| The greenhouse effect,caused by carbon dioxide emission,poses a serious threat to mankind.Clean coal & electricity is the main battlefield to achieve the goal of carbon neutralization and carbon peak.The ammonia de-carbonization technology for flue gas of the power plant is attractive.High efficiency gas-liquid absorption device is the core part for the ammonia de-carbonization technology.The Venturi jet is a highly efficient air bleed equipment.It is consisted of constriction section,inhalation chamber,throat,and diffuser section.It is reliable and flexible in operation with a good mass transfer and heat transfer.In this thesis,the quasi-steady state and steady state of the gasliquid flow in the Venturi jet under different outlet conditions,atmosphere or water,are studied.The JET-1 type Venturi jet was designed and fabricated of plexiglass.The inner diameter of the liquid phase inlet is 20 mm,the outlet diameter of the constriction section is 2 mm,the gas inlet diameter of the suction chamber is 10 mm,and the outlet diameter is 20 mm.The length of the throat is 20 mm,and the angle of the diffusion section is 9°.The Venturi jet flow characteristic experimental device is designed and constructed,which consists of frame,pipeline,centrifugal pump,water tank,valve,jet,pressure measurement device and gas flow measurement device.With water as the driving fluid and air as the secondary fluid,both the quasi-steady state and steady state of the gas-liquid flow in the Venturi jet under different outlet condition of atmosphere or water were tested,The pressure drop,air suction rate,air liquid ratio and energy efficiency were measured.A high-speed camera was used to capture the gas-liquid twophase flow state inside the jet.Fluent software was used to simulate the gas-liquid flow in the venturi jet,and a model that could better predict the gas-liquid two-phase flow of the jet was established,and the internal flow field of the jet was analyzed by numerical simulation.The liquid phase flow of the Venturi jet shows that the pressure drop increases with the increase of the liquid flow rate,and cavitation exists under higher liquid flow rate.When air is left in the air chamber,no cavitation can be observed in the jet,and the liquid jet becomes unstable with the increase of the liquid flow rate.For the gas-liquid flow in the jet,the gas-liquid interface fluctuates violently,and the liquid outflow is scattered as a state called under the pseudo-steady state.While for the steady state,the gas-liquid flow is stratified,and the interface between the gas and liquid is stable with a cylindrical shape for liquid flow.T The quasi-steady state can transfer to the steady state as a disturbance or a higher liquid flow rate than the critical value.The experimental results of gas-liquid two-phase flow for the Venturi outlet under the condition of atmosphere,show that the quasi-steady-state pressure drop is less than that of steady-state,while the gas-liquid ratio and energy efficiency in quasi-steady-state are higher than those of steady-state.For the Venturi outlet under the condition of water,the pressure drop,gasliquid ratio and energy efficiency are less than those of steady-state.The Fluent software is adopted for the 3D simulation of the Venturi jet.The simulation results show a good agreement with the experiment.The maximum error between the simulation result and the experimental result is 0.96%,and the maximum error of for the pressure drop is 1.26%.There is obvious gas-liquid stratification in the diffuser section of the Venturi jet.The gas-liquid two-phase streamline and turbulent kinetic energy both indicate that there is an annular vortex area near the wall of the diffuser section,and the velocity gradient in the vortex region is high. |
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