Motoyuki Hongoh

Firing Test of a Hypersonic Turbojet Engine Installed on a Flight Test Vehicle

Hypersonic turbojet engine with pre-cooling system is tested under sea level static condition. The engine is installed on a flight test vehicle, which will fly at Mach 2 speed by a free fall experiment from a stratospheric balloon. Liquid hydrogen fuel and gas hydrogen fuel is supplied to the engine from a tank and cylinders installed in the vehicle. Designated operation of major components of the engine is confirmed. Corrected rotation speed, corrected air flow rate and pressure ratio of the compressor is raised by pre-cooling with liquid hydrogen fuel. Corrected air flow rate and pressure ratio at the pre-cooling operation is reduced comparing from that without pre-cooling on the same corrected rotation speed. There is a deep temperature distortion at the inlet of the compressor and it may cause the performance reduction. Large amount of liquid hydrogen is supplied to the pre-cooler in order to obtain enough pre-cooling performance for Mach 5 flight. Then, fuel rich combustion at the after-burner is adopted. Cowl part of variable geometry nozzle is made with C/C composite material and it has no damage after the combustion test. Operation of the core engine by liquid hydrogen is attained by using a control valve with small effective diameter.

Performance Evaluation of Hypersonic Pre-Cooled Turbojet Engine

Pre-cooled turbojet engine is investigated to realize Mach 5 class hypersonic transport aircraft. The engine has been demonstrated under sea level static and Mach 2 flight conditions using hydrogen as fuel. In this study, Mach 4 propulsion wind tunnel test is performed and the performance of air intake, pre-cooler, core engine and exhaust nozzle are obtained. Liquid nitrogen is supplied to the pre-cooler as a coolant in place of liquid hydrogen. Gaseous hydrogen is supplied to the main burner to drive the turbine with the combustion gas. A protective screen is placed in front of the pre-cooler to prevent damages of it from high-speed particles. Bypass door is placed in front of the core engine to start the mixed compression air intake at low speed operation of the core engine. As a result, the engine performance data is obtained without any damage of pre-cooler. Air intake is started by the effect of bypass door at low speed operation of the core engine.

Mach 4 Wind Tunnel Experiment of Hypersonic Pre-Cooled Turbojet Engine

Pre-cooled turbojet engine is investigated to realize Mach 5 class hypersonic transport aircraft. The engine has been demonstrated under sea level static and Mach 2 flight conditions using hydrogen as fuel. Presently, Mach 5 propulsion wind tunnel test using liquid hydrogen is planned and the engine components such as pre-cooler, core engine, afterburner and exhaust nozzle are under development. The engine components were tested under Mach 4 simulating condition by connecting the pre-cooler inlet to an air supply facility. The engine was tested in a propulsion wind tunnel with Mach 4 flight condition. Liquid nitrogen was supplied to the pre-cooler as a coolant in place of liquid hydrogen. Gaseous hydrogen was supplied to the main burner to drive the turbine with the combustion gas. As a result, high temperature structure and cooling system was proved to endure Mach 4 high temperature airstream. Wind-mill starting sequence of the core engine under Mach 4 flight condition was confirmed. Gross thrust of the core engine was obtained as an initial evaluation of elemental performance.

Systems Analysis on Hypersonic Airplanes using Pre- Cooled Turbojet Engine

Systems analysis and evaluation of Mach 5 class hypersonic airplanes is performed. The airplane can fly across the Pacific Ocean in 2 hours. A multi-disciplinary optimization program with aerodynamic, thermal structure, propulsion and trajectory is used to define baseline shape. Pre-cooled turbojet engine is assumed as the propulsion system for the hypersonic airplane. The engine can be operated from takeoff to Mach 5, continuously. This engine has adopted pre-cooling cycle using cryogenic liquid hydrogen. The high temperature inlet air at the hypersonic flight will be cooled by liquid hydrogen for fuel. Surface flow of the airplane at hypersonic speed and low speed are evaluated using results of CFD analyses. The control characteristics with control wings and variation of aerodynamic characteristics by adding strakes are obtained by a low speed wind tunnel experiment. The heat flux distribution on the surface of the airframe at hypersonic cruise condition is evaluated by using the results of CFD analyses. The characteristics of heat shield materials for the surface of the fuselage at downstream of the exhaust gas is evaluated by an elemental experiment.

An Experimental Study on Aerodynamic Design of Hypersonic Airplane

JAXA is currently conducting studies of a Hypersonic Turbojet Experimental Airplane which involves a hypersonic flight test of a Small Pre-cooled Turbojet Engine. The stability of this airplane has improvement. Therefore, the shape was redesigned, and aerodynamic performance was examined at the JAXA hypersonic wind tunnel facility and the University of Tokyo Kashiwa hypersonic wind tunnel facility. As results, the aerodynamics center can move backward by expanding wing area and decreasing nose width. The results indicate that this airplane has static stability around the center of gravity, and a high lift-to-drag ratio when it has trim.

Hypersonic Flight Experiment Plan of Pre-Cooled Turbojet Engine

,Hypersonic technology experimental vehicle for flight experiment of pre-cooled turbojet engine is investigated. The vehicle is assumed to mount two pre-cooled turbojet engines at the bottom. The vehicle will be accelerated up to Mach 5 flight speed by an external booster rocket. The vehicle aims at demonstrating Mach 5 cruise capability for a short period. Aerodynamic performance, engine thrust and structure mass are analyzed for the baseline system. Lift to drag ratio has improved by adding a strake in front of the main wing. Engine thrust is estimated without considering the additional thrust at the external nozzle. Structure mass is estimated using an optimization program using finite element method. Force balance around the vehicle is summarized and it is confirmed that the vehicle will slightly descend and decelerate at Mach 5 flight condition, without considering the external thrust. Component tests of pre-cooled turbojet engine with simulated flight condition are conducted toward the flight experiment. Pre-cooler is tested with high temperature condition simulating Mach 4 flight condition. Core engine starting sequence is confirmed with low pressure condition. Fuel supply system for hydrogen fuel with super-critical condition is tested to attain precise fuel flow control for the core engine. High temperature tests and propulsion wind tunnel tests of the engine with simulating Mach 5 condition is planned.

Evaluation of Aerodynamic Performance of a Hypersonic Experimental Aircraft

Hypersonic Turbojet Experimental vehicle is a vehicle proposed for the flight test at Mach 5. The capacity of the installing equipment has increased at recent design review. Therefore, it is necessary to increase the body volume. In this study, aerodynamic performance of this vehicle was examined to evaluate effect of body volume on aerodynamic performance. And effect of body shape on aerodynamic performance was evaluated. As the results, the body height is found not to affect the longitudinal static stability, but the directional static stability. And the effect of flow around airframe on aerodynamic performance is small.