孔板倒角对平衡型低温流量计工作性能影响的数值分析

Numerical Analysis of Orifice Chamfer Effects on Performance of Balanced Flowmeter for Cryogenic Fluids

关键词:  平衡型流量计  多孔板  倒角  流出系数  压力损失系数

Key words:  Balanced flowmeter  Perforated plate  Chamfer  Discharge coefficient  Pressure loss coefficient

摘要:

平衡型低温流量计可用于低温推进剂的加注、分配、输送等环节，其孔板结构特征是影响流量计性能的关键因素。为了研究孔板倒角对平衡型低温流量计流出系数、压力损失系数和稳定性的影响，建立了基于Mixture多相流模型、Schnerr-Sauer空化模型和Realizable k- ε湍流模型的CFD数值模型，并结合文献中的水翼空化实验和多孔板流动实验的结果验证了模型的可靠性。模拟计算结果显示，开设前倒角会增大多孔板的流出系数，减小压力损失系数，但会增大流量计测量时的不稳定性；在一定的计算工况下，45°的前倒角使流出系数由0.674增大到0.907，适当开设前倒角可以有效提高流量计的工作性能。而开设后倒角对流量计性能的影响较小。用于流体流量的双向测量时，可对多孔板的前后端均开设45°的倒角。

Abstract:

Balanced flowmeter can be used for measurement during the filling, distribution and transportation of cryogenic propellants, and its structural features of the perforated plate are essential for the performance of flowmeter. To investigate the effects of orifice chamfer on the performance of balanced flowmeter for cryogenic fluids, including the discharge coefficient, the pressure loss coefficient and the stability characteristics, a CFD model based on mixture multiphase model, Schnerr-Sauer cavitation model and Realizable k- ε turbulence model was built and then validated by the results from the hydrofoil cavitation experiment and the perforated plate flow experiment in the literatures. The simulation results show that the orifice with front chamfer can increase the discharge coefficient and decrease the pressure loss coefficient, but also induce the measurement instability of the flowmeter. Under the operating conditions in the present work, a front chamfer can improve the flowmeter performance significantly, e.g., the front chamfer of 45° improves the discharge coefficient from 0.674 to 0.907, while a chamfer at the back end of the plate brings little influence. When applied for two-way flow measurement, the chamfers of 45° at both ends of the perforated plate are suggested.