Shock/shock interaction flow has been simulated to calculate nonequilibrium heat flux distribution along a circular cylinder surface. The present method uses Park’s two-temperature model for the description of thermochemical nonequilibrium process in high speed, but low temperature air, and solves the Navier-Stokes equations for a reacting gas mixture, using the HLLE and LU-SGS methods as numerical scheme. Heat flux as well as pressure has been calculated by changing cell size at the surface, because the calculated heat transfer is sensitive to the cell size in a boundary layer. The results show good agreement with experimental data, which suggests that nonequilibrium effect should be taken into account in the estimation of heat flux even in high speed, but low temperature air flow.
To obtain concrete information on the mechanism of unstable combustion of liquid oxygen-hydrogen rocket engines, a rectangular rocket chamber with four glass windows was developed. The chamber was designed to simulate a 100-kN-sized cylindrical rocket chamber. Combustion tests were conducted at a chamber pressure of 1.7MPa. Combustion flames and oxygen jets were visualized with a high-speed video at a rate of 4,000 frame/s during low frequency unstable combustion. Oxygen jet images with a backlight, combustion flame and intensity of combustion flame were obtained. Stability analysis based on the double time lag model by Szuch was conducted to assist the understanding of the mechanism of unstable combustion.
The first flight of H-I launch vehicle was performed successfully on August 13 (1986). Her second stage was powered by the cryogenic engine LE-5 driven by turbopump systems, developed in Japan, for the first time. Later, requirement for turbopump’s flow-rate was increased as 40% to apply for the next generation launch vehicle, but fundamental turbopump configuration was not changed. In 19 flights data of LE-5s (including derivatives), no trouble caused by turbopumps is recorded. This paper reports research and development aspects of the turbopump systems of the LE-5 engine family.
The effects of the inlet casing configurations on unsteady cavitation were examined with a 3-bladed inducer. The inlet flow and cavitation pattern in two different casings were visualized using PIV (particle image velocimetry) and high-speed video. It was found that the rotating cavitation would be suppressed when the tip clearance at the inducer inlet was increased. The vortex cavitation in tip leakage flow and cavitation in back flow is considered to affect the appearance of the rotating cavitation by the inlet casing configuration.
Vibrational relaxation of oxygen by O2-O collision is studied in the temperature range 2000–7000K with physical kinetics and molecular collision dynamics. This study shows that all the potential energy surfaces appearing in the collision must be considered to correctly calculate rate constants, and that the Bethe-Teller theory is inadequate to describe vibrational relaxation in strong non-equilibrium, and validates widely used experimental models for vibrational relaxation.
A tethered space robot, which is connected to a mother spacecraft through a peace of tether, is a new space system proposed in the previous work. The tethered subsystem is envisioned to be a multi-body system for a robot, whose attitude can be controlled under tether tension by its own link motion. This paper discusses about microgravity experiment for a tethered space robot. Design and mechanism of the experimental device, required for the proposed attitude control, were explained. Also, link motion control algorithm was designed for the experimental device. Characteristics of the proposed attitude control were confirmed by microgravity experiment using a drop shaft, which can provide high quality microgravity condition during 4.5s.
A simple variable Mach number nozzle for aerodynamic engine tests was designed and calibrated. In this new nozzle, only one hydraulic actuator made freestream Mach number change from 2 to 4 during a run of the wind tunnel. The optimization of the nozzle contours was conducted by the 2-D computational simulation. The CFD results predicted that the deviation of Mach number from the averaged value was less than 1% and flow angle was less than 1 degree in the test region. The results of the calibration tests of the nozzle showed that the deviations of Mach number distributions in the test core (60mm×60mm) were less than 1.5% from Mach 2 to 3.5 and 3.5% at Mach 4. This result assured that this nozzle was suitable for aerodynamic engine tests. The aerodynamic tests of scramjet engine models in acceleration/deceleration conditions were carried out with this nozzle. Air capture ratio and internal drag were measured. When freestream Mach number decreased, the soft unstart in the inlet was observed around Mach 3. It resulted in increase of the internal drags.