We have developed a new wind turbine system that consists of a diffuser with a broad-ring brim at the exit periphery and a conventional wind turbine inside it. The new wind turbine has demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about 2–3 compared with a bare wind turbine. This is because a very low-pressure region due to strong vortex formation behind the broad brim draws more mass flow to a turbine inside the diffuser.
Gas leakage through carbon fiber reinforcement carbon composites, C/Cs, was discussed so as to apply C/Cs to heat exchangers in an engine system for a future space-plane. Since C/Cs include many cracks and pores, gas easily leaks through C/Cs. To predict and to prevent the gas flow through a C/C, leakage rate was measured as a function of pressure and gas flow path was identified by micro-observation of the C/C. Then, several analytical models were examined to clarify principal mechanism yielding gas flow resistance. It was found that laminar flow models gave far small flow resistance compared with experimental results, but a model based on adiabatic expansion and compression flow, used for gas leak through labyrinth seals, resulted in reasonable agreement. Finally, Si impregnation in a C/C was examined to minimize the gas leakage. This treatment was shown to be an excellent measure to reduce the gas leakage through C/C.
Absorption spectroscopy has been applied to the measurement of the arc-heater plumes. Number density distributions of atomic metastable oxygen were obtained from the measured absorption line profile at 777.19 nm in argon-oxygen plumes generated by arcjet type arc-heaters. As a result, it was found that the oxygen is localized off axis at the nozzle exit, and diffuses from outside toward the centerline in the plume. Moreover, numerical simulation was conducted to investigate the diffusion process of the oxygen in the arc-heater. The result indicates that the maximum degree of oxygen dissociation would be at the level of 0.01%.
To establish a large deployable antenna, monitoring and collimation are essentially important for reliable and precise deployment. We have developed an analysis method to detect shifts in several images, in which the combination of cross-correlations between images and approximation at sub-pixel precision enables us to detect shifts in images with a precision of up to 0.01 pixels. The LDREX mission, which was a preliminary experiment for the large deployable antenna of ETS-VIII, was performed in December 2001. During this experiment, anomalies occurred in the deployable antenna, and deployment was aborted. To understand the cause of the anomalies, we used our visual analysis method. Using this analysis, we detected vibrating features of the deployable antenna, which were useful for explaining the anomalies. In this paper, we outline our visual analysis method and discuss its application to monitoring of the deployable antenna.
Calculations of reactions about the chemistry of nitric oxides and ozone were performed to study the effect of NOX emission in the stratosphere. They were conducted with parameters in the stratosphere. In addition, sensitivity analysis was performed to study the mechanism of their reactions. Measurements of NOX under an emission of a low-pressure mercury lamp were also conducted by NO and NO2-LIF method experimentally. A large evacuable chamber was used to simulate stratospheric condition. Numerical results and experimental ones were compared and chemical and photochemical reactions of NOX -ozone chemistry were discussed. As results, main reactions of ozone depletion by NOX and HOX were specified and simulation of reactions in the stratosphere was achieved qualitatively by laboratory-scale experiment.
Experimental study is reported on the rest-to-rest maneuver applied to a model of flexible space structures. Maneuver is sometimes required to move a flexible space structure from an initial rest state without any motion to a final rest state also without any motion. It is necessary for the flexible space structure to move in minimum time with least excitation on the bending moment of the flexible structure. The model consists of a rigid body equipped with a flexible beam and is actuated by a linear motor to follow a linear motion. Three types of minimum-energy maneuver are examined experimentally: a time-optimal minimum-energy maneuver, a robustified minimum-energy maneuver, and a combination of the time-optimal and the robustified minimum-energy maneuvers, i.e., the robustified time-optimal minimum-energy maneuver. The well-known bang-bang type time-optimal and the robust time-optimal control maneuvers are also examined experimentally in order to compare their performances. The present experimental study has verified the validity of these total five types of maneuvers and show excellent agreement with the results of the numerical analysis. The excellent performance of the robustified time-optimal minimum-energy maneuver is then concluded to have superior performance in the robustness persisting the properties of the minimum-time and less fuel consumption in the maneuver.