Publisher's Synopsis
Compressor surge is an axisymmetric oscillation of the mass flow and pressure rise. Surge is an instability phenomenon that is known to occur in centrifugal compressors under low flow conditions. The highly dynamic nature of the phenomenon limits the safe operating region and, hence, the available performance of these machines. The phenomenon is manifested as oscillations of the mass flow, pressure rise and rotational speed of the compressor. Surge is highly undesired, and can cause severe damage to the machine. Modeling and control of these oscillations is of substantial interest since surge limits the useful range of mass flows where the compressor operates soundly. Large amplitude surge can also damage the compressor. This volume provides state of the art techniques and trends in the field of centrifugal compressors covering all major aspects of design, operation, and maintenance. A detailed description of a new centrifugal compressor surge test rig is presented. The objective of first chapter is to study the surge phenomenon in centrifugal compression systems and to investigate the novel methods of surge control by active magnetic bearings. Further, third chapter shows that AMBs stiffness and damping have a great relationship with the control system and rotating speed. Specifically, at low rotating speed, the stiffness and damping can be obtained from the rotor static suspension by adding the same excitation frequency. However, at high speed, different from the static suspension situation, the AMBs supporting coefficients are not only related to the frequency characteristics of control system, but also related to the system operating conditions. Additionally, this work proposes the design of a fractional order proportional-integral-derivative controller that shows a high agreement between simulated and measured friction losses. Ball bearings are commonly used in high speed turbomachinery and have a critical influence on the rotordynamic behavior. Therefore, a simulation model of the bearing to predict the dynamic influence is essential. Hence, in eighth chapter, to investigate the influence of the elasticity of the outer ring, a comparison with a rigid formulation for several rotational speeds and loads is presented. In last, the dynamic analysis of two-rotor three-bearing system is presented. This work will be of interest for engineers in industries that involve turbocompressors and magnetic bearings, as well as for researchers and graduate students in the field of applied control.
