A winged helicopter is one of the concepts to speed up a conventional helicopter. The wing contributes to the realization of high speed forward flight by sharing lift with the rotor. However, download is generated on the wing in low speed forward flight or hover because the wing is considerably exposed to the rotor downwash. This adverse force causes the deterioration of aircraft performance. Therefore, it is important to grasp aerodynamic performance in hover quantitatively and to conduct fundamental research to reduce the deterioration of aircraft performance. In this paper, experimental studies are conducted in order to measure rotor thrust and wing download in both OGE（Out of Ground Effect）and IGE（In Ground Effect）under the condition that the rotor torque coefficient is constant while changing the vertical and horizontal distance between the rotor and wing. From the experimental results, the influence of wing position with respect to the rotor on hovering performance such as the rotor thrust coefficient, the wing download coefficient, the ratio of the wing download coefficient to the rotor thrust coefficient and the effective thrust coefficient defined as the difference between the rotor thrust coefficient and the wing download coefficient are clarified.
The Project of Osaka Institute of Technology Electric-Rocket-Engine onboard Small Space Ship (PROITERES) was started at Osaka Institute of Technology in 2007. After successfully launching the 1st PROITERES nano-satellite, the 2nd PROITERES nano-satellite with electrothermal Pulsed Plasma Thrusters (PPTs) has been developed since 2010. The main mission is powered flight with very long distance, i.e. changing more than 10km in altitude on near-earth orbits by high-power PPTs. In this research, a 30W-class PPT system was developed. The PPT achieved the maximum impulse bit of 2.47mNs, specific impulse of 342s and total impulse of 90.1Ns with repetitive 72,000 shots. Repetitive 100,000 shots could be also carried out using a newly developed Power Processing Unit (PPU). Furthermore, a long-time operation system with a Multi-Discharge-Room type PPT (MDR-PPT) head was developed. In the present paper, we explain development status of EM-PPT system including MDR-PPT, PPU, and capacitor.
To investigate the cause of scatter and deviation of knockdown factor, which is defined the ratio of experimental buckling load and theoretical buckling load, buckling test of CFRP (Carbon Fiber Reinforced Plastics) cylindrical shells was conducted. Because CFRP is lighter, higher strength and stiffness than metallic materials, it is used for cylindrical shells of satellites, aircraft, and rockets. For lightweight design, the cylindrical shell is required to be thinner, but buckling tend to occurs. Thus to investigate the cause of scatter and deviation of knockdown factor is important for lightweight design. It is said that the cause of knockdown factor is mainly shape imperfection, however, the shape imperfection cannot explain the knockdown factor. Hence the buckling test of CFRP cylindrical shells focusing on ply-gap, ply-overlap, which is typical problem of composite material manufacturing, was performed. In addition, to improve the prediction accuracy of the buckling load, the elastic moduli of cylindrical specimen were measured by tensile and compression tests. Moreover, effect of length to radius ratios, offset of the center of cylinders to the center of load, and thickness of strain gage which had not been focused on previously were also investigated.
Rocket Based Combined Cycle (RBCC) engine is considered to use the hydrocarbon fuel. Endothermic fuel and surrogate fuel of Jet A are including various hydrocarbon fuel and chemical reaction is complicated. It is necessary to investigate the ignition characteristics due to the difference in the mixing ratio of the hydrocarbon fuel mixture gas. However, there are few studies on ignition characteristics at different mixing ratios. In this study, the research was carried out to analyze the ignition delay time of hydrocarbon mixture gas that was the methane/ethylene mixture gas by using analysis of zero-dimensional chemical reaction. In the case of larger ethylene ratio than 50[%], ethylene fraction had little effect on ignition delay time. It could be inferred that these may be caused by C2H4+OH=C2H3+H2O. Because, in the case of high ethylene rate, easily H atoms abstraction reaction from ethylene and to fast formation rate of H2O.
Today, the need for micropropulsion systems for micro- and nanospacecraft is growing. Micro-nozzles generally lead to low Reynolds numbers nozzle flow. It has been reported that nozzle efficiency was decreased at low Reynolds numbers region. However, there were gaps of nozzle efficiencies at same Reynolds number in previous researches, and ambient pressure was suggested as one possible cause of the gaps. In this study, nozzle performance was measured by changing the ambient pressure at throat Reynolds number ranged from 50 to 800. As a result, it was shown that low ambient pressure leads high nozzle efficiency only at throat Reynolds numbers under 200. It suggested that nozzle efficiency was affected by both throat Reynolds numbers and ambient pressure.