| Developing efficient and energy-saving axial fan has great significance for saving energy, raising national economy and protecting environment. The principal factor that influence the performance of axial fan is blade designing and circulation distribution in blade designing represents distributing of energy raised by blade work directly, therefore circulation distribution model is crucial for design of fan. A variable circulation flow-circulation increase linearly along the radial direction was proposed owing to problems such as large pressure coefficient and relative loss, etc exist in small axial fan. Impact on fan performance by Variable circulation flow was probed, flow field property in fan was analyzed and relationship between maximum fan efficiency and variable circulation ratio was explored through numerical simulation and laboratory experiment combined.Formula fitting of experimental date diagram of cascade was conducted, aerodyn amic design was carried out by means of excel and circular arc blade was selected in t he paper. 5 kinds of impeller with variable circulation ratio-K is 1.15 、 1.2 、 1.25 、1.3 and 1.35 were designed and manufactured. Aerofoil diagram, die diagram and cutting diagram of impeller were drawn using 3-dimension software and die diagram was manufactured personally to guarantee manufacturing accuracy.Numerical simulation was conducted to five kinds of impeller. Results show that efficiency curves of 5 fans match the characteristic curves of axial fan and the highest efficiency increased firstly then decreased with the increase of variable circulation ratio. The highest total pressure efficiency occurs when K is 1.25. Pressure increases along the height direction of blade gradually on blade surface and at section of impeller outlet. Velocity increases gradually along the height direction of blade on its surface; airflow deflation angle is large and velocity is promoted greatly at section of impeller outlet, all fit in with the theoretical analysis.Pressure and efficiency curves were acquired through fan performance experiments. Results show that the highest efficiency increased firstly then decreased with the increase of variable circulation ratio and there is a optimal k. Internal flow field of fan at the highest efficiency was measured using 5-hole probe, total pressure and 3-dimensional velocity curves along radial direction at impeller outlet and guide vane middle section were acquired and the reasons that the curves are not completely consistent with curves designed were analyzed.Impact of Variable circulation flow on performance of low pressure axial fan was analyzed, experimental study of variable circulation axial fan was enriched and new approach of designing high efficiency variable circulation axial fan was provided through the author’s work. |
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