Design and fabrication of variable nozzle for precooled turbojet engine

The afterburner and the variable nozzle for the small precooled turbojet engine (S-engine) are fabricated and firing tests of the engine were conducted. The nozzle adopts rectangular configuration because throat area of the nozzle must vary for 2.5 times. A regenerative cooling is adopted on the ramp of the afterburner and fuel of the afterburner (liquid hydrogen) is reheated at the wall. C/C-Si composite material is adopted on the sidewall and the cowl of the nozzle, for weight reduction. After the structure tests of the C/C-Si subscale components, the sidewall and the cowl made of C/C-Si are designed and fabricated which has 12 mm of wall thickness. Four series of firing experiments are conducted for the S-engine by now. In these experiments, the afterburner was used at three experiments. Afterburner was turned on for approximately 10 sec for each firing tests. As a result of the experiments, we confirmed that temperature inside the afterburner was uniform. For the fuel rich combustor, it is important to pass the stoichiometric fuel flow rate during ignition to prevent the wall from overheating. However, if fuel flow rate increases rapidly, ignition fails.