Simulation And Experimental Study On The Effect Of Nozzle Surface Roughness On Internal Mixing Air Atomization Process

Power devices in the modern energy field often use nozzles to promote the full mixing and combustion of liquid fuel and air.By studying the atomization mechanism of the nozzle,the effect of atomization and combustion efficiency can be greatly improved,and the goal of energy saving and emission reduction can be achieved.As a type of air atomization,internally mixed air atomization has extremely broad application prospects.The nozzle structure has a crucial influence on the atomization performance.This article mainly studies the effect mechanism of the surface roughness of the nozzle on the internal flow performance of the nozzle,the primary atomization and the secondary atomization,and provides practical basis and reference for the design of the nozzle.This article uses numerical simulation and theoretical research and experimental verification to conduct research.A simulation model of the internal flow of the nozzle was established,and CFD(Computational Fluid Dynamics)software was used to simulate the flow characteristics inside the nozzle.The influence rule of volume fraction and other parameters;an internal mixed air atomizing spray system test platform was established,and the influence of the surface roughness of the nozzle on the primary atomization form and spray cone angle of the spray and the secondary atomization process were analyzed by the test method The effect of the number distribution of medium droplet size,the cumulative volume distribution of droplets,and the average diameter of droplets.At the same time,using the liquid film physical model and one atomization atomization model calculation,the effect of the surface roughness of the nozzle hole on the one atomization process was compared and analyzed.The internal flow simulation study found that the average turbulent kinetic energy of the outlet is the largest when the roughness is 0.8,and the atomization effect is the best.When the roughness is increased from 0.8 to 1.6,the difference between the outlet gas velocity and the gas-liquid velocity will increase greatly,but if the roughness is continued to be increased,the change between the two will be small.The surface roughness of the nozzle has little effect on the liquid velocity.The flow coefficient when the roughness is 0.8 is the largest under the same ALR(gas-liquid mass flow ratio),and the flow effect is the best.The flow coefficient is the smallest when the roughness is 1.6,and the flow coefficient is between the two when the roughness is 3.2.The test of the macro and micro characteristics of the spray found that: except for the case where the ALR is 0.05,in all other conditions,when the roughness increases from 0.8 to1.6,the spray cone angle value increases.When the roughness continues to increase,the spray cone angle decreases.The test parameters and simulation parameters are substituted into the liquid film model to calculate the thickness values of the two liquid films under different roughnesses,which are getting closer and closer as the roughness increases.But the effect of roughness on the thickness of the liquid film in the nozzle hole is not obvious.At the same ALR,as the nozzle roughness increases,the SMD decreases,and the fracture effect at the outlet becomes better.In the case of small ALR and large ALR,the SMD of one atomization at a roughness of 0.8 is significantly higher than that of the other two groups.But in other cases,changing the roughness has little effect.The change in roughness will only affect the secondary atomization SMD under small ALR conditions.As the ALR increases,the effect of roughness on the SMD of the secondary atomized droplets decreases.