Abstract
A hemispheric head cyclone separator has higher collection perfoemance of fine particles compareing with a conventional cyclone separator with a cylindrical head. In order to optimaize the shape model with hemispharic head, we have investigated the air flow in various shape cyclone models by making numerical and experimantal approaches. In the near future, we will propose the compact cylone with hemisperical head for use as an intake side pre-filter for fuel cell vehicles. In this study, we forcus a dust holder which requrires the most large space to achieve space-saving of an installation space in vehicles. We have used direct numerical simulation (DNS) to investigate the internal airflow characteristics of four hemispheric head cyclone separators of different lengths with the diameter of the dust holder being 55% of that of the previous model (D-M). The cyclone separator flow is known to have a large upward vortex swinging around the core, and it has been reported that the cyclone separator flow affects the collection rate of fine particles in a cylindrical cyclone flow. Therefore, the minimum pressure position in each x-y section was detected every 0.01 s as the instantaneous vortex core position of the upward vortex, and the turning center position and radius of the swing were calculated from the trajectory of the vortex core position. The larger the radius of runout, the lower the frequency of runout tends to be. As a result, the difference in the effect of the runout motion of the upward vortex on the reduction of the collection rate is expected to be small in the model with a smaller diameter and varying length of the dust holder, but the model with a larger radius of runout at the bottom of the conical (SD-L2), where particles transported to the outside are more easily captured, is expected to have a larger percentage of reduction in collection due to runout.
