Pyrometric Estimation of Exhaust Valve Temperature of an Internal Combustion Engine

The estimation of exhaust valve temperature of an internal combustion engine during its operation would be very useful for a more reliable and accurate design of valves and, more in general, of the whole valvetrain system. On the other hand, the direct temperature measurement of a valve is a big challenge because of its position inside the engine head, its high speed motion and the high temperature environment in which it works. To face this problem, an innovative experimental methodology is developed and shown in this paper. An experimental setup, based on the use of a pyrometer, is assembled and assessed thought several preliminary and on engine tests. The preliminary activity is focused on the estimation of the real emissivity of the exhaust valve surface and on the radiance attenuation due to the optical access and exhaust gasses interference. Once the measurement chain is assessed, several tests are carried out directly on an engine in working condition at the test bench. The tests allow to estimate the exhaust valve temperature in several stable engine working points as well as in transient conditions (load variation). In particular a first analysis of the correlations between valve temperature and some engine parameters like spark advance and air-to-fuel ratio is finally reported in this paper.