Numerical study for effects of axial clearance on low-pressure turbine steady and unsteady aerodynamic performance

In order to study the difference between steady calculation and unsteady calculation in the different axial clearances for showing that it is necessary to do the unsteady calculation and analysis in the turbine design, a high-loaded LP turbine was used for the numerical simulation on both steady and unsteady flow in the different axial clearances. And through analysing the effects of the axial clearances flow on the turbine aerodynamic performance in the rotor-stator interaction condition, the steady condition was compared to show the necessity of the unsteady calculation and analysis. The results show that only in a certain axial clearance range, the steady numerical results have a good reference value. Increased axial clearance makes both of the positive and negative incidence angle decrease. It is good for the improvement of the rotor flow condition. Momentum mixing loss in the unsteady flow has a converse effect. It makes the end transverse pressure gradient decrease and it results in the secondary flow loss being reduced.