This study experimentally investigated the influence of the mixture stratification on the cooling loss characteristics of hydrogen combustion in a constant-volume combustion chamber. The conclusions of the study are as follows: The stratified charge by the direct fuel injection into the lean mixture tends to reduce the heat transfer from the burning gas to the combustion-chamber wall and increases the apparent heat-release fraction in hydrogen combustion. The optimizations of the degree of stratification and the overall excess-air ratio achieve quite low cooling-loss fractions, while maintaining equivalent levels of the rate of heat release to homogeneous-charge stoichiometric combustion. The reduction of cooling-loss fraction by the stratified charge can be attributed to a lowered temperature of burned gas around the combustion-chamber wal1 by the leaner mixture there formed by the stratification. The direct-injection stratified charge, which reduces the cooling-loss fraction without deteriorating the degree of constant volume, is an effective way for improving the thermal efficiency in hydrogen-combustion engines. There is the optimum interval between fuel injection and spark ignition for cooling loss reduction. A shorter interval enhances the convection of burned gas, while a longer interval weakens the stratification and increases burned gas temperature around the wall.
Reduction of cooling loss in hydrogen combustion by direct injection stratified charge
2003
6 Seiten, 10 Bilder, 22 Quellen
Conference paper
English
Reduction of cooling loss in hydrogen combustion by direct injection stratified charge
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