Experiments on the effects of thermally cracked components of n-dodecane on the ignition and the combustion performance of a scram jet model combustor at Mach 2 were performed. Gaseous components of the thermally cracked n-dodecane at various temperature and 1MPa were measured by a gas chromatograph. Surrogate mixtures including hydrogen, methane, ethane and ethylene were injected into the supersonic air stream in the model combustor, and ignition and combustion behaviors were investigated at total temperatures of 1800 to 2400K. Pressure measurements on the combustor wall and optical observations of combustion using a high speed video camera were conducted. Results indicated that three combustion modes of intensive, transient and weak combustions were observed. Ignition was observed in the boundary layer positioned at the downstream of the cavity, and the flame propagated upward to the cavity. The ignition performance of ethylene was superior to methane and ethane, and their performances were elucidated from the reactivities predicted by a 0-dimensional calculation of chemical reactions for stoichiometric mixtures. An increase in the methane concentration reduced the ignition performance, and an increase in ethylene enhanced the ignition and combustion.
Low-level turbulence around airport poses a potential hazard to aircraft operations such as take-off and landing. An advisory system for such atmospheric turbulence is of great help in safe airport operations. Aiming for a part of the advisory system, we investigate terrain-induced low-level turbulence at Shonai airport by an integrated approach of meteorological model prediction and high resolution large eddy simulation. The predicted results by the integrated system are validated against Doppler radar observations focusing on strong-wind events. The results revealed that low-level turbulence is triggered by a hill located on the north side of the runway. Furthermore, the results showed the extent of the low-level turbulence in the wake of the hill, that is, the turbulent area increases vertically as well as horizontally in the downwind direction. The magnitude and the direction of winds vary in short period of time due to the turbulent nature of the terrain-induced turbulence. A simplified model is employed to estimate the vertical load of aircraft along a flight path from the predicted turbulent wind field. These findings would be used to predict the hazardous area to aircraft operations, which is an important part of the advisory system.
A 400-kW-class steady-state self-field magnetoplasmadynamic (MPD) thruster is numerically designed with a combination of magnetohydrodynamic (MHD) and thermal analyses, where a heat flux evaluated from the MHD analysis is imposed on the electrode as a boundary condition in the thermal analysis. The increase in the ratio of an anode radius to a cathode radius improves the thrust performance, but can rise the temperature locally at an anode downstream edge and a cathode tip due to the concentration of discharge current and/or insufficient heat removal. It is suggested, however, that a thruster without electrode melting is realizable even at such a high input power by setting an appropriate cathode radius and enhancing heat removal from the electrode by means of heat pipe. The thruster designed under the thermal constraint is expected to achieve a thrust of 17 N, a specific impulse of 990s, a thrust efficiency of 21% for argon propellant.
To land a helicopter on a flight deck of a ship is said to be one of difficult operations even for experienced pilots because the helicopter rotor is affected by complex flows, e.g. ship airwakes and interference flows formed between the rotor and superstructures, in addition to ship motions. Therefore, it is important to grasp quantitatively influence of these complex flows on the helicopter rotor for securing the safe deck-landing. In this paper, CFD analysis of helicopter rotor operating over a flight deck is done by solving unsteady 3D compressible Euler equations with an overlapped grid system. The superstructure on a flight deck is modeled by a simple sharp edged bluff body. Parameters for numerical analysis are landing spot and relative wind speed to the rotor and ship. Effects of these parameters on the rotor torque, flowfields around the rotor and inflow distributions on the rotor disc are clarified.