LIGS

A new facility has been commissioned for studying Laser Induced Grating Spectroscopy (LIGS) for measurement temperature and water vapour in the presence of soot. The technique uses a pulsed beam at 1064 nm to excite either air or water molecule lines to produce a density grating and an associated pressure pulse. The resulting density pattern is probed using a continuous wave laser.

The technique has been initiated in a previous EPSRC funded (EP/K02924X/1) project, and is currently funded by EPSRC grant EP/T030801/1, in a collaboration with Oxford and Cardiff Universities.

The particular advantages of the 1064 nm LIGS are :

• the very high precision which arises from the measurement of a frequency.
• easily available excitation line with high energies from Nd:YAG lasers
• can be used to excite electrostrictive modes to obtain temperatures in reactants or products
• works with sooty flows

The current version of the technique offers sufficient signal from 3 bar upwards for measurement of product temperatures.

[1] L. Weller, P. Shah, A. Giles, F. De Domenico, S. Morris, B. A. O. Williams, S. Hochgreb, Spatial temperature and water molar concentration measurements using thermal and electrostrictive LIGS during operation of a swirl burner at pressure, ASME Turbo Expo GT2023-101185

[2] F. De Domenico, T. F. Guiberti, S. Hochgreb, W. L. Roberts,G. Magnotti, Tracer-free laser-induced grating spectroscopy using a pulse burst laser at 100 kHz, Optics Express, 2019

[3] F. De Domenico, T. F. Guiberti, S. Hochgreb, W. L. Roberts,G. Magnotti, Temperature and water measurements in flames using 1064 nm Laser-Induced Grating Spectroscopy (LIGS), Combustion and Flame, 2019