DETERMINATION OF STEADY STATE GAS TURBINE OPERATION

Repeatable measurement of engine performance requires the system to be near steady state. A technique is presented to assess how close engine operation is to steady state. It estimates the rate of change of the assessed parameter across the sample time and provides an associated confidence interval. This allows a minimum amount of test time to characterize performance and provides consistent criteria to assess steady state. The technique can either be used online to determine when to take a steady state point or to find the optimal sample from a given data set. To make the technique feasible during testing a recursive method is developed to minimize the computational time. The technique is demonstrated on known functions with random noise to benchmark its capabilities. This is followed by a demonstration on test data from a small turbo jet engine operated in an altitude facility, a turboprop on an outdoor test stand and an after-burning turbofan in an indoor test cell.