1000 frame per second was used to follow
the ignition of jet-fuel spray by a single laser pulse. Analysis of the results
yielded an improved flame-speed measurement of laser-ignited Jet A fuel spray in
air. Selected images (in 3 ms
intervals) show a re-light of the droplet spray. Next, a persistent problem has
been the development of a method to deliver a high-power pulse of energy from
the laser to the interior of the combustor. To solve this problem, a hollow
light- guide was used to transmit a single-mode laser pulse to the droplets, and
subsequently ignite a string of methanol droplets in air. Finally,
optical-quality converging axicons, or conical lenses, were purchased, and a
butane lighter and a nominally diffraction-limited laser beam was used with an
axicon-lens combination to demonstrate spatially distributed ignition. The
spatial distribution of
intensity shows the axicon-lens focal volume characteristics. The extended and
ring pattern are notable.
Investigators: Dr. J.W.L. Lewis, Dr. C. Parigger, and Mr. J.D. Few
Sponsor: Allied Signal
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