Flow characterization in mine ventilation fan blade design using CFD

Abstract

In axial ventilation fans, the generation of a uniform flow velocity is desirable for better efficiency. To that end, different fan blade types have been developed to achieve better flow uniformity. This article aimed to characterize the flow distribution and its uniformity in four blade designs, namely constant chord, tapered blade, skewed blade, and tapered skewed blade, using Computational Fluid Dynamics (CFD). The study employs an iterative study where key study decisions are made as the study progresses. The study began with the selection of a blade profile for the study. A comparative study between the NACA seven-digit and four-digit series was conducted and for its higher flow throughput, the four-digit airfoil profile was selected. Next, with 30 and 40 Angle of Attack (AoA), the constant chord blade flow pattern is characterized. At 40 AoA flow disturbance and high-velocity spots were observed establishing the problem statement. Following that, three optimization strategies (tapering, skewing, and taper skewing) were applied in the design, and the flow pattern of each design was studied. Using a dispersion study a flow uniformity comparison between the models conducted. The property trade-off between three key performance indicators: Efficiency, flow rate, and flow uniformity studied. The result shows an axial fan having a higher efficiency doesn't necessarily mean it has higher throughput whereas lower flow dispersion relates to the system's higher efficiency. Therefore, it can be concluded that seeking higher efficiency and flow uniformity in the design and development of axial fans comes with system throughput trade-off.