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Centrifugal compressor - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Centrifugal_compressor

From Wikipedia, the free encyclopedia

Centrifugal compressors, sometimes referred to as radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.[1] The idealized compressive dynamic turbo-machine achieves a pressure rise by adding kinetic energy/velocity to a continuous flow of fluid through the rotor or impeller. This kinetic energy is then converted to an increase in potential energy/static pressure by slowing the flow through a diffuser. Imagine a simple case where flow passes through a straight pipe to enter centrifugal compressor. The simple flow is straight, uniform and has no swirl. As the flow continues to pass into and through the centrifugal impeller, the impeller forces the flow to spin faster and faster. According to a form of Euler's fluid dynamics equation, known as pump and turbine equation," the energy input to the fluid is proportional to the flow's local spinning velocity multiplied times the local impeller tangential velocity. In many cases the flow leaving centrifugal impeller is near or above 1000 ft./s or approximately 300 m/s. It is at this point, in the simple case according to Bernoulli's principle, where the flow passes into the stationary diffuser for the purpose of converting this velocity energy into pressure energy.[1]

Centrifugal impeller with a highly polished surface likely to improve performance

1 Historical contributions, the pioneers 1.1 Partial timeline 2 Turbomachinery similarities 3 Components of a simple centrifugal compressor 3.1 Inlet 3.2 Centrifugal impeller 3.3 Diffuser 3.4 Collector 4 Applications 5 Performance 5.1 Performance maps 5.2 Surge 5.3 Maximum flow line versus choke 5.4 Other operating limits 6 Dimensional analysis 6.1 theorem 6.2 Classic turbomachinery similitude 6.3 Other dimensionless combinations 6.4 Affinity laws 7 Aero-thermodynamic fundamentals 7.1 Conservation of mass 7.2 Conservation of momentum 7.3 Conservation of energy 7.4 Equation of state 8 Pros & cons 9 Turbomachinery 10 See also1 of 15

Jet engine cutaway showing the centrifugal compressor and other parts

7/12/2011 11:37 AM

Centrifugal compressor - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Centrifugal_compressor

11 References 12 External links

Over this past 100 years, applied scientists like Stodola (1903, 1927-1945[2]), Pfleiderer (1952[3]), Hawthorne (1964[4]), Shepard (1956[1]), Lakshminarayana (1996[5]) and Japikse (numerous texts including, 1997[6]) have tried to educate young engineers in the fundamentals of turbomachinery which apply to all dynamic, continuous-flow, axisymmetric pumps, fans, blowers, and compressors in axial, mixed-flow and radial/centrifugal configurations. This relationship is why advances in turbines and axial compressors frequently find their way into other turbomachinery including centrifugal compressors. Figures 1.1 and 1.2[7][8] illustrate the domain of turbomachinery with labels showing centrifugal compressors. Improvements in centrifugal compressors have not been achieved through large discoveries. Rather, improvements have been achieved through understanding and applying incremental pieces of knowledge discovered by many individuals. Figure 1.1 represents the aero-thermo domain of turbomachinery. The horizontal axis represents the energy equation derivable from The First Law of Thermodynamics.[1][8] The vertical axis, which can be characterized by Mach Number, represents the range of fluid compressibility (or elasticity).[1][8] The Zed axis, which can be characterized by Reynolds Number, represents the range of fluid viscosities (or stickiness).[1][8] Mathematicians and Physicists that established the foundations of this aero-thermo domain include:[9][10] Sir Isaac Newton, Daniel Bernoulli, Leonard Euler, Claude-Louis Navier, Sir George Gabriel Stokes, Ernst Mach, Nikolay Yegorovich Zhukovsky, Martin Wilhelm Kutta, Ludwig Prandtl, Theodore von Karman, Paul Richard Heinrich Blasius, and Henri Coand.

Figure 1.1 Aero-thermo domain of turbo-machinery

Figure 1.2 Physical domain of turbomachinery

Figure 1.2 represents the physical or mechanical domain of turbomachinery. Again, the horizontal axis represents the energy equation with turbines generating power to the left and compressors absorbing power to the right.[1][8] Within the physical domain the vertical axis differentiates between high speeds and low speeds depending upon the turbomachinery application.[1][8] The Zed axis differentiates between axial-flow geometry and radial-flow geometry within the physical domain of turbomachinery.[1][8] It is implied that mixed-flow turbomachinery lie between axial and radial.[1][8] Key contributors of technical achievements that pushed the practical application of turbomachinery forward include:[9][10] Denis Papin,[11] Kernelien Le Demour, Daniel Gabriel Fahrenheit, John Smeaton, Dr. A. C. E. Rateau,[12] John Barber, Alexander Sablukov, Sir Charles Algernon Parsons, gidius Elling, Sanford Moss, Willis Carrier, Adolf Busemann, Hermann Schlichting, and Frank Whittle.

Partial timeline