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To clear the differences of heat transfer coefficient of in-cylinder gas with fuel properties, the transient heat transfer coefficient of hydrogen gas is investigated by using the hydrogen fueled engine. The measured results were also compared with those of gasoline engine and several empirical equations. Transient heat transfer coefficients were determined by measurements of unsteady heat flux and instantaneous wall temperature in the cylinder head. As the main results, it is shown that transient heat transfer coefficients have remarkable differences according to fuel properties, and it's value for hydrogen engine is twice higher than that of gasoline engine. It means that equation of heat transfer coefficient that the effect of fuel properties is considered sufficiently, is needed to analyze or simulate the gas engine performance.
To measure of thermal loading in the combustion chamber of hydrogen engine with dual injection, instantaneous wall-surface temperature and unsteady heat flux of the cylinder head are measured and analyzed. The maximum wall surface temperature is shown in direct injection region which has large heat supplied. Partial and spatial temperatures have slight deviation in transient region of injection, though injection method change suddenly. All of thermal characteristics such as instantaneous temperature, temperature swing and heat flux of hydrogen engine with dual injection are remarkably higher than those of gasoline engine. It means necessity of additional countermeasure of thermal loading.
Instantaneous temperature probes were manufactured by pressing method. By using these probes. the instantaneous surface temperature and unsteady heat flux in the cylinder liner of DOHC engine were measured. The main results are as follows; i) the instantaneous surface temperature of cylinder liner are affected by the contact of piston ring as well as burning gas.<br/> ii) the wall temperature of the siamese portion is much higher than other parts, iii) it was shown that the rising trend of heat flux by burning gas are nearly limited to the 1/2-stroke distance from the top of cylinder liner.
As the preliminary stage for the countermeasure of thermal loading in miller cycle engine, coolant flows in the cylinder head of base engine including exhaust valve bridge were visualized and analyzed by using PIV technique. It was found that low coolant velocity regions were around exhaust valve bridge, around which stagnation of the coolant flow was observed due to the complex geometry configuration of water jacket. And velocity variation between each cylinder was remarkable. For the countermeasure of these, it is necessary to enhance coolant flow around exhaust valve bridge and to improve the deviation of coolant flow between each cylinder.
For the countermeasure of expected higher thermal load in miller cycle engine, coolant flows in the cylinder head of base engine with several coolant f1ow methods and drilled hole passages were measured by using PIV technique. And the cooling effect was e valuated by measurements of wall temperatures according to each coolant flow method. It was found that the series flow system was most suitable among the discussed 3 types of coolant flow methods since it had the best cooling effect in cylinder head by the fastest coolant flow velocity. It was also found that for drilled water passage to decrease the large thermal load in exhaust valve bridge, nozzle type is more effective compared with round type of water passage, and its size has to be determined according to the coolant flow pattern and velocity in each cylinder.
In order to assess the reliability of the auto-transmission control unit for automobiles, accelerated life test model and procedure are developed. By using this method, failure mechanism and life distribution are analyzed. The main results are as follows; ⅰ) the main failure mechanism is degradation failure that is, junction destruction of a semiconductor resin by high temperature. ⅱ) the life distribution of the auto-transmission control unit is fitted well to Weibull life distribution and the accelerated life model of that is fitted well to Arrhenius model. ⅲ) at the result of the life distribution, accelerated life test method is developed, and test time for life assessment will be shortened by 5,000 hours by this test method.