How to read a centrifugal compressor performance curve. Psig 1205 control concepts for centrifugal compressor applications 5 in general, changes are slow enou gh that the steady state compressor maps remain valid. Pdf performance comparison of capacity control methods for. Ok, it is clear that inlet guide vanes effectively controls the flow rate.
Centrifugal compressor operations process consulting services. Capacity volume flow q m3 hr power p kw brake horse power bhp kw gas horse power ghp kw. Thus, compressor capacity control methods are utilized to maintain a required delivery under variable. This publication provides information on the maintenance and operation of air compressor plants.
Manual purpose to be used for selection, application into the system, power and cooling water estimation. A centrifugal compressors flow and pressure are typically controlled by a combination of an inlet control device and unloading valve uv. Figure 3 shows an example of a fuel gas compressor arrangement for a gtcc plant, with two gas turbines and three fuel gas compressors connected by a common header. Centrifugal compressors are dynamic, and each has a characteristic curve of rising pressure as capacity decreases. Compressor capacity an overview sciencedirect topics. Understanding centrifugal air compressor capacity controls.
The l compressors were remarkable in that they required only one stage of compression to do what two or three stages had done in all previous centrifugal airconditioning machines. It may be noted that compressors operating under partial loads and low back pressure creates a condition where coil may freeze or damage may result. The cylinder valves control the flow of air through the cylinder. The inlet to a centrifugal compressor is typically a simple pipe.
Compressor surge is typically controlled by detecting when the compressor is nearing the surge line on the compressor characteristic curve and modifying the compressor operation to avoid entering into a surge cycle. Understanding centrifugal compressor capacity controls. If you are new to the compressor, this article will definitely make yourself familiar with the centrifugal compressor performance curve. To size a centrifugal compressor, you should consider the demand flow pattern of customer operation and site inlet conditions minimum average high for optimum performance. It is the quantity of air actually delivered by a compressor in m 3. Reliable, smart and efficient capacity control saving up to 9% energy at reduced compressed air demand. Principle, construction, working, types, advantages, disadvantages with its application. Centrifugal compressor capacities can be controlled by causing the compressor to move back on its characteristic curve.
Centrifugal compressors are dynamic and each has a characteristic curve of rising pressure as capacity decreases. The first is to insure that the available supply meets the flow and pressure demands of the plant. Centrifugal compressors an overview sciencedirect topics. It is therefore, necessary to provide some means to the control capacity of a compressors according to the load. Elliott technical services provides practical, timely and cost. Multi compressor capacity optimization a petrotech, inc white paper multi compressor capacity optimization 7thptc page 4 of 9 2. By closing the guide vanes, volumetric flows and capacity are reduced. Centrifugal compressor 1 mechanical engineering in. Pdf different capacity control methods are used for adjusting suction flow of. Anti surge control system for centrifugal compressors part 2. As the vane rotates toward the closed position capacity is reduced variable speed compressors affect the amount of vapor moved by operating the compressor at varying speeds.
Centrifugal compressor trains operating in parallel or series arrangements are. In case of conflict, manufacturers recommendations on use, care, operations, adjustment and repair. Unlike centrifugal pumps, the reciprocating compressor cannot selfregulate its capacity against a given discharge pressure, it will simply keep displacing gas until it is turned off. These types of compressors are also designed for higher capacity because flow through the compressor is continuous.
Choke and surge occur at the extreme ends of the performance curve and should be avoided. Capacity control system showing pressure transmitter pt and pressure controller pc. Electronics clean, dry, highquality air class 0 is essential, produced. Training lectures on industrial control systems and important applications. Dear all, i have a question about capacity control of fixed speed compressor. Mo206 maintenance and operation of air compressor plants. Process control and optimization, volume ii ftp directory listing. Unlike reciprocating compressors, centrifugal compressors are steady flow. Driving centrifugal compressor technology over the past century, atlas copco has built close relationships with customers. Pdf control concepts for centrifugal compressor applications. Control concepts for centrifugal compressor applications rainer kurz, solar turbine s incorporated, matt lubomirsk y, solar turbines incorporated, sidne y santos, at work rio engineering and.
There are two ways to control the volume flow rate of the centrifugal compressor in which will change in response to changes in head or changes in cooling required. For maximum benefit, this manual should be used in conjunction with equipment manufacturers manuals, parts lists and drawings. There are many refrigeration applications in which refrigeration load is not constant. Centrifugal compressors support a wide variety of refrigerants and thermodynamics and are also able to supply compression in water chiller cycles due to which it has a high demand for usage in. Understand your process, as well as the advantages and disadvantages of each centrifugal compressor configuration, in order to choose the optimal centrifugal compressor for your application. Hvac applications necessitate the compressor to operate over wide range of lift and cooling. Compressor capacity should be stated at plant conditions, which are actual cubic feet per minute acfm.
Plant engineering centrifugal air compressor basics. In this manner, a wide, smooth, capacity control range, i. A centrifugal compressors flow and pressure are typically controlled by a combination of an inlet control device and an unloading valve uv. A method for controlling multistage centrifugal compressors is provided. Axial and centrifugal compressors application guide. The antisurge controller is one of the most critical turbomachinery control applications that protect a compressor from surge by continuously calculating the distance between the compressor s operating point and its surge limit line. Pressure is the primary control independent variable in centrifugal air compressor control. Centrifugal and axial compressors are susceptible to surge which can cause catastrophic damage to your turbomachinery train. In the article, we will discuss how to read a centrifugal compressor performance curve. Suction throttling discharge throttling adjustable inlet guide vanes speed variation bearings. How capacity control is achieved by igvs in centrifugal. Antisurge control ccc compressor controls corporation.
Sorokes dresserrand selecting a centrifugal compressor inlet pressure p1 temperature t1. Builtin control logic ensures system reliability by precisely managing discharge pressure and maximizing throttle range. If you already know about the centrifugal compressor performance curve, definitely this article will refresh your knowledge. Typical antisurge control for centrifugal compressor ix.
Compressor loadsharing control and surge detection. Method for centrifugal compressors using active control casing treatment. Centrifugal compressors are most effective when running at full capacity. All of these additional devices have important uses in the control of the centrifugal compressor. Pdf control methods for centrifugal compressors, especially in oil and gas. Centrifugal air compressor controls and sizing basics. This is generally accomplished by throttling the discharge valve.
Performance and capacity controls elliott single stage centrifugal compressors operate in a wide range of conditions due to the standardized impeller design and the vaneless diffuser. The output of each controller is changed by 10%, and the resulting measurement. A capacity control for a refrigerant gas compressor is comprised of a throttle disk in a throttle intake passage leading to a nozzle intake passage extending to the intake portions of a rotatable centrifugal gas impeller and gas flow directing vanes are positioned within the nozzle intake passage to properly direct the gas flow from the throttle disk to the impeller vanes. Sas dick pond award in recognition of the best technical paper at the annual symposium held at san francisco in 1974. How capacity control is achieved by igvs in centrifugal compressor. Single stage centrifugal compressor is mainly used for booster duty in the compound low temperature refrigeration system. Discuss the methods of capacity control of a centrifugal compressor. It may include features such as a valve, stationary vanesairfoils used to help swirl the flow and both pressure and temperature instrumentation. Why and how we use capacity control on refrigeration and air conditioning applications where the load may vary over a wide range, due to lighting, occupancy, product loading, ambient weather variations, or other factors, some means of compressor capacity control. Cross point between flow and maximum tip speed 287 ms is at maximum about 20,000 rpm. Anti surge control system for centrifugal compressors part 5. This manual is intended as a guide for application engineers, consultants, sales engineers, and hvac designers to use hanbell rt series centrifugal compressors. The vanes of the variable geometry diffuser 60 are adjustable to control the capacity of the compressors 512, 612.
Surge control design for centrifugal compressor systems. Control and operation of centrifugal gas compressors, with an. The most efficient region for centrifugal compressor operation is in a. For readers who are familiar with older screw air compressor controls, centrifugal air compressor controls are a refined version of upperrange modulation and unloading, with a minimum throttle limit, as follows. Speed control and external recycle are also common control methods for centrifugal compressors. Capacity control the purpose of the capacity control system is twofold. Anti surge control system for centrifugal compressors part. He has pre sented papers on compressor control at various isa and other conferences.
The fuel gas compressor flow capacity is the same as that of the gas turbine. Complete patent searching database and patent data analytics services. Surge control design for centrifugal compressor systems three levels of dynamic surge analysis compressor reliability is directly affected by the interaction between the surge controller, piping system, valves, recycle lines and coolers. One of the control techniques used for fuel gas compressors that supply fuel gas to gas turbine combined cycle gtcc power plants is described in this paper. Unlike reciprocating compressors, centrifugal compressors are steadyflow. Fixed speed compressor capacity control industrial. On the other hand, for most centrifugal compressors, the control range is limited by design.
But, what i do not understand is the exact thermodynamic or physical phenomenon happening at. Centrifugal compressor is widely used in chemical and. High pressure, lowpressure, and absorption chilled water systems. This method is usually limited to a centrifugal compressor. Cagi and our centrifugal customers all share a common interest and goal to maximize the compressor system efficiency and optimize the system energy usage. It is defined as the ratio of volume of air before compression to the volume of air after compression. Figure 63 is a map for centrifugal compressors that shows the effect of specific speed n s and specific diameter d s on their efficiency. Capacity control continuously continuously step control. More effective control for centrifugal gas compressors operating in. The compressors 512, 612 can effectively control capacity without the need for inlet guide vanes. A well designed 4stage centrifugal air compressor will produce about 4. Further, the analysis contributes with new knowledge and models for choking pressure. Adjusting the inlet guide vanes is the most common method to control capacity of a centrifugal compressor.
In c impeller geometry, at flow 2000 m3 hr speed in the range of 11,000 up to 20,000 rpm or tip speed from 200 up to 287 ms. Fixed speed compressor capacity control posted in industrial professionals. Without any control system, the compressor would operate along this natural curve. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Centrifugal compressors, in general, are used for higherpressure ratios and lowerflow rates compared to lowerstage pressure ratios and higherflow rates in axial compressors. In air compressors, surge control can be accomplished by opening a discharge end bypass valve and venting air to the atmosphere.
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