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Rotating Machinery Vibration 2011 Part 3

Tham khảo tài liệu 'rotating machinery vibration 2011 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Lateral Rotor Vibration Analysis Models 29 troductory appreciation for all this is the objective of Table 1 which somewhat simplistically subdivides the degree of LRV complexity into three categories. The three categories in Table 1 could be further delineated as made clear in subsequent chapters with the aid of the applicable first principles covered in the remaining sections of this chapter. Chapter 3 deals with torsional rotor vibration TRV which involves torsional twisting of the rotor. In single-rotor drive lines it is rare for there to exist significant dynamic coupling between the lateral and torsional rotor vibration characteristics. Consequently these two types of rotor vibration while potentially coexisting to significant degrees in the same rotor practically do not significantly interact. There are a few exceptions to this e.g. high-speed refrigerant centrifugal compressors for high-capacity refrigeration and air-conditioning systems. Such compressor units are typically composed of two parallel rotor dynamically flexible shafts coupled by a two-gear single-stage speed increaser. In that specific type of rotating machinery the gear teeth forces provide a potential mechanism for coupling the lateral and torsional rotor vibration characteristics. Even in that exceptional application such lateral-torsional coupling is generally not factored into design analyses. Near the end of Chapter 3 subsequent to the coverage of applicable first principles for both LRV and TRY Table 1 is presented to show some Table 1 The Three Elementary LRV Complexity Categories System category Design considerations Max. speed below 80 of lowest critical speed Max. speed is near lowest critical speed or above one or two critical speeds but bearings arc sufficiently soft that critical-speed modes arc rigid body-like. Two-plane low-speed rigid-body balancing is all that is required. No elaborate analyses required. Max. speed near or above one or two more critical speeds and rotor .