Investigation On The Flow Characteristics Of Wet Gas In Venturi Tube

When the wet gas flows through the venturi tube,due to the presence of liquid phase,the differential pressure measured is higher than it would be when gas phase flows alone.This phenomenon is called over-reading.A lot of investigations have been done experimentally and theoretically on the measurements of wet gas in venturi,but the flow characteristics of wet gas in venture are still not fully understood.Though many researchers have established some wet gas measurement models on the basis of experimental study and mechanistic analysis in accordance with the theory of homogeneous flow and separate flow,however,these models did not consider the true flow characteristics of wet gas in venturi.Therefore,the error is relatively large and the use is restricted.In addition,due to the limitations of laboratory equipment in experimental study,no wet gas flow with large liquid volume fraction was studied.Computational fluid dynamics(CFD)simulation methods are very capble of providing the insight into the complex behavior of multiphase flow in venturi,which can overcome the aforementioned restrictions of laboratory tests,and have the advantage of high precision and less time-consuming.Therefore,this thesis uses the CFD numerical simulation method and theoretical analysis method respectively to research the wet gas flow characteristics in venturi.First,the Fluent software with standard k-? turbulence model and discrete phase model(DPM)was used to simulate the wet gas flowing through venturi.By comparing with the experimental data of the NEL,the relative error of simulation results is within ± 5%,the average root mean square error is less than 2.22%,and the the CFD model is verified.Next,the volume fraction of the liquid was further increased to simulate the wet gas in venturi,and the flow field distribution contours,liquid concentration distribution contours and wall static pressure curve were obtained.The simulation results were analyzed and discussed.Then,on the basis of annular-mist flow pattern,the static pressure distribution model of wet gas in venturi was established and validated using the Peining Yu et al and Norway SINTEF experimental data.By comparing with Peining Yu's static pressure model(relative error,± 15%),the new model is better and the relative errors are within ± 7%.The results show that the main factors affecting the total pressure drop is accelerated pressure drop,followed by the friction pressure drop.The droplet entrainment drop impact is relatively small.Finally,according to the definition of over-reading,De Leeuw model was improved.After comparing with CEESI and NEL experimental data,the improved model agrees well with the experimental data,and the error is within +5%.In comparation with previous wet gas measurement models of venturi tube,the root mean square error of the improved model is minimal,its performance is relatively good.