Research On The Air Flow Control And Adjustable LAVAL Nozzle

Pneumatic conveying means transforming the solid particles with pressure gas power,which is widely used in electric, chemical, food grain, metallurgy, rubber, building mateial, unload ship, medicine, feedstuff industry etc. The research of pneumatic conveying is involved in aerodunamics, gas-solid two phase flow and granule mechanics etc. The research is very significant for industrial production. In this paper, the influence of air flow to the process of pneumatic conveying is researched, air flow control of pneumatic conveying is analysed and adjustable laval nozzle is designed and simulated based on the mechanism of pneumatic conveying. First, the background about the thesis, meaning, method and thinking of the research are explained; the characteristic of pneumatic conveying is be summarized briefly; the updated research methods and result are introduced. Basic theories of pneumatic conveying research are represented succinctly.Basic air equation, equation governing the motion of air–granule two phase flow and basic granule character are introduced.Pneuamtic conveyings are classed based on the mechanism of pneuamtic conveying, the fluence of air velocity on conveying phase is researched by conveying phase diagram. The significancy of conveying air flow on conveying is proved. Parameters of pneumatic conveying design are analysed, the pressure loss of pneuamtic conveying of domestic and abroad scholars is introduced.The ways of pneumatic conveying air flow control are discussed, the current research situation of domestic and abroad on air flow control is compared. Computing formula of emptying air flow of non controllable by-pass booster is deduced and the value of emptying air flow is calculated, controllable by-pass booster can save energy is proved.Choked flow theory of fixed LAVAL nozzle and adjustable LAVAL nozzle are discussed, the air flow formula is deduced; the relationships between air flow, equivalent diameter, circulation area of adjustable laval nozzle and dispalcement of adjusting lever of adjustable laval nozzle are deduced with math tools such as Taylor series conversion etc., finite three-dimensional element model is constituted and griddings divided, flow field and static pressure field are simulated with finite element simulant software and critical ratio of adjustable laval nozzle confirmed.Test verification has been done to attest to save enegy, high critical ratio of LAVAL nozzle, exact air flow and low particle degradation using adjustable laval nozzle, the experimental system belongs to dense double pipe conveying, and by-pass pipe flow is controllable. The test results have confirmed theoretical analyse and calculation of adjustable laval nozzle.At last, the summing-up of the thesis is presentment, the prospect of pneumatic conveying air control especially adjustable laval nozzle for the future is put forward.