Abstract
A method for measuring the temporal temperature and number density in a rapid compression machine (RCM) using quantum cascade laser absorption spectroscopy near 7.6 μm is developed and presented in this paper. The ratios of absorption peaks at and are used for these measurements. In order to isolate the effects of chemical reactions, an inert mixture of argon with 2.87% water vapor is used for the present investigation. The end of compression pressures and temperatures in the RCM measurements are , 15, and 20 bar in the range of to 1200 K. The measured temperature history is compared with that calculated based on the adiabatic core assumption and is found to be within . The measured temporal number density of to an accuracy of 1%, using the absolute absorption of the two rovibrational lines, show that the mixture is highly uniform in temperature. A six-pass, 5.08 cm Herriott cell is used to calibrate the line strengths in air and broadening in an Ar bath gas.
© 2012 Optical Society of America
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