| In recent ten years, with the rapid development of the automobile industry, the demand of automobile air-conditioning has become increasing. As the core device in refrigeration system, compressor, especially the scroll compressor, has advantages in automobile air-conditioning system for its compact structure, high efficiency, low vibrancy and steady operation. Compared with commercial central air-conditioning, compressors used in automobile air-conditioning system must have high pressure-ratio, built-in volumetric ratio and volumetric efficiency. In order to meet these technical requirements, a new scroll profile or a kind of top profile shaped must be designed. Because of high built-in volumetric ratio, scroll compressor with symmetrical circular arc plus line-shaped top profile is fit for automobile air-conditioning system.At present, domestic and international researches on modified profile based on involute are mainly about double-arc-shaped top profile, little about symmetrical circular arc plus line-shaped top profile because the theory of symmetrical circular arc plus line-shaped top profile is far from perfect. Therefore, the mathematical models based on multi-objective can not be built. It is hard to analyze precisely and predict the performance of products. Design of scroll compressor involving the volume of compression chamber is based on graphical method in domestic enterprises. As a important part of geometry on modified profile, the volume of compression chamber will directly affect static balance of orbiting-scroll and the homeostasis’s design and analysis of crankshaft. So it is very important to promote the level of design, analysis and computer simulation for scroll compressor used in automobile air-conditioning system by studying and improving the theory of symmetrical circular arc plus line-shaped top profile.Based on the theory of arc-shaped top profile of involute, the methods of theory analysis, numerical simulation and experimental verification are adopted to in-depth research on the geometric property and volume constitute of compression chambers with symmetrical circular arc plus line-shaped top profile, and to analyze gas forces and discharge characteristic generated from the mesh process between fixed-scroll and orbiting-scroll in detail. The theory of symmetrical circular arc plus line-shaped top profile has been perfected. The results from simulation and experimental verification show that the theory of modified profile is correct. The range of modification angle that fits for automobile-air-conditioning compressor has also been studied in this paper. In the dissertation the major work and achievements are described as follows:① The dissertation reviewed and summarized the development progress, the current state and development tendency of scroll compressor used in automobile-air-conditioning system. Comprised to operating environment and condition between automobile-air-conditioning and commercial central air-conditioning, operating requirements and technical characteristics are concluded when used in automobile-air-conditioning system. In order to promote the performance of scroll compressor, it is necessary to design new type profile or to improve original profile.②Geometric theory of symmetrical circular arc plus line-shaped top profile is studied. Based on the arc-shaped top profile theory, geometric characteristics of this top profile shaped are studied deeply. The method of scroll wrap generated by this type profile is found. The feature parameters of this kind of profile different from others are indicated and discussed.③The relationship between arbitrary cycle of scroll and number of compression chamber is studied. The mathematics models existing are about scroll whose cycle is almost integer. Though there are a few reports about the relationship between non-integer cycle of scroll and number of compression chamber, the results do not in accord with the facts. These deficiencies make it difficult to built mathematics models of scroll compressor with arbitrary cycle. Therefore, the work constructing the relationship between them has been done. By the way, in view of scroll compressor with non-integer cycle, it is only necessary to modify properly the number of compression chamber, and the volume of compression chambers can be calculated accurately.④Mathematics models of compression chamber in scroll compressor with modified profile used in automobile-air-conditioning system are established. According to the feature that reduction of centre compression chamber is due to an increase in wall thickness of top profile, the calculation formula of mesh-apart angle is derived elaborately and the methods to calculate the expanded volume of wall thickness of top profile and discharge angle after modification are presented.⑤Mathematics models of gas forces generated when fixed-scroll and orbiting-scroll meshes are established. Suction angle will change when cycle of scroll varies. Suction angle may greater than, less than or equal to invading angle. That causes the number of compression chamber changeable. Operating characteristics in different process of scroll compressor with arbitrary cycle are analyzed in detail.⑥The dissertation utilizes the mathematic models above to simulate the scroll compressor with top profile shaped in VB6.0. The results show variation of parameters of scroll compressor with different modification angles and the range of modification angle when the scroll compressor is used in automobile-air-conditioning system. Moreover, UG is used to format fixed-scroll and other accessories. This lays the foundations for later manufacturing the scroll compressor.⑦The last part in the dissertation is about manufacture and experimental verification of scroll compressor with symmetrical circular arc plus line-shaped top profile. Its modification angle equals 119°. The results show that the theory of symmetrical circular arc plus line-shaped top profile is correct, and that the value of modification angle ranging from 95° to 135° is fit for scroll compressor used in automobile air-conditioning system. |
PDF Full Text Request