Numerical prediction of transient discharge coefficient in orifice flow meter
Li Zhifeng1,2,Wu Peng1,2,Wu Dazhuan1,2,Dai Weiping1,2,Wang Leqin1,2
(1.Institute of Process Equipment,Zhejiang University,Hangzhou,Zhejiang 310027,China; 2.Engineering Research Center of High Pressure Process Equipment and Safety,Ministry of Education,Hangzhou,Zhejiang 310027,China)
Abstract：To study the characteristics of the orifice flow meter when measuring linear accelerating flow rate,taking the curves of the transient discharge coefficient(C) as the study object,the computational fluid dynamics(CFD) method was used to simulate the C and the evolutions of the corresponding flow field.The transient turbulent flow was described by the Realizable detached eddy simulation(DES).For comparative analysis,the accelerating process was discretized to separate steady-state conditions at different points of flow rate.The Realizable k-ε model was chosen as the steady-state turbulent closure.The error between curves of present steady discharge coefficient(C0) and the ISO data is less than 3%,so the current calculation results is validated.Comparison of discharge coefficients between flow acceleration process and steady-state condition was performed.Comparison results show that the transient C curve increases from 0 to a constant value gradually and the steady C0 remained in the vicinity of 0.6.The discharge coefficient together with the evolutions of velocity and pressure field were combined to further analysis the internal flow mechanisms.Reasons of deviation between transient and steady discharge coefficients are that the vortex of the acceleration state lags behind the steady-state conditions,so the pressure energy was not able to transform into the kinetic energy at the early process within a short distance.Contents of current study can serve as the reference of the instantaneous flow measurements.
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