This paper presents a technique for optimising the performance of a diffuser in an industrial gas turbine using validated CFD modelling. The combustor module of the Rolls Royce RB211-DLE industrial engine was modelled from diffuser inlet to combustor inlet, using a hybrid meshing procedure. A CFD model of the current RB211-DLE diffuser and casing was validated against perspex single sector rig data, including pressure probe measurements, oil dot flow tests and a sensitivity analysis. A three-dimensional design process was then undertaken to determine how the shape of the diffuser affects the loss through the system, and hence which type of diffuser would provide the best opportunity for maximising the engine performance. The best two general diffuser designs were optimised using an iterative two-dimensional design process. The performance of these optimised designs was then confirmed by full three-dimensional modelling. This work suggests that a significant improvement in sfc (based on a constant turbine temperature) would be achieved if the optimum diffuser design is installed into the RB211-DLE engine.

This content is only available via PDF.