Measurement Research On The Transient Processes Of High-Temperature Gas Parameters Inside Shock Tube Based On Absorption Spectroscopy

Accurate temperature and species-concentration time-history measurements play an important role in thermal processes.The laser absorption spectroscopy is a high-sensitive,non-intrusive and high-selective technology for rapidly and accurately measuring time-resolved temperature and species concentrations in high-temperature flow field.The shock tube can provide a“stable”high-temperature environment in a certain time scale(1–3 ms)for the researches of high-temperature measurements,high-temperature spectroscopy and high-temperature reaction kinetics.This study used the laser absorption spectroscopy and the shock tube to measure temperature,CO-and CO₂-concentration time-histories during hydrocarbon-fuel reaction behind reflected shock waves.The main research contents were summarized as follows:Experimental researches:1)this study designed a shock-tube system,which is available to mimic the high-temperature transient environment.2)This study designed a laser-absorption-spectroscopy system based on fixed-wavelength wavelength-modulation-spectroscopy method for CO₂-concentration time-history measurements behind reflected shock waves with time resolution of microsecond using CO₂ P70 line in v₁+v₃ vibrational band(2.74?m).3)This study designed a two-line laser-absorption-spectroscopy system based on fixed-wavelength direct-absorption-spectroscopy method for simultaneous temperature and CO-concentration time-history measurements with time resolution of microsecond using CO P20/R21 and P8/R21 line pairs(P20:v"=0,4.85?m;P8:v"=0,4.73?m;R21:v"=1,4.56?m).Researches on the transient processes of high-temperature gas parameters behind shock waves:1)this study used the“stable”high-temperature environment inside the shock tube to measure the collisional broadening coefficients of P8/R21 lines in the CO fundamental band and the broadband CO₂ absorption cross-section at the linecenter of the two lines.The measured data filled a gap for the spectral database of CO and CO₂ in specific spectral range,and improved the basic parameters for the high-temperature-gas diagnostics in combustion processes.2)This study used the fixed-wavelength first-harmonic-normalized-second-harmonic method to suppress the H₂O-absorbance interferences in the air.The accurate measurements of CO₂ time-history during the combustion processes of n-butane/H₂ mixtures validated the aviability and accuracy of the method above.3)This study measured the temperature and CO-concentration time-histories behind reflected shock waves under high-temperature/low-temperautre(P20/R21),high-pressure(P8/R21),and fuel-pyrolysis(P8/R21)conditions.The measured temperature profiles further validated the evolution rules of high-temperature-gas parameters behind reflected shock waves at various conditions.This study quantitatively analyzed the influences of CO neighboring lines on temperature measurements at intermediate and high pressures,and presented the method for accuarate temperature measurements at high pressures.This study compared the measured temperature profiles with kinetics predictions based on constant-volume,constant-internal-energy assumption and constant-pressure,constant enthalpy assumption.This study proposed to use the measured pressure time-history profiles as inputs during kinetics simulation to improve the accuary of temperature predictions.