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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 variable intake systems tend to be adopted in gasoline engines for fuel economy and emission regulation. In the cases, because both swirl and tumble flows are together induced to the cylinder, in-cylinder flow pattern becomes very complicated so that we can not decide this flow as one major pattern like swirl or tumble. The purpose of this study is to find new evaluation index for in-cylinder flow characteristics instead of current swirl or tumble coefficient using a steady flow test rig on intake port systems. To this end, port flow rig tests were conducted on the DOHC head varying lift of intake valves. Finally angular flow coefficient and inclination angle were introduced as new evaluation indexes for in-cylinder angular flow characteristics.

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.