Authors: Mruthunjaya Uddi, Apurba Kumar Das, Chih-Jen Sung
Direct link to the paper: http://dx.doi.org/10.1364/AO.51.005464
A method for measuring the temporal temperature and number density in the Rapid Compression Machine (RCM), using quantum cascade laser absorption spectroscopy near 7.6 µm is developed and presented in this paper. The ratios, of H2O absorption peaks at 1316.55 cm-1 and 1316.97 cm-1 is 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 PC=10, 15, and 20 bar and in the range of TC=1000–1200 K. The measured temperature history is compared with that calculated based on the adiabatic core assumption and is found to be within ±5 K. The measured temporal number density of H2O to an accuracy of 1%, using the absolute absorption of the two rovibrational lines show that the mixture is highly uniform in temperature. A 6-pass, 5.08 cm Herriott cell, is used to calibrate the line strengths in air and broadening in Ar bath gas.
Citation: M. Uddi, A. K. Das, and C. J. Sung, “Temperature Measurements in a Rapid Compression Machine using Mid-IR H2O Absorption Spectroscopy near 7.6 µm”, Applied Optics 51, 5464-5476 (2012).