Turbine Hot Gas Path Components Research Articles

Measurement of Internal Heat Transfer Distribution of Highly-Loaded Gas Turbine Blade by Combined Experimental/Numerical Method

To ensure a passable life span of gas turbine hot gas path components the measurement of metal surface temperature is paramount. Experimental analyses on internally cooled devices are often performed on simplified or scaled up geometries, which reduces the applicability of the results to the actual real hardware. A more reliable estimation of cooling performance could be obtained if the real engine component is directly studied. To achieve this goal, an experimental campaign is performed to investigate the internal heat transfer distribution of an industrial blade, cooled by means of an internal U-shaped channel. During the experiment the blade is heated to a known temperature, then a coolant is introduced through the internal channel to induce a thermal transient, during which the external surface temperature is measured with the help of an infrared camera. Then a transient thermal finite element simulation is performed with the same boundary and inlet conditions of the experiment. Based on the output of the simulation, the internal heat transfer distribution is updated until convergence between simulation output external temperature and the experimental temperature is achieved. In order to start the iterative procedure, a first attempt estimation of the internal heat transfer distribution is obtained with a lumped thermal capacitance model approach. Different experiments were performed with different mass flow rates and the results are compared with available literature data. The obtained results allow to observe detailed heat transfer phenomena, strongly bound to the relevant features of the actual real cooling system.

Experimental and CFD analyses of a highly-loaded gas turbine blade

The estimation of metal temperature is paramount to ensure an adequate life span of gas turbine hot gas path components. An experimental campaign was carried to investigate pressure loading and metal temperature distribution of an industrial blade cooled by means of straight smooth channels. Changing mainstream and coolant mass flow rates it was thus possible to characterize the thermal response at different operating conditions. CFD simulations allowed to relate the metal temperature distribution to the processes of laminarization and transition of the boundary layer. Further sensitivity analyses aimed at estimating the impact of the uncertainty associated with certain boundary conditions highlighted that a reduction in mainstream turbulence at leading edge of 30% can reduce metal temperature up to 5%, whereas coolant turbulence plays a minor role. The same effect was pointed out when the actual surface roughness of the internal channels was accounted for. Particular attention should be paid to this parameter in the thermal design of additive manufactured components when surface finishing is not feasible.

Degradation Assessment of Gas Turbine Hot Gas Path Components

Hot gas path component consists of components designed to burn air-fuel mixture in combustion section and provide hot gasses to the turbine section where mechanical power is produced. The aim of this research project is expected to improve the current practices of managing degradation of hot gas path components. Understanding the damage mechanisms is of great interest in reducing the damage and failure risk. In this research, a study was conducted on F-Class type gas turbine hot gas path components assembly. It involved extensive examination and testing of the components which had been in operations for 24,000 hours since the last shutdown. Various factors such as installation, operating conditions, hardness and material of constructions were also investigated. This paper reports the initial findings of the study of hot gas path components degradation. It describes the damage observed on the affected areas of the components and proposes the factors that contribute to the damage processes. Potential solutions for mitigating the damages are also discussed.

A guide to condition assessment of gas turbine hot gas path components

Maintenance and/or replacement of hot gas path (HGP) components in gas turbines represent a major fraction of the cost of installation and operation. Condition assessment of HGP components can increase reliability and minimise costs, based on sound metallurgical and mechanical analysis. In this paper relevant improvements to condition assessment procedures and analyses are described, including γ’ precipitate sizing and lifing techniques used on precipitation-hardened Ni-based superalloys. Non-destructive testing, optical metallography and miniature creep testing are also covered. Understanding the operation and possible failure mechanisms of the component in service is the key to selecting an appropriate assessment procedure to facilitate optimisation of component lives and repair cycles

A guide to condition assessment of gas turbine hot gas path components

Maintenance and/or replacement of hot gas path (HGP) components in gas turbines represent a major fraction of the cost of installation and operation. Condition assessment of HGP components can increase reliability and minimise costs, based on sound metallurgical and mechanical analysis. In this paper relevant improvements to condition assessment procedures and analyses are described, including γ’ precipitate sizing and lifing techniques used on precipitation-hardened Ni-based superalloys. Non-destructive testing, optical metallography and miniature creep testing are also covered. Understanding the operation and possible failure mechanisms of the component in service is the key to selecting an appropriate assessment procedure to facilitate optimisation of component lives and repair cycles

OS6-5 Development of Risk-Based Maintenance Software for Gas Turbines

"RISKWISE^<TM> for Gas Turbines" has been developed to perform risk-based maintenance and inspection planning on gas turbine hot gas path components. The software allows the user to easily prepare a risk matrix, plotting every active damage mechanism for each hot gas path component. Based on the result of the risk assessments the components can be ranked, allowing inspection plans to be focused and prioritised and aiding the user to identify the most appropriate and effective risk mitigating activity within the software. Risk assessments are performed on a component by component basis, with the software's scope including all combustor and turbine hot gas path components. The software also contains comprehensive help documents to aid the user in identifying and assessing peculiar damage mechanisms and prescribing the most effective inspection methods for gas turbines.

3405 遮熱コーティングの酸化層形成シミュレーションとはく離応力解析(S16-2 遮熱コーティング(TBC)(2),S16 コーティング材料の皮膜特性とその評価)

Diffusion and stress simulation analyses were conducted for the oxide layer causing TBC spallation, often observed in gas turbine hot gas path components. Diffusion analysis was based on two processes, that is, the formation of Al_2O_3 layer with internal Al, and formation of composite oxide layer inside of Al_2O_3 layer through diffusion of oxygen. Using the simulated oxide layer shape, elastic analyses were conducted to estimate thermal stress under cyclic thermal conditions and internal stress due to oxide layer expansion. These simulation results showed reasonable shapes and stress distribution of oxide layer and coating system proving that those methodologies were useful for predicting the spalling event for TBC systems.