结合吸收光谱与互相关法的燃气速度测量方法研究

针对可调谐半导体激光器吸收光谱(TDLAS)基于多普勒效应测速方法在燃气流速测量中频移量小、误差较大的问题,提出了结合固定波长吸收光谱法与互相关法的燃气速度测量方法。考虑碳氢燃料燃烧产物特点,选取H2O分子7 185.597cm~(-1)吸收谱线,通过布置上下游两束固定波长吸收光谱测点,分析两信号的互相关特性来计算得到燃气速度。利用平面火焰炉实验系统对该方法测量燃气速度开展实验研究,获得了变工况下燃气速度随时间的变化情况。在相同工况下开展数值计算,将测量结果与数值模拟计算结果进行对比,相对偏差不超过8%。同时将该方法初步应用于煤油燃料火箭基组合循环发动机(RBCC)的高速羽流速度测量,获得了上下游探测器脉动信号,通过互相关分析计算得到了羽流速度,验证了该方法的可行性。实验结果表明,该燃气速度测量方法具有测量范围宽、测量精度高,环境干扰小等优点。提出的方法为发动机燃气速度测量提供一种简单可靠的测量方法。

Research on Measurement Method of Gas Velocity Combined Absorption Spectroscopy Technique and Cross-Correlation

For the small frequency shift and large error of tunable diode laser absorption spectroscopy (TDLAS) velocity method based on Do ppler Effect in measuring the gas velocity,velocity measurement method combined fixed wavelength absorption spectroscopy and cross correlation is proposed in t his paper.Considering the characteristics of the hydrocarbon fuel combustion pr oducts,7 158.597 cm-1 absorption line of H2O molecular was selected.Through arranging two beams of fixed wavelength absorption measurement point of upstream and downstream,the gas velocity can be calculated by analyzing the cro ss-correlation properties of the two signals.The flat flame burner experiment system was used in the experimental research of the velocity measurement.The ch ange of gas velocity with time under variable working condition was obtained.Un der the same condition,numerical calculation is carried out.And the measuremen t results are compared with the results of the numerical simulation with relativ e deviation less than 8%.Then the method is preliminarily applied to measure th e high speed plume of the kerosene-fueled Rocket Based Combined Cycle (RBCC) en gine,and the upstream and downstream fluctuant signals of detectors were obtain ed.The velocity of the plume was calculated with cross correlation analysis whi ch verifies the feasibility of this method.The experimental results show that t he gas velocity measurement method has a wide measuring range with high measurin g accuracy and little environment interference.The method proposed in this pape r provides a simple and reliable method for the measurement of engine gas veloci ty.