Numerical Analysis Of Micro-clearance Leakage And Counterweight Power Loss In Scroll Compressors

As a new high performance and low noise positive displacement device, the scroll compressor has unique advantages compared with other types of compressors in many fields. With the development of modern manufacture techniques, the scroll compressor has been used in areas of air conditioning, power engineering and so on. Because of its own structural features, internal leakage losses are the main factors that influence the performance of the scroll compressor; a counterweight is installed on the crankshaft to balance the inertia and moment of orbiting scroll during rotation. This paper focuses on the characteristic of micro-clearance leakage process and power loss of rotary counterweights.Formulae for the suction volume, discharge volume, build-in volume ratio are set up based on the geometric characteristic of scroll teeth.According to the N-S Equation, Continuance Equation, State Equation of Hydrodynamics, the mathematic models of leakage are made for the radial clearance, the axial clearance and the clearance between orbiting scroll and framework, by studying the features of gas leakage in the small gap.The effect of surface roughness upon leakage flow was not considered in theory model of scroll compressor. Based on micro-scale clearances and low pressure drop leakage flow, the effects of the height, density and distribution of roughness elements upon fully developed leakage flow were studied in the paper with the help of numerical simulation software, FLUENT. The effects upon leakage flow depend on the height, density and distribution of roughness elements. It is concluded that under the same conditions of the height of clearances and the inlet pressure, the flow resistance increases and the leakage rate decreases by increasing the height and density of surface roughness elements.In order to balance inertia force and moment of the rotary orbiting scroll, a counterweight is installed on the crankshaft. Some power is lost because the rotary counterweight interacts with the surrounding gas. Numerical simulation method was used and the computational fluid dynamics software FLUENT was applied to establish the Moving Mesh model. The influence of rotation speed and counterweight's structure to the power loss were calculated and analyzed. The resistance moment and power loss of the counterweights under different rotational speed were obtained. Results show that the power loss decreases obviously when the radial sides are chamfered.