Centrifugal compressors rotor

Boyce, M.P., Morgan, E., and White, G., Simulation of Rotor Dynamics of High-Speed Rotating Machinery, Proceedings of the First International Conference in Centrifugal Compressor Technology, Madras, India, 1978, pp. 6-32. 

Centrifugal compressors can have problems at the inducer and blade tips. These parts of the blade can be excited by aerodynamic forces. Blade discs can have stresses at the rotor tips, which lead to cracks. To solve this problem, the offending part is removed and a scalloped disc results as seen in Figure 21-20. This type of disc experiences some efficiency loss (about 2 %). 

The centrifugal compressor is composed of a casing containing a rotating element, rotor, which is supported by a set of bearings. For most multistage compressors, shaft end seals are located in-board of the bearings. 

The API mechanical standards for the rotary and centrifugal compressor have a test specified for proof of rotor insensitivity. This would normally be the test invoked at this point to ultimately prove the rotor. The fifth edition of API 617 expanded on this test and changed the acceptance criteria from those based on amplification factor to an acceptance level based on internal seal clearances. 

Selection of construction materials for rotors and casings is more limited than for centrifugal compressors. 

Figure 3-83). As in the centrifugal compressor, the kinetic energy of the high-velocity flow exiting each rotor stage is converted to pressure energy in the follow-on stator...

Dynamic compressors impart energy to the gas by velocity or centrifugal force and then convert this to pressure energy. The most common type is the centrifugal compressor. Suction gas enters axiallyinto the eye of a rotor which has curved blades, and is thrown out tangentially from the blade circumference. 

FIG. 10-122 Rotor response plot. This plot is Figure 7 in API Standard 617, Centrifugal Compressors for General... 

A little bit of entrainment is not always bad. For example, entraining a clean naphtha mist into the suction of a wet-gas centrifugal compressor is fine. The mist helps keep the rotor parts clean. If the steam from a boiler is to be used to reboil towers, entrainment is of no consequence. 

Figure 9.5 Sectional view of an integrated two-stage compressor-motor unit (one centrifugal compressor stage at each rotor side) for natural gas.

Axial-flow compressors pass the gas between numerous (for example, 20) rows of blades arranged in an annulus see Fig. 9.10. The gas is successively accelerated by a [moving row of rotor blades and then slowed by a stator blade, which converts the kinetic energy imparted by the rotor blades to pressure (i.e., injection Work). The advantages of the axial-flow compressor over centrifugal compressors are the small cross-sectional area perpendicular to the... 

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