New insights into component matching mechanism in the compression system of double bypass engine

Abstract

Variable cycle engine (VCE) is one of the most promising technologies for the next-generation aircraft, the matching of different components in the compression system is a key difficulty VCE faced. To investigate the component matching mechanisms in the VCE compression system, an advanced throughflow program is employed to calculate the characteristic lines of each component, and a zero-dimensional method is developed to capture the component performance deviation during the coupling working process. By setting the compressor stall and choke conditions as the boundary, the operation range of the compression system is first clarified, and the aerodynamic performance in the operation zone is discussed, thus providing a theoretical basis for optimization of the engine operating control scheme. Results show that the efficiency of the core flow is optimum at the left-bottom corner of the operation region, while the total pressure ratio peaks at the right-top area, hence a balance is needed when deciding the matching point. Regulations of component control parameters will change the position of the operation zone, as well as the corresponding aerodynamic performance. Decreasing the core driven fan stage rotating speed can improve the total bypass ratio, yet the total pressure ratio of the core flow will be decreased. Closing the core driven fan stage inlet guide vane can increase the total bypass ratio without changing the core flow aerodynamic performance significantly. The bypass ratio of the compression system can also be increased by increasing the fan stall margin or decreasing its rotating speed, both ways will decrease the total pressure ratio of the core flow. Results of the study will benefit the variable cycle engine design process in operation point evaluation and thermodynamic cycle optimization.