The Influences of Trailing Edge Base Pressure on the Profile Loss of Low-Pressure Turbine Blades

Abstract The knowledge of the pressure at the base of the trailing edge (base pressure) is important for the prediction of profile loss of low-pressure turbine (LPT) blades. It is known that base pressure varies with a surface velocity profile and a Reynolds number, and that a lower base pressure increases the losses, and a higher base pressure decreases the losses. However, in the airfoil design, it is difficult to predict the base pressure. This is because the physical mechanism to determine the base pressure level is not well understood. This paper aims at clarifying the mechanism to determine the base pressure level for a low speed LPT cascade and investigating the influences of the base pressure on the profile loss by using the results of numerical simulations. In the study, two kinds of LPT blade design with different levels of the base pressure are used. One is the design with the base pressure higher than the far downstream static pressure (Blade A) and another is the design with the base pressure lower than the far downstream static pressure (Blade B). Based on the findings from the study, the correlation parameter BP calculated by the numerical simulation results is proposed for the prediction of base pressure. The prediction method using the parameter BP is applied to low speed cascade test data and compared with the measured base pressure. It is concluded that the method reasonably predicts the base pressure for blades with no laminar separation and predicts the base pressure within the range of an engineering allowable error for blades with a closed separation bubble.