Jialin Zheng and Daren Yu
DOI Number XXX-YYY-ZZZ
Conference Number HiSST 2018-0809
The transition thrust pinch occurs in an over-under Turbine Based Combined Cycle (TBCC) engine when the parallel operation of the turbojet and ramjet is not possible, under which the vehicle cannot continue accelerating because of the poor net thrust. Instead of turning to developing newly revolutionary propulsion systems, this paper proposes an alternative strategy to solve this problem via trajectory optimization. A loosely coupled integrated vehicle powered by a ramjet engine is considered, while the turbojet is reasonably simplified into the various initial conditions to represent mode transition. By applying Gauss Pseudospectral Method (GPM) to the integrated aircraft/propulsion system model, optimal trajectories under different constraints are calculated. The result shows that this strategy is to some extent beneficial for the transition thrust pinch situation. In addition, both the dynamic pressure and the combustor temperature constraints will largely affect the scale of improvement so that those constraints should be taken into consideration to make this strategy productive. Although the total energy of the vehicle decreases because of the cost to reallocate the balance between the kinetic and potential energies, this strategy is reasonable and effective with propulsion systems at hand.