In order to attain combustion of methane fuel in supersonic airstreams of relatively low temperature, hydrogen fuel was added to the fuel as a ignition promotor. In experiments, rectangular combustor with backward step was adopted and the methane-hydrogen mixture fuel was injected into supersonic airstreams. The region where the self-ignition occurs was confirmed by high speed direct photographs, and self-ignition characteristics were investigated with parameters of equivalence ratio and fraction of hydrogen in the fuel. The injection form was refined with use of the obtained results to attain self-ignition with low fraction of hydrogen. The combustion of methane-hydrogen mixture fuel was compared with that of hydrogen fuel by using wall static pressure distributions and OH/CH emission images of the flame. As results, it is confirmed that the combustion of methane fuel in the airstreams is obtained by addition of hydrogen fuel, and it is considered that the self-ignition in refined injection form is obtained under same conditions as that of hydrogen fuel, independently of the fraction of hydrogen in total injected fuels. The static pressure distribution and the flame shape in methane-hydrogen mixture fuel case were similar to those in hydrogen fuel case.
This paper discusses several types of global satellite constellations applied for the integrated satellite mission which accomplishes radio navigation, mobile communication and earth observation globally, and mainly considers position determination (navigation) accuracy achieved by these constellations. Satellite constellations in low altitude orbits are unsuitable for continuous positioning because numerous satellites must be deployed on orbits and the maintenance cost becomes expensive, so satellite orbits more than 20, 000km are investigated in this paper. Furthermore, this paper discusses the continuous expansion of satellite deployment which enables the improvement of the integrated satellite mission for the developing phase.
Supersonic combustion in a rectangular duct was investigated experimentally. Hydrogen fuel was injected parallel to an air flow from a two-dimensional slot injector. Two-dimensional flame was established downstream of the injector and so-called precombustion shock was observed. The shock wave originated at separation region in air flow boundary layer upstream of the injector. The relationship between the strength and the position of the shock wave was different from that in perpendicular injection case. In slot injection case, it is supposed that the separation region and reacting region interacted to act as a large wedge and generate the rather strong shock. Combustion without generation of the precombustion shock was achieved with conversion duct. However, the combustion efficiency was low and the ignition delay distance was large in this case. The shock wave was expected to enhance the reaction by rising the static temperature and pressure.
One of the most important issues for microgravity experiments on low-Earth orbiting spacecraft is the “residual acceleration.” The residual acceleration is induced by various kinds of environmental disturbance sources (e. g. gravity gradient, rotational motion of spacecraft, solar radiation pressure, aerodynamic drag, vibration caused by spacecraft's flexibility, rotating machines and crew activities, etc.). To minimize the residual acceleration, it is essential to know what the residual acceleration is and how it is induced. In this paper, the residual acceleration is formulated in terms of dynamic variables describing spacecraft's attitude and orbital motion and is evaluated by numerical simulations using a simple rigid spacecraft model. The results are summarized as a function of time, or a position within spacecraft for typical attitude control schemes, which identifies the effects of environmental disturbance sources.
Resistance spot welding concepts for fastening and attaching structural components made of CFRTP composite laminates are presented. Due to the presence of touching fibers, CFRTP laminates exhibit electrical conductivity in the direction transverse to fiber axes as well as in the fiber direction. Therefore, passing an electric current through two overlapping CFRTP laminates, which are sandwiched between upper and lower electrodes, Joule heat is generated in the region of current concentration to melt them together. When the current flow ceases, their contacting surfaces rapidly cool down and are joined together in one spot. One and three dimensional transient heat transfer analyses have been carried out to provide welding variables appropriate for the spot welding of CFRTP laminates. In the experiment, two pieces of CFRTP coupon specimen made of a commingled yarn prepreg are spot welded for various current and time combinations to investigate the effects of welding variables on the weld strength. Although the material properties of CFRTP composites which directly influence the weldability, —anisotropy, resistivity, thermal conductivity and melting temperature, etc. —are significantly different from those of metals, sound spot welds are produced by the present method.