Technical Paper
Thermal Stress on a Piezoelectric Pressure Transducer in the Combustion Chamber of an SI-Engine
1985-02-01
850375
Cylinder pressure traces of internal combustion engines measured with piezoelectric pressure transducers are significantly influenced by long- and shorttime temperature changes. Transducer sensitivity changes due to temperature up to 1 %/100°C are possible. This requires calibration of pressure transducers regarding the real temperatures given by engine operating conditions. Experience at Volkswagen Research with small transducers without separate watercooling - often the only possible alternative because of space problems in small engines - showed damage due to thermal stress when operated under knock conditions. This gives an indication of high temperatures in the front part of the transducer which are considerably higher than those in the surrounding material of the cylinder head.
