Experimental measurement and characterisation of the effect of offtake flow on the time constants of a compressor casing

Authors

Andrew Pilkington - University of Oxford
Leo Lewis - University of Oxford
Marko Bacic - University of Oxford
Andrew Dann - University of Queensland

Abstract

This paper describes measurements of the thermal response times of a compressor casing from a large civil engine as a function of offtake flows. The experiments used a full-size engine compressor casing and full-sized offtake mass flow rates. The experiments were performed using the Oxford Transient Heat Transfer facility (THTF).The temperature response rates of the casing to a fast ramp change in input air temperature were measured at several metal and air locations. It is shown that the transient temperature behaviour at each location can be accurately characterised by a single time constant. The variation of time constant with offtake mass flow is also shown.Such characterised experimental data can provide valuable validated information on casing thermal response much earlier than the approach of waiting for an engine development programme thermocouple test, and thus bring forward the achievement of optimum transient casing behaviour.