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Different Types Of Air Compressors. written by: sriram balu • edited by: Lamar Stonecypher • updated: 2/24/2010 Though the reciprocating air compressor is the most commonly used one, there are also many different types of air compressors which are used in various industries. Get the insight about the reciprocating air compressor and rotary compressors like screw, lobe, vane and scroll compressors. Introduction: The usage of compressed air is not limited only to industries, but they are also used in manufacturing, welding, constructions, power plants, ships, automobile plants, painting shops, and for filling breathing apparatus too.
Thus there are so many types of air compressors used specifically for the above purposes. Let us discuss on various types of air compressors. Types of Air Compressors: Compressors are classified in many ways out of which the common one is the classification based on the principle of operation. Types of Compressors: 1. Positive Displacement and 2. Roto-Dynamic Compressors. Compressor Parts www. compressor-parts. com 2000 psi to 6000 psi – Air and Gas Scuba, Fire, Paintball, Military Screw Compressor Supplier www. Alibaba. com Supplies Made to Order from World’s Largest Supplier Base.
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Top Deals! Refrigeration Compressor www. equipmentimes. com Screw Refrigeration Compressor Advanced technogoly,high efficiency Ads by Google Positive displacement compressors cab be further divided into Reciprocating and rotary compressors. Under the classification of reciprocating compressors, we have 1. In-line compressors, 2. “V”-shaped compressors, 3. Tandem Piston compressors. 4. Single-acting compressors, 5. Double-acting compressors, 6. Diaphragm compressors. The rotary compressors are divided into 7. Screw compressors, 8. Vane type compressors, 9.
Lobe and scroll compressors and other types. Under the Roto-dynamic compressors, we have 10. Centrifugal compressors, and the 11. Axial flow compressors. The compressors are also classified based on other aspects like 12. Number of stages (single-stage, 2-stage and multi-stage), 13. Cooling method and medium (Air cooled, water cooled and oil-cooled), 14. Drive types ( Engine driven, Motor driven, Turbine driven, Belt, chain, gear or direct coupling drives), 15. Lubrication method (Splash lubricated or forced lubrication or oil-free compressors). 16. Service Pressure (Low, Medium, High)
The Attached picture shows the clear classification of different types of compressors. Reciprocating In-line Compressors: These are most commonly used compressors with varying pressure ranges. These are simple in design with almost very little automation. The cylinders of various stages are found in a straight line when seen from top. These compressors are commonly direct driven by electric motors or diesel engines. Refer the attached diagram of the reciprocating in-line compressors. “V”-Shaped Compressors: These are usually air cooled compressors with concentric valves mounted on each cylinder head unit.
The compressor has different units displaced usually by 90 degrees, may or may not be connected to same crank pin on the crank shaft. Higher capacity compressors are water cooled. Better torque and balancing is achieved by displacing the units by certain angle. Single-Acting Compressors: These are usually reciprocating compressors, which has piston working on air only in one direction. The other end of the piston is often free or open which does not perform any work. The air is compressed only on the top part of the piston. The bottom of the piston is open to crankcase and not utilized for the compression of air.
Double-Acting Compressors: These compressors are having two sets of suction/intake and delivery valves on both sides of the piston. As the piston moves up and down, both sides of the piston is utilized in compressing the air. The intake and delivery valves operate corresponding to the stroke of the compressor. The compressed air delivery is comparatively continuous when compared to a single-acting air compressor. Thus both sides of the pistons are effectively used in compressing the air. The rotary compressors are not of reciprocating nature, therefore does not have any pistons and crankshaft.
Instead, these compressors have screws, vanes, scrolls, and other devices which rotate and thus compress air. The rotary compressors are classified into screw type, vane type-lobe type, scroll type and other types. Rotary Compressors: These compressors are not of reciprocating nature, therefore does not have any pistons and crankshaft. Instead, these compressors have screws, vanes, scrolls, and other devices which rotate and thus compress air. The rotary compressors are classified into screw type, vane type-lobe type, scroll type and other types.
The screw compressors are efficient in low air pressure requirements. Two screws rotate intermeshing with each other, thus trapping air between the screws and the compressor casing, forming pockets which progressively travel and gets squeezed and delivering it at a higher pressure which opens the delivery valve. The compressed air delivery is continuous and quiet in operation than a reciprocating compressor. The Vane type Air Compressor is having a fixed casing and a rotary rotor disc which has slots for holding the sliding plates as shown in the figure.
As the rotor rotates, the disc also rotates, thus allowing the sliding plates to slide as the inner surface of the casing is eccentric. Thus the sliding plates moves away from the center, huge quantities of air will be trapped in, thus as the plates converge, the air gets compressed and thus results in compressed air. The Scroll type compressors are having scrolls driven by the prime mover. The scrolls outer edges trap air and then as they rotate, the air travel from outwards to inwards thus getting compressed due to the reduction in the area.
Thus the compressed air is delivered through the central space of the scroll to the delivery air line. The Lobe type air compressor is very simpler type with no complicated moving parts. There are single or twin lobes attached to the drive shaft driven by the prime mover. The lobes are displaced by 90 degrees. Thus if one of the lobes is in horizontal position, the other at that particular instant will be in vertical position. Thus the air gets trapped in between these lobes and as they rotate they get compressed and delivered to the delivery line.
Main types of compressors used in industrial refrigeration are screw, piston, centrifugal and rotary vane. Another type, which is produced in large quantities, a scroll compressor, but still these compressors are not available in the amount normally encountered in industrial refrigeration. Rotary vane compressorsare still used as a low stage compressors, but very little installed. Centrifugal compressors are standard in large chemical and processing industry, where they are driven by electric or steam or gas turbine. Centrifugal compressors are also used extensively for water cooling in air-conditioning systems.
Manufacturers use such refrigerants R-123 and R-134a in these packages. After condensation of a long list of types of compressors, two that are left and those that will be discussed in this book, reciprocating and screw compressors. This Chapter focuses on reciprocating compressors, and Chapter 5 concentrates on screw compressors. Two styles of construction compressors are open and hermetically sealed. In open-type compressor, as shown in Fig. 4. 1, shaft extends compressor and externally connected to an electric motor which drives the compressor.
In a hermetically sealed motor-compressor, the entire Assembly is encapsulated and only line of the refrigerant and the electrical connections, and not rotating shaft penetrate into the housing. These sealed units are always used for household refrigerators, window-type air conditioners, and other small appliances. They should work for decades without refrigerant leakage. A few more semi-hermetic reciprocating compressors, where the heads of the compressors can be removed to gain access to pistons and valves for maintenance.
– Semi-hermetic compressors available on the market, as a rule, limited to the maximum cooling capacity of approximately 150 kW (40 tons of cooling). In hermetic or semi-hermetic block, the refrigerant is in contact with the motor windings Halocarbon refrigerants that do not attack the copper used in this type of compressor. Because ammonia will react with copper, ammonia compressors of open type. At one time the shaft seal was alarming, the cause of the leak of ammonia, but the quality of the shaft seal is gradually improving.
However, development pressurized ammonia compressor remains attractive goals and approaches such as the use of aluminium windings encapsulation rotor so that the ammonia contact engine windings1, or connecting the motor and the compressor through the magnetic drive2 all approaches is considered. On the other hand, open-type compressor is typically more efficient than hermetic type, because the suction couple in hermetic compressor enters the engine to cool down, and in this superheated steam, which requires more energy to compress.
Central attention in this Chapter : the effect of suction and discharge pressure of the cooling capacity and power consumption. Suction and discharge pressure the main influence on the rest of the system of the compressor. The nature of the cooling load on the evaporator strongly affects the suction pressure and the external conditions of transfer across the capacitor control the discharge pressure. The characteristics that are most important for the user compressor cooling capacity and power consumption.
The compressor has a dominant influence on system performance, therefore, the ability to predict the consequences of changes in the conditions imposed on the system, such as the temperature of the liquid in the evaporator or the temperature at the condenser requires an understanding of the performance of the compressor. Some idealizations initially basis explaining specifications, and then the Chapter shows that these idealized trends prevail in the real compressors. In the last part of the Chapter describes some of the capabilities and limitations of piston compressors, and describes assistive devices for reliable operation.
Piston Compressors Piston compressors are one of the most widely used types of refrigeration compressors. They piston and cylinder as the location of the car engine. Reciprocating motion of the piston due to external forces compresses the refrigerant inside the cylinder. There are three types of piston compressors: hermetic, semi-hermetically closed and open-ended. Open piston compressors can be of the same type cylinder or multi-cylinder type. Screw Compressors piston compressors and used widely. It can be used as refrigerants R12, R22, and others.
Rotary Compressors rotary compressors has two rotating elements, like gears, between which the refrigerant is compressed. These compressors can pump refrigerant below or moderate the pressure of condensation. Because they can handle small amounts of gas, and produce less pressure, they are used in fewer applications. Centrifugal Compressor The centrifugal compressor impeller or blower, which can handle large volumes of gas, but at a relatively low pressure of condensation. It is suitable for work with refrigerants such as R-11, R-113 and other spiral Compressors
Scroll compressor consists of two interleaved scrolls, one of which is fixed and the other to the eccentricity of the orbit without rotation. During its motion with small gaps are created between the scrolls, where the refrigerant is compressed. Scrolls can have different shape, as involute, Archimedean spiral, or hybrid curve. In other arrangement scrolls can turn its beating to recompress. .. The three basic types of air compressors are reciprocating rotary screw rotary centrifugal These types are further specified by: the number of compression stages cooling method (air, water, oil)
drive method (motor, engine, steam, other) lubrication (oil, Oil-Free where Oil Free means no lubricating oil contacts the compressed air) packaged or custom-built Reciprocating Air Compressors Reciprocating air compressors are positive displacement machines, meaning that they increase the pressure of the air by reducing its volume. This means they are taking in successive volumes of air which is confined within a closed space and elevating this air to a higher pressure. The reciprocating air compressor accomplishes this by a piston within a cylinder as the compressing and displacing element.
Single-stage and two-stage reciprocating compressors are commercially available. Single-stage compressors are generally used for pressures in the range of 70 psig to 100 psig. Two-stage compressors are generally used for higher pressures in the range of 100 psig to 250 psig. Note that 1 HP ~ 4 CFM at 100 psi and that 1 to 50 HP are typically for reciprocating units. Compressors 100 hp and above are typically Rotary Screw or Centrifugal Compressors. The reciprocating air compressor is single acting when the compressing is accomplished using only one side of the piston.
A compressor using both sides of the piston is considered double acting. Load reduction is achieved by unloading individual cylinders. Typically this is accomplished by throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor. Capacity control is achieved by varying speed in engine-driven units through fuel flow control. Reciprocating air compressors are available either as air-cooled or water-cooled in lubricated and non-lubricated configurations and provide a wide range of pressure and capacity selections.
Rotary Screw Compressors Rotary air compressors are positive displacement compressors. The most common rotary air compressor is the single stage helical or spiral lobe oil flooded screw air compressor. These compressors consist of two rotors within a casing where the rotors compress the air internally. There are no valves. These units are basically oil cooled (with air cooled or water cooled oil coolers) where the oil seals the internal clearances. Since the cooling takes place right inside the compressor, the working parts never experience extreme operating temperatures.
The rotary compressor, therefore, is a continuous duty, air cooled or water cooled compressor package. Rotary screw air compressors are easy to maintain and operate. Capacity control for these compressors is accomplished by variable speed and variable compressor displacement. For the latter control technique, a slide valve is positioned in the casing. As the compressor capacity is reduced, the slide valve opens, bypassing a portion of the compressed air back to the suction. Advantages of the rotary screw compressor include smooth, pulse-free air output in a compact size with high output volume over a long life.
The oil free rotary screw air compressor utilizes specially designed air ends to compress air without oil in the compression chamber yielding true oil free air. Oil free rotary screw air compressors are available air cooled and water cooled and provide the same flexibility as oil flooded rotaries when oil free air is required. Centrifugal Compressors The centrifugal air compressor is a dynamic compressor which depends on transfer of energy from a rotating impeller to the air. Centrifugal compressors produce high-pressure discharge by converting angular momentum imparted by the rotating impeller (dynamic displacement).
In order to do this efficiently, centrifugal compressors rotate at higher speeds than the other types of compressors. These types of compressors are also designed for higher capacity because flow through the compressor is continuous. Adjusting the inlet guide vanes is the most common method to control capacity of a centrifugal compressor. By closing the guide vanes, volumetric flows and capacity are reduced. The centrifugal air compressor is an oil free compressor by design. The oil lubricated running gear is separated from the air by shaft seals and atmospheric vents.
Sponsored Links TYPES OF COMPRESSOR The compressor is the element that represents the heart of the refrigerant circuit. Its purpose is to control the circulation of refrigerant inside the circuit, drawing in gas refrigerant at low pressure and low temperature, and delivering it at a higher pressure and temperature. Thanks to this process, the compressor allows the refrigerant to dissipate its own heat to the air flowing through the condenser, after which it absorbs heat again inside the evaporator.
Not all air-conditioning applications have the same capacity requirements, and for this reason there are different types of compressors available: reciprocating compressors (divided into hermetic, semi-hermetic and open-type) are mostly used for applications with higher capacity requirements; rotary compressors, including scroll, vane and screw compressors (suitable for high capacity applications, up to 1200 kW) and centrifugal compressors (used for applications that require higher capacities). Reciprocating compressors
In this type of compressor, the pistons are designed in similar fashion to those used in a car engine: they slide inside a cylinder, drawing in and compressing the gas refrigerant. Each cylinder features a suction valve for the gas refrigerant and a delivery valve through which the gas refrigerant is sent to the condenser after having been compressed. Reciprocating compressors are defined as open-type when one end of the crankshaft protrudes outside of the crankcase (the casing that contains the pistons and the mechanisms inside the compressor).
In semi-hermetic compressors, on the other hand, both the compressor itself and the drive motor are housed inside the casing, which is designed so as to be opened for inspection and maintenance. In this case, the drive shaft and the crankshaft are one single piece. Semi-hermeticcompressors are made so as to prevent air or dust from entering the mechanisms. Reciprocating compressors are defined as hermetic when the casing is welded closed and sealed, and the heads of the cylinders cannot be accessed for inspection or maintenance.
These are used in household refrigerators and freezers and in medium-capacity air-conditioning units. Rotary compressors The category of rotary compressors includes all compressors that perform the compression function using mechanisms that involve impellers, involute scrolls or screws. Scroll compressors (or orbiting scroll compressors) are based on a mechanism patented in 1905. This features two involute scrolls: one stationary, and one orbiting (but not rotating) around the first.
Thanks to this motion, the gas contained between the two elements reaches a very high pressure and discharged through a hole in the centre. Stationary or rotary vane compressors work due to the effect of the vanes located inside the cylinders. The vanes may rotate on a cam in the centre of the cylinder (rotary), or be fixed to the walls of the cylinder (stationary). In both cases, the vanes are responsible for the movement of the gas, contributing fundamentally to the suction and compression phases. Screw compressors are based on a mechanism made up of two threaded rotors (screws) that are coupled together.
The gas is compressed due to the progressive overlapping of the lobes, causing a reduction in the volume occupied by the gas. There are also single-screw compressors that operate by the rotation of just one cylindrical screw with a helical thread, onto which two identical rotors are coupled. Centrifugal compressors are made up of a rotor located inside a special chamber. The rotor is rotated at high speed, imparting high kinetic energy to the gas, which is forced through the narrow outlet opening, thus increasing its pressure. This type of compressor is used for high and very high cooling capacities.