Pythia: An object-orientated gas path analysis computer program for general applications

For both civil and military aero gas turbines, technological advances and high cost of ownership have resulted in considerable interest in advanced maintenance techniques. Some of these techniques are now ready for application to industrial gas turbines. This thesis attempts to give an overview of engine maintenance and engine health monitoring techniques. One way to tackle the high cost is to employ Gas Path Analysis techniques. Gas Path C Analysis helps to identify deteriorated components of a gas turbine in terms of performance parameter changes with respect to each other. The changes can be analysed and actions taken to minimise the life cycle costs of a gas turbine. A generalised Gas Path Analysis computer program Pythia has been developed that incorporated new techniques such as a non-linear multiple fault diagnostics scheme. In order to develop reliable software a structured methodology, conforming to quality standards, has been introduced. The program Pythia is based on an object-oriented programming method that can be run with a modem PC. •Pythia has been applied to a wide range of gas turbine engines. As a result, the Gas Path Analysis technique showed statistically significant improvements with the non-Iinear solution. The non-linear GPA technique was able to successfully identify sets of instrumentation for all engines. Finally, the thesis presents further developments of the non-linear GPA technique. In particular, instrumentation error, creep life estimation and low cycle fatigue estimation are some of the techniques.