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

本研究的目的是通过实验研究超音速气流中燃料与空气的混合增强和燃烧增强。在气流和燃油流之间形成的混合层的不稳定性是通过注入声干扰来激发的。位于流道壁上的空腔被用作声干扰源。期望通过声干扰来增强混合，从而提高燃烧效率。非燃烧实验：第一阶段进行非燃烧实验，研究声干扰对混合层生长的影响。氢气作为气体燃料与超音速气流平行注入。在超声速混频层注入声扰动，探索声扰动对混频的增强作用。对混合层内导频压力分布进行了测量，并利用CCD相机对混合层进行了图像增强，结果表明，有声源干扰时混合层的生长速度比无声源干扰时大。这表明声扰动的注入对于增强空气和燃料的混合是有效的。燃烧实验：在燃烧的混合层注入声干扰，得到燃烧效率，研究上述混合增强对燃烧行为的影响。燃烧效率是通过测量燃烧室壁面压力曲线得到的。有声干扰的燃烧效率比没有声干扰的燃烧效率高。结果还表明，利用声干扰可以稳定地产生强燃烧模式。这些结果表明，在超声速流动中，声扰动的注入有助于增强混合和提高燃烧效率。少

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