title: Aerothermal Impact of Time-Resolved Inlet Boundary Conditions in High-Pressure Turbine Simulations
Creators: name: Wouw, Jonathan van de
Publisher: name: UNSPECIFIED
Year: 2024

description: The high-pressure turbine in a jet engine, and in particular the initial stage of it, is significantly influenced by the flow in the combustor upstream. The presence of high temperature nonuniformities, large flow angles, and high levels of turbulence results in a reduction in turbine efficiency and an increased demand for an efficient turbine cooling scheme. To ensure that the turbine is designed to meet lifetime requirements and to achieve optimal efficiency, it is of paramount importance to comprehend the interaction mechanisms between the combustor and turbine and to incorporate all the crucial combustor-related effects into the design of the turbine.
Numerical simulations play a pivotal role in the design of combustor and high-pressure turbine and the analysis of the combustor-turbine aerothermal interaction (CTI), as they offer a cost-effective and efficient means of understanding the complex flow and thermodynamics in both components. Due to the harsh conditions in this part of the engine, measurements and experiments are often limited. In most cases, the combustor and turbine are treated in separate simulations, with 2D mean field data transferred at the interface to be used as inlet boundary conditions in the high-pressure turbine. This approach, however, fails to account for unsteady effects from the combustor, which can significantly impact the design of the turbine. It has long been known that scale-resolving simulation methods can increase the predictive accuracy of CFD simulations. The increasing availability of computational power enables design teams to use unsteady and scale-resolving simulations more frequently. This is also the case for the combustor and turbine component of a jet engine. However, this increased fidelity comes at a cost in terms of both computational resources and time, as well as the production of significantly higher amounts of data, which must be stored and handled. For a standalone turbine simulation, this also means that the demands for the inlet boundary conditions are much higher. For a scale-resolving turbine simulation, combustor unsteadiness and turbulence must be applied at the inlet boundary.
This work presents a method for the efficient storage of unsteady snapshot time series from a combustor simulation, which can then be used as inlet boundary conditions for a subsequent turbine simulation. This is achieved by employing a combination of Proper Orthogonal Decomposition (POD) and Fourier series development in the PODFS method. By considering only that portion of the data which has energetic relevance, a reduced order model of the snapshot data is created that is independent of time. The application of these unsteady inlet boundary conditions to scale-resolving turbine simulations reveals significant differences in the thermal fields and film cooling effectiveness on the turbine vanes when compared to standard RANS simulations using mean fields as inlet boundary conditions. The aerodynamics of the vanes are minimally influenced by the selection of inlet boundary conditions. The pronounced impact of unsteady inlet boundary conditions on the thermal behavior of the vanes highlights the significance of the choice of inlet boundary conditions that match the scale-resolving character of the simulation scheme when numerically investigating high-pressure turbines.