The two-spring injection nozzle used in D.I. diesel engines is known to be effective in reducing idle combustion noise by suppressing initial fuel injection rate. An increased injection pressure, however, decreases the noise reduction, because the pressure drop at the initial stage of needle lift (pre-lift) is not enough to lower the initial injection rate at a needle lift of 0.06 mm which is the minimum pre-lift from the viewpoint of production precision and reliability for a DLLA-S-type nozzle. For this reason, the author has proposed a new type of injection nozzle equipped with a groove needle which reduces the level of combustion noise to that of a two-spring nozzle with a smaller needle lift. Experiments revealed that the groove can increase the pressure drop between the upper part of the needle seat and nozzle sac, and reduce combustion noise at an idling condition with almost the same level of engine output and exhaust emissions as the engine equipped a two-spring nozzle with the minimum pre-lift.

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The volumetric efficiency markedly affects the performance of reciprocating internal combustion engines. Intake systems can be tuned to improve charging efficiencies at a particular engine speed. We introduce a simulation technique for air flow in intake systems of reciprocating engines. The method is based on the one-dimensional wave equation. We can use this method to predict the variations in pressure in the intake manifold and the volumetric efficiency simply. Comparisons of experimental and predicted pressure waves and volumetric efficiencies are presented. The results of numerical simulation are very similar to those of measurement. It is confirmed that the method is useful for determining the intake manifold geometry at the initial design stage.

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In the HAT (humid air turbine) cycle plant, fuel is burned with highly humid air generated by passing compressed air through a water tank heated by the exhaust gas from the turbine. Basic thermodynamic features of the HAT cycle plant, NO_x formation, temperature at the outlet of the combustion chamber and thermal efficiency, are demonstrated by extensive cycle analysis with varying air ratio, bypass ratio and moisture content of the air. In the evaluation of the thermodynamic properties, thermodynamic equilibrium was assumed. The efficiency obtained is substantially higher than that of the conventional open-type Brayton cycle plant, while the formation of NO_x is reduced. Enthalpy and entropy balances of the ideal gas mixture reacting in a steady open system are described in the appendix.

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In order to clarify the dynamic characteristics of a self-controlled Darrieus-Savonius hybrid wind turbine system, a system consisting of a hybrid wind turbine and an AC generator was tested under various wind conditions in the wind tunnel. We took up four types of wind blowing change for the test ; ramp, sinusoidal and square wind velocity changes and a similar wind velocity change to the field wind. A series of tests substantiated the effectiveness of our operating scheme wherein the tip speed ratio is maintained at a constant value. On the other hand, theoretical studies have been carried out on the characteristics of the system. A simulation model is presented in order to describe the system characteristics not only for the steady-state behavior but also for the dynamic behavior. In spite of its simplicity, the model can predict both characteristics of the system well. The appropriateness of the simulation model is confirmed by comparing with the experimental results. In addition, the field test data are discussed. As a result, it is confirmed that the system is operated and controlled satisfactorily in the field.

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