Unsteady pressure measurement

Pressure measurement and turbomachinery have been intimately linked since f low field diagnosis was employed in verifying the operation of the first ga s turbines. In the early years, time-mean pressures were required and exten sive use of pneumatic connections between the measurement points and pressu re transducers was made. Over the last two decades or so there has been a r equirement to measure time-varying pressures in turbomachinery applications to bandwidths of order 100 kHz and the silicon piezoresistive pressure sen sor has been the device which has been at the heart of many of the measurem ents. Although we mention other new developments in technology that are und er way, this paper concentrates on the silicon piezoresistive sensor. The o peration of the device in the context of gas turbine applications is outlin ed and some of the special issues which arise and must be addressed for acc urate 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 disc ussed, technological implementation details given and sample data displayed and briefly discussed. Contemporary work elsewhere is included in the disc ussion. Finally, conclusions are drawn and the future context for the piezo resistive device is outlined.