One stage of Variable Area Nozzle Turbine (VANT) was designed for a Variable Cycle Engine (VCE) as the low pressure stage. The design method is presented in this article, where one of the objective conditions of the turbine is chosen as design condition while other objective conditions are simulated by CFD tools to verify its performance. The turbine profiles were designed with a three-dimensional (3D) profile design method based on S1 stream surfaces according to the chosen condition. Steady numerical simulations were used to acquire a series of turbine characteristic maps under many operating conditions with different vane stagger angles, and as anticipated, the turbine has reached high efficiency and met both the flow rate and expansion ratio demands under at least two objective conditions, which verifies that the design method is feasible and successful, however performance differences were found between the two objective conditions. In order to analyze deeply the differences, steady and unsteady flows of the turbine in both objective conditions were also simulated. Based on the blades pressure distribution, total pressure loss distribution, velocity distribution and wake transport, the results revealed the causes of low efficiency under off-design condition and different unsteady fluctuations between two objective conditions, which provides more reference for the design method of VCE turbine in the future.

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