Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
The understanding of secondary flow behavior has become an important aspect in the design of modern gas turbines. Secondary flow gives rise to aerodynamic losses, distorts the thermal field and affects the flow conditions at the exit of a passage negatively. Therefore, reducing secondary flow is a major concern for efficiency improvement. Many passive control-methods have been suggested by turbine designers and researchers, and one very promising modification is blade leading edge contouring near the endwall. At the Division of Heat and Power Technology KTH, Stockholm, a detailed experimental investigation of three filleted nozzle guide vanes in an annular sector cascade has been performed, providing excellent experimental data for numerical validation of complex turbine flows.
Based on the above, a numerical study and aerodynamic investigation for a leading edge filleted vane and baseline vane has been performed. The potential effect of the leading edge fillet on flow structure and secondary losses has been evaluated based on a number of flow parameters, and computational predictions have been compared to experimental results.
The numerical investigation has shown some differences in the flow behavior between the filleted and baseline case. All results indicate that the fillet affects the flow structure in regions close to the hub endwall. It shifts the position of vortices and loss core. However, the overall effect on reducing secondary losses downstream of the passage is insignificant. Additionally, the numerical results show good qualitative agreement with experimental results.