Experimental Work on Exhaust Valve Life at Thornton Research Centre

Abstract

Experience gained during the development of a bench test for assessing exhaust valve life has shown that the operating conditions of the engine are important in deciding not only the absolute valve life, but also the relative effect of fuel and lubricant combinations. It is concluded that short cuts in the estimation of exhaust valve life can give misleading results. The preparation of the engine for test and the test procedure are described, together with some details of the equipment used to observe the movement of the exhaust valves of a running engine.

The stress gradient due to temperature variation across an exhaust valve head is estimated. The temperatures from which the estimate was made were obtained by measuring the hardness of a specially heat-treated valve after it had been in service. The shape of the temperature contours agreed with those found by others, and using published stress rupture data it was found that calculated valve life periods, based on the thermo mechanical stresses set up due to temperature variations, were of the same order as those found in practice

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