1684-渦旋式空氣壓縮機(jī)

1684-渦旋式空氣壓縮機(jī),渦旋式,空氣壓縮機(jī) Development of a three-dimensional scroll compressorDOI: 10.1243/09544089JPME189Abstract: Scroll compressor has been employed in various appliances due to its advantages such as high efficiency and low vibration. For the purpose of further performance improvement in scroll compressor, the authors have developed a new conceptual three-dimensional compression mechanism (three-dimensional scroll) by adding an axial compression to the conventional radial compression. By realizing three-dimensional compression, which has been impossible for the conventional scroll, higher efficiency, higher reliability, and smaller size are achieved. Since the three-dimensional scroll has steps in scroll tip and end plate, the key point of efficiency improvement in the three-dimensional scroll is to minimize the gas leakage in the steps. Through cylinder pressure measurements and visualization tests, characteristics of the leakage in the steps are obtained and the optimum clearance ranges are determined. Based on this, the authors have developed high efficiency, small size, and lightweight three-dimensional scroll compressor for commercial air-conditioner. The developed three-dimensional scroll compressor archived 35 per cent smaller size, 26 per cent lighter weight, and 5.5 per cent improvement of efficiency compared with the conventional one.Keywords: compressors, design, refrigeration, control, performance, development, simulation1 INTRODUCTIONA demand for saving energy has been extensively increasing from the viewpoint of environmental conservation against global warming. Since most energy in refrigerating and air-conditioning appliances is consumed by the compressor, its efficiency improvement is indispensable for saving energy. Meanwhile,these appliances are often restricted in their installation space. Therefore, miniaturization of each component including the compressor is required to enhancethe flexibility of installation. Today, scroll compressor, which has advantages such as high efficiency and low vibration, has been used for various appliances to meet the demandfor saving energy and its use is expected to spread increasingly. For the purpose of further performance improvement in scroll compressor, the authors have developed a new conceptual three-dimensional compression mechanism (three-dimensional scroll) that adds an axial compression to the conventional radial compression. This article describes the efficiency improvement technology in the three-dimensional scroll and the development of the three-dimensional scroll compressor for commercial air-conditioner.2 STRUCTURE OFTHETHREE-DIMENSIONAL SCROLL2.1 Features of the three-dimensional scrollFig. 1 Three-dimensional scroll compressorFigure 1 shows the developed three-dimensional scroll compressor forcommercial air-conditioneranda photograph of the orbiting scroll.Refrigerant gas flows into the compressor through the suction pipe placed on the side body. Then, it reaches the compression chamber getting compressed from the outer side to the inner side. The compressed refrigerant is discharged from the centre of the fixed scroll.Fig. 2 Sectional view of the conventional and the three-dimensional scrollFigure 2 shows a schematic diagram of the sectional view of the conventional and the three-dimensional scroll. The wrap height of the conventional scroll is constant throughout the compression process, and the refrigerant is compressed two-dimensionally from the outer side to the inner side as the compression chamber continuously becomes smaller in volume.For the three-dimensional scroll, in contrast, the outer wrap is higher than the inner one by installing steps in the scroll tip and the end plate. Therefore, threedimensional compression, radial and axial direction, becomes possible. The three-dimensional scroll has the following features.1. Higher compression ratio is obtained by radial and axial compression.2. The strength of scroll wrap is improved and higher reliability is obtained by decreasing the height of inner wrap, which receives a heavy load.3. Larger capacity is obtained without extension of the outer diameter of scroll by increasing the height of outer wrap, and thus the three-dimensional scroll has smaller size and lighter weight.2.2 Compression mechanism and leakage clearances in the three-dimensional scrollFig. 3 Compression mechanism of the three-dimensional scrollThecompressionmechanismof the three-dimensional scroll is shown in Fig. 3. The three-dimensional scroll has steps in the scroll tip (tip step) and the end plate (bottom step). When these steps are not engaged (see Figs 3(b) and (d)), compression chambers across the step have the same pressure. Therefore, no leakage occurs in the steps. On the other hand, when these areengaged (see Figs 3(a) and (c)), seal lines are formed by the engagement of both steps.Figure 3 also shows the enlarged view of the step and the sectional view in the longitudinal direction of the orbiting scroll. Leakage clearances in the step (hereafter called step clearances) can be broadly classified into tip clearance and side clearance, and the gas leakage occurs from the high-pressure chamber to the low-pressure chamber through these clearances. Therefore, the key point of efficiency improvement in the three-dimensional scroll is to minimize the gas leakage in the steps by optimization of step clearances.