A Study on Control of Supersonic Combustion using Mixing Enhancement by Instability Excitation

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The objective of the present study is to investigate experimentally mixing enhancement of fuel and air and combustion enhancement in supersonic air flows. The instability of the mixing layer which formed between air flow and fuel flow is excited by injection of the acoustic disturbances. The cavity which is located on the wall of the flow channel is used as the source of acoustic disturbances. The mixing enhancement is expected to be appeared by acoustic disturbances, and consequently the combustion efficiency is expected to increase.Non-Combustion Experiments : Experiments without combustion are conducted at the first stage in order to investigate effects of acoustic disturbance on the growth of the mixing layer. Hydrogen is injected as a gaseous fuel parallel to the supersonic air flow. The acoustic disturbance is injected to the supersonic mixing layer in order to explore mixing enhancement by acoustic disturbances. Measurements of Pilot pressure distribution in the mixing layer is … More conducted and Schlieren photography is used for the visualization of the mixing layer by a CCD camera with the image intensifies The results show that the growth rate of the mixing layer is larger with the acoustic disturbance than that without it. This suggests that the injection of the acoustic disturbance is effective for the enhancement of the mixing of air and fuel.Combustion Experiments : The acoustic disturbance is injected to the mixing layer with combustion and the combustion efficiency is obtained in order to investigate effects of mixing enhancement mentioned above on the combustion behavior. The combustion efficiency is obtained from the measured wall pressure profiles in the combustion chamber. The combustion efficiency with the acoustic disturbance is larger than that without it. The results also show that the intense combustion mode appears stably using acoustic disturbances.These results indicate that, the injection of the acoustic disturbance is useful for the enhancement of mixing and increase in the combustion efficiency in the supersonic flow. Less