Unsteady pressure measurement

Abstract

Pressure measurement and turbomachinery have been intimately linkedsince flow field diagnosis was employed in verifying the operation of thefirst gas turbines. In the early years, time-mean pressures were required andextensive use of pneumatic connections between the measurement points andpressure transducers was made. Over the last two decades or so there has beena requirement to measure time-varying pressures in turbomachinery applicationsto bandwidths of order 100 kHz and the silicon piezoresistive pressure sensorhas 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 ofthe device in the context of gas turbine applications is outlined and some ofthe special issues which arise and must be addressed for accurate measurementsare discussed. Following this, two example fields of the application ofpiezoresistive sensors are discussed in some detail, namely, rotating bladestatic pressure measurements and fast response aerodynamic probes. In boththese cases instrumentation design considerations are discussed, technologicalimplementation 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 isoutlined.