| In the process of modern large-scale pig breeding,due to the good confinement and high feeding density,a large amount of harmful gases such as ammonia,hydrogen sulfide and carbon monoxide are generated in the piggery during the pig feeding process,and if these harmful gases are not discharged in time,it will lead to depression,loss of appetite,decrease of immunity and susceptibility to diseases of pigs.Therefore,axial fans with the advantages of easy installation,safety and stability,and good ventilation effect are often used for ventilation to solve the problem.However,with the change of feeding conditions such as season and type of pigs,the required ventilation quantity is different,and the fan air flow or mass flow rate is usually adjusted by changing the impeller speed or closing part of the fan,which leads to the reduction of fan efficiency and energy efficiency ratio,and the uneven ventilation of piggery.Therefore,this paper takes an axial flow fan for piggery as the research object to explore the fan to maintain high efficiency and energy efficiency ratio at different mass flow rate,in view of the fact that impeller speed and blade installation angle(referred to as speed and angle)have a large impact on the performance of fan mass flow rate,efficiency and energy efficiency ratio,so the impeller velocity triangle theory,Computational Fluid Dynamics(CFD),experimental Dynamics(CFD)and experimental methods are used to analyze the influence of rotational speed and angle on the performance of fans,and to study the influence of the combination of rotational speed and angle on the performance of fans at different mass flow rates based on the enumeration method,in order to improve the efficiency and energy efficiency ratio of fans when used at different mass flow rates.To this end,the main contents and conclusions carried out in this paper are as follows.First,analyze the law of influence of rotational speed and angle on fan performance Analyze the influence of rotational speed and angle on fan mass flow rate and efficiency through the impeller velocity triangle theory,and get the mass flow rate increases with the increase of rotational speed and angle,respectively.The efficiency increases and then decreases with the increase of speed and angle respectively.Secondly,CFD method is used to simulate the performance of the fan and verify its reliability.Solid Works software is used to establish the computational domain model of the studied fan,and the grid is divided,and the performance of the fan is simulated by CFD method.In order to verify the reliability of the simulation method,carry out experimental research on the performance of the wind turbine,compare and analyze the simulation and test data,the results show that the CFD numerical simulation method used in this paper is reliable.Again,the CFD method is used to study the effect of rotational speed and angle on fan performance.The CFD method is used to analyze the effect of rotational speed and angle on the performance characteristic curves of fan mass flow rate,efficiency and energy efficiency ratio,etc.,to further derive the effect of rotational speed and angle on fan performance,and to verify that the impeller velocity triangle theory analysis is credible.Finally,to study the effect of speed and installation angle combinations on the performance of fans at different mass flow rates Based on the enumeration method to study the effect of speed and angle combinations on the performance of fans at different mass flow rates,we obtained four sets of speed and angle combinations at different mass flow rates with an average fan efficiency of 41.2%and an average energy efficiency ratio of 24.2 m~3/(h·W).In order to verify the credibility of the study conclusions,a performance test study was conducted on the fans after the installation angle change,and the simulation and test data were compared and analyzed,and the results showed that the study conclusions were credible.Therefore,by changing the rotational speed and angle,the fan can still maintain a high efficiency and energy efficiency ratio when meeting different ventilation demands of the piggery,which solves the problems of lower efficiency and energy efficiency ratio and uneven ventilation of the piggery caused by changing the impeller rotational speed or shutting down part of the fan.The results of this study can not only provide an effective method to solve the problems of lower efficiency and energy efficiency ratio of fan and uneven ventilation of piggery when meeting different ventilation requirements of piggery,which is of great significance to reduce energy consumption and improve economic efficiency of breeding,but also provide theoretical reference for the design and promotion application of axial flow fan. |
