Research On Flow Field In Nozzle Of Fluidized Bed-type Jet Mill

At present, jet mill is one of the major technologies and methods of preparing ultra-fine powder materials, jet mill can prepare ultra-fine powder materials to a higher purity. Fluidized bed-type jet mill is the most advanced jet mill equipment. Compressed air is accelerated into supersonic through the Laval nozzle jet in the system of Fluidized bed-type jet mill and smashed into the room. Particles of materials are accelerated by high-speed airflow and smashed in the mutual impact collision and mutual friction in the interchange of nozzle jet.Laval nozzle is a key part of producing supersonic airflow. In order to speed up the compressed air into supersonic airflow with a larger Mach number and greater speed through Laval nozzle, the shape of the internal cavity of Laval nozzle must be reasonable, the value of airflow pressure difference between import section and export section of nozzle must be appropriate. Under the premise of the certain airflow pressure of airflow pressure of import section and export section of nozzle, design quality of internal cavity of Laval nozzle weigh overall performance of Fluidized bed jet mill. In this paper, the purpose of the study is that design a reasonable shape of the internal cavity of Laval nozzle, accelerate compressed air into supersonic airflow with a larger Mach number and greater speed through Laval nozzle, crush material particles fully, increase productivity, reduce production costs.In this paper, the study object is QLM-II Fluidized bed-type jet mill nozzle in the laboratory in School of Materials and Metallurgical in Northeastern University. Establish airflow parameters in entrance section of Laval nozzle through the basic theory related to fluid dynamics and gas dynamics;Research gas flow field in Laval nozzle through the one-dimensional steady isentropic theory of gas, research the state of movement of airflow in the nozzle and affecting factors of the state of movement of airflow, identify conditions producing a supersonic airflow, establish relationships of gas flow field in the nozzle; Simulate the gas flow field in Laval nozzle with the help of the software of FLUENT; Establish the reasonable values of gas stagnation pressure and nozzle back-pressure, Design the shape of Laval nozzle internal cavity, make airflow in exit section of Laval nozzle become supersonic airflow with a larger Mach number and greater speed; Calculate nozzle jet by the basic theory of gas jet, simulate nozzle jet by the software of FLUENT, ensure that compressed air be accelerated to be supersonic jet through Laval nozzle; Through the study of nozzle jet, verify that compressed air is accelerated to be supersonic jet through Laval nozzle, design of internal cavity shape of Laval nozzle meets the requirement of production of fluidized bed-type jet mill.