Gas turbine field performance determination: sources of uncertainties

This paper presents an analysis of the uncertainties in the determination of gas turbine health state, which arise by using a method of gas path analysis. This method uses field measurements to estimate, through a mathematical model of the gas turbine thermodynamic cycle, the characteristic geometric and performance parameters, which are indices of gas turbine health state. The investigated sources of uncertainties are the influence of measurement accuracy and the a priori selection of the characteristic parameters that have to be considered constant during the calculation. This fact implies that variations occurring on these parameters in the actual gas turbine cause an estimation error on the characteristic parameters used as problem variables. The analysis leads to the selection of the appropriate measurements to be used in the gas turbine health state determination and to the identification of both the most critical measurements and parameters