Abstract
The self-excited oscillation pulsed atomizing nozzle can effectively and evenly spray the high-speed solid cone jet without any extra power. The primary atomization of the jet at the outlet of nozzle directly affects the final spray quality, and the turbulence and cavitation at the outlet of the atomizing nozzle are the other two main factors affecting the atomization. In this work, multi-objective optimization depending on nozzle parameters was established by using mathematical optimization techniques and computational fluid dynamics to improve the jet atomization quality at the outlet of the nozzle. The central composite design method and the response surface method were used to obtain the approximate mathematical model of the primary atomization quality of the jet at the outlet of nozzle. Finally, the non-dominated sorting genetic algorithm with elitist strategy (NSGA-II) and the grey theory were used in combination to optimize the nozzle parameters. Through combining with the NSGA-II and the grey theory, the nozzle parameters were optimized in order to obtain the best primary atomization at the outlet area of nozzle. The optimization results verified the nozzle design with multi-objective optimization method. The optimized values of the turbulent kinetic energy F1 and the vapor volume fraction F2 increased by 28.26% and 5.56%, respectively, and the corresponding nozzle parameters of the chamber diameter D, the lower nozzle diameter d2 and the upper nozzle inlet pressure Pin were, respectively, optimized to 28.056 mm, 5.472 mm and 3.999 Mpa.
Highlights
Liquid atomization is a physical process in which the liquid is driven by the additional energy to form atomizing droplets in the gas environment
This paper proposes an approach based on the mathematical optimization and computational fluid dynamics (CFD) methods for designing the parameters of the self-excited oscillation pulsed atomizer
The calculated values of F1 and F2 by these two methods are very close. It illustrates that the mathematical model of the primary atomization near the jet nozzle is correct, which can approximately substitute the simulation method
Summary
Liquid atomization is a physical process in which the liquid is driven by the additional energy to form atomizing droplets in the gas environment. Atomization technology is widely used in the combustion fields such as spraying, dusting, Technical Editor: Daniel Onofre de Almeida Cruz, D.Sc. The self-excited oscillation pulsed cavitation nozzle is a rotor with a hollow structure. The special nozzle structure and specific boundary conditions generate the self-exited oscillation pulse and transform the continuous jet to the pulsed jet by increasing the pressure peak at the nozzle outlet without the external energy, which improve the spray quality. Using the pulsed jet with self-excited oscillation to improve the atomizing quality is a new spray technology that can effectively address the challenges of hollow jet and uneven spray [5,6,7]. The use of self-excited oscillation pulsed jet technology on liquid atomization and the optimization for qualifying the design the atomizing nozzle possess an exciting prospect for development
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