| Summary: | 碩士 === 國立臺北科技大學 === 能源與冷凍空調工程系碩士班 === 105 === Dry scroll vacuum pumps (DSVP) are gradually prevailing in semiconductor industry, chemical engineering, pharmacy, scientific instrument and other industries and fields due to their advantages of oil-freeness, dependable performance, wide working range, low noisy, low vibration and so on. Therefore, a higher-performance DSVP is continuously required by the industries. Because the volumetric ratio caused by new involute profile of variable-radii circle scroll pair is higher than that by traditional circle-involute one, the scroll vacuum pump with variable-radii circle involute can enhance its volume ratio, pumping speed, ultimate pressure or shortening of time required to achieve the specified degree of vacuum without changing the size and operating mechanism of vacuum pump, and meet the future needs of the industries.
The purpose of this study is to design a dry scroll vacuum pump with involute of variable-radii circle. Both transient thermal-flow-pressure field characteristic inside the compressed chamber and system performance of DSVP will be explored numerically. The research method adopted in this study is as follows. First, a geometric model of scroll profiles, constructed from an involute of circle with variable radii, will be built by computational-aided drawing technology according to the existing relative references and the mechanics theory available for scroll vacuum pump. Then, combining the meshing modification at the center of the scroll profile, both feasibility of the meshing motion and the improvement of the effectiveness on this scroll system will be investigated. Second, the computational fluid dynamic (CFD) method is conducted to analyze numerically the characteristics of transient temperature, velocity and pressure fields inside the compressed chamber and system performance under different operating conditions during the process of pumping/compressing. In additional, a comparison of the performance of DSVP with involute of variable-radii circle and with involute of constant-radii circle (Anest Iwata isp250c) is examined for the basis of modification.
The simulation results show that: (1) compared with the traditional fixed circle radius circular involute dry scroll vacuum pump, variable base-radius circle involute dry scroll vacuum pump can achieve lower ultimate pressure; (2) At the same scroll height and the number of scrolls, the exhaust speed of the variable base circle radius circular involute dry scroll vacuum pump will increase with the decrease of the variable radius radius correction δ0 value; (3) In the case of δ0 = -0.05, the suction volume is increased by 58.72% than the case of δ0 = 0, thus increasing in the pumping speed and shortening in the time to reach the ultimate vacuum pressure by 35% and reducing in ultimate vacuum pressure by 6% ; (4) Due to the lower pressure difference between the two adjacent compression chambers, the radial leakage is less for DSVP with involute of variable-radii circle than with involute of constant-radius circle.
|
|---|
