A Burst-Mode Ultraviolet Laser System for High-Speed PLIF Measurements in Large-Scale Model Engine
Due to the short operation time(～hundreds of milliseconds to seconds)and high laser energy requirement(＞1 mJ)of the large-scale scramjet model engine,the conventional ultraviolet laser system cannot meet the fine measurement requirements of the combustion flow-field.The ultraviolet laser system used for high-speed planar laser-induced fluorescence(PLIF)measurements is required to meet the demands of short pulse interval and high laser output energy simultaneously,and the system possesses high reliability and high environmental adaptability.In the paper,a burst-mode ultraviolet laser system for high-speed PLIF measurement of a real engine ground test bench is designed,and it can obtain the effective flame dynamics data.The burst-mode ultraviolet laser system adopts the self-developed burst-mode laser to pump the dye laser,which has the functions of energy monitoring,wavelength monitoring and sheet distribution monitoring to correct the influence of laser parameters on the PLIF measurement results.The pump laser employs electro-optic Q-switch,burst-mode and MOPA technology,allowing the pump laser to have high pulse energy output(～50 mJ@532 nm),short pulse width(～10.8 ns)and high the burst frequency(20 Hz).The time interval of burst is 50 ms,which is 1/200 of the burst interval compared with the foreign burst-mode laser.The overall conversion efficiency is 6％,and the ultraviolet output energy is 2.95 mJ@283 nm,which is 7 times the typical value of foreign continuous laser output.The engineering-available 10 kHz PLIF system is self-integrated.It has anti-vibration,moisture-proof and dust-proof functions,improving the environmental adaptability of the high-speed PLIF system.At the same time,the system adopts the model design to improve the efficiency and reliability,making the system"adjust-free".It solves the problems of rapid installation,debugging,movement and test operation of high-speed PLIF systems in engine ground tests.For the first time in China,the long-distance and large field-of-view(～15 cm)measurement of the scramjet model combustor was conducted successfully in the CARDC's pulsed combustion wind tunnel.The results obtained hydrogen and ethylene fuel's high dynamic flame evolution process with high signal-to-noise ratio(SNR).In the future,the combustion condition and dynamic process can be studied with the spectral image feature extraction and analysis methods,which supports the study of complex flow-combustion mechanisms,CFD simulation and enginedesign improvement.
Combustion diagnosisBurst-mode laserPLIFLarge-scale model engine
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NSTL
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