Numerical investigation on the impact of corner radius on the performance of convergent-divergent nozzle

The structure of convergent-divergent nozzle has a great effect on its performance. In this paper, the cylindrical section and the diffusion section of the nozzle were connected with a rounded corner, and 0, 5, 9, 15, 25 mm were respectively selected as the rounded corner. Numerical simulations of convergent-divergent nozzles with different corner radius were conducted. And the impact of the corner radius on the nozzle performance was investigated. Based on the finite volume method, the RNG k-ε turbulence model and the Mixture multiphase flow model were adopted in the two dimensional flow simulations of the nozzles. The simulation results indicated that the connection by a rounded corner between the cylindrical section and the diffusion section of the nozzle could improve its performance. The connection by a rounded corner reduced local hydraulic loss and induced flow separation in the arch area near the throat to increase the potential core length and the effective target distance, and the bigger axial velocity of nozzle exit could be got. Besides, the connection by rounded corner could promote cavitation of the nozzle.