Nitric oxide concentration and temperature measurement for shock tunnel free stream using mid-infrared absorption spectroscopy

In this paper,JF-10 shock tunnel is driven by H2/O2 detonation and the free-stream contains some trace components which are generated by non-equilibrium processes such as ionization and dissociation.Tunable diode absorption spectroscopy (TDLAS)is used for tempera-ture and concentration measurement of nitric oxide in the free-stream and this quantitative meas-urement is helpful to understand the non-equilibrium processes.In the experiments,the test sec-tion’s static pressure of JF-10 shock tunnel is just several hPa.Thus,Doppler broadening domi-nates,which is caused by random thermal motion of the absorber species.The half width of Doppler broadening is temperature dependent and this functional relation provides a method for gas temperature and species concentration measurement.A mid-infrared quantum cascade laser of 5.2μm central wavelength is used and gas temperature and nitric oxide concentration are meas-ured using a single line of 1909.7cm-1 wavelength by direct absorption-wavelength scanning method under 2kHz scanning frequency.The measured partial pressure of nitric oxide is about 0. 33Pa which represents its concentration and the temperature is about 600K in the free-stream.