Performance Analysis of Mode Transition of a Triple Combined Cycle Engine

For a reusable hypersonic cruise vehicle with the ability of horizontal take-off and landing, triple combined cycle engine is a suitable choice in a short term. The triple combined cycle engine in this paper is a combination of turbine engine, ramjet engine and DMSJ (dual mode scramjet) engine. It can operate at three modes. The transition of the three modes is crucial to the performance of the engine. This paper establishes the performance calculation model of the triple combined cycle engine. Providing the control schedule of the engine, the engine performance during mode transition is studied. The design of the turbine-to-ramjet mode transition zone and the performance during of the ramjet-to-DMSJ mode transition are analyzed. The principle of turbine-to-ramjet mode transition is that the increase of airflow rate caused by ram duct air supply and the decrease of installation loss can compensate the loss of specific thrust. Therefore, it can be assured that the thrust can transit smoothly and is higher. Performance simulations show that the influence between the two flow paths is small, thus the thrust transition is stable during the ramjet-to-DMSJ mode transition.