Influence of Operation Mode On The Performance and Component Matching and Multi-Objective Optimization of A Multi-Stream Adaptive Cycle Engine

Abstract

The multi-stream adaptive cycle engine (ACE) represents a transformative propulsion concept for next-generation aircraft, offering the capability to dynamically balance thrust, efficiency, and thermal management across widely varying mission conditions. By incorporating multiple variable-geometry mechanisms and controllable bypass or adaptive streams, the ACE can transition seamlessly between high-thrust and high-efficiency modes. However, these additional degrees of freedom complicate component matching, stage coordination, and overall performance control, particularly during transitions between operating modes. The present study investigates the influence of operation mode on both the performance and component matching characteristics of a representative multi-stream ACE (three streams in total). A one-dimensional thermodynamic cycle model incorporating a mode-switching valve, variable-area injectors, and variable-area nozzles is developed to adjust flow distribution among the core, bypass, and adaptive streams. Controlled adjustments of these variable-geometry components enable sequential transitions from triple-bypass mode (M3) to dual-bypass modes (M13/M12), and ultimately to single-bypass mode (M1). The simulation results indicate distinct performance trade-offs across operating modes: the single-bypass mode provides the highest thrust at reduced fuel efficiency, the dual-bypass modes offer a balanced compromise between thrust and economy, and the triple-bypass mode achieves the highest efficiency with moderate thrust. During mode transitions, compressor operating points shift toward the choking boundary, whereas turbine operating points migrate toward lower-flow, lower-pressure-ratio regions of their characteristic maps.