BISOPE series 45- A Collection of Vibration Causes of Fluid Machines

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In rotating machines, vibration occurs due to centrifugal force due to mass imbalance and friction and impact between solids, but there is another source of vibration. It is self-excited vibration caused by friction between a solid and a fluid. This self-excited vibration is a type of nonlinear vibration that is difficult to predict and is accompanied by various causes and results. The root cause is that dynamic loads (mass and velocity) also exist in the fluid.

Representative fluid machines have a fan and a pump, and are classified according to whether the transported fluid is gas or liquid. Blower (more than 0.1kg/m²) and Compressor (more than 1kg/m²) are also called names.

Types of Fluid Vibration

 

Fluid vibration occurs in various ways, such as when the fluid is caused by an ideal balance of pressure, when irregular vibration is induced by the occurrence of turbulence, or when it is generated on the rear surface by friction with a solid.

The vibration time waveform shows irregularity, and the form of the spectrum has various expressions, such as when floor noise is large, when a frequency group is formed over a certain period (wide band), or when it appears as narrow-band discrete frequencies. The following table summarizes various phenomena of fluid vibration.

 

 

type of vibration

Causes and Symptoms