Effects of Impeller Tip Clearance on Centrifugal Compressor Efficiency

2007 ◽  
Author(s):  
Jari L. H. Backman ◽  
Arttu Reunanen ◽  
Juha Saari ◽  
Teemu Turunen-Saaresti ◽  
Petri Sallinen ◽  
...  
Keyword(s):  
Control System ◽  
Steady State ◽  
Mach Number ◽  
Centrifugal Compressor ◽  
Tip Clearance ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Centrifugal Compressors ◽  
Compressor Efficiency

The paper describes the results of tip clearance variation experiments in centrifugal compressors. The compressors work at different peripheral Mach number speeds either with vaneless or vaned diffusers. In the experiments, the compressors were operated in a thermally steady state after which the axial positions of the shafts were changed. The changes in the performance of the compressors were recorded and analyzed. The clearance between the impeller and its housing affects the efficiency of the centrifugal compressor. The clearance is optimized to adapt to various phenomena: thermal expansions, impeller tip deflections, shaft bending and gyroscopic motions. The compressors of this study are equipped with active magnetic bearings. They contain a control system, which constantly measures and controls the position of the shaft. This gives useful information about impeller clearance variation, and the measured results are precise within 1/100 millimeters.

Influence of the Different Design Parameters to the Centrifugal Compressor Tip Clearance Loss

2011 ◽  
Author(s):  
Teemu Turunen-Saaresti ◽  
Ahti Jaatinen
Keyword(s):  
Centrifugal Compressor ◽  
Tip Clearance ◽  
Design Parameters ◽  
Clear Correlation ◽  
Compressor Stage ◽  
Centrifugal Compressors ◽  
Blade Number ◽  
Overall Performance ◽  
Specific Speed

In this paper the effect of the tip clearance was studied with six different centrifugal compressors and data available in literature. The changes in the overall performance of the compressor stage were examined. The aim was to study the influence of the different design parameters to the tip clearance loss. It was evident by the previous studies that the sensitivity of the centrifugal compressor to the tip clearance loss varies with different designs. However, for the designer it is important to know the effect of the tip clearance loss in order to initially evaluate the quality of different designs. Analysis of the data demonstrated that no clear correlation between the sensitivity of the tip clearance loss and the specific speed, the diffusion ratio, the blade number and the ratio of blade heights exists.

Modeling and Vibration Control of a Flexible Rotor by Using Magnetic Bearings

2011 ◽  
Author(s):  
Takuya Nomoto ◽  
Daisuke Hunakoshi ◽  
Toru Watanabe ◽  
Kazuto Seto
Keyword(s):  
Control System ◽  
Control Method ◽  
Design Procedure ◽  
Modeling Method ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Flexible Rotor ◽  
Modeling And Control ◽  
Elastic Modes ◽  
And Control

This paper presents a new modeling method and a control system design procedure for a flexible rotor with many elastic modes using active magnetic bearings. The purpose of our research is to let the rotor rotate passing over the 1st and the 2nd critical speeds caused by flexible modes. To achieve this, it is necessary to control motion and vibration of the flexible rotor simultaneously. The new modeling method named as Extended Reduced Order Physical Model is presented to express its motion and vibration uniformly. By using transfer function of flexible rotor-Active Magnetic Bearings system, we designed a Local Jerk Feedback Control system and conducted stability discrimination with root locus. In order to evaluate this modeling and control method, levitation experimentation is conducted.

Two-Level Control Structure of Magnetic Bearings

1993 ◽  
Vol 5 (5) ◽  
pp. 438-442 ◽  
Author(s):  
Nobuyoshi Taguchi ◽  
◽  
Takakazu Ishimatsu ◽  
Takashi Shimomachi ◽  
◽  
...  
Keyword(s):  
Control System ◽  
Vibration Control ◽  
Control Structure ◽  
Active Vibration Control ◽  
Experimental Results ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Level Control ◽  
Whirling Motion ◽  
Active Vibration

Active magnetic bearings have several advantages over conventional mechanical and fluid bearings. However, when the magnetic bearings are used at high rotational speeds, whirling motions and vibrations synchronized with the rotation of the rotor should be considered. In order to suppress these unfavorable vibrations of rotor which is supported by magnetic bearings, we have developed an active vibration control system with a two-level control structure. Experimental results show that our active bearings system effectively suppresses the whirling motion.

Axial Inlet Conversion to a Centrifugal Compressor With Magnetic Bearings

1992 ◽  
Author(s):  
Tom Novecosky
Keyword(s):  
United States ◽  
British Columbia ◽  
Natural Gas ◽  
Centrifugal Compressor ◽  
Axial Compressor ◽  
Magnetic Bearings ◽  
Operating Costs ◽  
Eastern Canada ◽  
The Past ◽  
Compressor Efficiency

NOVA’s Alberta Gas Transmission Division transports natural gas via pipeline throughout the province of Alberta, Canada, exporting it to eastern Canada, United States and British Columbia. It is a continuing effort to operate the facilities and pipeline at the highest possible efficiency. One area being addressed to improve efficiency is compression of the gas. By improving compressor efficiency, fuel consumption and hence operating costs can be reduced. One method of improving compressor efficiency is by converting the compressor to an axial inlet configuration, a conversion that has been carried out more frequently in the past years. Concurrently, conventional hydrodynamic bearings have been replaced with magnetic bearings on many centrifugal compressors. This paper discusses the design and installation for converting a radial overhung unit to an axial inlet configuration, having both magnetic bearings and a thrust reducer. The thrust reducer is required to reduce axial compressor shaft loads, to a level which allows the practical installation of magnetic bearings within the space limitations of the compressor (Bear and Gibson, 1992).

Design Considerations for High Pressure Turbo Expanders Supported by Active Magnetic Bearings

2019 ◽  
Author(s):  
Alice Innocenti ◽  
Francesco Cangioli ◽  
Giuseppe Iurisci ◽  
Davide Biliotti
Keyword(s):  
High Pressure ◽  
Control System ◽  
High Density ◽  
Magnetic Bearings ◽  
Process Efficiency ◽  
Main Process ◽  
Cfd Analysis ◽  
Active Magnetic Bearings ◽  
Turbo Expander ◽  
Force Signal

Abstract Nowadays industrial processes are going toward high power density solutions. This can be read as a general increase in pressure (more than 200 barA) and fluid density indicating Turbo Expander (TEX) as a worthwhile solution to boost main process compressors and increasing process efficiency. On the other hand, inlet high pressure and high density fluids could lead to strong pressure pulsations on the impeller with consequences on the rotordynamic behavior, rotor stability and bearing integrity. For this purpose, a full annulus unsteady CFD analysis of the flow path through the inlet plenum, nozzles and impeller has been performed and analyzed in terms of resulting force FFT on the impeller. The force signal is used as an input of the rotor model supported by Active magnetic bearings (AMB), including their control system and transfer function. The aim of the study is the investigation of the influence of high density gas in TEX applications, coupling the results of unsteady CFD analysis with the dynamic response of the mechanical system. The control system parameters of magnetic bearings are included into the analysis and a sensitivity to different inlet nozzles numbers and inlet pressure levels is performed verifying the feasibility of the rotor.

Effect of Specific Load of Bearing on the Centrifugal Compressor Rotordynamic Stability

2015 ◽  
Author(s):  
Weimin Wang ◽  
Qihang Li ◽  
Lifang Chen ◽  
Jinji Gao ◽  
Paul Allaire
Keyword(s):  
Centrifugal Compressor ◽  
Large Scale ◽  
Damping Ratio ◽  
Stability Margin ◽  
Logarithmic Decrement ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Specific Load ◽  
Tilting Pad ◽  
The Stability

With the ever increasing of the centrifugal compressor capability, such as large scale LNG and CO2 re-injection, the stability margin evaluation and instability control is crucial both for the centrifugal compressor OEM and end users. An industrial scale experimental test rig with two 5-pads tilting pad journal bearings and two active magnetic bearings was introduced. Tilting pad bearings were used to support the rotor, and active magnetic bearings were used to exert static load and sub-synchronous sine load to excite the rotor. The logarithmic decrement identification method of rotor-bearing system was presented. Here, weighted instrument variable and directional frequency response function were combined to improve anti-noise performance and separate forward/ backward whirl vibration. Thermoelastohydrodynamic bearing model was used to investigate the effect of hot clearance on the stability prediction of centrifugal compressor. Also, the contribution of bearing specific load on the stability was studied numerically. Also, experimental work was carried out to investigate the damping ratio of rotor under different rotating speed and bearing specific loads. The numerical results correlate with the test results very well. The results of the investigation indicate that: (i) Hot clearance is very important for centrifugal compressor rotordynamic instability prediction; (ii) The effect of pad mechanical deformation are smaller than that of thermal deformation; (iii) With the increase of bearing specific load, the logarithmic decrement is decreasing.

Control System Design of Frequency-Feedback Magnetic Bearings

1997 ◽  
Author(s):  
Takeshi Mizuno ◽  
Kenji Araki ◽  
Hirotaka Namiki
Keyword(s):  
Control System ◽  
Digital Signal ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Digital Control System ◽  
Load Impedance ◽  
Displacement Sensors ◽  
Digital Format ◽  
Converted Signal ◽  
Counter Circuit

Abstract The structures and features of control system are discussed for active magnetic bearings (AMBs) with frequency type of displacement sensors. The control systems are classified according to the signal conversions performed there. One of them uses a counter circuit for converting the frequency to a digital format, and the converted signal for digital signal processing. It is also pointed out that self-sensing operation can be realized by using hysteresis amplifiers because their switching rates are sensitive to load impedance. A digital self-sensing AMB, which uses a counter circuit for interface and hysteresis amplifiers for energizing the electromagnets, is manufactured for experimental study. The experimental results show that accurate suspension can be achieved with the proposed digital control system.

A New Modeling Technique and Control System Design of a Flexible Rotor Supported by Active Magnetic Bearings for Motion and Vibration Control

2003 ◽  
Author(s):  
Mitsuhiro Ichihara ◽  
Hideo Shida ◽  
Takahito Sagane ◽  
Hiroshi Tajima ◽  
Muneharu Saigou ◽  
...  
Keyword(s):  
Control System ◽  
Vibration Control ◽  
System Design ◽  
Physical Model ◽  
Magnetic Bearings ◽  
Control System Design ◽  
Active Magnetic Bearings ◽  
Flexible Rotor ◽  
Reduced Order ◽  
And Control

This paper proposed a new modeling technique and control system design of a flexible rotor using active magnetic bearings (AMB) for motion and vibration control. The purpose of the research was to pass through a critical speed and achieve high-speed rotation. To achieve this, it is necessary to control both vibration and motion. Even though reduced order physical model [1] that we used before is available technique in expressing vibration, this technique cannot express motion. Thus we propose an extended reduced order physical model [2] that can simultaneously express motion and vibration. Further, by using the model we apply the design of a new controller that combined proportional integral derivative (PID) with linear quadratic (LQ) control to a flexible rotor. The procedure we propose is verified by simulations as being effective for a flexible rotor.

Sign in / Sign up

Export Citation Format

Share Document