基于周向涡量的农用通风机叶片表面凹槽分析

Analysis of surface grooves of agricultural fan blades based on circumferential vorticity

针对农用轴流风机风量小、能效比低的问题,以MODEL YJD90S-4镀锌铁皮农用轴流风机为研究对象,采用风室试验、逆向建模、CFD数值模拟、周向涡量分析等方法,以叶片表面凹槽宽度D=6、8、10、12mm,凹槽半径为25%h(h为叶高)、50%h和75%h,开单、双槽3个因素进行排列组合,制定了24种开槽方案,对所有方案进行数值模拟并进行周向涡量分析,筛选得出D=10mm、R=25%h、开单槽(方案1),D=10mm、R=75%h、开单槽(方案2)和D=10mm、R=25%h、75%h、开双槽(方案3)为较优方案,并对此3种方案风机风量和能效比模拟结果进行研究。结果表明:1)采用逆向建模方法建立的镀锌铁皮农用轴流风机几何模型,其数值模拟计算结果能够很好的与原型风机性能试验测试结果吻合,表明逆向建模技术能够运用于农用轴流风机研究;2)在农用轴流风机常用的进口工作压力工况下,3种方案的风机流量和能效比相对原型风机都有提高,其中采用D=10mm、R=75%h、开单槽(方案2)时提高最为明显,风量约提高了90m^(3)/h,能效比约提高了3.2%。3)分析周向涡量3D映射发现,采用D=10mm、R=75%h、开单槽(方案2)时轮毂处的正周向涡量向叶顶处移动,正周向涡量向叶片顶部聚集,增加其对总压流的正贡献,使分布在70%h处的负周向涡量向叶片根部移动,叶片根部附近的负周向涡量呈现出收拢的现象,负周向涡量向叶片根部聚集以减小其对总压流的负贡献。

In order to solve the problems of low air volume and low energy efficiency ratio of agricultural axial flow fan,this study took MODEL YJD90S-4 galvanized iron sheet agricultural axial flow fan as the research object.The Wind chamber test,reverse modeling,CFD numerical simulation,circumferential vorticity analysis and other methods were adopted,and the groove width of blade surface D=6,8,10,12mm and the groove radiuses 25%h,50%h and 75%h (h was blade height)were set,These three factors of single slot and double slot were arranged and combined to develop a total of 24slotting schemes.The numerical simulation and circumferential vorticity analysis were carried out for all schemes.D=10mm,R=25%h,single slot(Scheme 1),D=10mm,R=75%h single slot(Scheme 2)and D=10mm,R=25%h,75%h,double slot(Scheme 3)were identified the better schemes,and the results of air volume and energy efficiency ratio of the three schemes were studied.The results show that:1)When the geometric model of galvanized iron sheet agricultural axial flow fan is established by reverse modeling method,the numerical simulation results are in good agreement with the performance test results of prototype fan,indicating that reverse modeling technology can be applied to the study of agricultural axial flow fan;2)Under the static pressure condition of19.6Pa inlet commonly used for agricultural axial flow fans,the fan flow rate and energy efficiency ratio of the three schemes are improved compared with the prototype fan,and the improvement is most obvious when D=10mm,R=75%h and single slot(Scheme 2)are adopted.The air flow rate is increased by about 90m^(3)/h and energy efficiency ratio is increased by about 3.2%.3)By analyzing the 3Dmapping of circumferential vorticity,it is found that when D=10mm,R=75%h and a single slot is opened(Scheme 2),the positive circumferential vorticity at the hub moves to the tip of the blade,and the positive circumferential vorticity gathers at the top of the blade,increasing its positive contribution to the total pressure flow and making the negative circumferential vorticity distributed at 70%h of the blade move to the blade root.The negative circumferential vorticity near the blade root shows a phenomenon of closure,and the negative circumferential vorticity gathers at the blade root to reduce its negative contribution to the total pressure flow.