5.3. Separation efficiencyThe size distribution of COF particulate matter from Li et al.’sexperiments [39] fits the Rosin Rammler Equation [40]. The completesize range is divided into 10 intervals, each represented bya mean diameter for which trajectory calculations were performed.The density of particles is 960 kg/m3. The cumulative particle sizedistribution and parameters, such as the minimum, maximum,mean, and spread diameter (n) are shown in Table 9.for particle tracking. Centre of the impeller is set as the rotationaxis origin and the rotation axis direction is z-axis positive direction.In general, it requires each blade to rotate through a distanceof one blade spacing in 15 time steps [41]. In this study, the rotationalspeed of the impeller was 1268 rpm at orifice diameter0.12 m. As there are 29 blades in the optimised novel range hood,the time step was set as 1.08 104 s based on Eqs. (14) and (15).Particles are released from the surface of the oil fume inlet after thefully development of the unsteady gas phase flow field. Surface ofinjection type is employed and the number of particle released is4.16 103 for single size. In the process of particle tracking, aDPM boundary condition is set as the trap for the blade surface,outer cylinder inside wall, inner cylinder outside wall, diffuser,and guide vane surface. According to the trapping principle ofthe novel range hood, the separation efficiency (g) is affected byblade interception (gb) due to inertial force, outer cylinder trapping(gc) due to centrifugal inertial force, guide vanes (gg), and diffus