Combustion Characteristics In Supersonic Combustor Equipped With Strut/Wall Fuel Injection

Lower mass, lower cost, higher specific impulse and higher speed are the advantages of scramjet, which makes the scramjet being the best propeller under the atmosphere. The whole system is extremely complex, one of the key issues is the combustion organization. At the same times, a high heat flux would be produced following the running of the scramjet, so it is necessary to take the initiative cooling to combustor wall. Fuel is a good choice to act as the coolant. This paper has proposed a strut/wall combined fuel injection strategy with the aim to decrease the heat flux of the wall. In this paper, a strut is used to make the combustion stable and inject fuel into the center of the combustor. Compared with other stabilizer, like cavity stabilizer, strut could make flame formed in the center of the combustor, which could cut down heat flux form the source. In this case, in order to decrease the heat flux further, the strut/wall combined fuel injection is proposed, separating some fuel to wall injection. The fuel in normal atmospheric temperature injected into combustor from wall could drop the wall temperature. The main studies of this paper are as follows:Some researches has been done to design the size of the scramjet combustor. The length of each section and the expansion ratio are confirmed according some empirical formula. The instruduction of the the direct-connect rig is involved in this chapter.Some 3D numerical simulation about strut/wall combined fuel injection has been done. Simulation results show that, the miscible efficiency would be improved if spearting some fuel from strut injection to wall injection. The average distributed strut/wall injection mode shows the best performance among all those modes. Different wall injection position would affect the combustion performance. At the axial wall fuel injection position, the mass fraction of oxygen is higher near the side wall than that near the up-and-down wall. It is a better choice to take the side-wallinjection mode than the up-and-down-wall injection for improving the combustion efficiency.The paper has investigated the inlet unstart charact eristics and combustion profermance through experimenting on the direct-connect rig. Experiment results show that, it is propitious to avoiding inlet unstart if the fuel from the strut is moved to the wall. Combustion characteristics would be affected if s eparating some fuel from strut to wall. The combustor pressure in strut/wall combined fuel injection strategy is lower than that in strut fuel injection strategy, which proofs that employing combined fuel injection could lower combustion effects to a certa in degree.Some researches has been done to contrast the heat flux between the strut only fuel injection and the combined fuel injection. Researches show that the heat flux is lower in strut/wall combined fuel injection than that in strut only fuel injection. On one hand, strut fuel ratio is lower in combined fuel injection mode, and lower ratio leads to a lower combustor temperature and lower heat flux. On the other hand, fuel injected from the wall injection acts as the coolant, with the help of which, the heat flux near the wall would be cut down. What’s more, wall fuel would be on fire to improve combustion efficient.The profermance of the scramjet would be changed by taking the combined fuel injection mode instead of the strut only fuel injectio n mode. The average distributed strut/wall injection mode shows the best combustion performance.