Investigation of Ash Deposition Behaviour From Biogenic Solid Fuel Under Gas Turbine Conditions With Film Cooling

Abstract In the current state of technology, gas turbines operate mainly with fossil fuels. In order to achieve a sustainable energy supply with gas turbines alternative fuels have to be used. In the past, many attempts have been made to use alternative fuels, such as solid biogenic fuels. The main problem with the use of these fuels has been the fouling of the turbine stages during operation. To counteract this problem, the use of film cooling as a protective mechanism to reduce deposits is considered in this work. In the past, studies have already shown that this application can reduce particle deposits. For this purpose, test blades with film cooling were created and exposed to an increased particle load in a test rig. Synthetically produced ash, which corresponds to the typical components of biogenic utilization, was used as test ash for the deposition tests. The deposits were analysed by means of a visual inspection paired with a REM-EDX examination. The deposition tests were additionally supported by CFD simulations and compared with the particle Stokes number. Overall, film cooling appears to be a suitable means of reducing deposits on a turbine blade. However, the geometric design needs to be modified compared to the classical film cooling setup. In addition, low momentum flux ratios and a delay of the flow seem to be favourable for film cooling as a protective mechanism. The blade deflection angle also plays an important role in the implementation of the new design.