Method For Gas Turbine Fault Diagnosis Based On Discrete Operating Point Sets

The unscheduled maintenance or outages of gas turbines due to degradation cannot only induce great additional costs and lost revenues but also influence the safety andreliability of gas turbines. Gas path diagnostics and prognosis can be used to assessengine conditions in real-time and predict the failure time in the future, so the predictivemaintenance actions can be performed. The benefits of predictive maintenance actionsare improved usability, safety and reliability as well as reduced life cycle costs.Therefore, the study of gas path diagnostics has great significance.Gas path diagnosis can derive the deviations of component performanceparameters when a set of measured parameters’ deviations are available. In order tosolve the underdetermined gas path diagnostic problem and reduce the impact of theexternal environment conditions on fault diagnosis accuracy, this paper focuses on theresearch on the gas path diagnostic method:Firstly, the linear gas path fault models on steady and transient state are established,and under the reasonable assumption that gas turbine faults are time-invariant, thesolvability condition of underdetermined gas path diagnostic problem is analyzed basedon the degree of observability analysis method. Therefor augmenting the linear faultequations based on discrete operating points is presented to solve the described problem,which can be used to diagnose the component fault of gas turbines. The analysis of avariety gas path diagnostics results demonstrates the capability and accuracy.Secondly, considering the effect of the external environmental conditions onmeasurable parameters, two kinds of gas turbine fault diagnoses, based on steady statecharacteristic curves and the output trajectory of equilibrium manifold expansion modelunder the standardized input, are studied. The characteristic curves described by theparameter expression of equilibrium manifold and state-space matrix of equilibriummanifold expansion model are analyzed and proved to reflect the system characteristicson some degree, which provides the theoretical basis for the gas turbines fault diagnosesbased on the characteristic curves. Using the output trajectory of equilibrium manifoldexpansion model under the standardized input as feature of fault detection is discussed.The analysis of a variety gas path diagnostics results demonstrates that both the twoproposed fault diagnosis methods are effective in reducing the impact of changes in theexternal environment and improve the fault classification accuracy, compared to thefault diagnosis method directly using measured parameters.Thirdly, according to practical application of gas path diagnosis， finger-printanalysis method is developed for gas turbine fault location, by using the angle between a reference vector and the relative direction vector of measurements deviation.