采用仿鲤科鱼C型启动构型叶片的多翼离心风机气动性能研究

Aerodynamic Performance of Multi-Blade Centrifugal Fan with Bionic Blades Inspired by C-Type Start of Cyprinidae

受鲤科鱼类C型启动逃逸反应时高效率游动姿态及其周围涡流特征的启发,进行叶片仿生设计,以提升多翼离心风机的气动性能。首先,采用逆向工程方法获取了鲤科鱼C型启动姿态时鱼体中心线方程和水平剖面轮廓线方程,以C型启动时鱼体中弧线为基准,设计了仿生等厚叶片。其次,通过多翼离心风机气动性能数值计算和实验测试,得到了具有最佳进口安装角的仿生等厚叶片(O-BETB),采用O-BETB的多翼离心风机的风量增加了6.8%,噪声下降了0.5 dB(A)。最后,将仿生重构的鱼体流线型轮廓与O-BETB相耦合,得到仿生耦合叶片(CBB),以进一步提高多翼离心风机气动性能。结果表明:当采用CBB时,多翼离心风机的风量增大了8.3%,噪声下降了1.1 dB(A)。基于流场分析,发现具有仿生中弧线和鱼体轮廓特征的耦合叶片在前缘进口角及叶片型线具有更好的引流导向作用,叶间流道的低速分离旋涡明显小于另外两种叶轮;叶片尾缘的尾迹涡脱落引起气流不均匀性程度也最弱,有效缓解了尾流与蜗舌、蜗壳之间的非定常相互作用。通过多翼离心风机声场特性的分析,发现多翼离心风机的气动噪声主要集中在中低频段。CBB的采用,叶轮通道内分离涡被抑制,叶片尾流与蜗壳壁面之间非定常作用减弱,叶片表面和蜗舌处的声压脉动得到有效的控制,这也是CBB风机中低频噪声降低的主要原因。

Inspired by the high-efficiency swimming posture of cyprinid C-type escape reaction and the characteristics of eddy-current around the fish body,the bionic blades are designed to improve the aerodynamic performance and reduce the noise of a multi-blade centrifugal fan.Firstly,the reverse engineering method is used to obtain the center line equation and horizontal profile equation of cyprinidae in C-type starting posture,and bionic equally-thick blades are designed and optimized based on the C-type middle-arc.Through the comparison of numerical calculation and experimental results of fan aerodynamic performance,bionic equally-thick blades with the optimal installation angle(O-BETBs)are obtained.After applying the O-BETB to the prototype fan,the fan flow-rate increases by 6.8%while the noise decreases by 0.5 dB(A).Further,the reconstructed geometric profile of fish body is coupled into the O-BETB to obtain a coupled bionic blade(CBB)to further improve the aerodynamic performance of the multi-blade centrifugal fan.The results show that the flow-rate of a CBB fan is increased by 8.3%while the noise is reduced by 1.1 dB(A).The flow field analysis shows that the coupled blade with bionic middle arc and fish body contour has better guidance effect at the leading edge inlet angle and blade profile,and the low-speed separation vortex in the inter-blade channel is significantly smaller than that of the other two impellers;The wake vortex shedding at the trailing edge causes the weakest degree of air flow heterogeneity,which alleviates the unsteady interaction of the wake with the volute tongue and with the volute.Analysis of sound field characteristics shows that the aerodynamic noise of the multi blade centrifugal fan is mainly concentrated in the middle and low frequency bands.The reduced noise of CBB fans in the middle and low frequency bands is also mainly attributed to the use of the CBB,the suppression of separation vortex in impeller channel,the weakening of unsteady interaction between wake and volute wall,and the effective control of sound pressure pulsation on the blade surface and volute tongue.