In the manufacturing process of turbine blades and vanes, there are some deviations from design criteria. These geometry variations have negative effects on turbine performance. In the present paper, influences of these variations (listed below) on turbine performance are investigated. For precise calculation of turbine performance, a three-dimensional CFD code, which solves Reynolds Average Navier-Stokes (RANS) equations, is used. The code is validated against existing Hannover turbine experimental data. The test case for studying geometry variations is second stage of Avon turbine. The investigated variations are: (I) twist, (II) offset, (III) trailing edge and leading edge thickness, (IV) tilt, (V) lean, and (VI) bow. Results show that blade twist and offset have significant effect on the stage mass flow rate. In addition, blade offset has much more negative effect on stage efficiency than other defections. On the other hand, blade bow and leading edge and trailing edge thickness have minor effect on the stage efficiency. In addition, the combination of aforementioned deviations is also studied. The results show that combination of all of these deviations causes the stage mass flow rate and efficiency to change, significantly.

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