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Turbochargers for vehicle use have been utilized for passenger cars and trucks to achieve high power, high torque, low fuel consumption and as a countermeasure for low emission of CO, HC, NOx, etc. Turbochargers are expected to play a major role in future to improve the performance of automobiles. Moreover, life of turbochargers has been increased steadily in spite of severe heat and stress condition due to requirement from engine manufactures. In case of truck use turbochargers, great efforts have been made to increase turbocharger life from 500,000 kms to 1,000,000 kms though the stress of the wheels has been raised due to increased boost pressure. Also, life of passenger-car use turbocharger has been increased in spite of higher exhaust gas temperature. This paper describes our experience of durability problems and our solution.

The Variable Orifice Nozzle (VON), has been developed to improve diesel combustion by changing the cross-sectional area of the injection hole. The area of the nozzle orifice is continuously controlled by the rotary valve, one component of the VON. The discharge coefficient of the VON was increased by simulating an internal flow in the nozzle tip. The VON performances were evaluated by its rate of injection, injection pressure, spray droplet diameter and instantaneous photographs taken by a high speed camera. These results show that, injection characteristics and spray patterns respond to the nozzle orifice area which is changed by the rotary valve from larger to smaller. The orifice area controlled nozzle provides higher maximum pressure and a longer injection duration than the conventional hole nozzle without full-load point of the injection pump. A smaller nozzle orifice has a wider spray angle compared with larger nozzle orifice.

Reduction of flow resistance in an intake system is essential for increasing the output of a four-stroke engine. Evaluation method regardless engine displacement or number of valves or cylinder must be required in intake system design. This study proposes intake loss coefficient as total evaluation method from flow in an intake port to charging flow into a cylinder. A three-dimensional, general-purpose Computational Fluid Dynamics (CFD) code was used to calculate an intake loss coefficient. A correlation was confirmed between an intake loss coefficient and the engine power output. Intake loss coefficients and the CFD technique may be used for efficient optimization of the shape of an intake system.

Improvements of interior and exterior noise are important targets in vehicle engineering. There are many reports concerning the reduction of radiator cooling fan noise. But, most of those reports are associated with studies of air flow noise. A radiator cooling fan connected to a crankshaft occasionally radiates structure-borne noise in addition to air flow noise. This structure-borne noise is caused by fan blade vibration excited by torsional vibration of a crankshaft. In this paper, we surveyed the mechanism of the structure-borne noise and discussed some methods for the noise reduction. And, as a result, we developed one of the noise reduction technique aiming at isolation of crankshaft vibration by modifying viscosity of the oil in a fan clutch.

An Eulerian model of evaporating transient sprays and a new method to describe air-atomization near the injector exit to predict the mean size and velocity of droplets have been developed to study the influence of operating conditions of an air-assist hollow-cone injector and the influence of fuel atomization on the spray structure. Good agreement between the results of the computation and experiment in terms of spray shape has been achieved. The numerical results show the typical structure of sprays from the air-assisted fuel injector and show the influence of atomization on the structure.

The government has been imposing a stricter diesel engine efficiency standard to reduce carbon dioxide, NOx and other particulate emissions. Diesel combustion improvement is a major concern, and many researchers have examined diesel combustion and its sprays. One possible method to solve the technical problems is applying the Variable Orifice Nozzle (VON) to fuel injection systems. The VON, which nozzle cross-sectional area is changed continuously, has been developed for direct injection (DI) diesel engines. The orifice changing mechanism is composed mainly of a rotary valve, drive shaft and small pulse motor. The VON's standard deviation (SD) of injection quantity in injection pump operation range is the same as the conventional hole nozzle's due to the rotary valve that is fixed by a spring. The smaller orifice of the VON has produced a higher injection pressure and produced a longer injection duration than that of a larger orifice.