CFD Investigation of the Performance of a Military HP Axial Turbine Subjected to Inlet Temperature Distortion

It is known that the exit flow from the combustor entering a turbine stage will have wide spatial variations in temperature both radially and circumferentially. This phenomenon is amplified in military engines, due to the higher temperatures involved, and can affect also the performance of a highly loaded, high-pressure axial turbine. Computational Fluid Dynamic (CFD) simulations are an innovative and powerful tool for studying inlet temperature distortion and can be integrated in the early phases of the design process. This paper discusses the 3D CFD steady state simulation of the performance of a single stage axial flow high pressure turbine at design point, off design and on several constant speed lines. The study also addresses the behaviour of the turbine when subjected to uneven inlet total temperature distribution. In addition to the ideal case (uniform inlet temperature), three types of distorted inlet temperature conditions have been investigated. These are: simple radial distortion, hot streak aligned to the mid passage of the stator and hot streak impinging on the leading edges of the stator. The analysis demonstrated that temperature distortion does not have a significant effect on the performance of the high pressure turbine apart from a small reduction in efficiency. It has been found that this drop in efficiency can be reduced by directing (clocking) the hot streaks towards the stator blades. The commercial CFD package, CFX-TASCflow, has been used in this study.