Experimental investigation of effects of pulsed injection on flow structure and flame development in a kerosene-fueled scramjet with pilot hydrogen

The effects of pulsed injection on the flow structure and flame development in a scramjet were investigated experimentally with a pilot hydrogen equivalence ratio (ER) of 0.1 and a kerosene ER of 0.3; the pilot hydrogen was used to enhance the kerosene combustion. In the steady injection flow, the non-reacting flow structure changed periodically, and the monitor pressure built up rapidly when the pilot hydrogen self-ignited at t = 0.0096 s, increasing from 0.03 MPa to 0.037 MPa. The pilot flame was stable and filled the whole cavity until the kerosene began to be injected into the combustor at t = 0.05 s; the kerosene combustion occurred only in the cavity shear layer. After a very short time, the pilot flame was blown off by the kerosene. In the pulsed injection flow, the kerosene kept burning with the help of the pilot flame, and the monitor pressure stayed at a high value that was about six times that in the non-reacting flow. The mixture of pilot hydrogen and kerosene flame could propagate into the isolator, which was discontinuous and a distinct fault could be seen in the flame images. The kerosene combustion under pulsed injection was very intense, and even when the pilot hydrogen was removed, the cold room-temperature kerosene could still burn steadily for some time. Comparing with the flame development process under steady injection conditions, it is concluded that pulsed injection helps greatly to realize kerosene ignition and stable combustion.