Chung-Hyo Jung, Jin-Tak Kim and Yun-Ho Choi*
The Journal of Mechanical Science and Technology, vol. 25, no. 6, pp.1465-1474, 2011

Abstract : An automatic washing machine undergoes rotational unbalance due to unbalanced mass during the spinning process. A liquid balancer is an assembly that plays a role in controlling this unbalance. In recent years, washing machines (drum and automatic types) are becoming larger to handle large laundry items such as comforters. A large-sized washing machine generates a huge centrifugal force in its high speed rotating drum. Thus, a specific vibration reduction technique is required. The design of a liquid balancer has, to date, depended on conventional methods such as experiments and dynamic models. A dynamic model classifies the behavior of liquid inside the balancer into three different patterns, and solutions can be obtained by approximating these patterns as rigid bodies. This method, however, is limited to two-dimensional (2-D) analysis for simple geometry. In the present study, a three dimensional (3-D) computational fluid dynamics (CFD) method is used to analyze flow characteristics inside the liquid balancer for various design parameters. The main parameters include rotational speed, eccentricities of the center of rotation, viscosity of the liquid, gravity orientation, surface tension, and the number of baffles. In particular, the effects of these parameters on the hydraulic force (restoration force) of the liquid balancer are studied.

Keyword : Automatic washing machine; Liquid balancer; CFD; Dynamic model; Free surface; VOF; Centrifugal force; Baffle; Restoration force; Eccentricity