The Influence of Interstage-Turbine Mixing Cycle on Engine Performance

The optimization of the Brayton cycle has gained an increasing worldwide attention, in order to improve the specific thrust for achieving super cruise. This paper proposes a novel Interstage-Turbine Mixing (ITM) cycle, which guide vanes and rotor blades of turbine would be used as mixing chambers in the expansion process, and presents an analytical methodology by which ITM can be simulated at actual state. The motivation and the working principle of the ITM cycle are explained in detail. In this paper, the variable components method is used to establish the simulation program of the turbine stage mixing cycle. Then parametric cycle studies are performed with the variation of mixing ratio, bypass ratio and fan pressure ratio respectively. The interrelationships between cycle parameters and their effects on cycle performance are discussed. The results show that the mixing ratio of engine with the maximum specific thrust is 0.923, the mixing ratio with the maximum specific fuel consumption is 0.613, the mixing ratio with the best comprehensive performance is 1.127. The above conclusions are independent of the bypass ratio and fan pressure ratio. The predicted engine performance shows that the ITM cycle concept exhibits a competitive specific thrust with respect to engine in the state of non-afterburning, and might be a promising propulsion system for super-cruise air-breathing flying vehicles.