Investigation Of Multi-field Coupled Atomization Characteristics And Parameters Optimization Of Gas-liquid Twin-fluid Nozzle

With the rapid growth of social economy and the rapid development of urbanization and industrialization in China,the huge resource demand and energy consumption have added a heavy environmental burden to social development.The generation and spread of a large amount of atmospheric particulate matter,such as PM_2.5,PM₁₀,and TSP,not only adds many health and safety risks to urban residents,but also causes permanent pneumoconiosis damage to the employees.Moreover,it will cause the related industries to rectify or even stop production due to excessive pollution,which poses a serious threat to the sustainable development strategy and ecological civilization construction of China.Related researches and applications show that ultra-fine water mist generated by the gas-liquid twin-fluid atomization technology can effectively improve the efficiency of adsorption,adhesion and sedimentation during the wet removal process of fine particles.This method has a significant influence on improving the emission control effect of atmospheric particulate matter,and it shows a great potential and value of application.Therefore,in order to improve the twin-fluid atomization technology and the effect of wet removal of particulate matter,and reduce the cost and cycle of the atomization equipment research and development,the gas-liquid twin-fluid atomization nozzle,the core component of atmospheric particulate matter prevention equipment,is employed as the research object in this paper.The multi-field coupled atomization characteristics and parameters optimization of gas-liquid twin-fluid nozzle are investigated.To lay a theoretical foundation for development and application of twin-fluid atomization nozzle,the influence of the operating parameters and structural parameters on the atomization characteristics are revealed,and the flow-solid-sound multi-field coupled atomization numerical simulation and multi-variable multi-objective optimization are investigated.Firstly,in this paper,the theory and method of fluid mechanics and spray are adopted,the atomization principle,droplet breakup and droplet surface wave breaking mechanism are analyzed,and the essence and process of atomization of the twin-fluid nozzle are dissected.Meanwhile,based on the theories of computational fluid dynamics,structural dynamics and aeroacoustics,the methods of bidirectional fluid-solid coupling,discrete phase model and computational aeroacoustics are adopted.A flow-solid-sound multi-field coupling model of the twin-fluid atomizing nozzle is built,and a multi-field coupled atomization numerical simulation method was determined.To fully understand the comprehensive atomization behavior of the twin-fluid nozzle,the multi-field coupling numerical simulation investigations of the flow field and sound field characteristics of the twin-fluid nozzle are carried out.The effects of different operating parameters and structural parameters on the dynamic pressure,velocity distribution and velocity vector of the internal and external flow fields of the nozzle are revealed.Moreover,the variations of the sound pressure level along the axial and radial directions of the twin-fluid nozzle with the changes of operating parameters and structural parameters are analyzed.Secondly,a twin-fluid atomizing test system is built based on the phase Doppler particle analyzer?PDPA?and the conditions and methods of the twin-fluid atomization tests are determined,which lays a foundation for the subsequent experimental study of atomization characteristics of the twin-fluid nozzle.The phase Doppler particle testing technology is used,and the experimental investigations of the atomizing range and spray cone angle under different operating parameters and the spatial distribution of droplet diameter,velocity and number under different operating parameters and spatial measuring points are carried out.The influence of different air flow rates and water flow rates on the atomization characteristics of the twin-fluid nozzle is revealed.Thirdly,the experimental investigation of the influence of the vibrating cavity structural parameters on the atomization characteristics of the twin-fluid nozzle is carried out,and the droplet characteristics of the twin-fluid nozzle in the atomization flow field are analyzed.The effects of vibrating cavity structure and different structural parameters on the droplet mean diameter,droplet mean velocity,droplet velocity fluctuation and droplet turbulence of twin-fluid nozzle in the flow field are revealed.Finally,based on the orthogonal experimental matrix analysis,BP neural network algorithm and genetic algorithm,a multi-variable multi-objective optimization method is proposed.The air flow rate,water flow rate,orifice diameter,orifice depth,distance between the nozzle outlet and the vibrating cavity and the nozzle outlet diameter are determined as optimized parameters,and the droplet diameter,atomization range and sound pressure level are selected as the multi-objective characteristic indexes.Furthermore,the investigation of multi-variable multi-objective optimization of twin-fluid nozzle is carried out.The main influencing factors under the multi objectives of twin-fluid nozzle and the primary and secondary order of each factor are explored,and the optimal parameters and optimal objective values in the global scope are obtained.The studies in this paper can not only lay a theoretical foundation for the atomization performance evaluation and optimization design of gas-liquid twin-fluid atomizing nozzle,but also provide theoretical reference and data support for its development and application.The research results will contribute to the improvement of the atomization performance of gas-liquid twin-fluid nozzle and the control effect of atmospheric particulate matter.Furthermore,it has great theoretical guidance and engineering practical significance for promoting the scientific and technological progress of Chinese environmental protection industry and accelerating the progress of air pollution prevention and industrial clean production in China.