Research On The Application Of Focused Ultrasound Assisted Mist Cooling System In The Grinding Zone

Because of the high speed rotation of the grinding wheel in the grinding process,the air surface layer named gas barriers exists on its surface.However;gas barriers leads to the problem of low efficiency and poor cooling effect of the traditional cooling method.To solve the problem,ultrasonic atomization and ultrasonic focusing have been combined based on acoustic dynamic effect and strong heat transfer capacity of steam mist medium,so that the mist effectively overcomes the surface of the grinding wheel and reaches the surface of the heat source.Heat transfer performance and cooling efficiency of mist has been improved.It is of great significance to realize green precision grinding.On the basis of previous research,Focused Ultrasound Assisted Mist Cooling System which contains ultrasonic atomization and ultrasonic focusing has been proposed.Use Finite Element Analysis(FEA)method to optimize the size of system.The study of atomization characteristics shows that the maximum atomization can reach 30ml/s and the atomization state of the system is related to the coolant flow rate.Based on the theory of spherical ultrasonic focusing and the Helmholtz's integral theorem of the sound field,the focusing characteristics of the focused ultrasonic mist cooling system are simulated and the result have been verified by experiments.The impedance characteristics,vibration characteristics,atomization characteristics and sound field focusing characteristics of the focused ultrasonic mist cooling system meet the requirements.The steady state heat transfer characteristics of the focused ultrasonic mist cooling system under the condition of plane heat source are simulated by using Ansys Workbench software and the influence of the distance between the specimen and the center of the sphere,the coolant flow rate and the ultrasonic power on the surface temperature distribution,the surface heat flux and the heat transfer coefficient were studied.The test results show that the specimen in the mist convergence regions of specimen during central region of the lowest temperature,increasing the cooling liquid flow helps to reduce the surface temperature but the influence on the surface temperature distribution is very small,when the ultrasonic power is sufficient to ensure that all the cooling liquid is atomized under the condition of increasing ultrasonic power to still contribute to steam heat exchanger.In order to verify the simulation results,the steady state heat transfer test was carried out under the condition of plane heat source.The center plane and spherical atomization on two different atomization state of specimen center temperature variation were studied,analyzed the heat transfer characteristics of steam in the sound field under the action of combined with the focusing characteristics of longitudinal bending hybrid vibration field,the results show that when the specimen is located in the loop at the point of ultrasonic focused ultrasound is helpful to strengthen the center heat.Research on the relationship between grinding force and grinding zone temperature and ultrasonic vibration parameters shows that when the coolant flow rate is the same,compared with the ordinary water cooling,the focused ultrasonic mist cooling has a stronger heat transfer capacity on the condition that focused ultrasonic mist cooling system applies in ultrasonic vibration assisted grinding.