鋁合金渦卷之洩漏與效率分析

Abstract

壓縮機性能的評比一般多以容積效率之高低來作為標準，因為容積效率若提高，將連帶提升壓縮機的冷房能力及能源效率比值(E.E.R.)。然而影響容積效率的最主要的因素就是壓縮機本身的洩漏問題，只是直接實際量測渦卷壓縮機的洩漏情形相當困難，數值準確度也不易令人信服，因此本論文改以分析模擬的方式進行推算，粗略的了解渦卷洩漏流量之多寡，提供予設計者一參考之值。 本論文是利用嚙合原理和微積分的觀念來推導延伸漸開線形渦卷的幾何數學模式及其相關性質，再將這些性質加上理想流體的假設狀況以求得渦卷的洩漏數學模式，且配合有限元素法分析所得到之渦卷受冷媒壓力和溫度的結果，發現渦卷會因承受壓應力和熱應力而產生變形，導致原本密封線上相嚙合處產生間隙，把此結果代入所推演之渦卷理論洩漏數學模式，便可求得渦卷的洩漏情形。 利用此分析模式可建立渦卷在設計上可以變動的設計參數與渦卷洩漏流量之間的關係，同時計算其容積效率與壓縮效率並歸納出可供參考之建議，期許對往後渦卷的設計有些許貢獻。當然最終目的是得到一組渦卷設計參數的最佳值，希望此組設計參數可使渦卷壓縮機獲得較高的效率和贏得更多在市場上的競爭優勢。

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.