Research On Center Bluff Body Cavity Scramjet Combustion Organization Technology

Since the development of hypersonic air breathing vehicle will realize high speed flights in the future, scramjet,with its excellent performance in hypersonic flights, has attracted the attention of many. In researching of the vehicle, it is desiderated that technologies concerning the supersonic combustion organization be researched.This paper proposes a center bluff body-cavity structure supersonic combustor design plan: by taking advantage of two bluff bodies put in the center flow field and creating a cavity, both of which constitute the center ignition and flame stability combustion organization, the high temperature combustion region will locate at the center of the flow field, adding the heat from the combustion into the main flow so as to improve the efficiency, meanwhile reducing the thermal load of the combustor's wall. In experiments done, by means of numerical simulation, the flow and combustion performances of the center bluff body cavity were researched with different structure parameters and fuel injection schemes. The main study results are as follows:(1) The scramjet combustor structure was designed, including the straight isolator section, the center bluff body cavity flame stability section(including cavity, bluff body and the compensate section at two sides of the bluff body cavity) and the combustor model surface. With all three combined, a preliminary scheme of center bluff body cavity scramjet combustor was achieved.(2) Based on a binary scramjet 2D model, the influence of configuration parameter on the combustor performance was studied. When the combustor performance was studied with different cavities' length-width ratios and different heights of the bluff body, it is found that if the center cavity is too small, the flame in the cavity can't ignite the outside gas; if the center cavity is too large, a lot of flow lost will be occurred. When the different bluff body's parameter was researched, it was found that if the bluff body's cone angle is too small, the outside main flow can hardly ignited; if the bluff body's cone angle is too large, the combustor's mass flow rate was affected and easily lead to thermal choke. When the compensate section was researched, it was found that if the area expansion is too small, the heat which released from fuel would bring the combustor to subsonic combustion mode;, if the area expansion is too large, the flame in the cavity can`t ignite the outside mixture, thus combustion can't occur in main flow. When the combustor performance was researched with different dilatation angles or directions, it was found that they have little influence on combustion performance in a certain range.(3)Based on a binary scramjet 3D model, the influence of the fuel injection position on the combustion organization was explored. It was found that alternating expression fuel injection positions is beneficial for improving combustion organization with better distributed fuel and higher efficiency; the equivalent ratio's increase improves the combustor's performance, but thermal choke could also be brought when the equivalent ratio is too large.