High Frequency Pressure Measurements With an Uncooled Fast Insertion Probe at Turbine Exit in a Turbojet Engine

Abstract

This paper concerns the development and testing of a novel high frequency pressure probe for high temperature turbomachinery flow measurements. The probe has a measurement bandwidth from DC to 100 kHz and has been demonstrated in conditions of up to 6 bar and 1900 K. The 4 mm diameter probes are uncooled whilst in the flow and employ a fast insertion traverse to limit immersion times to of the order of 0.1 seconds. The probe was calibrated against a hot wire anemometer in a known turbulent flow. Data acquired downstream of the turbine in a turbojet engine is presented. The unsteady pressure data is decomposed into periodic and random components. Power spectra, turbulence intensity and length scale are derived. Short duration gas turbine measurements using fast insertion techniques have been under development for some years at the University of Oxford. The current fast-insertion probe is more compact and robust than previous designs. The present work demonstrates that it can resolve useful flow parameters in hostile gas turbine flows. These can be difficult or impossible to obtain using other methods. The rapid probe insertion technique should add to the armoury of diagnostic tools used by the gas turbine developer.