Numerical Simulation And Experimental Research Of Grass Trimmer's Internal Flow Field

In this dissertation, giving a brief research progress of the grass trimmer and a survey of PIV and turbo machine internal flow field technology at home and abroad; comparing all kinds of simulation models of single-phase air flow, establishing the model fitted to grass trimmer's flow channel; introducing the grid generation and their features, establishing the flow passage's model and generating unstructured grid by GAMBIT; choosing the k-s model to enclose the rotating flow field, and adopting some hypothesis to the model, using the SIMPLE method to simulate the flow field, giving some results such as velocity, pressure and kinetic energy distribution, analyzing the length of blade and rotating speed velocity of motor how to effect the flow field's distribution; designing and making a fixable experiment table, completing PIV flow field testing experiment.The result of simulation indicates that the internal flowing in flow field is a symmetric distribution comparing to the basic surface. The length of blade and velocity of motor effect the flow field and grass trimmer's cutting ability, noise control and the ability of dripping grass. A longer blade and higher motor rotating speed can get a better cutting ability. a longer blade when the rotating speed is fixed can get a bigger pressure drop which can make grass dripping out of the flow field in time. longer blade when the rotating speed is fixed can make a bigger velocity pulse which will make the noise more higher.The experiment indicates that the velocity in flow field is a symmetric distribution comparing to the basic surface. The results anastromose between experiment and numerical simulation. The length of blade effects the flow field's features. The main reason is that the fluid in the gap may be absorbed to the low pressure area inside in addition to rotating movement, which makes the flow field disorderly.