Carbon fiber reduces the concentration of pure NO gas through the reaction between NO gas and carbon fiber in the temperature range 100∼400°C. This study reveals that the mechanism of NO adsorption and reaction can be analyzed by several tests, and verifies the high NO_x reduction efficiency at the initial stage of operation using the previously surface-modified carbon fiber with HNO₃, for pure NO gas atmosphere. Also this paper presents good test data of more effective efficiency of NO_x reduction as compared to the standard carbon fiber for the 1171 ml gasoline engine.

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This paper is a semiempirical report on the development of a prediction algorithm of pressure drop for impingement cooling of heat sinks with pin fin arrays. The inlet orifice is relatively large and is placed over the center of the heat sink. A physical model suitable for heat sinks with pin fin arrays is considered based on the flow visualization results of our previous study. According to this model, the flow region is divided into five parts : i) the inlet orifice, ii) the region under the inlet orifice, where the flow is parallel to the pin fins, iii) the fin base area, iv) the region where the flow is perpendicular to the pin fins except under the inlet orifice, and v) the outlet of the heat sink. Values are predicted for pressure drop of the heat sink with pin fin arrays for a variety of orifice diameters, gaps, pin diameters, fin heights and numbers of fins. These values agree with the experimental data within ±30%.

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A combustion model for turbulent diffusion flames is estimated frequently through the comparison of the simulated result with the experimental one. Usually, profiles of time-averaged concentration and temperature are used in that comparison, because the local reaction rate cannot be directly measured. However, since their profiles are also influenced largely by transport phenomena, it is difficult to estimate the combustion model properly with this method. Therefore, it is desirable to calculate the local reaction rate from experimental results and compare it with the simulated one. In the present study, from this point of view, an attempt was made to obtain the lacal reaction rate by numerical calculation using measured values for a hydrogen jet diffusion flame. Then, it was suggested through the comparison of the obtained result with the simulated one that the method proposed here can provide reliable values for the local reaction rate.

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Studies were made on the behavior of droplets and the air flow in a hollow-cone spray, paying attention to the hollow-cone liquid sheet formed at the atomizer orifice. The shape of the liquid sheet was investigated by taking photographs with a flush of Nd-YAG pulse laser. Numerical simulation was carried out based on the transient Eulerian equations for the gas and the Lagrangian equation for the droplets. The averaged shape of the liquid sheet was incorporated in the simulation. Predicted results were compared with previous experimental data. It was revealed that simulation gives good prediction by considering the existence of the liquid sheet. Predicted results suggest that the movement of the liquid sheet induces strong air stream and that this air stream selectively transports small droplets and plays an essential role in classification of droplets by size. Accordingly, the existence of the liquid sheet is significant for the dispersion of droplets. In addition, the evaluation of the shape of the liquid sheet based on a simplified equation of motion suggests that the shape of the liquid sheet is predominated by the surface tension of the liquid.

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A new method of evaluation on gas tubine cycle with heating or cooling during compression or expansion is examined in this study. First, it is assumed that compression or expansion is a polytropic process, and the compressor and turbine work ratios are newly defined as the ratio of the work in a polytropic process to that in an adiabatic one. Next, some conditions for restricting a cycle are set. For example, the expansion work is never more than the energy supplied. As a result, it has been shown that the new method has been useful, the optimum pressure ratio for the maximum efficiency under a certain temperature ratio has been obtained and beyond this optimum value, the power and the thermal efficiency have declined rapidly.

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A laser-light sheet method using an argon-ion laser and high-speed photography was applied to visualize soot clouds formed during combustion in a direct-injection diesel engine. Soot clouds at a cross section on the scattered-light images were not observed until the middle parts of the combustion process, and were distributed on the outer edges of the luminous flames and in the clearance space. This suggests that soot does not exist within the hot flaming zone but is formed by cooling the fuel rich spots in the flame. In addition, from the effects of fuel quantities, injection timings and chamber geometries on soot clouds, it might be concluded that soot in the clearance space was significant in exhaust smoke.

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