Lü Weiling,Xi Guang,Gong Wuqi,Zhang Wei
(School of State Laboratory of Fluid Machinery,Xi'an Jiaotong University,Xi'an ¡¡710049,China)
Abstract£ºA test rig system was built which can perform the performance and flow field measurement of a forward curved multiª²blades centrifugal fan. A particle image velocimetry system was used to measure the secondary flow in the volute crossª²section and the blade wake flow. The result shows that the fluctuation intensity of the wake flow reaches about 20%-70%. Near the designed working condition the effect area of the blade wake is small while the effect region increases under the off-design working condition.The radial width of the blade wake accounts for 15%-25% of the radial width of volute and is about 2-3 times of the blade chord height.The secondary flow vortex does exist in the cross section of the volute, which has relationship with the different working ability of the blade axial segment that results in a different blade outlet total pressure.Because of the back-to-back configuration of the double inlet fan, the secondary flow is symmetrically arranged along the profile curve of volute. When the flow reaches the volute outlet,however,the two secondary flow vortexes combine into one at a small flow rate while the two vortexes maintain till to the volute outlet at a large flow rate.
Keywords:particle image velocimetry; forward curved multi-blades centrifugal fan; blade wake; vortex;secondary flow