Pneumatic Blasting Mechanism Based On Cfd Blast Flow Field Characteristics

The pneumatic sand blasting takes compressed air as motive force, and the abrasive spraysthe part surfaces after the acceleration of the nozzle, it is available in surface strengthen andsurface cleaning etc, it should be extensively applied in machinery, petroleum, chemicalindustry, automobile and shipping etc.The nozzle is one of the critical parts in the pneumatic sand blasting system, and its effectis to change the motion and the motive force property of the gas-solid-two-phase fluid, itgreatly influences the cleaning efficiency. To study pneumatic sand blasting mechanism basedon the CFD technology, analyzing and studying the relation of gas-solid-two-phase fluidparameters and as well as geometry parameters of section changed nozzle, provides the basisfor the design of the high efficiency nozzle. Studying the pneumatic sand blasting flow field,we can find the influence relation of gas-solid-two-phase fluid parameters and geometryparameters to pneumatic sand blasting flow field property by analyzing free jet particles fieldof gas-solid-two-phase fluid and studying impinging corrosion property of effect surface, itprovides theoretical instruction of high efficiency work for the pneumatic sand blasting system.Therefore, the study on the pneumatic sand blasting mechanism and sand blasting flow fieldproperty has important practical significance.The Discrete Phase Model which follows the Euler-Lagrange approach is used to simulategas-solid-two-phase fluid in the nozzle at the aspect of pneumatic sand blasting mechanismresearch. Applying Fluent software, the distribution of the pressure field and the velocity fieldof gas are gained by adopting standard k-ε model to simulate gas flow field in the nozzle;thekinematic trajectory, velocity and dynamic property are gained by simulating solid particlesmovement in the gas flow field. The research indicates: the influence of the gas is more evidentwhen the particles diameter becomes smaller;the solid particles of different diametercorrespond to different maximal momentum in the outlet and the nozzle diminishing-angle, andwhen the particles gain maximal momentum, the nozzle diminishing-angle becomes smallalong with particles diameter becoming big.The Spalart-Allmaras Model is Applied to simulate free jet and impinging jet on flat, thechain form flow field configuration of supersonic underexpanded jet, the plate shock andstagnation bubble of impinging jet in the nozzle outlet are gained;when solid particles areadded in the gas flow filed, its flow field structure is scattering form;we find that the particlediameter between 0.3mm and 0.8mm has great impinging effect in the center of the flat bycomparing the mean impinging momentum of different diameter particles colliding samelocation flat. The level of impinging erosion decreases along with the increasing of the distanceof the nozzle and plate, except the plate greatly close to the nozzle when the accumulation ofparticles affects the efficiency of impinging erosion.