Effects of rotor solidity and leakage flow on the unsteady flow in axial turbine

Abstract

Partial admission turbine plays an important role in power control, which strengthens the unsteady flow. The effects of rotor solidity at partial admission condition can be more complicated, and leakage flow deeply strengthens the unsteadiness. Hence, the investigations of rotor solidity and leakage flow on the unsteady flow are of great significance for turbine designs. Turbines including five kinds of solidity at full and partial admissions are modeled based on 3D viscous compressible NS equation. In addition, the leakage flow model including tip leakage, inlet and outlet cavity is investigated. The results show that the solidity effects on partial admission turbine are not exactly the same as that on full admission turbine. The differences are identified, especially the axial unsteady aerodynamic force. Moreover, the attack angle tends to be negative with rotor solidity increasing; meanwhile, the low pressure region varies with solidity due to flow separation or throat area reduction. Leakage flow model is more able to reveal the unsteady flow, and the comparative analysis of flow phenomenon under the combined effects of leakage flow and partial admission flow is conducted. The change of rotor inlet parameters is smoothed down for leakage model and the axial exciting force is relative lower.