摘要
文丘里流量计广泛应用于湿气流量测量领域.为探索长喉颈文丘里管喉部取压位置对其湿气测量模型的影响,从理论上对其各个部分压力降进行研究.设计内径为50mm、节流比为0.4的文丘里试验样机,取压位置距离喉部入口分别为喉部直径的0.5倍、3.75倍和7倍.在天津大学流量实验室双闭环中压湿气装置上进行试验验证.试验压力为0.2～0.8 MPa,干度为0.5～1.根据试验数据,针对不同的喉部取压位置,分析虚高梯度与L-M参数之间的关系;同时分析差压比K参数灵敏度与液气质量比qml/qmg之间的关系,发现虚高和K参数均受喉部取压位置的影响.建立基于K参数、Froude数、气液密度比的虚高模型和液气质量比模型,通过迭代算法求出气相和液相流量.分析基于不同取压位置的测量模型对湿气两相流气相和液相流量预测结果误差和不确定度的影响,得出取压位置为距离喉部入口3.75倍喉部直径时效果最好的结论,该位置模型气相测量不确定度为5.06％,液相为2.15％.
Venturi tubes are widely used for wet gas metering.To explore the influence of longer throat Venturi tube pressure tappings position to wet gas measurement model,a theoretical analysis of Venturi pressure drop at various parts is presented at first.A Venturi prototype with longer throat is designed,which inner diameter is 50 mm and beta ratio is 0.4.The distances between pressure tappings and the entrance of throat are 0.5,3.75 and 7 times the throat diameter,respectively.The experiment verifications are carried out at the wet gas test double closed loop in Tianjin University.The range of operational pressure is from 0.2 MPa to 0.8 MPa and the dryness ranging from 0.5 to 1.Based on the test data,the relationship between over-reading gradient and Lockhart-Martinelli parameter is acquired,as well as the regularity between the K value sensibility and liquid-gas mass ratio.The length of throat has a significant impact on over-reading and K value.Over-reading model and liquid-gas mass ratio model are built based on K value,Froude number and the gas-liquid density ratio,and gas and liquid flow rates are calculated by using iteration method.Through analyzing the influence of different pressure tappings position to the relative error and uncertainty of the gas and liquid flow rates,it is advised that 3.75 times the throat diameter away from the entrance of the throat is the optimum pressure tappings position,where the uncertainty of the gas and liquid flow rates are 5.06％ and 2.15％,respectively.
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2014年第12期157-164,共8页
Journal of Mechanical Engineering
基金
国家自然科学基金(60974118)
国家高技术研究发展计划(863计划
2007AA04Z180)资助项目
关键词
湿气测量
长喉颈文丘里
取压位置
虚高模型
液气质量比
不确定度
wet gas metering
long throat Venturi tube
pressure tappings position
over-reading model
mass ratio of liquid and gas
uncertainty
