Optimal Design Of Mist Annular Flow Experimental System Of Vortex And Research On The Characteristics Of Two-Phase Measurement

The flow measurement of wet gas is very cruical for oil,natural gas and other industries.When the gas velocity is high,the mist annular flow is the dominant flow pattern.The Vortex flowmeter,which is widely used in single-phase and two-phase flow measurement,is suitable for the wet gas measurement,although its accuracy is affected by the over-reading of volume flow.In addition,there may be the phase change of moist gas which affects the mass flow measurement of vortex flowmeter.In order to investigate the measurement characteristics of vortex flowmeter under different operation conditions,it is necessary to accurately measure and control the two-phase flow parameters of experimental facility,such as pressure,flow rate,temperature,humidity and droplet fraction.In this paper,a two-phase parameter control system based on PLC+MCGS was established,and its performance was optimized by fuzzy control method.The over-reading of the vortex flowmeter in mist annular flow was measured by the proposed facility and its influencing factors are discussed.The main contents and achievements are as follow:Aiming at the coupling problem of gas pressure and flow-rate,a fuzzy PI self-tuning control scheme was proposed.The decoupling control for pressure and flow-rate is achieved based on the Relative Gain Method.The pressure ranges from 100 to 600kPa and the flowrate from 5 to 25 m3/h.The stability is 0.5%,and the adjustment time is about 30 s.For temperature and humidity control,the structure and size of evaporator were designed and optimized by using the droplet evaporation model and CFD simulation.The fuzzy PID control scheme without overshoot was put forward.The gas humidity ranges from 0 to 100%and temperature from 0 to 80?.The stabilities of both temperature and humidity are better than 0.5%.Based on the experimental device,the measurement characteristics of mist annular flow of vortex flowmeter are studied.The experiments showed that the humidity only affects the mass flow measurement of vortex flowmeterin single-phase flow.In mist flow,the over-reading of gas flow-rate will increase with liquid mass loading and its growth rate is positive related to the operation pressure and Reynolds number.It is speculated that the over-reading may be related to the droplet entrainment rate.To verify the hypothesist the liquid film collecting metering device was designed and the actual droplet loading ?p was obtained.The results showed that the growth curve of OR-?p is basically overlapping at different operation condition,which indicates that droplet loading ?p is the main influence parameter of the over-reading.