Unsteady pressure measurement

Abstract

Pressure measurement and turbomachinery have been intimately linked since flow field diagnosis was employed in verifying the operation of the first gas turbines. In the early years, time-mean pressures were required and extensive use of pneumatic connections between the measurement points and pressure transducers was made. Over the last two decades or so there has been a requirement to measure time-varying pressures in turbomachinery applications to bandwidths of order 100 kHz and the silicon piezoresistive pressure sensor has been the device which has been at the heart of many of the measurements. Although we mention other new developments in technology that are under way, this paper concentrates on the silicon piezoresistive sensor. The operation of the device in the context of gas turbine applications is outlined and some of the special issues which arise and must be addressed for accurate measurements are discussed. Following this, two example fields of the application of piezoresistive sensors are discussed in some detail, namely, rotating blade static pressure measurements and fast response aerodynamic probes. In both these cases instrumentation design considerations are discussed, technological implementation details given and sample data displayed and briefly discussed. Contemporary work elsewhere is included in the discussion. Finally, conclusions are drawn and the future context for the piezoresistive device is outlined.