| Summary: | 博士 === 國立中央大學 === 機械工程研究所 === 99 === Twin screw compressors are for decades widely used in industry owing to advantages over other types of compressors. Due to machining imperfections, thermal expansion, pressure deformation, and assembly misalignment, these deviations from the theoretical profile often causes interference between the rotors. To compensate such deviations, it is necessary to apply clearance between the main and the gate rotors which will still provide minimum clearance to reduce the interference. However, the clearance may result in a change of the meshing conditions, such as imperfect contact, discontinuity of the sealing line, backlash and decreasing efficiency caused by the leakage of gas from a high-pressure region to a low-pressure region. Although the clearance may also lead to the above drawbacks, it is still necessary to design clearance between the rotors. Thus, the appropriate clearance between the rotors should be design carefully. Conventionally, clearance measurement must depend on the specific machines and spend lots time and effort. Also, the analysis software has limits for simulate the clearance. So, the aim of this study is to develop a new meshing simulation and clearance evaluation method to predict the real condition after assembly.
The methods developed in this study can be classified into the following three issues. The meshing simulation method is proposed to define the real meshing position for rotors by the geometry of rotor profile and angle iteration method. The clearance evaluation method is to calculate the clearance along the sealing line by the method of multiple transverses iteration. The procedure for searching the closest point between massive points and surface is based on the triangular mesh of surface and iterative method in order to comptute more rapidly. By the combination of the above methods, the meshing position and clearance can be computed correctly regardless the data type of rotor profiles or the variation simulation conditions. Specifically, the difference between this study and past researches is that the simulation method in this study considers the all lobes but not the single lobe at the same time for the purpose of approximate real meshing. Computer simulations are compared with commercial software to demonstrate the accuracy of the proposed method. Also, experimental results are presented to verify the feasibility for clearance prediction.
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