CO concentration and temperature measurements in a shock tube for Martian mixtures by coupling OES and TDLAS

Abstract

CO concentration and gas temperature distribution are diagnosed behind a strong shock wave simulating the Martian atmosphere entry processes by coupling optical emission spectroscopy (OES) and tunable diode laser absorption spectroscopy (TDLAS). The strong shock wave (6.31 ± 0.11 km/s) is established in a shock tube driven by combustion of hydrogen and oxygen. Temperature of the shock-heated gas is inferred through a precise analysis of the high temporal and spatial resolution experimental spectral of CN violet system (B 2 R ? ?X 2 R ? , Dv = 0 sequence) using OES. A CO absorption line near 2,335.778 nm is utilized for detecting the CO concentration using scanned-wavelength direct absorption mode with 50 kHz repetition rate. Combined with temperature results from OES, CO concentration in the thermal equilibrium region is derived. The current experimental results are complementary for determining an accurate rate coefficient of CO 2 dissociation and validation relevant chemical kinetics models in Mars atmosphere entry processes.

A new flux splitting scheme for Euler equations of gas dynamics

“…This work completes our previous work 24 and illustrates the feasibility the potential of TDLAS system for species concentration measurements during space probe entry phase. Existing experimental results will be very helpful to understand CO 2 dissociation and provide verification data of ground-state densities for studying chemical kinetic processes occurring in the shock layer.…”

“…Experiments have been carried out in the mixture constituted of 70% CO 2 and 30% N 2 , despite the difference from the exact composition of the Mars atmosphere, such a ratio allows the CN radicals emission signal-to-noise (SNR) to be significantly improved whereas the chemical kinetics processes remain the same. Based on the previous experiments 24 , two initial pressure/shock velocity conditions are investigated: P i = 100 Pa and V s = 7.09 ± 0.05 km/s (called the low-pressure condition), and P i = 300 Pa and V s = 5.68 ± 0.07 km/s (called the high-pressure condition). The optical diagnostic system consists of two parts: the OES system and the TDLAS system.…”

Experimental and Numerical Study of Carbon-Dioxide Dissociation for Mars Atmospheric Entry

“…Consequently, the development of accurate quantitative diagnostic techniques for shock-tube experiments would be highly beneficial. Tunable diode laser absorption spectroscopy (TDLAS) is a powerful tool with which to probe atoms and molecules nonintrusively and has seen use in many areas such as combustion diagnostics, chemical sensing, and environment monitoring [18][19][20]. In contrast with other optical diagnostic applications, the ground state can be assessed.…”

“…In contrast with other optical diagnostic applications, the ground state can be assessed. Our preliminary experiments illustrated the potential for using TDLAS to study high-temperature flows for entry into the Martian atmosphere [20]. However, the range of the measurement needs to be significantly improved; essentially, only one condition was studied, and only a few measurement points were quoted.…”

Compact all-fiber quartz-enhanced photoacoustic spectroscopy sensor with a 30.72 kHz quartz tuning fork and spatially resolved trace gas detection

“…12 The H 2 O absorption line located at 7168.4 cm À1 was selected for laser excitation and the laser power for each sensor branch was $4.83 mW. The all-fiber QEPAS sensor performance using the three QTFs with f 0 of 30.72 kHz was evaluated.…”