Heat transfer in combustion chamber of piston engines
Treść / Zawartość
Measurements were made during downward propagation of a flat flame in a lean limit methane/air mixture. It was observed that the limit flames are very thick and that heat losses to the walls caused extensive cooling of the product gases within 0.05 m behind the propagating flame. Analysis of all data from well synchronized measurements as well as the results of following to them numerical calculations made possible to understand in detail physical picture of heat transfer from the hot gases to the cold walls. It is a unique way for explanation of heat transfer phenomenon. Measurements and calculations were used to prepare heat balance in a flammability tube. In the next step measurements were carried out in a rotating cylindrical combustion chamber. This chamber was treated as a model of piston engine combustion chamber with swirl. Temperature changes on a surface of the rotating combustion chamber were transmitted towards motionless data acquisition system. The temperature measurements were carried out with the use of special thermocouples located at the front wall of the chamber. Influence of rotation velocity on heat transfer was investigated in the range from 1000rpm to 5000 rpm. For a constant mixture concentration maximum temperature rise depended on the rotation velocity. Increased rotation velocity initially intensified heat transfer to the wall, with following to it increase of peak temperature, but further rise of rotation velocity resulted in local flame extinction near the s idę walls, decreased volume of combustion gases, and as a result of these, decreased value of peak temperature at the wall surface. Presented techniques make possible estimate heat losses to the walls in a combustion chamber of piston engines.
Bibliogr. 10 poz., rys.
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