Regenerative Life Support Systems (RLSS), which maintain human lives by recycling substances essential for living, are comprised of humans, plants, and material circulation systems. The plants supply food to the humans or reproduce water and gases by photosynthesis, while the material circulation systems recycle physicochemically and circulate substances disposed by humans and plants. RLSS attracts attention since manned space activities have been shifted from previous short trips to long-term stay activities as such base as a space station, a lunar base, and a Mars base. The present typical space base is the International Space Station (ISS), a manned experimental base for prolonged stays, where RLSS recycles only water and air. In order to accommodate prolonged and extended manned activity in future space bases, developing RLSS that implements food production and regeneration of resources at once using plants is expected. The configuration of RLSS should be designed to suit its own duty, for which design requirements for RLSS with an unprecedented configuration may arise. Accordingly, it is necessary to establish a conceptual design method for generalized RLSS. It is difficult, however, to systematize the design process by analyzing previous design because there are only a few ground-experimental facilities, namely CEEF (Closed Ecology Experiment Facilities) of Japan, BIO-Plex (Bioregenerative Planetary Life Support Systems Test Complex) of the U.S., and BIOS3 of Russia. Thus a conceptual design method which doesn’t rely on previous design examples is required for generalized RLSS from the above reasons. This study formalizes a conceptual design process, and develops a conceptual design support tool for RLSS based on this design process.
In this report, we apply high frequency impulsive glow discharge technique for obtaining the flow pattern upstream of a compression corner. For purpose of comparison, schlieren visualization using high speed video camera is also performed. These experiments are carried out in a hypersonic gun tunnel at Mach number 10 and Reynolds number based on the frontal plate chord length 2.1×105. The corner angles studied are in the range from 0 to 30deg at zero incidence. Time lines are obtained successfully even for separated flow cases and the boundary layer edges visualized by the discharge-tracer technique correlate well with those defined through the schlieren images. The extent of the upstream influence becomes large with increasing corner angles and the separated boundary layer is transitional to turbulent flow for the largest angle case tested. Free interaction similarity using Newtonian theory is presented and it seems reasonable with respect to the present experimental results.
The design of a wave rotor requires an understanding of the pressure wave dynamics in the rotor passages. The present paper describes a two-dimensional numerical simulation and an experimental visualization of the wave rotor compression process. First, a unique experimental apparatus with fixed cells and rotating ports was constructed for visualization and direct measurements; this arrangement is opposite to the conventional setup. Next, experimental and numerical results were compared to verify the simulation modelling, particularly with regard to the propagation velocity of pressure waves in the passages. Lastly, the effects of gradually opening the passage to the ports and leakage through the clearance, which are considered to be dominant factors in wave rotor operation, on the pressure wave dynamics were carefully investigated. The results showed that the gradual passage opening greatly influences the primary shock wave, whereas the leakage mostly influences the secondary (reflected) shock wave. Moreover, it was revealed that the leakage generates an extra pressure wave during the compression process due to the interaction between adjacent passages.
The precise estimation of pressure waves generated in the passages is a crucial factor in wave rotor design. However, it is difficult to estimate the pressure wave analytically, e.g. by the method of characteristics, because the mechanism of pressure-wave generation and propagation in the passages is extremely complicated as compared to that in a shock tube. In this study, a simple numerical modelling scheme was developed to facilitate the design procedure. This scheme considers the three dominant factors in the loss mechanism —gradual passage opening, wall friction and leakage— for simulating the pressure waves precisely. The numerical scheme itself is based on the one-dimensional Euler equations with appropriate source terms to reduce the calculation time. The modelling of these factors was verified by comparing the results with those of a two-dimensional numerical simulation, which were previously validated by the experimental data in our previous study. Regarding wave rotor miniaturization, the leakage flow effect, which involves the interaction between adjacent cells, was investigated extensively. A port configuration principle was also examined and analyzed in detail to verify the applicability of the present numerical modelling scheme to the wave rotor design.
The optimization of flowfield of a self-field magnetoplasmadynamic (MPD) thruster was conducted by two soft-computing methods. Both the genetic algorithm (GA) and a new method to obtain a minimum/maximum based on the path integral were used to establish the optimum geometry that produces the highest thrust for specified operating conditions within a quasi-one-dimensional framework. The optimum geometry was found to be a quickly convergent and divergent geometry regardless of the method employed, and the optimized geometry was found to be the same that was obtained by the classical variational methods. This fact as well as their applicability to parallel computers assures that the soft computing methods are suitable for a more complicated multi-dimensional flowfield optimization problem.
Gas flow over a two-dimensional airfoil at very low Reynolds number is investigated in order to understand basic aerodynamic characteristics related to design of Micro Air Vehicle (MAV) for planetary exploration. Before the investigations, verification was conducted for the current numerical approach, which are commonly used and validated for high Reynolds number flow analysis, showing good applicability for low Reynolds number flow analysis. Flow around NACA4402 has been investigated for the condition of Mach number of 0.1 and Reynolds number of 1,000. Investigation shows that Reynolds number has a substantial influence on aerodynamic characteristics of the airfoil in low Reynolds number flow. In contrast, Mach number has a slight influence in comparison with Reynolds number.