Abstract
The operation of a propulsion system in terms of horizontal takeoff/landing and full-speed range serves as one of the main difficulties for hypersonic travelling. In the present work, a three-dimensional inward-turning inlet with tri-ducts for combined cycle engines is designed for the operation of three different modes controlled by a single rotational flap on the compression side, which efficiently simplifies the inlet structure and the flap control mechanism. At high flight speed between Mach 4 and 6, the pure scramjet mode is switched on, whereas both the ejector and the scramjet paths are open for a moderate Mach number between 2 and 4 with a larger throat area guaranteeing the inlet startability. In the low flight speed range with Mach number below 2, the additional turbojet path will be turned on to supply air for the turbine engine, whereas the other two paths remain open for spillage. Numerical simulations under different operation modes have proven the feasibility and good performance of the designed inlet, e.g., a nearly full mass flow ratio and a total pressure recovery around 0.5 can be achieved at the cruise speed. Meanwhile, the inlet works properly at low flight speeds which overcomes the typical starting problem of similar inlet designs. In the near future, wind tunnel experiments will be carried out to validate our inlet design and its performance.
Highlights
People have dedicated to achieve higher and higher flight speeds
The isobaric surfaces above the inlet leading edge and that under the cowl lip are due to the wall thickness which leads to additional external shocks
The mass flow ratio, which is defined as the mass flow rate that really enters the duct over the mass flow rate that theoretically can be captured by the intake area, is nearly unity; whereas the total pressure recovery, which is defined as the total pressure at the end of the duct over the total pressure of the inflow, reaches 0.61
Summary
People have dedicated to achieve higher and higher flight speeds. Imagining a flight trip from Shanghai to New York within only two hours is incredibly promoting. The difficulty lies mostly on the propulsion system when considering its requirement of both horizontal takeoff/landing and full-speed range operation. In this case, only combined cycle engines can satisfy the rigorous expectation since any single engine faces deficiency, e.g., turbojet engine operates up to Mach 3; ramjet engine cannot generate efficient compression inside the inlet below Mach 3; the specific impulse of ejector engine is relatively low due to its selfloading oxidant. We are thinking of developing a three-dimensional inward-turning inlet with only a single rotational flap on the compression side for combined cycle engines.
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