Pressure measurement by Piezo-electric transducers in reciprocating combustion engines

Abstract

The properties, use and construction of quartz Piezo electric transducers are briefly described. The dynamic calibration of quartz pressure transducers have been investigated using a Balanced-Disc pressure pick-up as a standard. The temperature effect on the static and dynamic output of these transducers has also been examined. Various types of engine indicators and their limitations are discussed. Piezo-electric pressure transducers and strain gauges were used for constructing an inertia-free pressure-volume indicator to produce a P-V diagram on an oscilloscope screen from which the trace was recorded. This included a simple and accurate method for obtaining top-dead-centre on pressure-time records. Some aspects of diesel combustion were considered using P-T diagrams from a variable compression Lister F.R.I diesel engine running at different loads and compression ratios. The effect of the shape of transducer passage on the accuracy of P-T diagrams is observed. Volumetric efficiency was measured using a crystal pressure transducer. The assumptions of this method was checked by comparison with the volumetric efficiency obtained by. two other established methods.