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Cavitation, represents one of the most important limitations of all types of hydraulic machinery so as to automotive water pump, is the result of a reduction of the local pressure in a disturbed or flowing liquid to a level at, or near to, its vapor pressure. This paper focused on the criterion for the generation and prevention the cavitation for automotive water pumps. The test was performed on a water pump motoring rig and mixture of 50% antifreeze, ethylene glycol, with 50% water were used for the coolant. The test was carried out for various system pressure and for various coolant temperature which were controlled. The present study shows that the cavitation of water pump is strongly depending on the vapor pressure of the coolant and coolant temperature as well.

The direct-injection spark-ignition engine is one of the promising gasoline engine designs for achieving higher engine performance and lower fuel consumption while maintaining the excellent driving performance and low emissions. Thus an in-cylinder spray flow motion plays an important role in the adjustment of mixture preparation with fundamental spray characteristics and in- cylinder flow field as well. In this study, the fundamental spray characteristics such as drop size, velocity distribution, spray angle, in- cylinder spray flow motion in order to optimize intake port, piston top land and combustion chamber shapes in the development stage of mass-produced GDI engine. For this purpose, the PDPA measurements and Mie scattering technique were used for detailed spray characteristics. In-cylinder spray motions were captured by ICCD camera through the single-cylinder optical engine.