tailieunhanh - Sổ tay kỹ sư cơ khí P1

Tham khảo tài liệu 'sổ tay kỹ sư cơ khí p1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 61 AIR COMPRESSORS Joseph L. Foszcz Senior Editor Plant Engineering Magazine Des Plaines Illinois INTRODUCTION 1865 SELECTION 1876 TYPES 1865 COST OF AIR LEAKS 1876 SIZING 1875 INTRODUCTION Compressed air provides power for many manufacturing operations. Energy stored in compressed air is directly convertible to work. Conversion from another form of energy such as heat is not involved. Compressed air can be supplied by several different types of compressors Fig. . The choice depends on the amount pressure and quality of air a plant system requires. The reciprocating compressor is manufactured in a broad range of configurations. Its pressure range is the broadest in the compressor family extending from vacuum to 40 000 psig. It declined in popularity from the late 1950s through the mid-1970s. Higher maintenance costs and lower capacity when compared to the centrifugal compressor contributed to this decline. The sudden rise in energy cost and the downsizing of new process plants have given the higher-efficiency though lower-capacity reciprocating compressor a more prominent role in new plant design. Rotary compressors as a group make up the balance of positive displacement machines. This group of compressors has several features in common despite differences in construction. Probably the most important feature is the lack of valves as used in reciprocating compressors. The rotary is lighter in weight than the reciprocator and does not exhibit the shaking forces of the reciprocating compressor making foundation requirements less rigorous. Though rotary compressors are relatively simple in construction their physical design can very widely. Rotor design both multiple and single is one of the main items that distinguishes different types. For certain applications compression chamber lubricant oils cannot be tolerated in compressed air. The demand for oil-free air in processes where compressed air comes in direct contact with .