| The objective of the proposed work is to simulate the airflow behavior inside a lawn mower housing using computational fluid dynamics (CFD). A lawn mower is a common machine found in suburban households. The mower could be one of several types, including walk-behind mowers and lawn tractors. A mower has a power part or engine, which provides motion to a blade or blades encased in a housing. As the blades revolve, the grass is cut. Inside the housing, air flows due to the interaction between the geometry of the blade and housing. The mower blade-housing geometry resembles a rotor (blade)---stator (housing) arrangement. Because of area changes in the three-dimensional geometry on both the housing and the blade, the problem is complex, and no analysis for this rotating equipment is available in the open literature. In this work, the flow characteristics in terms of velocity and pressure distributions throughout the enclosed domain are presented for two angular velocities of 100 and 320 rad/sec. A feasibility analysis using a simplified single rotor case is first performed before proceeding into the more complicated 2-D multiple blades in a mower housing profile case, and the 3-D flow prediction around the geometry of a real lawn mower blade. Three cases of the two-equation turbulent model and the Reynolds stress turbulent method are used to calculate the flow characteristics. Mixing pattern behavior in the high aspect ratio housing and its circulation in the profile are found dependent on the blade end tip clearance to the housing. Turbulent flow patterns once established are found to be stable in shape, changing only in magnitude as the velocity increases. The analysis methodology proposed in this dissertation will help not only designers of lawn mower equipment but also others in the agricultural and food processing industries. |
