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Numerical Investigation on the Influence of Nozzle Lip Thickness on the Flow Field and Performance of an annular jet pump

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Journal of Harbin Institute of Technology(New Series) 2014年第3期21卷 59-67页

作者： Long-Zhou Xiao Xin-Ping Long Xue-Long Yang School of Power and Mechanical Engineering Wuhan University Key Lab of jet Theory and New Technology of Hubei Province

The performance of an annular jet pump( AJP) is determined by its area ratio A( ratio of cross sectional area of throat and annular nozzle) and flow rate ratio q( ratio of primary and secondary flow rate,Qs/Qj),while the nozzle lip thickness is neglected in the present studies. This paper presents a study on the effect of the thickness on the flow field and performance of an AJP with A = 1. 75. With the increasing flow rate ratio and nozzle lip thickness,a small vortex forms at the nozzle lip and keeps on growing. However,as the flow rate ratio or nozzle lip thickness is extremely low,the vortex at the lip vanishes thoroughly. Moreover,the recirculation width varies conversely with the nozzle lip thickness when the flow rate ratio q ≤ 0. 13. While the deviation of the recirculation width with different nozzle lip thickness is negligible with q ≥ 0. 13. Additionally the existence of nozzle lip hinders the momentum exchange between the primary and secondary flow and leads to a mutation of velocity gradient near the nozzle exit,which shift the recirculation downstream. Finally,based on the numerical results of the streamwise and spanwise vortex distributions in the suction chamber, the characteristics of the mixing process and the main factors accounting for the AJP performance are clarified.

关键词： annular jet pump nozzle lip recirculation streamwise vortex spanwise vortex

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Numerical investigation of turbulent flow coherent structures in annular jet pumps using the LES method

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Science China(Technological Sciences) 2018年第1期61卷 86-97页

作者： XU MaoSen YANG XueLong LONG XinPing LYU Qiao JI Bin Hubei Key Laboratory of Waterjet Theory and New Technology Wuhan University Wuhan 430072 China School of Power and Mechanical Engineering Wuhan University Wuhan 430072 China Research Institute of Nuclear Power Operation Wuhan 430074 China

annular jet pumps that are used in hydraulic machinery have a very simple structure but very complex internal flow fields. Large eddy simulations were used to study the coherent structures in the turbulent flows in annular jet pumps with various area ratios,m. The distribution, movement and evolution of the coherent structure in the annular jet pumps are described based on vorticity,pressure and Q criteria. All the criteria demonstrate that the vortexes are mainly distributed in the recirculation region and in the mixing and the boundary layers, which have large velocity gradients. The various characteristics of the coherent structures are shown by the different criteria with the vorticity criterion describing the distribution, movement and evolution of the vortexes,the pressure criterion describing the movement and the Q criterion describing the vortex movement and evolution. The vorticity variation in the spanwise direction is larger than the variation in the streamwise direction; however, the streamwise vortex is the main mechanism driving the entrainment of the secondary flow and the mixing. The annular jet pump with m=3.33 had a higher vortex shedding frequency(about 1000 Hz) than that with m=1.72(313–417 Hz). The azimuthal instability is the main reason for the generation of the streamwise vortex from the spanwise vortex. The vortex structures in the recirculation region are very strong,but small and disordered with no periodic vortex rings.

关键词： annular jet pump coherent structure large eddy simulation turbulent flow

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