On the Development and Application of the FRAP® (Fast-Response Aerodynamic Probe) System for Turbomachines: Part 1 — The Measurement System

Abstract

Ill I II I 111111111 HM I • ABSTRACTThis contribution gives an overview of the current state, performance and limitations of the fast-response aerodynamic probe measurement system (MAP* System) developed at the Turbomachinery Lab of the ETH Zurich. In particular, the following topics are addressed:Probe technology: Miniature probes with tip diameter ranging from 0.84 to 1.80 mm (1-sensor and 3-sensor probes respectively) have been developed. New technologies derived from microelectronics and micromechanics have been used to achieve an adequate packaging of the microsensor chips used. Both the sensor packaging and the sensor calibration (time-independent and time-dependent) are crucial issues for the DC accuracy of any measurement. Aerodynamic probe calibration:The methods used for the sensor calibration and the aerodynamic probe calibration, the pertinent automated test facilities and the processing of the output data are briefly presented. Since these miniature probes are also capable of measuring the mean flow temperature, aspects related to the recovery factor and the self-heating of the probe tip are treated and some recommendations related to sensor selection are given. Measurement system and data evaluation:The early measurement chain described in GOSSWEILER, KUPFERSCHMIED and GYARMATHY 1995 has evolved into the FRAF° System. This automatic system incorporates dedicated measurement concepts for a higher accuracy and a more efficient operation in terms of time and failures. An overview of the data evaluation process is given.The FRAP® System has been tested in real-sized turbomachines under industrial conditions within the temperature limits of I40°C imposed by the sensor technology (axial-flow turbofan compressor, axialflow turbine, centrifugal compressor). These applications confirmed the potential of the system and encouraged its further development. Now, the system is routinely used in the facilities of the Turbomachinery Lab and in occasional measurement campaigns in other laboratories.

Technology Development of Fast-Response Aerodynamic Pressure Probes

“…The FRAPP concept comes from the combination of fast-response pressure transducers, typically of the piezoresistive kind, with aerodynamic directional pressure probes. The transducers can be flush-mounted on the probe head [14], enhancing the frequency response despite fragility; in other examples [6,[15][16][17], the researchers preferred to embed the transducers within the probe head to enhance the probe strength. Excellent reviews on the early stages of FRAPP development can be found in [18][19][20].…”

Stator-Rotor Interaction in Axial Turbine: Flow Physics and Design Perspective

“…All these issues have been addressed both experimentally and by proper CFD simulations; experiments require high promptness instrumentation like FRAPP (among others [29][30][31][32]) or LDV and PIV. Simulation, as well, requires high performance codes and schemes able to face the sliding of rotors with respect to the stationary components.…”

Unsteady Wet Steam Flow Measurements in a Low-Pressure Test Steam Turbine

“…Therefore, by using the FRAP-HTH with the sampling frequency of 200 kHz, approximately 16 and 21 measured data can be acquired in one pitch downstream from the L-1 and L-0 stages, respectively, when a moving blade passes the fixed traversing position. The design and operation of the current fast-response aerodynamic probes are based on the developments made over the past two decades at the Laboratory for Energy Conversion at ETH Zürich [10][11][12]. The newly developed FRAP-HTH has some similarities to the probe developed by Lenherr et al [11].…”