A MOMENTUM-INTEGRAL METHOD TO CALCULATE WINDAGE LOSSES ON A ROTATING DRUM WITH SUPERPOSED FLOW

The evaluation of windage losses plays a significant role in the rapid analysis and design of the secondary air system in aero-engines. However, there is a lack of an effective model to calculate the windage losses of drums in aero-engines, since most of the empirical correlations derived from enclosed drums would be invalid when axial through-flow is supplied. Thus, an evaluation model based on the Von Karman-type momentumintegral method is presented to calculate the windage losses on the rotating drums with superposed flow. A 1/nth power law for the velocity profile is assumed, and the 1/7th power law is used for discussion purposes. Two cases are considered in this study: a rotating drum in an infinite space (Case 1) and a rotating drum in a rotor-stator cavity (Case 2). The results indicate that the moment coefficient exhibits a monotonic decline trend with an increase in rotational Reynolds number, inlet pre-swirl ratio, aspect ratio, and a reduction in Rossby number. Comparison results between the proposed theoretical model and CFD numerical method showed that the maximum discrepancy in the moment coefficients is less than 10% for Rossby numbers ranging from 0.1 to 1, rotational Reynolds numbers ranging from 0.4×106 to 2.5×106, and inlet pre-swirl ratios ranging from 0 to 0.9. The relatively large discrepancy observed at low Rossby numbers is primarily attributed to the underestimation of the axial velocity.