Combustion Behavior of n-Decane in a Scramjet Model Combustor

This study carried out experiments to investigate the combustion behavior of n-decane at Mach 2.03 and stagnation temperature between 800 and 1100K using a supersonic combustion with two serial cavities flame holder. All experiments were performed in the direct-connect supersonic combustion facility with regenerative storage air-heater. n-decane with ambient temperature was directly injected into a supersonic crossflow upstream of the first cavity. CH chemiluminescences was performed along with measurements of the combustor wall pressure. Two flameholding modes of n-decane, flame held with two cavities and flame held with one cavity were identified by the location of a rise in wall pressure and the CH chemiluminescence emission. The flame held with two cavities was stabilized through the interaction between the jet wake and a recirculation zone in the cavity. On the other hand, the flame held with one cavity was stabilized through the interaction between the separation of boundary layer, which was induced by shock wave, and a recirculation zone in the cavity. As the stagnation temperature decreased, the flame held with two cavities turned to one cavity until it couldn't be stabilized. The transition temperature from flame held with two cavities to one cavity and the flameholding temperature of n-decane were 876K and 842K, respectively. The result of the one-dimensional analysis show that the combustion efficiency and stagnation pressure recovery coefficient are higher when the flame held at two cavity.