Effect of Suction Slot Location and Width on the Performance of Centrifugal Fan

The aim of the present study is to find the best slot location and appropriate slot width at that location. The flow pattern is then analyzed and simulated with no slot and with a slot at six different radial locations; namely S1, S2, S3, S4, S5, and S6 with fixed slot width W of 2.5 mm. The computationally generated characteristics of unsteady flow demonstrated that the slots added at S3 i.e. near the midpoint of the blade span gives the highest fan efficiency and largest increase in static pressure. Slots at S3 suppress secondary flow at the blade passages and push it to the blade tip. Additionally, streamlines and velocity distributions in impeller passages and over the blade surfaces validated the slots' benefits. Computations with different slot width; namely 1.5 mm, 3.5 mm, and 5 mm are carried out to find the best slot location and width at the best slot location S3. At the optimal efficiency point, the calculated performance of the employed fan with slot location S3 and 2.5 mm width, showed a 2.7 % increase of efficiency and 1.5% increase in static pressure rise as compared to fans with slot at S1 with same width of 2.5 mm. However, it showed a positive impact on the boundary layer buildup and flow separation over the blade suction side for the impeller studied.