Optimum Design Of Box And Deflector Of Plenum Fan

Plenum fan is a kind of centrifugal fan.Compared with the traditional centrifugal fan,plenum fan has the advantages of smaller sizes,low noise and any air supply direction,but it also has the problems of insufficient static pressure and lower efficiency.Therefore,it is necessary to study how to improve the performance of plenum fan.In this paper,in order to improve the performance of the fan,the numerical simulation method is used to optimize study the structure of box and deflector of plenum fan.According to the characteristics of the plenum fan,the flow rules and energy loss characteristics of the plenum fan are analyzed,and the three important structure sizes of plenum fan are studied: the box width,the outlet area and the axial length in order to improve the performance of the fan.The results show that the airflow trajectory of plenum fan with axial air supply presents a spiral flow along the wall of the box.Compared with traditional centrifugal fan,plenum fan has two main energy losses: the loss caused by the larger space at the outlet of the impeller and the impact loss caused by the high-speed airflow hitting the wall of the box.For the prototypical impeller the optimum box width is 1.8D.The side length of the outlet area should be greater than 0.7 times of the box width as far as possible.The axial length has little effect on the static pressure.In this paper,the radial and axial clearance clearance problems encountered in the process of setting the deflectors are studied,the advantages and disadvantages of the two multi-deflector setting modes are discussed,and the further studies influence of the distance between the deflector and the box wall and the number of deflectors on the performance.The results show that setting deflectors can improve the static pressure.It is more economical to adopt concentric reducing circles to set up multiple deflectors.2mm is the best radial clearance and 0mm is the best axial clearance.The optimal size of the spacing between deflectors and the wall of the box is 30 mm.On the rated conditions the number of deflectors is 5.The structure of box and deflectors were optimized by Response Surface Methodology with static pressure and efficiency as optimization objectives.The results show that the prediction model provided by Response Surface Methodology can fit the simulation results well.Compared with the prototype,the optimized model improved the static pressure by 16.9% and the total pressure efficiency by 3.4%.