Advances in Traceable Calibration of Cylinder Pressure Transducers

Accurate and reliable dynamic pressure measurements are needed for optimizing performance in modern combustion engines, manufacturing processes and aerospace applications. Besides fast pressure transients, these applications subject dynamic pressure transducers to elevated temperatures. Both of these quantities effect the sensitivity of transducers. Therefore, transducers should be calibrated at conditions that corresponds to the operating environment. To answer these needs, the National Metrology Institute VTT MIKES has developed its drop weight dynamic pressure primary standard further. Developments include improved control and measurement of the falling weight, extension of the pressure range to combustion engine pressures down to 3 MPa and a heating option for dynamic pressure transducers under calibration. These advances enable traceable calibration of cylinder pressure transducers at conditions relevant to engine applications. The overall uncertainty (k = 2) of calibration is estimated to be around 1.7%. The performance was demonstrated by calibrating a piezoelectric pressure transducer in the pressure and temperature range from 7 MPa to 30 MPa in 20 °C, 120 °C and 180 °C, respectively. As a result, traceable calibrations of dynamic pressure transducers can be performed at conditions relevant for engine applications. This improves the reliability and accuracy of in-cylinder pressure measurements.