Hideyuki TANNO, Shuto YATSUYANAGI, Kouichiro TANI, Sadatake TOMIOKA
DOI Number: 10.82241/ceas-hisst-2024-326
Conference number: HiSST-2024-326
A series of combustion tests were conducted in the free-piston shock tunnel HIEST in hypersonic free-stream using a 1.1-meter-long integrated scramjet airframe model, NAMaSU (New Airframe integrated Model with a Scramjet Unit). The NAMaSU is a wall-compression scramjet/airframe integrated model with a so-called lifting body concept, in which the scramjet is installed under the airframe. It is made entirely of aluminum alloy (A7075), is 1067 mm long and 224 mm wide, and weighs 37.8 kg, including all onboard equipment. The model is equipped with an internal gas-hydrogen fuel tank, a quick-acting solenoid valve, batteries, control timers, sensor and data recorders, enabling full autonomous operation as soon as the test starts. For fuel injection, the quick-acting valve was opened by a control timer triggered by a deactivation signal for the electric-magnets model holder, and gas hydrogen of up to 7 MPa was supplied from a 600 mL capacity gas-hydrogen fuel tank to the injection manifold and injected vertically into the combustor through four injection holes of Φ2 mm orifice diameter. The aerodynamic coefficients of the three components (drag, lift, and pitching moment) were measured using the free-flight aerodynamic measurement method. The model was in free flight during the test and was aerodynamically completely non-interfering in the HIEST hypersonic free stream. The model was designed with the inlet and combustor with flight equivalent Mach number 11 conditions as nominal operating conditions. In this test series, tests were conducted on equivalent flights Mach number 9 and Mach number 11. In the tests, the hydrogen equivalent ratio was set to 1.1 by fixing the gas hydrogen tank’s initial pressure, and comparative tests with and without combustion were carried out using air and pure nitrogen as test gases to extract the effect of combustion by hydrogen gas. In both the equivalent flight Mach number 9 and Mach number 11 conditions, a large pressure increase due to hydrogen combustion was observed in the combustor. Still, the measured thrust did not reach a level equivalent to the drag force of the entire model.