Multi-objective Parameters Optimization Design Of Self-excited Oscillation Pulsed Atomizing Nozzle Based On The Modified Cavitation Model

The self-excited oscillation pulsed atomizing nozzle can effectively obtain the high-speed solid cone jet and spray evenly without increasing the external power consumption,so it can be used in the new application field of the atomization.The primary atomization effect of the jet near the nozzle directly affects the final spray quality,and the turbulence effect and cavitation effect at the outlet of the atomizing nozzle are the two main incentives of the jet primary atomization.In the paper,the two factors will be improved by optimizing the parameters of the atomizing nozzle to obtain the better primary atomization quality of the jet.Currently,the experimental and numerical methods are the main optimization design methods of the self-excited oscillation pulsed atomizing nozzle.However,it is time-consuming and costly by using these methods,and because of the lack of sampling data,the obtained optimization structure is not the optimal.Therefore in the paper,a multi-objective optimization design for the nozzle parameters is presented based on the mathematical optimization technology and CFD(computational fluid dynamics)for aiming at the optimization of the primary atomization of the jet near the nozzle.The main contents in the paper are as follows:(1)In order to enhance the accuracy of the experimental data for the multi-objective optimization design obtained by numerical simulation,a modified cavitation model which considers the influence of the shear stress and the pressure pulsations induced by the turbulent kinetic energy on the cavitaion inception is proposed according to the cavitation mechanism of the nozzle.(2)The contours of the vapor phase volume fraction in a pulsed period are analyzed and the simulation results of the nozzle outlet pressure peaks under different inlet pressures and chamber diameters are compared with the previous experimental data for verifying the validity of the modified cavitation model.Furtherly,the influences of shear stress and pressure pulsation produced by turbulent kinetic energy on the cavitation as well as the influence degree of the two factors on the cavitation and the ability of the cavitation inception under different inlet pressures are studied and analyzed.(3)Central composite design is adopted for the experimental design.Response surface methodology is adopted to establish the approximate mathematical model of the primary atomization near the nozzle.The multi-objective optimization design of the nozzle parameters is conducted by adopting the NSGA-II algorithm and gray theory to obtain the optimal primary atomization quality.And the optimal result is studied and analyzed to verify the validity of the multi-objective optimization design method.