Research On Swirling Atomization Characteristics Of Biomass Fuel And Its Simulation Analysis

With the increasing depletion of fossil fuels and increasingly serious environmental pollution,the research and use of clean,green and renewable energy became an important choice for the development of countries around the world.Biomass fuel as one alternative to fossil fuels,with its clean,green and renewable.And other advantages attracted wide attention and research scholars at home and abroad.However,when biomass fuel is applied in the industrial field,its atomization effect is not ideal due to its high viscosity,density and other physical and chemical properties,which results in unstable combustion and poor emission characteristics.Therefore,studying the atomization mechanism of material fuel and improving the atomization quality of biomass fuel is of great significance to the promotion of biomass fuel application and commercial development.In this paper,the physical and chemical properties of Jatropha oil and its biodiesel,waste oil and its biodiesel,rubber seed oil and its biodiesel were tested and analyzed.The size of several physical parameters that affect the quality of atomization,such as viscosity,density,and surface tension,are obtained.According to different nozzle structure parameters,a swirling atomizing nozzle of biomass fuel was designed by combining experiment and simulation,and the flow characteristics of the internal flow field in the swirling atomizing nozzle were revealed.A simulation model of the external flow field was built by using the optimal nozzle structure under the injection oil pressure of 0.2-1.0MPa.And the atomization characteristics of the external flow field were clarified under different oil pressures.Finally,the total air volume in the burner was determined,the proportion of primary air and oil pressure were changed,and the internal flow field simulation model was established,which revealed the influence law of primary air and oil pressure on the flow characteristics inside the swirling nozzle-air mixing chamber.This paper draws the following conclusions:(1)By combining numerical simulation and theoretical analysis,the axial and tangential velocity distributions of different nozzle structural parameters were analyzed.Then,through experimental verification,the optimal structural parameters of the swirling nozzle were obtained.The nozzle aperture was 0.7mm,the channel cross-sectional area was 1mm2,the swirling core pitch was 4mm,and the channel shape was trapezoidal.(2)Under isothermal conditions,as the injection oil pressure gradually increases,the nozzle outlet velocity,atomization penetration distance,atomization cone angle,atomization area and volume gradually increase.At the same time,when the oil pressure increases from 0.5MPa to 0.9MPa,the turbulent kinetic energy of the atomized flow field gradually increases,and the maximum value of the turbulent kinetic energy at the center of the flow field increases from 0.22 k to 0.24 k.(3)Under the condition of constant pressure,the particle size of droplets in the atomized flow field decreases first and then increases.And the small droplets are mainly concentrated in the middle of the flow field.When the oil pressure is 0.5MPa,22.79% of the droplets in the flow field have particle size less than 50?m,37.63%have particle size less than 100?m,and 50.85% have particle size less than 150?m.At the same time,near the flow field,the droplet particle size fluctuates sharply in the range of 25-250?m.(4)The addition of primary air can increase the edge velocity of the fuel liquid column,effectively reduce the fuel velocity attenuation and the fuel momentum loss in the mixing chamber,increase the tangential velocity of the liquid column.And enhance the diffusion ability of the biomass fuel to the periphery.