The influence of descent and taxi profiles on the thermal state of a jet engine at shutdown

摘要

Thermal rotor bow is a condition experienced in gas turbine compressors following shutdown. It occurs due to a vertical thermal gradient resulting from hot air rising during cooling, which causes vertical differential thermal expansion and a 'bow' in the compressor. Previous work to analyse the effect of this thermal bow have often been taken from a start state of the engine running at full capacity before being shut down. In reality this ideal engine state is not the case. During the final stages of flight before shutdown, the engine will go through various stages of operation that will create engine conditions different to those assumed. This work evaluates the effect various parameters have on the thermal condition of the compressor at shutdown using a model built in MATLAB. A six-parameter, two-level, full-factorial design of experiment study demonstrates that ambient temperature, taxi time and pressure ratio in the engine have a significant effect on the metal temperature distribution of a compressor at shutdown, with the first two minutes of taxi resulting in a 90 K reduction in hot end compressor temperature through the test cases run.