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Chapter 14
Radial Compressors
© Springer Science+Business Media Dordrecht 2015
E. Dick, Fundamentals of Turbomachines, Fluid Mechanics and Its Applications 109,
DOI 10.1007/978-94-017-9627-9_14
Abstract Radial compressors (or centrifugal compressors) resemble radial fans
and radial pumps for basic operation aspects. So, based on the study of fans and
pumps, which we have done in previous chapters, we can understand the basic
operation of centrifugal compressors. In this chapter, we repeat the analysis of the
working principles of centrifugal machines, but applied to centrifugal compressors.
We discuss applications and the aspects that are particular for centrifugal compressors. These are the inducer part at the inlet of a rotor for large work and the diffuser
downstream of the rotor. We also analyse the operating characteristics with the limits caused by stall and choking.
14.1 Construction Forms and Applications
14.1.1 Rotor Types
Figure 14.1 shows a radial or centrifugal compressor for use in chemical plants
and refineries and for transport of natural gas. The terms radial and centrifugal
are equivalent with compressors. The successive rotors have increasingly smaller
through-flow areas due to increasing density. A rotor is mostly called an impeller,
which means the element that actuates the fluid. The rotors of Fig. 14.1 have a
shroud, so are closed, and the blades are moderately swept backward at the outlet.
There is no strong difference with rotors of a centrifugal pump. At the rotor inlet,
blades begin downstream of the orthogonal inlet plane. At the leading edge of the
rotor blades, the velocity has both an axial and a radial component. Blades with a
leading edge positioned so far downstream of the inlet plane of the rotor such that
there is no axial velocity component are very rare. This means, with centrifugal
pump terminology, that blades mostly are extended into the suction eye. The blades
feature double bending, which means that the bending in different orthogonal sections differs, but the axial variation of the bending is very moderate. Compared to
pumps, the ratio of the inlet diameter to the outlet diameter of the rotors is mostly
higher (this ratio lowers in the successive rotors), and the backward sweep of the
blades at rotor outlet is less. This means that flow factors and work factors are
Chapter 14
Radial Compressors
© Springer Science+Business Media Dordrecht 2015
E. Dick, Fundamentals of Turbomachines, Fluid Mechanics and Its Applications 109,
DOI 10.1007/978-94-017-9627-9_14
Abstract Radial compressors (or centrifugal compressors) resemble radial fans
and radial pumps for basic operation aspects. So, based on the study of fans and
pumps, which we have done in previous chapters, we can understand the basic
operation of centrifugal compressors. In this chapter, we repeat the analysis of the
working principles of centrifugal machines, but applied to centrifugal compressors.
We discuss applications and the aspects that are particular for centrifugal compressors. These are the inducer part at the inlet of a rotor for large work and the diffuser
downstream of the rotor. We also analyse the operating characteristics with the limits caused by stall and choking.
14.1 Construction Forms and Applications
14.1.1 Rotor Types
Figure 14.1 shows a radial or centrifugal compressor for use in chemical plants
and refineries and for transport of natural gas. The terms radial and centrifugal
are equivalent with compressors. The successive rotors have increasingly smaller
through-flow areas due to increasing density. A rotor is mostly called an impeller,
which means the element that actuates the fluid. The rotors of Fig. 14.1 have a
shroud, so are closed, and the blades are moderately swept backward at the outlet.
There is no strong difference with rotors of a centrifugal pump. At the rotor inlet,
blades begin downstream of the orthogonal inlet plane. At the leading edge of the
rotor blades, the velocity has both an axial and a radial component. Blades with a
leading edge positioned so far downstream of the inlet plane of the rotor such that
there is no axial velocity component are very rare. This means, with centrifugal
pump terminology, that blades mostly are extended into the suction eye. The blades
feature double bending, which means that the bending in different orthogonal sections differs, but the axial variation of the bending is very moderate. Compared to
pumps, the ratio of the inlet diameter to the outlet diameter of the rotors is mostly
higher (this ratio lowers in the successive rotors), and the backward sweep of the
blades at rotor outlet is less. This means that flow factors and work factors are