An integrated sensor technology for measurements of specific heat ratio of combustion gases in supersonic flow

We present an integrated probe system for measuring the specific heat ratioγof combustion gases by combining Pitot tube and laser beam tracking system.The key benefit of the measurement system is the elimination of the complicated gas chromatography apparatus.The pressure ratio and the angle of refraction of a laser beam across the normal shock wave generated by Pitot tube are simultaneously measured with this system.The angle of refraction of the laser beam is expected to be accurately recorded by the laser tracking system consisting of two CCD cameras and a mobile spatial coordinate measuring system (MScMS).Moreover,the density rati-o across the shock wave is deduced with Gladstone-Dale relation and Snell’s law.The specific heat ratioγis accordingly quantified by its relation to the pressure ratio and the density ratio across the shock wave.This technique may effectively reduce the time taken to obtainγ.Uncer-tainty estimation shows that the uncertainty brought by the laser beam tracking system and Pitot tube measurement are limited within 5 .5%for any Mach number if the stagnation temperature is lower than 1000K.Feasibility analysis present that the technique is physically realizable but a few technical issues need to be addressed before it can be implemented.