Exhaust Port Heat Rejection in a Piston Engine a Preliminary Report

While it is well known that engine exhaust temperature has an exponential effect on the thermal oxidation of carbon monoxide and unburned hydrocarbons and that the exhaust temperatures of seemingly similar engine designs vary markedly, little is known regarding the effect of exhaust port design on exhaust temperature. This paper describes an experimental program currently in progress that defines the magnitude of heat loss in exhaust ports and the effect of some geometric design variables and of several exhaust port liner designs on exhaust heat loss. The paper reveals that a port designed for minimum heat transfer may result in a 250°F increase in exhaust gas temperature. These results indicate a significant reduction in radiator requirements as well as for greatly improved thermal reactor performance.