Experimental and computational studies on supersonic mixing by slotted injection with various injection angle have been conducted. In the experiment flat plate model is installed into supersonic free stream of Mach number of 4 and fully developed turbulent boundary layer is established on the flat plate. The secondary jet is injected through slot nozzle set on the flat plate model in order to simulate SCRAM-jet supersonic mixer. Experiments are conducted by changing injection angle of helium gas in order to observe the effect of injection angle to the supersonic mixing. The flow fields are visualized by the Schulieren method. Also surface pressure distributions and spatial distributions are measured. The same flow fields are simulated by solving tow-dimensional full Navier-Stokes equation of mixture gas of air and helium and calculated results are compared with experiments. Quite good agreement is obtained in wall pressure distributions. And qualitative agreement is obtained in volume fruction distribution. By using the calculated results, the correlations between the mixing rate and the total pressure loss of the flow field are obtained.
The wing shape of flyback booster for a Two-Stage-To-Orbit reusable launch vehicle has been optimized considering four objectives. The objectives are to minimize the shift of aerodynamic center between supersonic and transonic conditions, transonic pitching moment and transonic drag coefficient, as well as to maximize subsonic lift coefficient. The three-dimensional Reynolds-averaged Navier-Stokes computation using the modified Spalart-Allmaras one-equation model is used in aerodynamic evaluation accounting for possible flow separations. Adaptive range multi-objective genetic algorithm is used for the present study because tradeoff can be obtained using a smaller number of individuals than conventional multi-objective genetic algorithms. Consequently, four-objective optimization has produced 102 non-dominated solutions, which represent tradeoff information among four objective functions. Moreover, Self-Organizing Maps have been used to analyze the present non-dominated solutions and to visualize tradeoffs and influence of design variables to the four objectives. Self-Organizing Maps contoured by the four objective functions and design variables are found to visualize tradeoffs and effects of each design variable.
This paper describes a new control algorithm for achieving any arbitrary attitude and angular velocity states of a rigid body, even fast and complicated tumbling rotations, under some practical constraints. This technique is expected to be applied for the attitude motion synchronization to capture a non-cooperative, tumbling object in such missions as removal of debris from orbit, servicing broken-down satellites for reparing or inspection, rescue of manned vehicles, etc. For this objective, we have introduced a novel control algorithm called Free Motion Path Method (FMPM), which was first formulated as an open-loop controller. Following the previous paper, which derives the conservative state variables formulation of the rotating motion of rigid body, this paper describes a feedback controller using these conservative variables as the state vectors to realize the closed-loop FMPM. It is shown in this paper that with this controller, we can explicitly limit the maximum required torque, as well as guarantee the stability, regardless of the speed and complexity of the target tumbling motion.
Low power Hall thrusters with circular cross-sectional discharge chambers, named TCHT-series were investigated to obtain the performance characteristics and plasma features. Hall thrusters with circular cross-sectional discharge chambers will be suitable for low power Hall thrusters because of the large volume-to-surface ratio which suppresses overheating of inner magnetic coils and ion losses on the chamber wall. TCHT-2 achieved 25% of thrust efficiency in the input power range of 100–200W. From RPA and double probe measurements, it is expected that the ionization region is located near the anode in which strong radial magnetic field exists. The Hall thruster TCHT-3 is downsized thruster for lower power operation, and the effect of magnetic field profiles on thrust performance was examined. TCHT-3 were classified into TCHT-3A and TCHT-3B. The Hall thruster TCHT-3A has the similar magnetic field configuration to TCHT-2, and the peak of radial magnetic flux density is located near the anode. On the other hand, TCHT-3B has the peak of radial magnetic flux density near the thruster exit. Such magnetic profile suppressed the discharge current. However, the specific impulse decreased. As a result, the thrust efficiency of TCHT-3B was lower than that of TCHT-3A. In the input power range of 120–180W, TCHT-3 achieved higher thrust efficiency than TCHT-2 did. TCHT-series showed that Hall thrusters with circular cross-sectional discharge chambers were suitable for low power Hall thrusters.
An experimental study on the energy conversion process of a continuous wave (CW) laser thruster is presented. The effect of the flow parameters on two dominant loss mechanisms of a CW laser thruster was investigated by using a CW CO2 laser with output power of 700W. The laser transmission and radiation from the laser sustained-plasma (LSP) were measured for several flow velocities and pressures, which were independently controlled. CCD camera was employed in order to observe the shape and position of the LSPs. We found that the energy conversion process is optimized when the LSP is in the vicinity of the focal point of the condensing laser beam.
Wind tunnel tests were conducted to investigate static roll characteristics of an SST model at high angles of attack. The Reynolds number based on the mean aerodynamic chord was 6.2×104. Normal force and rolling moment measurements have been done at different roll angles for the cranked arrow wing SST model. Smoke visualizations and Particle Image Velocimetry (PIV) measurements were also performed. Force measurement results were compared both with flow visualization pictures and with PIV measurement results. It was shown that the vortex breakdown has strong influences on the static roll characteristics of the cranked arrow wing.