Evaluating Piezo-electric Transducer Response to Thermal Shock from In-cylinder Pressure Data

One of the major effects limiting the accuracy of piezo-electric transducers for performing in-cylinder pressure measurements is their sensitivity to the cyclic thermal loading effects of the intermittent combustion process.

This paper compares five different methods for evaluating the effect of this so- called thermal shock from the measured pressure signal. All of these methods were applied to seven different types of piezo-electric pressure transducers in different locations and placement configurations. This set of transducers was selected such that it is representative of the pressure transducers presently used for engine development purposes. It includes several water-cooled transducers typically used for accurate thermodynamic analysis and a number of uncooled, smaller but more robust pressure transducers typically used for engine monitoring.

The results from this study show that no single method fully characterizes the effects of thermal shock. By combining these methods it is however possible to describe these effects and to rank different pressure transducers according to their sensitivity to thermal shock. It is furthermore confirmed that by using special adapters the effect of thermal shock can be minimized.