Theoretical And Experimental Researches On The Spray Performance And Dust Suppression Performance Of A New Nozzle

In recent years,with the rapid development of economy and the high demand of resources,the particles produced by coal,stone during mining,processing and transshipment have become one of the main sources of air pollution.It is difficult to capture and remove the fine particles(such as PM_2.5,PM₁₀)when they spread into the atmosphere,which will have an extremely harmful to the humans and environment.This problem has drawn great attention from the society,and the human survival and sustainable development have been threatened.The emission standard of particulate matter in our country has become stricter for solving the air pollution problems.Although the traditional dust removal technology for the total particulate matter has better control effect,but it has low removal efficiency for large amount of fine particulate matter.How to overcome this difficulty become urgently.It is an important technological approach to control the particulate matter by spraying in an unorganized environment.As a new method has great potential of application,ultra-fine water mist is beneficial to promote the fine participate matter coalescence and settlement,which could be produced by improving the atomizing technology.This dissertation aims to the theoretical and experimental researches on the spray performance and dust suppression performance of a new nozzle.The velocity distribution of the atomizing core flow field of atomizing nozzle,the effect of different operating parameters on atomizing characteristics of atomizing nozzle,the effects of atomizing core on droplet characteristics of atomizing nozzle,optimization of structure and operating parameters of atomizing core,and the effects of different factors on spray dust suppression efficiency of atomizing nozzle are systematically investigated.In order to investigate the way to improve the atomizing performance and obtain the fine droplets,the atomizing core of the atomizing nozzle is changed according to the supersonic principle of Laval nozzle,and a new nozzle is obtained.The velocity distributions law of the nozzle flow field is obtained by using computational fluid dynamics software Fluent.Then the atomizing effect of nozzle is analyzed and compared before and after the atomizing core being changed by atomizing experiment.Furthermore,the atomizing performance influence rule of atomizing nozzle is experimental investigated under different operational parameters.The supersonic airflow could be produced and the velocity difference of air phase and water phase has a great effect on the atomizing performance are verified.Compared to the original nozzle,the atomizing characteristics of new nozzle have great improved.In order to further reveal the influence of atomizing core of the new nozzle on droplet characteristics in the spray flow field,the droplet diameter,droplet axial velocity and droplet numbers of spray under different atomizing cores were measured with phase Doppler particle analyzer?PDPA?.The changing characteristics of the droplet Sauter mean diameter?SMD?,the droplet arithmetic mean diameter?AMD?,the droplet axial velocity,the droplet turbulent fluctuation velocity,and the droplet numbers are analyzed and discussed systematically.Meanwhile,the influence of atomizing core of the new nozzle on atomizing performance and droplet velocity stability are investigated.Based on the theory and method of computational fluid dynamics,the CFD model of the new nozzle is established.The realizable k-?turbulence model solver and Lagrange discrete phase model are used to solve this issue.Furthermore,the structure and operating parameters of atomizing core are optimized according to the orthogonal experimental method,and the optimal parameters are obtained.The flow field characteristics of the new nozzle are comparative analyzed under optimal parameters.It is verified that the comprehensive atomizing performance of the new nozzle have been improved after optimized when compared with before.In order to investigate the dust suppression performance of the new nozzle,the spray dust suppression experiments of the new nozzle are carried out.The effect of different nozzle structures,different operating parameters,different spray angles on spray dust suppression efficiency are researched.The optimal value of nozzle structure,operating parameter and spray angle are identified for high spray dust suppression efficiency.The research results will lay an applied foundation of spray dust suppression for the new nozzle.Meanwhile,the experimental data will be provided as a reference for the further research on the new nozzle.