Flow resistance and particle separation efficiency of a rectangular-spoke rotating disk: Influence of spoke configuration and number

Abstract

How to effectively separate oily particles before they enter exhaust ducts and thus reduce their accumulation has always been a challenge. This paper proposed a general rotating disk with three different spoke configurations, namely, straight spoke (SS), backward-curved spoke (BCS), forward-curved spoke (FCS), and compared their airflow characteristics and capture performance in a specified exhaust duct. Affected by the divergence effect, the BCS disk has the highest flow resistance (ΔP) and lowest separation efficiency, while the FCS disk has the lowest ΔP and highest efficiency due to the convergence effect. Subsequently, two refining methods were applied to the disks with the three spoke configurations to improve the particle separation efficiency. The FCS disk consistently maintains the highest separation efficiency (ηp), e.g., 0.83 and 0.70 for 5 μm particles at 3000 rpm under equal refining and gradient refining methods, respectively. When being refined equally, the quality factor (QF) of the FCS disk increases with the rotating speed, reaching 0.038 Pa−1 at 3000 rpm, almost equivalent to the initial QF of the fiber filter and spacer fabric, significantly higher than that of the SS disk (0.026 Pa−1) and the BCS disk (0.024 Pa−1). When gradient refining is used, however, the maximum QFs of SS, BCS, and FCS disks appear at 2200, 1800, and 2600 rpm, respectively, thus making the gradient refining method economical only at a lower rotating speed. Finally, on the base of the area under curve index and the straight linear cluster method, the applicability of disks with different spoke configurations in a residential kitchen, which is a typical scenario for collecting oily particles in civilian buildings, was evaluated. Gradient-refined SS disk, equal-refined FCS disk, and equal-refined SS disk can meet the requirements of maximum exhaust attenuation. The gradient-refined SS disk and equal-refined FCS disk have the highest quality, with ηp reaching 0.61 and 0.48, respectively. The findings can provide solid support for the design of rotating disks to separate oily particles, especially in residential kitchens.