Session: 01-03 Advanced Concepts III

Paper Number: 80505

80505 - Modeling and Cycle Parameter Matching of a High-Speed Variable Cycle Turbofan-Ramjet Engine 

Variable cycle turbofan-ramjet (VCTR) engine is a promising propulsion system candidate for future Mach 4+ vehicles. Compared to conventional turbine engines, the VCTR engine has a higher thrust-to-weight ratio, a smaller diameter and a more compact structure. A component-based simulation model has been developed to explore the operating characteristics of a high-speed VCTR concept. Modeling of variable geometry components, including mode selector valve, forward variable area bypass injector, rear variable area bypass injector, exhaust nozzle, outlet guide vane of the fan, variable guide vane of low pressure turbine, and inlet guide vanes of both fans and compressors, was characterized firstly in this paper. Then the way to build the VCTR model solver was described. The simulation model was validated by the numerical and experimental results of double bypass variable cycle engines from the NASA technical reports. Performance and control law of the VCTR engine along the flight trajectory with Mach number varying from 0.5 to 4.0 were optimized to maximize net thrust and compared with that of a conventional two-spool afterburning mixed-flow turbofan(MFTF). The result shows that the VCTR’s performance is highly dependent on the fan characteristics and limited by various operating constraints. Under low-speed conditions,  the VCTR net thrust is mainly constrained by the lower limit of fan surge margin in the single bypass mode and that of forward variable area bypass injector extraction ratio in the double bypass mode, respectively. In contrast, its high-speed performance is mainly constrained by the upper limit of both the turbine inlet temperature and the compressor discharge temperature.  Compared to the variable-geometry MFTF, the double bypass mode VCTR produces a higher net thrust above Mach 1.7, while its low-speed thrust and specific impulse are relatively lower. The thrust differences at high speeds between the two are relatively small, implying that the variable-geometry MFTF would be a better choice for its much less variable geometries if various thrust requirements could be satisfied; otherwise, the VCTR is still a favored choice for Mach 4+, high-speed applications.

Presenting Author: Yao Yao Northwestern Polytechnical University

Presenting Author Biography: I am a Ph.D. Candidate coming from Northwestern Polytechnical University. My research field is aero-engine performance design.

Authors:

Yao Yao Northwestern Polytechnical University
Xiao Bo Zhang Northwestern Polytechnical University
Ming Yang Zhang AECC Guiyang Aero-Engine Research Institute
Zhan Xue Wang Northwestern Polytechnical University