An efficient multi-fidelity simulation method for adaptive cycle engine ejector nozzle performance evaluation

Abstract

The three-bypass duct structure of Adaptive Cycle Engine (ACE) provides unique performance advantages while also challenging the design of its exhaust system. The separated exhaust nozzles widely adopted in current research may not meet the performance requirement of ACE. The feature of combining two exhaust streams to discharge makes the ejector nozzle suitable as the exhaust system of ACE. However, due to the connection between the third bypass duct and the ejector nozzle, the ejector nozzle and ACE form a highly coupled system, thus it is necessary to perform an integrated simulation of the ejector nozzle and ACE. The multi-fidelity simulation could offer accurate performance simulation as well as consider the complicated component matching working relations. In this paper, a multi-fidelity simulation method for ACE ejector nozzle simulation is developed for fast and accurate performance evaluation, and the design requirements of ACE ejector nozzle are initially explored. A multi-fidelity joint simulation method for the (0-D) ACE performance model and the (2-D) ejector nozzle Computational Fluid Dynamics (CFD) model is constructed through a dynamically optimized and updated surrogate model. The result shows, when ensuring the ejector nozzle does not affect the ACE working point, the peak gross thrust coefficient occurs in subsonic cruise condition as 0.9895. The gross thrust coefficients of acceleration conditions decrease with the increase of flight Mach number due to the increase of shroud divergent angle. Only 350 times CFD simulations are required to complete multi-fidelity simulations of 29 ACE operating points (As a comparison, the de-coupled method requires about 105 times CFD simulations for the whole characteristics, and the fully integrated method requires about 100 times CFD simulations for one ACE operating point). The diameter of the ejector shroud shoulder must be variable, otherwise it will cause a maximum thrust loss of 22.6% at dry acceleration condition and fan surge at cruise and reheat acceleration conditions. This method can further realize the evaluation of the installed performance and the control law optimal design of the ACE ejector nozzle.