Piston Crown Temperatures in a Compression-ignition Engine with “Comet” Head

Abstract

The paper describes tests on a high-speed compression-ignition engine of 120 mm. bore fitted with a Ricardo “Comet” head in which the piston was of “Y” alloy. The temperatures were measured by thermocouples in the crown, the connexions to the temperature-measuring apparatus being intermittent, and made only when the piston approached bottom dead centre. Thermocouple voltages were measured on a potentiometer, using the “null deflexion” method. Piston crown temperatures were measured for various loads, speeds, and cylinder liner temperatures, and were found to be higher than those obtained in previous investigations because of the very high turbulence induced by the “Comet” type antechamber. Confirmatory tests were made by using temperature-indicating paints, but these were not as satisfactory as had been expected. The results are discussed in the light of knowledge gained in former work on this subject; and, in particular, comparison is made with temperatures obtained in tests on a Mirrlees-Ricardo sleeve valve engine of similar speed and using a piston of the same design and material.