Thermal Impact of Axial Reynolds Number on Aircraft Engine Compressor Disks

The axial flow compressors of new generation aircraft engines are designed to operate at high rotational speeds (≈15,000 r.p.m) and air temperatures (≈1000 K). This results in the compressor disks experiencing increased levels of mechanical and thermal stresses limiting their field operating life and effecting compressor reliability. Also the compressor disks sometimes experience premature failure causing unscheduled maintenance disrupting scheduled flight operations. The engine manufacturers hence recommend regular engine checks resulting in longer aircraft maintenance effecting airline operations and business. To minimize the thermal stresses and improve compressor reliability a certain percentage of compressor main flow known as the Secondary Flow is extracted either to heat or cool the compressor disks to lower their temperature gradients. The design of the Secondary Flow System needs to be highly effective in reducing these temperature gradients and also efficient in utilization of the compressor main flow for better engine performance and improved fuel economy. This necessitates a comprehensive understanding of the Secondary Flow System heat transfer and it’s effectiveness to changes in various Secondary Flow and compressor design features . But owing to the complexity and range of inter dependent factors that effect compressor disk temperatures it is almost impractical to perform experiments over all possible range of design variations. Hence it becomes inevitable to conduct numerical estimations of flow and heat transfer characteristics of the Secondary Flow System using computer aided models validated with experimental results. The current research investigates the impact of a wide range of Secondary Flow System and compressor design features on the performance of Secondary Flow heat transfer and it’s impact on compressor disk temperature gradients critical to compressor reliability. The investigations are carried out with support of computer aided models validated with experimental results. This paper reports a part of this wider investigation wherein the impact of design of Axial Reynolds Number on the performance of Secondary Flow System and it’s critical influence on compressor disk temperature gradients is investigated. The investigation is carried out by simulating the flow and thermal conditions of the Secondary Flow System inside an experimental rig with conditions similar to a real engine using Computational Fluid Dynamics ( CFD ) and Fin