Performance Analysis of Turbofan Engine Integrated Modulated Pre-swirl System

With the increase of the turbine inlet temperature of aero engines, the secondary air system (SAS) of modern aero engines has a bleed ratio exceeding 25% to ensure safety and reliable operation, which rarely contributes to thrust. Thus, considerable air used in secondary air system may cause engine performance degradation. The fixed bleed ratio method used in aero engine air system wastes a lot of cooling air when the turbine inlet temperature is low, which is not conducive to improving engine performance. An adjustable pre-swirl system that can adjust the bleed ratio of the secondary air system by adjusting the angle of pre-swirl nozzle guide vanes was proposed in this article. A low-dimensional model of a modulated pre-swirl system was established in this article. Compared with public literatures, the accuracy of this model was verified. Subsequently, with coupling modeling methods between the performance model and the air system model, we coupled this low-dimensional model with the CFM56 engine performance model. Performance analysis of the proposed modulated pre-swirl system was carried out with the consideration of several safety concerns, including the effectiveness of rim sealing, axial force and turbine blade temperature. This research investigated the effects on the secondary air system and engine performance of the modulated pre-swirl system. Modulation of the pre-swirl system has a great impact on internal airflow distribution in air system, where rim sealing is most affected. The swirl ratio and temperature drop of the pre-swirl system increase with decreasing pre-swirl nozzle guide vane angle. Furthermore, overall engine performance with the modulated pre-swirl system was assessed. Reducing pre-swirl nozzle guide vane angle during cruise condition can reduce secondary airflow rates thereby effectively reducing fuel consumption. Results show that fuel consumption reduces by 0.6% during cruise condition.