Analyses of Leakage and Efficiency of Aluminum Alloy Scrolls
Dr. Chung-Biau Tsay
Generally, the performance evaluation of a compressor is based on its volumetric efficiency. Because a higher volumetric efficiency results in a higher refrigerating capacity and E.E.R.(energy efficiency ratio) of a compressor. The most important issue for the volumetric efficiency of a compressor is the leakage problem. However, it is difficult to measure the leakage flow of a scroll compressor directly, and the accuracy of the measurements are not completely convincing. Therefore, this thesis tries to use a numerical method to roughly calculate the leakage of the mating scrolls to provide designers a referable result. This thesis uses the equation of meshing and calculus to get the geometric shape model of an extended involute scroll and some properties of the scrolls. The leakage model of scrolls can be attained by putting these properties to operate with ideal-fluid assumptions. Then, observing the FEM results that scrolls sustain to refrigerant’s pressure and temperature loads, we can detect the deformations of scrolls which receive pressure stress and thermal stress, and the clearance at the contact lines can obtain as well. Taking these results into the leakage model of scrolls, the leak flow rate of the scrolls can be calculated. An analytic model is established to find a relationship between the design parameters of scrolls and leakage, and the efficiency of scrolls are gotten at the same time. In addition, a set of optimum design parameters can be obtained to improve the efficiency of scrolls. It is hope that the suggestions made in this thesis are helpful to the design of scrolls of scroll compressors and provide competitive superiorities for scroll compressors in the market.
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