Study on Line CARS for Temperature Measurement in Combustion Flow Field

Abstract

Some laser beams meet at a single point by a convex len in normal coherent anti-Stokes Raman scattering (CARS), and the CARS signal with temperature information of the focal piont yields under phase matching. Normal CARS can only get the temperature of one spatial piont in one measurement, which can not meet the needs of deep research on combustion flow field. In order to get more information in one test and improve the measuring capacity of CARS, line CARS (L-CARS) was presented. In L-CARS, convex lens are replaced by cylindrical convex lens to get a focal line, and nearly all the points on the line meet the phase matching. So, the CARS signal of each point on the line yield in one test. Cylindrical convex lens are also used in subsequent beam path to focus the CARS signals into spectrometer, and ICCD camera transfers the signals to computer to acquire the temperature of each point. Then, the measuring capacity of CARS is advanced from piont measuring to line measuring. Experimental results based on plain flame furnace suggest that L-CARS can acquire about 200 points’ temperatures effectively in one test, and the length of the measuring line is about 3.6mm. The spatial resolution is about 18μm and the uncertainty is less than 7%, which is as the same as the ordinary CARS’s.