Compressors are widely used for the pressurization of fluids. Applications involve air compression for use in aircraft engines and pressurization and transportation of gas in the process and chemical industries. The article focuses on two commonly used types of continuous flow compressors: the axial compressor, where the gaseous fluid is processed in a direction parallel to the rotational axis, and the radial or centrifugal compressor, where the pressurized fluid leaves the compressor in a direction perpendicular to the rotational axis. In these machines, the entering fluid is pressurized by first accelerating it via the kinetic energy imparted in the rotors and then converting the kinetic energy into potential energy by decelerating the fluid in diverging channels. Toward low mass flows, stable operation of axial and radial compressors is constrained by two aerodynamic flow instabilities: rotating stall and surge. The article gives an overview of the current state of modeling and control of these instabilities.

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Modeling and control of compressor flow instabilities

In this chapter a general introduction of centrifugal compression systems is presented. The unstable surge phenomenon in compressors is discussed, as well as possible means to avoid or suppress this instability. From an assessment of the current state of the art in control-oriented modeling and identification, the research objectives are formulated. 1.1 General introduction The general topic of this thesis is surge in centrifugal compression systems. In particular it deals with the modeling and identification for control of the surge phenomenon. Surge is an unstable operating mode of a compression system that occurs at low mass flows. Surge not only limits compressor performance and efficiency but it can also damage the compressor and auxiliaries due to the large thermal and mechanical loads involved. Furthermore, the vibrations associated with surge can result in unacceptable noise levels. A promising technique to cope with surge is the active suppression of aerodynamic flow instabilities. When successful, active surge control enlarges the operational envelope of the compressor towards lowermass flows. Thereby, surge control makes the compression system more versatile and it allows the machine to run at the most efficient operating points, which are usually located near the surge initiation point. Research efforts over the past decades have led to important advancements in the field of surge control. Progress has been made with the analysis, modeling, and suppression of surge and promising experimental results on laboratory setups were reported. However, a real breakthrough in the practical application of active surge control on industrial scale installations has not been achieved, yet. The current research originates from work by Willems (2000) and Meuleman (2002) within theCompressor Surge Control project at the Department of Mechanical Engineering, Technische Universiteit Eindhoven. The project provided valuable new insights in the

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Centrifugal compressor surge : modeling and identification for control

• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers.

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Modeling and bounded feedback stabilization of centrifugal compressor surge

http://www.dct.tue.nl/New/Heemels/WilHee_02_Automatica.pdf

Brief Positive feedback stabilization of centrifugal compressor surge

Results on the feasibility and benefits of model based predictive control applied to a gas turbine are presented. For a laboratory gas turbine installation, the required dynamic simulation model and the real-time (nonlinear) model predictive control (MPC) implementation are discussed. Results on both model validation and control performance are presented. We applied a nonlinear MPC configuration to control the laboratory gas turbine installation and succeeded in a real-time implementation. Although the available computation time for prediction and optimization of the model limits the sample time, the advantages of MPC, i.e. constraint handling, and anticipation to future (set-point) changes are fully reached, and the control performance is good. Special attention is paid to the performance of the applied filter that compensates for inevitable mismatches between model and process measurements. In general, the opportunities of model based control of turbomachinery are promising.

Nonlinear Model Predictive Control Experiments on a Laboratory Gas Turbine Installation

Dynamic simulation of the operation of a compressor station requires mathematical modeling of the dynamic behavior of the compressor unit and various piping elements. Such models consist of large systems of nonlinear partial differential equations describing the pipe flow together with nonlinear algebraic equations describing the quasi-steady flow through various valves, constrictions, and compressors. In addition, the models also include mathematical descriptions of the control system, which consists of mixed algebraic and ordinary differential (mad) equations with some inequalities representing controllers' limits. A numerical technique for the solution of the gas dynamics equations is described, based on the transfer matrix formulation relating the state vector time difference at one side of an element to that on the other side. Simulation results and comparison with actual field measurements of three case histories: simulation of a compressor surge protection control process, unit startup, and slow transient of a compressor station responding to changes in the discharge pressure set point

Dynamic Simulation of Compressor Station Operation Including Centrifugal Compressor and Gas Turbine

Dynamic simulation of the operation of a compressor station requires mathematical modelling of the dynamic behaviour of the compressor unit and various piping elements. Such models consist of large systems of non-linear partial differential equations describing the pipe flow together with non-linear algebraic equations describing the quasi-steady flow through various valves, constrictions and compressors. In addition, the models also include mathematical descriptions of the control system which consists of mixed algebraic and ordinary differential (mad) equations with some inequalities representing controllers’ limits.In this paper a numerical technique for the solution of the gas dynamics equations is described, which is based on the transfer matrix formulation relating the state vector time-difference at one side of an element to that on the other side. This approach facilitates incorporation of all elements transfer matrices into an overall transfer matrix according to the system geometrical connectivity. The paper also presents simulation results and comparison with actual field measurements of three case histories: 1) simulation of a compressor surge protection control process; 2) unit startup; and 3) slow transient of a compressor station responding to changes in the discharge pressure set point. Good agreement between simulation results and field measurements is demonstrated.© 1990 ASME

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D. B. Mah

Papers

Dynamic Simulation of Compressor Station Operation Including Centrifugal Compressor and Gas Turbine

Dynamic Simulation of Compressor Station Operation Including Centrifugal Compressor and Gas Turbine