Simultaneous temperature, H2O concentration and pressure measurement in a scramjet combustor with combined operation mode using wavelength modulation spectroscopy

Wavelength Modulation Spectroscopy (WMS) was utilized to study the exhaust flow of a scramjet combustor with a combined operation mode in this work. 8 optical probes for WMS, 5 vertically with a spacing of 5cm and 3 horizontally with a spacing of 3cm, were mounted on the jet nozzle of the combustor, which was operated in 3 combustion stages, H-2 combustion at first, kerosene combustion in oxygen-rich condition and fuel-rich condition, sequentially. The WMS system recorded the complete process of combustion, then simultaneously inferred the temperature, H2O concentration and pressure from each sensor. Measured results showed that the parameters of interest in all the 3 stages, during 5.4s combustion period, had relatively stable values. However, when the stage transited to the next, the combustion parameters leaped rapidly in 20ms. The WMS system had fast enough response speed and successfully caught the leaping. The 2D distributions of temperature and H2O concentration were also reconstructed, which illustrated that the combustion flow was not uniform in each stage.