| The atomization of high viscosity liquid is always a difficult scientific problem in the field of atomization research.Through the experimental research and Simulation Research on the atomization of high viscosity liquid,this paper reveals the atomization characteristics of high viscosity liquid in the gas-liquid coaxial three channel direct current nozzle.The research in this paper will not only promote the development of high-efficiency atomization application of high viscosity fuel in thermal equipment,but also promote the development of high-efficiency atomization application of high viscosity liquid in other industries(Aerospace propellant,powder metallurgy,particle manufacturing,etc.).In order to study the atomization characteristics of high viscosity fluid in all directions,this paper designs the relevant atomization test methods and numerical simulation methods for the coaxial three channel nozzle(Chapter 2),and then studies the experimental and numerical simulation atomization characteristics of the nozzle for high viscosity liquid,Finally,combined with engineering practice,the application of coaxial three channel nozzle in coal water slurry atomization is studied.In general,the main work of this paper is as follows:The atomization test method is introduced in detail.The experimental research device mainly includes back pressure chamber,coaxial three channel nozzle,winner 318 a laser particle size analyzer,plantom V12 high-speed camera and supporting conveying pipeline and regulating system.Atomizing particle size measurement and flow field photography were CGRried out with a particle size analyzer and a camera.Industrial glycerin(742 m Pa·s)was used as high viscosity liquid,and compressed air with adjustable pressure was used as atomizing gas medium.Then,the effects of different gas-liquid ratio,atomizing gas ratio,nozzle structure and counter pressure conditions on atomized particle size and spray shape of high viscosity liquid were studied by experiments.It is found that increasing the gas-liquid ratio can improve the atomization effect when the liquid flow rate is stable.The atomization effect of small nozzle is good under low load flow,and the large nozzle can adapt to high load flow.There are three obvious atomization structures after the liquid leaves the nozzle: 1)continuous liquid film zone near the nozzle;2)the liquid area in the spray area.3)fine droplet area near the central axis of spray.The length and number of liquid filament outside the spray increased with the increase of central gas ratio,and the number of droplets in the center of spray decreased.Based on the experimental conditions,the atomization process of coaxial three channel nozzle was simulated by the combined calculation method of internal flow and external atomization.The VOF method is used to simulate the inner flow of the nozzle,and the film thickness,exit velocity and angle at the exit section of the middle nozzle are obtained,which are assigned to the DPM method as the initial conditions to simulate the liquid film atomization.Through the simulation,it is found that the liquid film is annular distribution on the outer wall of the nozzle,and the shape of the liquid film is related to the distribution of turbulent kinetic energy.The thickness of the liquid film fluctuates,and the wave characteristics are quasi periodic.On the basis of considering the increase and fluctuation characteristics of the surface wave in the nozzle,the improved air atomization model of coaxial three channel nozzles is proposed by combining the liquid film fluctuation model and the original Air-blast atomization model.The improved model can obviously improve the spray cone angle and the SMD calculation accuracy.The throat gas velocity of the inner gas nozzle is higher,and the local supersonic blocking flow will appear.Increasing the central gas ratio can reduce the spray cone angle and droplet size.When the central gas ratio is 16.98%and 22.01%,the droplet size reaches the lowest value.With the increase of reaction pressure,droplets are more easily broken,and the mean diameter of each radial section of spray field decreases gradually,and droplet size distribution is more uniform.Based on the application of coal water slurry gasification in coal chemical industry,the importance of coal water slurry atomizer was analyzed.Combined with the design experience of the process nozzle in the existing coal water slurry gasification device,the change of gasification effect caused by the change of coal water slurry flow rate is analyzed,and it is found that the change of coal water slurry atomization performance is the main factor of the change of coal water slurry gasification efficiency.To meet the needs of industrial users to expand production capacity,combined with physical analysis and optimization theory,the structural parameters of the new process nozzle are obtained,and the process nozzle with capacity expansion of 20% is designed.After the actual production test,the gasification effect of the expansion process nozzle reaches the expected goal,thus validates the correctness of the effect of the nozzle structural parameters on the spray characteristics of the high viscosity liquid.Finally,the paper summarizes the full text,puts forward the innovation points,and looks forward to the future research direction. |
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