Numerical Investigation On Aerodynamic And Acoustic Performance Of An Axial Flow Fan With Skewed Or Swept Blades

The variable pitch axial flow fan is widely used in power plants and other fields due to its high efficiency,high flow rate,easy adjustment,etc.However,its power consumption accounts for more than 25% of the plant's electricity consumption,and the aerodynamic noise is relatively large.Therefore,research on the aerodynamic performance and noise of such fans has important practical significance for energy saving and emission reduction and environmental noise reduction.The effects of different skewed or swept angles on the aerodynamic and acoustic performance of a single-stage variable-pitch axial fan of type OB-84 with rear guide vanes were simulated with Fluent and Ansys finite element analysis module.The aerodynamic performance and internal dynamics of the fan before and after blade skewing or sweeping were examined numerically,the static structure features were investigated and the noise was predicted,and numerically explored the adaptability of the effects on the fan performance with the best skewed or swept angle in the range of the selected angles under variable-design conditions.Results show that circumferential skewed and chordwise swept blades have a observed impact on fan performance.For the fan with forward-skewed blades,the total pressure rise is improved by the skewed blades and the promotion is apparent in the large flow rate.The best forward-skewed angle is 3° at the design point,and the total pressure rise and efficiency are increased by 3% and 0.16%.For the variable blade angles of ?=29and 35°,the total pressure raise and efficiency of the fan with ?=3.0° under the point of maximum efficiency are changed by-0.55%,-0.53% and 1.39%,2.11%,respectively.Under different blade angles,the forward-skewed blades enhance the working ability of the middle and lower parts of the blade,inhibit the leakage of the blade tip,and delay the emergence of separation flow in blade root,resulting in a more stable flow,the improved effects of the forward-skewed blade on the flow field near the tip and root enhances with the increasing blade angle.The forward-skewed blades reduces acoustic noise of the fan,and the noise reduction is notable under the case of ?=29°.After the blade skewing,although the blade deformation increases,it still meets the requirements of static strength checking.For the fan with forward-swept blades,the performance of the fan is improved bythe swept blades,especially in the small and large flow rate;the forward-swept angle of?=8.3° has the best performance at the design point,the total pressure and efficiency are increased by 2.1% and 1.68%.The forward-swept blade can effectively raise the working ability of impeller and pressure recovery ability of guide vanes,decrease the entropy generation rate at the top and weakens the occurrence of the top leakage and subsequent the leakage loss.After the blades swept,the aggravated deformation still meets the requirements of material strength.The maximum sound power level of the forward-swept blades is 5.56% higher than the original fan,and noise reduction measures should be taken in actual running.The best forward-swept angle obtained at the design blade angle is suitable for fans operating at rated loads.