| As a new type of fluid machine,the plenum fan has been widely used in many fields such as petrochemical,heating and ventilation,and industrial production.The improvement of the inefficiency,noise reduction and long life of the plenum fan can effectively reduce energy loss and improve industrial production efficiency.In order to improve the internal flow of the plenum fan and improve the static pressure efficiency of the plenum fan,the internal flow of the plenum fan is numerically calculated to analyze the low flow,rated flow and large flow conditions.The internal flow field summarizes the loss mechanism during the operation of the plenum fan.The internal flow is improved by installing the splitter blade and the static pressure efficiency of the plenum fan is improved.The main work includes:1.The three-dimensional steady calculation of the internal flow of the original plenum fan is carried out.The numerical simulation results show that under low flow conditions,the separation vortex generation and flow separation at the suction surface of the blade are the main factors affecting the efficiency of the fan.Under the rated flow condition and large flow condition,the separation vortex at the suction surface of the blade is gradually reduced,the influence of the separation vortex on the internal flow is weakened,the complex flow such as secondary flow is enhanced and a "jet-tail" structure is formed at the exit of the fan impeller.The uneven distribution of the outlet airflow leads to a decrease in fan efficiency;under large flow conditions,the increase in the axial impact of the airflow is also one of the main causes of fan efficiency loss.2.According to the cause of the internal flow loss of the fan under full-flow conditions,the structure of the plenum fan was improved by using the splitter blade structure,and the influence of the length of the splitter blade on the internal flow loss of the fan and the fan efficiency was studied.Through numerical calculation of the internal flow of the modified fan,it is found that under the low flow condition,when the chord length of the splitter blade is half of the length of the flow path,the separation vortex at the suction surface of the blade can be effectively destroyed,and the plenum fan is eliminated.The internal flow loss is reduced,and the static pressure efficiency of the fan is improved.Under the rated flow and large flow conditions,the splitter blade structure reduces the loss caused by complex flow such as secondary flow to a certain extent,and weakens the "jet".The wake" structure makes the exit velocity more uniform,increasing the radial velocity of the airflow at the exit,and the static pressure efficiency of the plenum fan is improved.3.Study the influence of the circumferential installation position of the splitter vane on the internal flow loss and the outlet velocity distribution of the plenum fan.The internal flow of the plenum fan was simulated by a higher precision turbulence model.The numerical results show that when the splitter blade is installed in the intermediate flow channel or close to the pressure surface of the main blade,the internal flow can be optimized and the separation vortex can be reduced.The resulting flow loss;when the splitter vane is installed at the suction surface of the main vane,a separation vortex is generated at the suction surface of the main vane and at the suction surface of the split vane,and the complex flow such as secondary flow is increased under large flow conditions.Effectively reduce the "jet-tail" phenomenon,there is no significant increase in the distribution of airflow at the exit.By comprehensive comparison,the installation of the splitter vanes in the center of the flow passage is one of the most effective means to improve the internal flow of the plenum fan and improve the efficiency of the fan.4.Consider factors that affect the efficiency of a plenum fan.Based on the orthogonal experiment,the inlet and outlet angle of the fan,the diameter ratio of the inlet and outlet,the number of blades,and the number of split blades are considered.The effects of various factors on the efficiency of the fan were studied,and the structure with the most obvious improvement in the efficiency of the non-volute centrifugal fan was summarized from the comparison of 16 groups.The optimal structure is compared with the original fan model,and the efficiency improvement mechanism is summarized,and the direction for the subsequent research work is pointed out.The main innovations of the research are: the application of the split-blade structure,which has been fully studied in the field of centrifugal pumps and compressors,to the new type of plenum fan,which effectively improves the internal flow of the plenum fan and makes the exit The airflow is more uniform,reducing the static pressure loss of the fan and improving the static pressure efficiency.The orthogonal experiment method comprehensively considers the influence of the impeller inlet and outlet angle,the diameter of the inlet and outlet,the number of blades,the number of split blades in a single flow channel,and other factors on the static pressure efficiency of the fan.Finally,the structure with the most obvious improvement of the efficiency of the fan is summarized. |
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