Variance in Compressor Turndown When Implementing Surge Control Fallback Strategies

2020 ◽  
Author(s):  
Sean W. Garceau
Keyword(s):  
Control System ◽  
Specific Gravity ◽  
Pressure Ratio ◽  
Compressor Pressure Ratio ◽  
Performance Map ◽  
Prevention System ◽  
Compressor Surge ◽  
Surge Control ◽  
Compressor Performance ◽  
Surge Protection

Abstract A centrifugal compressor surge prevention system is used to protect a compressor from surging while in operation. When using an invariant coordinate system for the compressor performance map within the surge protection system, reduced head versus reduced flow, surge control fallback strategies can be implemented within the control system to maintain operation of the compressor when instrumentation fails without placing the unit into a surge event, increasing unit availability. This paper reviews the different fallback strategies that can be implemented based on the function of the instrumentation that faulted and determine the variance between the calculated and actual turndown when different fallback strategies are active. Depending on the fallback strategy implemented, additional turndown margin may be required to ensure compressor surge is prevented by the surge prevention control system. This paper also reviews how the specific gravity, compressor pressure ratio, and compressor flow impact the variance between actual and calculated turndown when a given fallback strategy is active. Knowing the variance in the turndown allows the operator of the compressor to correctly select the desired fallback strategies and determine the needed control margin to safety operate the compressor without process disruptions. Several recommendations are outlined in the paper.

Predictive Surge Control and Optimization for a Centrifugal Compressor

1986 ◽  
Vol 108 (1) ◽  
pp. 82-89 ◽  
Author(s):  
D. Patlovany ◽  
A. B. Focke
Keyword(s):  
Control System ◽  
Supervisory Control ◽  
Control Method ◽  
Energy Costs ◽  
Operating Region ◽  
Stable Operating ◽  
Performance Map ◽  
Surge Control ◽  
Compressor Performance ◽  
Supervisory Control System

This paper details the installation of a retrofit supervisory control system on a large air compressor for the purpose of minimizing energy costs and protecting the compressor from surge. The paper discusses how an accurate prediction of the compressor’s stable operating region can be calculated to develop a compressor performance “map” and how this map can then be used to cut energy consumption by the compressor driver. The compressor is protected from surging by a “predictive” control method. Instead of waiting for the compressor to surge, and then reacting, the system calculates when surge is about to occur and takes action to avoid a surge event before it occurs. The installation of a control system of this type can result in a substantial dollar savings in energy costs, while guaranteeing that a compressor will be protected from any damage from a severe surge event. This system has been installed in our plant and proven in practice. The paper details the installation of this system and its results.

Dynamic Model of Multistage Centrifugal Compressor With a Stage-by-Stage Anti-Surge Recirculating System

2021 ◽  
Author(s):  
Nicola Casari ◽  
Michele Pinelli ◽  
Alessio Suman ◽  
Matteo Manganelli ◽  
Mirko Morini ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Suction Side ◽  
System Level ◽  
Low Flow ◽  
Return Flow ◽  
Control Line ◽  
Compressor Surge ◽  
Surge Control ◽  
Surge Line

Abstract The operability region of a centrifugal compressor is bounded by the low-flow (or high-pressure ratio) limit, commonly referred to as surge. The exact location of the surge line on the map can vary depending on the operating condition and, as a result, a typical Surge Avoidance Line is established at 10% to 15% above the stated flow for the theoretical surge line. The current state of the art of centrifugal compressor surge control is to utilize a global recycle valve to return flow from the discharge side of a centrifugal compressor to the suction side to increase the flow through the compressor and, thus, avoid entering the surge region. This is conventionally handled by defining a compressor surge control line that conservatively assumes that all stages must be kept out of surge at all the time. In compressors with multiple stages, the amount of energy loss is disproportion-ally large since the energy that was added in each stage is lost during system level (or global) recycling. This work proposes an internal stage-wise recycling that provides a much more controlled flow recycling to affect only those stages that may be on the verge of surge. The amount of flow needed for such a scheme will be much smaller than highly conservative global recycling approach. Also, the flow does not leave the compressor casing and therefore does not cross the pressure boundary. Compared to global recycling this inherently has less loss depending upon application and specific of control design.

A Centrifugal Compressor Performance Map Empirical Prediction Method for Automotive Turbochargers

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Antonios Fatsis ◽  
Nikolaos Vlachakis ◽  
George Leontis
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Small Diameter ◽  
Impeller Speed ◽  
Ic Engine ◽  
High Rotational Speed ◽  
Characteristic Lines ◽  
Performance Map ◽  
Compressor Performance ◽  
Compressor Map

Abstract Centrifugal compressor performance map prediction is of primary importance for safe and effective operation of turbochargers. This article is a contribution on compressor map prediction using empirical relations based on automotive turbocharger manufacturers’ performance maps. The present method evaluates the minimum and the maximum air flow rates, as well as the maximum compressor pressure ratio by original empirical equations exploiting impeller geometrical data. Newly introduced equations based on the mass flows and the maximum pressure ratio acquired above provide the compressor characteristic lines. The method is validated by applying it to various commercial automotive turbochargers with known performance maps from their manufacturers. At intermediate values of impeller speed, where the turbocharger is expected to match the engine, the computed compressor map agrees to the manufacturer’s data, while, differences are observed at the maximum impeller speed line. From the cases examined, it can be stated that the present model can be applied to predict small diameter, high rotational speed compressor performance, particularly at the high efficiency region that the turbocharger is supposed to match the IC engine.

Application of Three Methods in Determining the Effectiveness of Surge Protection Systems in Gas Compressor Stations

2012 ◽  
Author(s):  
K. K. Botros ◽  
D. Bakker
Keyword(s):  
Dynamic Instability ◽  
Pressure Ratio ◽  
High Volume ◽  
High Pressure Ratio ◽  
Compressor Surge ◽  
Fast Transients ◽  
Complementary Nature ◽  
Discharge Gas ◽  
Surge Protection ◽  
Rapid Transients

Compression Systems are designed and operated in a manner to eliminate or minimize the potential for surge, which is a dynamic instability that is very detrimental to the integrity of the unit. Compressor surge can occur when compressors are subjected to rapid transients such as one following emergency shutdown (ESD) or power failure. To prevent this from occurring, compressor stations are designed with recycle systems and special types of recycle valves, which are required to open upon ESD. These recycle valves must have specific characteristics to cope with such fast transients and protect the compressor for undergoing surge. This paper describes three methods for determining the effectiveness of any specific recycle system and recycle valve characteristics. These three methods are: i) the concept of the Inertia number, ii) a simplified method based on system impedance, and iii) full dynamic simulation of the compression system. These three methods are applied to a high pressure ratio (up to 3.5) natural gas compressor station involving very high volume of piping and equipment contained within the recycle loop. There is a heat exchanger to utilize the heat of compression to heat the condensate separated downstream in the discharge scrubber, two large aerial coolers to cool the high temperature discharge gas from the compressor, and the discharge scrubber itself. This equipment and associated large volume capacitance contained therein presented a significant challenge and demand on the surge suppression system in all aspects of operation; particularly during ESD. Results are presented from all three methods which show the consistency and complementary nature of these methods.

Numerical Evaluation of the Effects of Low Pressure EGR Mixer Configuration on Turbocharger Compressor Performance

2018 ◽  
Author(s):  
Amin Reihani ◽  
John Hoard ◽  
Stefan Klinkert ◽  
Chih-Kuang Kuan ◽  
Daniel Styles
Keyword(s):  
Flow Field ◽  
Incidence Angle ◽  
Pressure Ratio ◽  
Low Flow ◽  
Exhaust Gas ◽  
Compressor Pressure Ratio ◽  
Compressor Performance ◽  
Velocity Triangle ◽  
Induced Flow ◽  
Compressor Efficiency

Low-pressure exhaust gas recirculation (LP-EGR) is an EGR configuration in which clean exhaust gas is taken downstream of the turbine and aftertreatment, and then reintroduced upstream of the compressor (1). Employing LP-EGR on Diesel engines can improve fuel economy by reducing pumping losses, lowering intake manifold temperature and facilitating advanced combustion phasing (2, 3). The LP-EGR can also improve compressor and turbine performance by moving their operating points towards higher flow rate and higher efficiency points, which is reflected as a net reduction in pumping losses of the engine. In this study, we focus on effects of introducing LP-EGR on the compressor pressure ratio, and isentropic total-to-total efficiency. The flow field of LP-EGR and air mixing upstream of the compressor as well as the entire compressor stage were studied using a CFD RANS model. The model was validated against turbocharger gas stand measurements. A T-junction mixer was chosen as the design baseline, and various configurations of this mixer were evaluated. The impact of the geometric configuration of the mixer was studied by varying mixing length, EGR jet introduction angle, and EGR-to-air cross section area ratio over a wide range of relevant engine operating conditions. The flow field upstream of the compressor is strongly affected by the dimensionless quantity EGR-to-air momentum ratio. At intermediate momentum ratios, stream-wise counter-rotating vortex pairs (4) are induced in the flow. These vortices can reach the impeller inlet, and depending on vorticity and length scale, perturb the local velocity triangle. At low and high momentum ratios, creeping or impinging jets respectively are formed. In addition prewhirl can be induced by eccentric introduction of EGR. The EGR-induced prewhirl acts similar to an inlet guide vane and can alter the incidence angle at the impeller inlet. The performance of the compressor is altered by the EGR-induced flow field. Compressor pressure ratio is either increased or decreased depending on the direction of EGR-induced prewhirl with eccentric EGR introduction. The compressor efficiency decreases at low flow rates by introduction of concentric EGR due to perturbation of the velocity triangle at the impeller inlet. On the other hand, at low flow rates compressor efficiency can be improved by eccentric EGR introduction, which generates prewhirl in the direction of rotation of the impeller leading to improved incidence angle. The extent to which the compressor is influenced by the EGR-induced flow field is generally reduced by increasing the EGR mixing length, due to viscous damping and breakdown of large-scale EGR-induced vortices. The LP-EGR configuration provides a potential pathway towards improvement of compressor performance, not only by increasing compressor flow rate, but also by manipulation of the flow field. Given that the engine pumping losses are strongly dependent on compressor performance, specifically the compressor efficiency, this study indicates that LP-EGR provides an important path towards reducing pumping loss and improving fuel conversion efficiency.

scholarly journals Design and Characterization of a Centrifugal Compressor Surge Test Rig

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Kin Tien Lim ◽  
Se Young Yoon ◽  
Christopher P. Goyne ◽  
Zongli Lin ◽  
Paul E. Allaire
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Fluctuations ◽  
Magnetic Bearing ◽  
Tip Clearance ◽  
Active Magnetic Bearing ◽  
Test Rig ◽  
Compressor Surge ◽  
Surge Control ◽  
Compressor Performance

A detailed description of a new centrifugal compressor surge test rig is presented. The objective of the design and development of the rig is to study the surge phenomenon in centrifugal compression systems and to investigate a novel method of surge control by active magnetic bearing servo actuation of the impeller axial tip clearance. In this paper, we focus on the design, initial setup, and testing of the rig. The latter two include the commissioning of the rig and the experimental characterization of the compressor performance. The behavior of the compressor during surge is analyzed by driving the experimental setup into surge. Two fundamental frequencies, 21 Hz and 7 Hz, connected to the surge oscillation in the test rig are identified, and the observed instability is categorized according to the intensity of pressure fluctuations. Based on the test results, the excited pressure waves are clearly the result of surge and not stall. Also, they exhibit the characteristics of mild and classic surge instead of deep surge. Finally, the change in the compressor performance due to variation in the impeller tip clearance is experimentally examined, and the results support the potential of the tip clearance modulation for the control of compressor surge. This is the first such demonstration of the feasibility of surge control of a compressor using active magnetic bearings.

scholarly journals Centrifugal compressor anti-surge control system modelling

2022 ◽  
Vol 12 (2) ◽  
pp. 1419
Author(s):  
Nurlan Batayev ◽  
Batyrbek Suleimenov ◽  
Sagira Batayeva
Keyword(s):  
Control System ◽  
Natural Gas ◽  
Centrifugal Compressor ◽  
Block Diagram ◽  
System Modelling ◽  
Energy Balancing ◽  
Control Block ◽  
Gas Compression ◽  
Surge Control ◽  
Surge Protection

<span>From the middle of XX century, natural gas is an important mineral, widely used in the energy sector. Transportation of natural gas is carried out via gas pipeline networks and compression stations. One of the key features which need to be implemented for any centrifugal gas compressor is a surge protection. This article describes the method and develops software application intended for simulation and study of surge protection system of a centrifugal compressor used in modern gas compression stations. Within the article research method, modelling environment’s block diagram, proposed algorithms and results are described. For surge cases control and prediction, Anti-surge control block implemented which based on practical experience and centrifugal compressor theory. To avoid complicated energy balancing differential equations the volumetric flow calculation algorithm proposed which is used in combination with Redlich-Kwong equation of state. Developed software’s adequacy test performed through modeling of one-stage gas compression scheme at rated speed with comparison of parameters with reference commercial software and verification of the anti-surge control system.</span>

Introducing Back-up to Active Compressor Surge Control System

2012 ◽  
Vol 45 (8) ◽  
pp. 263-268 ◽  
Author(s):  
Nur Uddin ◽  
Jan Tommy Gravdahl
Keyword(s):  
Control System ◽  
Compressor Surge ◽  
Surge Control

scholarly journals Influence of Seal Cavity Leakage Flow on Compressor Performance Investigated with a Circumferentially Averaged Method

2021 ◽  
Vol 11 (2) ◽  
pp. 780
Author(s):  
Dong Liang ◽  
Xingmin Gui ◽  
Donghai Jin
Keyword(s):  
Flow Field ◽  
Pressure Ratio ◽  
Interaction Mechanism ◽  
Main Flow ◽  
Leakage Flow ◽  
Destructive Effect ◽  
Through Flow ◽  
Compressor Performance ◽  
Overall Performance ◽  
Flow Blockage

In order to investigate the effect of seal cavity leakage flow on a compressor’s performance and the interaction mechanism between the leakage flow and the main flow, a one-stage compressor with a cavity under the shrouded stator was numerically simulated using an inhouse circumferentially averaged through flow program. The leakage flow from the shrouded stator cavity was calculated simultaneously with main flow in an integrated manner. The results indicate that the seal cavity leakage flow has a significant impact on the overall performance of the compressor. For a leakage of 0.2% of incoming flow, the decrease in the total pressure ratio was 2% and the reduction of efficiency was 1.9 points. Spanwise distribution of the flow field variables of the shrouded stator shows that the leakage flow leads to an increased flow blockage near the hub, resulting in drop of stator performance, as well as a certain destructive effect on the flow field of the main passage.

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