Gas sampling and analysis in pulse combustion wind tunnel tests

The gas composition at the scramjet combustor exit is necessary for the combustion efficiency evaluation. Based on the testing condition of the pulse combustion wind tunnel and the flow field environment at the exit of the scramjet combustor, a gas sampling analysis system was designed and established for the oxygen concentration calibrating in the flow field of the pulse combustion wind tunnel and then for the gas composition measuring at the exit of the scramjet combustor. The flow characteristics and the chemical reaction frozen in the probe during sampling were analyzed. The results indicated that the gas inbreathed by probe could be availably cooled and the chemical reaction could be quenched. The gas composition at the nozzle exit of the pulse combustion wind tunnel was measured for checking the gas sampling analysis system. The control sequence of the gas sampling system could suffice for the pulse combustion wind tunnel testing. The experimental results of the percentage composition of O₂ were agreed with the calculation results, and the deviation was less than 5%, even approached to 0.4%. At present, with the working condition of Ma=2.6 and fuel injection, the main components at the exit of the scramjet combustor, such as O₂, N₂ and CO₂ were measured directly. The apparent combustion efficiencies for different locations were acquired through the experimental results. The variation of the apparent combustion efficiencies, in a manner, was found to be agreed with the fuel distribution.