Effects Of Variable Geometry Guide-Vane On Turbine Stage Performance

To meet the request that the gas turbine has good performance under different condition and environment, the gas turbine has to have an adaptable ability. Using the Variable Geometry Turbine (VGT) is an important way to satisfy the request. In the current literature on VGT,almost all of the VGT models adopt simplified models. Generally, two aspects are adopted to simplify the model. One is that the tip clearance is uniform, another is the vane shaft is ignored.So, the first study in this thesis is that, the first stage of a certain turbine is adopted to establish the model of VGT, and the endwall of the turbine is cylindrical endwall. Then, many numerical simulations are preceded to analysis the characteristic and the flow field. There is a clearance both on the top of the stator vane and at the bottom of the stator vane in variable geometry turbine to rotate it. The clearance is uniform, and it means the clearance is changed naturally with the vane rotated. The clearance loss is occurred because of the clearances. The turbine clearance loss is also the focus during its working, so the leakage is analyzed in this thesis. In real case, to insure that the vane can rotate freely, a shaft is needed. Because of the limitation of the turbomachine software, it is difficult to establish a vane model and mesh. In most cases, the simplified model and mesh are adopted, and the effect of shaft is ignored. So, another important study in this thesis is on the basis of real case, and establishes the model and mesh which have a shaft. By comparing with the VGT which is no shaft, some numerical simulations are proceeded to analyze the shaft effect on the performance of turbine.This thesis analyses the VGT tip which is uniform and the shaft effect on VGT performance, and provides some qualitative bases on VGT design or performance study...