If the influence of other factors is neglected, let MF and MT be in the same plane and perpendicular to each other. The radial force generated by these two moments is: F=MFt and FT=MTt, t is the middle sleeve of the coupling. The center span of the end teeth. The additional radial force to which the bearing is subjected is: Fx = F2F + F2T = M2F + M2T / t. Similarly, due to the influence of the frictional force L, the maximum additional axial force is: Fymax = LP = LMkmaxdcosA, L friction coefficient.
Due to the misalignment of the rotor, the working state of the rotor journal and the bearing surface is changed, and a vibration superimposed waveform is generated, which reduces the bearing capacity and stability of the bearing. Therefore, the additional radial force and the additional axial force generated by the misalignment of the coupling are the causes of the vibration of the unit, and are also an important factor that aggravates the bearing damage.
The diaphragm concentricity deviation large turbine compressor is a high-speed rotating mechanical seal device. Due to the seal pressure difference and high rotation speed, a large excitation force is easily generated at the small gap between the rotor air seal and the diaphragm. To this end, we checked the concentricity of the partitions and found that the concentricity differed greatly. The radial deviation and axial deviation of the concentricity of each partition were almost 1.5mm or more, and the maximum difference was 4.25mm. The pressure difference caused by the difference in the seal gap is likely to generate an exciting force. The cause of the vibration is as shown in the labyrinth seal. The pressure before and after the sealing device is P0 and P2, and P0>P2. The pressure P1 in the sealed chamber depends on P0, P2 and the gaps D1 and D2. If the partition D1>D2 and the rotor is in the eddy state due to the initial disturbance, the sealing gap between the rotor and the diaphragm will change periodically. . When the rotor moves radially to the diaphragm, the gap between the discharge end and the inlet end of the sealed chamber is reduced, but since the original gap of the discharge end is small, the relative gap reduction ratio is larger than that of the inlet end, so that the inflow of the sealed chamber The amount of gas is greater than the amount of gas flowing out. Due to the accumulation of gas, the pressure P1 in the chamber is increased to form a downward force acting on the rotor. When the rotor moves radially away from the diaphragm, the relative clearance of the discharge chamber is smaller than the inlet end. The expansion is faster, the outflow volume in the cavity is greater than the inflow volume, and the pressure drops, forming an upward force, so the force acting on the rotor is a superposition of the two forces. However, the pressure change in the sealed chamber is not in phase with the rotor displacement, but lags behind the rotor displacement by an H angle.
Eliminating the exciting force In order to eliminate the exciting force, while ensuring the coaxiality of the impeller, the bushing and the gas seal on the rotor, and adjusting the concentricity of the partition, the adjustment method is as follows. Since the adjusting screw at the lower part of the baffle is corroded in the corrosive gas medium, we use the method of shoveling and screwing the screw to remove the corroded screw and reassemble it with stainless steel 1Cr18Ni9Ti material. The volute partition is adjusted by pulling the steel wire, and the lower volute partition is adjusted by the dummy shaft, and the concentricity is adjusted to be 0.50 mm in the radial direction and 0.10 mm in the axial direction. After adjustment, the screws are spot welded with electric welding to prevent the screws from loosening, so that the alignment size is no longer changed, thereby reducing and preventing the rotor from whirl and exciting to eliminate vibration.
Conclusion Through the analysis, searching and improvement in recent years, the vibration of the D480 turbo compressor has been significantly reduced. The amplitude of the vibration measured by the condition monitor during operation is greatly reduced compared with that before the improvement. The effect is obvious and long. Cycle safety and stable production provide a guarantee.
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