Rotating Machinery Vibration 2011 Part 2

Tham khảo tài liệu 'rotating machinery vibration 2011 part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 4 Chapter 1 eral expression for the motion of the unforced underdcunped system is commonly expressed in any one of the following four forms. sin Ct dt ự or sin wdt ự s v t Xea OR cos dt or cos wdt dv 5 X single-peak amplitude of exponential decay envelope at t 0 wd wnor damped natural frequency phase angle f ột ộc 90 and ị ộc yield same signal a dim real part of eigenvalue for underdamped system n y khn undamped natural frequency i V 1 . Self-Excited Dynamic-Instability Vibrations The unforced underdamped system s solution as expressed in Eq. 5 provides a convenient way to introduce the concept of vibrations caused by dynamic instability. In many standard treatments of vibration theory it is tacitly assumed that c 0. However the concept of negative damping is a convenient way to model some dynamic interactions that tap an available energy source modulating the tapped energy to produce so-called self-excited vibration. Using the typical later shown multi-degree-of-freedom models employed to analyze rotor-dynamical systems design computations are performed to determine operating conditions at which self-excited vibrations are predicted. These analyses essentially are a search for zones of operation within which the recd part a of any of the system s eigenvalues becomes positive. It is usually one of the rotor-bearing system s lower frequency corotational-orbit-direction vibration modes at a natural frequency less than the spin speed frequency whose eigenvalue real part becomes positive. That mode s transient response is basically the same as would be the response for the 1-DOF system of Eq. 3 with c 0 and c2 4km which produces a 0 a positive real part for the two complex conjugate roots of Eq. 4 . As Fig. 3 shows this is the classic self-excited vibration case exhibiting a vibratory motion with an exponential growth envelope as opposed to the exponential decay envelope for c 0 shown in Fig. 2. The widely accepted fact that safe reliable operation of rotating .

Không thể tạo bản xem trước, hãy bấm tải xuống
TỪ KHÓA LIÊN QUAN
TÀI LIỆU MỚI ĐĂNG
Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.