The Prediction of Surge Margins During Gas Turbine Transients

Abstract

This paper describes how allowance for the thermal effects of non-adiabatic flow, altered boundary layer development, changes in tip clearances and changes in seal clearances have been incorporated into a general gas turbine transient program. This program has been applied to a two-spool bypass engine. Revised predictions of surge margins in three common tn"ns Lents have been obtained. When the eneine undergoes a 'cold' acceleration, the thermal effects on the trajectory and on the surge line give a much increased proportion of unused surge margin in the H.P.Co. pressor, as compared to adiabatic predictions. In a 'hot' a,;celeration this iITprovement is considerably reduced.