Axial compressor surge pdf

The conventional technique of predicting the surge line by comparing the discharge pressure to the differential pressure across the compressor suction bell is not adequate for an axial compressor if the inlet guide vanes are not fixed.

This added variable must be accommodated in order to accurately predict the location of the compressor surge line. Figure 1 — when the inlet guide vanes are in their normal position, the velocity vector of the gas entering the rotating blade passage is turned into the rotation of the blades. If the inlet guides are twisted about their axis in such a way that gas velocity vector is more in the direction of the rotation of the rotor, the energy imparted to the gas will be less.

Figure 2 — Typical performance map for an axial compressor with variable inlet guide vanes. The adjustment of the inlet guide vane angle will increase or decrease the compressor throughput by changing the head produced by the compressor. The conventional surge prediction technique can be modified by monitoring the angle of the guide vanes and interpolating the surge line based on the predicted or tested surge lines for various guide vane angles.

This technique provides accurate surge line prediction for all operating conditions. The primary disadvantage of incorporating the guide vane angle into the prediction algorithm is the source of the guide vane position value. If the guide vane positioner does not include position feedback, the command to the positioner must be used for the surge line prediction algorithm.

And, even if a position feedback signal is available, this signal can be unreliable. For a critical service machine such as the regeneration air blower in an FCCU, instrumentation that cannot be serviced online or supplied in redundant configurations is undesirable.

An alternate technique for predicting the surge line for an air compressor with variable inlet guide vanes is to modify the surge line based on the suction temperature.

Surge suppression and control methods rely on accurate terized by large-amplitude axisymmetric flow oscillations. Surge instability can cause extensive damage to the system, plant models to design a surge control law that is able to stabilize the compression system pass the surge point. Two different approaches to environmental changes in the compressor and suppress the surge oscillations. On the other hand, active surge controllers, exist to deal with the surge instability in turbomachineries.

The most common approach in industry is surge avoidance, which were first proposed by Epstein et al. This leads to a significant drop in by Arnulfi et al. An important point to consider compressor efficiency by limiting the compressor output.

The second approach is surge control, where an active or passive in designing a surge control system is the selection of the appropriate actuator. Simon et al. Common actuators for passive control systems control of surge instabilities has been investigated intensively are the movable plenum wall and the hydraulic oscillator, over the years, motivated by the potential benefits from which induce a pressure variation in the compression system expanding the stable operating region of these machineries.

On the other hand, and Reviews of modeling techniques for compression systems common actuators in active control schemes are the close- can be found in [1] and [2]. Emmons et al. The use of AMBs for the control of other compres- the compression system and a self-excited Helmholtz res- sor instabilities was proposed in [20]. On the other hand, onator. Using the same principle, Greitzer [4] later intro- the use of the AMB for the control of surge in single- duced a two-state nonlinear lumped-parameter model of a stage centrifugal compressors with unshrouded impeller was compression system.

This model was first derived for axial proposed by Sanadgol in [21]. Yoon and Z. Lin are with Charles L. Goyne, and P. A mathematical model describing the compression system with AMBs was introduced by Sanadgol, although no experimental results were available.

Later, experimental validation of the theoretical model was presented by Yoon et al. In this paper we address the design and implementation of the active surge controller for a compression system with active magnetic bearings. A surge controller for a compres- sion system with variable impeller axial clearance is derived and implemented in an experimental setup described in [24]. Additionally, issues encountered during the implementation of the surge controller are also discussed here.

The remainder of the paper is organized as follows. A description of the experimental setup is given in Section Fig. Experimental compressor setup. The mathematical model describing the dynamics of the test rig, including the effects of varying the impeller axial clearance on the compressor output, is presented in Section III.

In Section IV we derive the control law for the impeller tip clearance to stabilize the compression system in surge condition, and the controller is tested in simulation. Finally, Section V discusses the preliminary observations on the implementation of the surge controller and draws a brief conclusion to the paper. The setup shown in Fig. The single stage centrifugal compressor in the experimental an unshrouded impeller and a vaneless diffuser, a modular setup operates with an unshrouded impeller and a vaneless diffuser.

The exhaust piping system that forms the plenum volume, and rotor is radially supported by two radial AMBs, and a single thrust AMB provides the axial support. An innovative feature of this experimental setup is the implementation of AMBs, which not only provide The layout of the experimental setup is shown in Fig. The size of the plenum volume and the static shroud. The final objective of this setup is to can be varied by moving the throttle valve to one of the develop an active surge controller that uses the AMBs to cre- three predetermined locations along the exhaust piping.

By ate pressure waves by changing the impeller tip clearance for modifying the plenum volume this way, we can change the the active control of compressor surge. A detailed description intensity of the observed surge in the compressor.

Pressure of the experimental setup can be found in [24]. The steady state mass flow rate and center the rotor about its rotating axis.

The axial support is given by an orifice flow meter installed in the return of the rotor is provided by a thrust AMB located at the mid- section of the exhaust piping. For the initial testing of the section of the compressor, which also controls the clearance compressor, the throttle valve is located at the position closest between the impeller tip and the shroud with high bandwidth to the compressor, and the operating speed is selected to be and precision.

The maximum end-to-end displacement of the AMBs is 20 mils 0. The compressor is powered by a prototype dynamics of our experimental setup is described in detail induction motor from KaVo, which is rated to produce 95 kW in [21].

Here we present a brief overview for the purpose of power at the design speed of RPM. Layout of the experimental setup, including the compressor, 1. Connected Content. Power, 98, pp. Issue Section:. You do not currently have access to this content. View full article. Sign In or Register for Account. Sign in via your Institution. Learn about subscription and purchase options.

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