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This paper investigates the relationship between design parameters and creep life consumption of stationary gas turbines using a physics based life model. A representative thermodynamic performance model is used to simulate engine performance. The output from the performance model is used as an input to the physics based model. The model consists of blade sizing model which sizes the HPT blade using the constant nozzle method, mechanical stress model which performs the stress analysis, thermal model which performs thermal analysis by considering the radial distribution of gas temperature, and creep model which using the Larson-miller parameter to calculate the lowest blade creep life. The effect of different parameters including radial temperature distortion factor (RTDF), material properties, cooling effectiveness and turbine entry temperatures (TET) is investigated. The results show that different design parameter combined with a change in operating conditions can significantly affect the creep life of the HPT blade and the location along the span of the blade where the failure could occur. Using lower RTDF the lowest creep life is located at the lower section of the span, whereas at higher RTDF the lowest creep life is located at the upper side of the span. It also shows that at different cooling effectiveness and TET for both materials the lowest blade creep life is located between the mid and the tip of the span. The physics based model was found to be simple and useful tool to investigate the impact of the above parameters on creep life.

The determination of the rate of heat transfer from the turbine blade in a cross flow is important in hot section gas turbine life assessment. For design purposes, the rate of heat transfer is normally fixed by semi-empirical correlations. These correlations require knowledge of fluid properties which depend on temperature. For gases these properties are normally available only for the dry state, thus the possible effect of the water vapour content has been overlooked. Many gas turbines operate in environments in which air humidity is very low and therefore has little influence on gas turbine performance. However humidity becomes more important in hot, humid climates where there are large variations in ambient absolute humidity, especially in hot and humid climates. The aim of this paper is to investigate and present the effect of humidity at different operating conditions on the turbine blade coolant heat transfer and blade creep life. The effect of humidity was considered only on the air coolant side. he The heat transfer coefficient on the hot side was calculated for dry hot gas. This avoided the balancing effect of each other (heat transfer coefficient coolant side and hot side). The WAR at each operating point is quantified based on the ambient temperature and the relative humidity (0%–100%). Results showed that with increasing WAR the blade inlet coolant temperature reduced along the blade span. The blade metal temperature at each section was reduced as WAR increased, which in turn increased the blade creep life. The increase in WAR increased the specific heat of the coolant and increased the heat transfer capacity of the coolant air flow. Different operating points were also evaluated at different WAR and Tamb to identify the effect of WAR on the creep life. The results showed that an increase in WAR increased the blade creep life. The creep life of the blade at each section of interest was obtained as a function of the blade section stress and the blade metal section temperature using the LMP approach.

Peak load operation requires gas turbines to operate at high firing temperature with consequence reduction in the useful lives of components. This paper studies the quantitative relationship between gas turbine power setting and the hot gas-path components’ life consumption. A 165MW gas turbine engine is modelled and investigated in this study. A comparative lifing model, which performs stress and thermal analyses, estimates the minimum creep life of components using the parametric Larson Miller method. This lifing model was integrated with in-house performance simulation software to simulate the engine performances at design point and off-design conditions. The results showed that the combined effect of the operating environment and the power demand could have significant impact on blade creep life. Predicting this impact will aid gas turbine users in the decision making processes associated with gas turbine operation.

The cooling of high temperature gas turbines has been the subject of intensive work over the past few decades. Analysis of the metal temperature of cooled blades requires the solution of the equations governing the heat flow through the blade given the internal and external distributions of the boundary gas temperatures and heat transfer coefficients. An analytical model to investigate the influence of Water Air Ratio (WAR) on turbine blade heat transfer and cooling processes (and thus the blade creep life) of industrial gas turbines is presented. The method is based on a blade with convective cooling and a thermal barrier coating (TBC). The approach is based on engine performance, heat transfer models (hot side and cold side model), in addition to a method that accounts for the changes in thermal conductivity, viscosity, density and the gas properties of moist air as a function of WAR. The evaluation of heat transfer data in this model is considered by using non-dimensional parameters namely: Reynolds number, Nusselt number, Stanton number, Prandtl number and other related parameters. The aim of this paper is to present an analytical model to investigate the influence of humidity on the turbine blade heat transfer and cooling processes which, in turn, affect blade creep life. The developed model can be used to assess the main parameters that influence blade cooling performance, such as cooling methods, alternative cooling fluids, blade geometry, gas properties and material and thermal barrier coatings. For a given off-design point, the WAR was varied from dry to humid air (air/water vapour mixtures). The whole cooled blade row is regarded as a heat exchanger with the presence of TBC subjected to a mainstream hot gas flow from the combustion chamber.