ASSESSMENT OF PARTIAL-ADMISSION CHARACTERISTICS IN TWIN-ENTRY TURBINE PULSE PERFORMANCE MODELLING

One-dimensional modelling of a twin-entry turbine usually considers only the full-admission characteristic in their analysis. However, due to out-of-phase exhaust flow, the actual operating environment is constantly under the intermittent combination of full, unequal and partial-admission conditions. This leads to unsatisfactory on-engine performance prediction, even though some present models have already accounted the finite twin-entry volute and interaction between the volute entries. This paper explores the potential improvement in twin-entry pulse flow model by including the partial-admission characteristics through the established one-dimensional model domain. The predicted results are validated against the experimental data obtained from the Imperial College pulse flow testing facility. In addition, influences of the quality of partial-admission performance map are also analysed. The mathematical prediction methodology, which was revised from literature works, derived the twin-entry turbine partial-admission characteristics from the known full-admission performance. This study is intended to outline the importance of twin-entry turbine partial-admission characteristics in pulse performance modelling. In comparison to the literature findings, current model has satisfactorily resolved the twin-entry out of-phase pulse flow performance, particularly the instantaneous actual power. The model prediction shows a twin-entry turbine unsteady swallowing capacity is mostly encapsulated within the quasi-steady full and partial-admission characteristic lines. On the other hand, the unsteady actual power hysteresis curve is found beyond quasi-steady characteristic lines at most instant throughout the pulse cycle.