Gas Turbine Instrumented Exhaust System Structural Assessment

Abstract There is a constant demand from the market for the new gas turbines or enhancement of an existing gas turbines. There are several aspects which triggers this market demand, like changing environmental regulations, market competition, energy efficiency, technological advancements, need for fuel flexibility, to name only few. Prototype tests are conducted to validate the design input parameters considered at the time of development and the expected output parameters to gain more confidence of this new gas turbine or enhancement of an existing gas turbine. Typical design input parameters are pressure, temperature, speed, load, etc. and product output parameters are heat rate, efficiency, power output, speed, exhaust temperature values, estimated vibration levels, strain levels, clearance values between rotor to stator parts, etc. Several instrumentations are required at the identified locations of the critical parts and subsystems from the inlet to the exhaust of the gas turbine during the prototype testing. The gas turbine is tested with all these instrumentation with several identified operating conditions, viz. speed, load, etc., to gather actual values of the operating parameters and responses of the subsystem and the parts at these operating conditions. All these instrumentations require modification of the parts for the placement of the instruments and its routing of the cable to the data acquisition system. Pressure probes, thermocouples, strain gages, accelerometer, etc. are placed at the identified locations after necessary modifications are made to the part for installing the instruments. Use of pressure probes and thermocouples for the flow-path measurement needs additional fixtures which are verified for flutter and flow disturbance. All these modified parts and the additional fixtures are validated through appropriate analytical simulations to ensure design robustness for successful test campaign and data acquisition. Exhaust system is one of the vital parts of any gas turbine which facilitate handling the exhaust gas efficiently. Measurement of temperature, pressure and vibration levels are some of the critical parameters needed to ensure design robustness of the exhaust system. This paper is intended to describe the steps followed in performing analytical assessment to achieve design robustness of the instrumented exhaust system.