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A centrifugal compressor uses _____ for capacity control. The compressor discharge pressure set point will be set at the desired level, and the IBV or IGV will modulate the compressor inlet to maintain constant discharge pressure over the control (A®B) range. Below this range, there is insufficient airflow through the machine to overcome the pressure at the discharge. Without any control system, the compressor would operate along this natural curve. CABP: How do you control and protect from these situations arising during operation? This is generally accomplished by throttling the discharge valve. Provisional Patent Application No. 0�À��X�� |�wp?�3��N9�8 �r:� SMC Corporation Announces Partnership with Soft Robotics Inc. Other conditions affect the action of a constant-speed centrifugal capacity control… The load set point of a centrifugal compressor is typically at a given pressure, so when the system pressure falls below a given level, the compressor will load. Why have you selected centrifugal compressor capacity controls for this interview, and can you give a brief introduction? Explain the limitations on minimum refrigeration capacity of centrifugal compressors using velocity diagrams 5. 2.10), large amount of evaporation centrifugal-accelerated high speed and the speed of the energy is converted pressure. The motor current can be correlated with compressor flow. Speed control varies the compressor capacity and power by changing the stroke speed of the machine. Our members can also assist in the operation of existing equipment and systems. A. Centrifugal compressor B. Axial compressor C. Pumps D. All of the above 21. Centrifugal compressors are dynamic, and each has a characteristic curve of rising pressure as capacity decreases. YORK’s early Turbopaks could be furnished with an acoustic enclosure if a customer wanted an enclosure. Conversely, capacity may be decreased by reducing compressor speed. %PDF-1.4 %���� - Control valves - Fin-fans - Shell and tube exchangers - Flow metering However, the impact of suction and discharge system changes on compressor capacity is not the same. The performance characteristic of centrifugal compressors is more easily affected by changes in air conditions than is the performance of reciprocating compressors. Centrifugal. This analysis has to be made in cooperation with the manufacturer based on required flow profiles to determine optimum system design. 0000001831 00000 n At the minimum throttle point (C), the IBV or IGV valve stops closing, allowing the discharge pressure to rise to the unload set point. Without any control system, the compressor would operate along this natural curve. Chillers with centrifugal compressors have a 'Centrifugal Compressor Map' that shows the "surge line" and the "choke line." Manufacturers all use surge anticipation control to ensure reliable operation. Explain the methods of capacity control of centrifugal compressor 6. To read more articles about Compressor Controls, please visit www.airbestpractices.com/technology/compressor-controls. The operating envelope of a centrifugal compressor is limited by the maximum allowable speed (or, for other control means, the maximum guide vane angle), the minimum flow (surge flow), and the maximum flow (choke or stonewall), and the minimum speed (Figure 1). CABP: You mentioned that regulation could be impacted to a large degree by external factors, such as counter-pressure, suction temperature, and cooling temperature. 6, 2015, which is hereby incorporated by reference. Automated capacity control sequences must be communicated so that the same set of loading steps is considered in the acoustical analysis, torsional analysis and control panel logic. Perhaps a future interview on this topic may be in order, but could you give us a sneak preview and condensed version of these impacts? 175 24 Surge anticipation control optimization: To optimize surge anticipation control, the controller monitors the actual position of the surge line with respect to the existing ambient inlet conditions, and prevents the compressor from surge by opening the unloading valve when the compressor flow reaches the surge point. 3. CAGI: Surge is the phenomenon of aerodynamic instability that can occur in centrifugal compressors. Then, via the capacity control which is inherent in the concept, the capacity of the unit during cooling can be controlled to achieve proper comfort control. xref Explain the phenomenon of surging 7. Compressor capacity-control methods are utilized to maintain a required delivery under variable process conditions. 0000013629 00000 n Centrifugal impeller [ edit ] The key component that makes a compressor centrifugal is the centrifugal impeller, Figure 0.1, which contains a rotating set of vanes … Centrifugal compressor packages. The most common method, within centrifugal compressors, is to use vane guides. Surge is not a desirable condition, and may damage the compressor or cause nuisance shutdowns, therefore, if demand is reduced below the turndown range at a given pressure, the compressor must control in a different ma… The compressor includes a plurality of adjustable inlet guide vanes, a motor connected to regulate the inlet guide vanes position, and an electrical speed motor connected to drive the compressor. The minimum flow is determined when the pressure ratio reaches the pump limit and the machine reaches maximum pressure. Regulation range is also affected by external factors, such as inlet air conditions (temperature, pressure, and humidity), and coolant temperature. guide vanes. 2. Manufacturers take into consideration surge events when designing their compressors, and thus the occurrence of a single or even multiple surges will not reduce the life or damage the compressor. A centrifugal compressor's flow and pressure are typically controlled by a combination of an inlet control device and an unloading valve (UV). Capacity control by speed variation is the most effective way to maximize the operating flexibility of a centrifugal compressor. endstream endobj 176 0 obj <>/Outlines 28 0 R/Metadata 38 0 R/PieceInfo<>>>/Pages 37 0 R/PageLayout/OneColumn/OCProperties<>/OCGs[177 0 R]>>/StructTreeRoot 40 0 R/Type/Catalog/LastModified(D:20151120142457)/PageLabels 35 0 R>> endobj 177 0 obj <. The chief protecting agent of a centrifugal compressor is the anti-surge line/valve that recycles cold gas from the discharge side cooler back to the suction scrubber to … Constant Pressure Control with Modulating Unloading Regulation (UV) (See Figure 2). With compressor capacity control the heat pump can be sized for a greater heating capacity, thereby having a lower balance point and eliminating some of the auxiliary heating. CAGI:  Well, since a centrifugal compressor’s controls are a bit more complex, we will walk readers through the systems and the options available. Larger turndowns can be achieved, but result in lower aerodynamic efficiency. The regulation range, or turndown, is determined by the design of the machine. Some controls can also provide for a maximum unloading valve (UV) position to be programmed. One of the techniques to control the capacity of the compressors is by changing the compressor speed by a speed-reduction gear. 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