A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface This page is about the physical properties of gas as a state of matter The volume of any solid plasma vacuum or theoretical object is how much three- Dimensional space it occupies often quantified numerically
Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. For information on Wikipedia project-related discussions see WikipediaVillage pump. FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code A pipe is a tube or hollow cylinder used to convey materials or as a structural component As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible, so the main action of a pump is to transport liquids.
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Types of compressors
The main types of gas compressors are illustrated and discussed below:
Centrifugal compressors
Centrifugal compressors use a rotating disk or impeller in a shaped housing to force the gas to the rim of the impeller, increasing the velocity of the gas. Centrifugal compressor, (sometimes referred to as radial compressors) are a special class of radial-flow work-absorbing Turbomachinery that includes pumps An impeller is a rotor inside a tube or conduit to increase the pressure and flow of a fluid A diffuser (divergent duct) section converts the velocity energy to pressure energy. They are primarily used for continuous, stationary service in industries such as oil refineries, chemical and petrochemical plants and natural gas processing plants. An oil refinery is an industrial Process plant where Crude oil is processed and refined into more useful Petroleum products, such as Gasoline A chemical plant is industrial process plant that manufactures (or otherwise processes Chemicals usually on a large scale Petrochemicals are chemical products made from raw materials of Petroleum or other Hydrocarbon origin Natural gas processing plants or fractionators are used to purify the raw Natural gas extracted from underground gas fields and brought up to the surface by [1][2][3] Their application can be from 100 hp (75 kW) to thousands of horsepower. With multiple staging, they can achieve extremely high output pressures greater than 10,000 psi (69 MPa).
Many large snow-making operations (like ski resorts) use this type of compressor. A ski area is a developed recreational facility usually on a Mountain or large Hill, containing ski trails and vital supporting services They are also used in internal combustion engines as superchargers and turbochargers. A turbocharger, or turbo, is an air Compressor used for forced-induction of an Internal combustion engine. Centrifugal compressors are used in small gas turbine engines or as the final compression stage of medium sized gas turbines. A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas An engine is a mechanical device that produces some form of output from a given input
Diagonal or mixed-flow compressors
Diagonal or mixed-flow compressors are similar to centrifugal compressors, but have a radial and axial velocity component at the exit from the rotor. A diagonal or mixed-flow compressor is effectively a cross between a centrifugal and Axial-flow compressor. The diffuser is often used to turn diagonal flow to the axial direction. The diagonal compressor has a lower diameter diffuser than the equivalent centrifugal compressor.
Axial-flow compressors
Axial-flow compressors are dynamic rotating compressors that use arrays of fan-like aerofoils to progressively compress the working fluid. They are used where there is a requirement for a high flows or a compact design.
The arrays of aerofoils are set in rows, usually as pairs: one rotating and one stationary. The rotating aerofoils, also known as blades or rotors, decelerate and pressurise the fluid. The stationary aerofoils, also known as a stators or vanes, turn and decelerate the fluid; preparing and redirecting the flow for the rotor blades of the next stage. [1] Axial compressors are almost always multi-staged, with the cross-sectional area of the gas passage diminishing along the compressor to maintain an optimum axial Mach number. Mach number (\mathrm{Ma} or M (generally ˈmɑːk sometimes /ˈmɑːx/ or /ˈmæk/ is the speed of an object moving through air or any Fluid Beyond about 5 stages or a 4:1 design pressure ratio, variable geometry is normally used to improve operation.
Axial compressors can have high efficiencies; around 90% polytropic at their design conditions. A polytropic process is a Thermodynamic process that obeys the relation P V^n = C where P is pressure V is volume However, they are relatively expensive, requiring a large number of components, tight tolerances and high quality materials. Axial-flow compressors can be found in medium to large gas turbine engines, in natural gas pumping stations, and within certain chemical plants. A gas turbine, also called a combustion turbine, is a rotary Engine that extracts energy from a flow of Combustion gas
Reciprocating compressors
Reciprocating compressors use pistons driven by a crankshaft. A reciprocating compressor is a compressor that uses Pistons driven by a Crankshaft to deliver gases at high pressure A piston is a component of Reciprocating engines Pumps and Gas compressors It is located in a cylinder and is made gas-tight by Piston They can be either stationary or portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines. [1][4] [5] Small reciprocating compressors from 5 to 30 horsepower (hp) are commonly seen in automotive applications and are typically for intermittent duty. Larger reciprocating compressors up to 1000 hp are still commonly found in large industrial applications, but their numbers are declining as they are replaced by various other types of compressors. Discharge pressures can range from low pressure to very high pressure (>5000 psi or 35 MPa). In certain applications, such as air compression, multi-stage double-acting compressors are said to be the most efficient compressors available, and are typically larger, noisier, and more costly than comparable rotary units. [6]
Rotary screw compressors
Rotary screw compressors use two meshed rotating positive-displacement helical screws to force the gas into a smaller space. A rotary screw compressor is a type of gas compressor which uses a rotary type positive displacement mechanism A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i [1][7][8] These are usually used for continuous operation in commercial and industrial applications and may be either stationary or portable. Their application can be from 3 hp (2. 24 kW) to over 500 hp (375 kW) and from low pressure to very high pressure (>1200 psi or 8. 3 MPa). They are commonly seen with roadside repair crews powering air-tools. This type is also used for many automobile engine superchargers because it is easily matched to the induction capacity of a piston Engine
Rotary vane compressors
- See also: Rotary vane pump
Rotary vane compressors consist of a rotor with a number of blades inserted in radial slots in the rotor. A supercharger is an air compressor used for Forced induction of an Internal combustion engine. A piston is a component of Reciprocating engines Pumps and Gas compressors It is located in a cylinder and is made gas-tight by Piston A rotary vane pump is a positive-displacement Pump that consists of vanes mounted to a rotor that rotates inside of a cavity The rotor is mounted offset in a larger housing which can be circular or a more complex shape. As the rotor turns, blades slide in and out of the slots keeping contact with the outer wall of the housing. [1] Thus, a series of decreasing volumes is created by the rotating blades. Rotary Vane compressors are, with piston compressors one of the oldest of compressor technologies.
With suitable port connections, the devices may be either a compressor or a vacuum pump. They can be either stationary or portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines. Dry vane machines are used at relatively low pressures (e. g. , 2 bar) for bulk material movement whilst oil-injected machines have the necessary volumetric efficiency to achieve pressures up to about 13 bar in a single stage. A rotary vane compressor is well suited to electric motor drive and is significantly quieter in operation than the equivalent piston compressor.
Scroll compressors
A scroll compressor, also known as scroll pump and scroll vacuum pump, uses two interleaved spiral-like vanes to pump or compress fluids such as liquids and gases. A scroll compressor (also called spiral compressor, scroll pump and scroll vacuum pump) is a device for compressing air or refrigerant For information on Wikipedia project-related discussions see WikipediaVillage pump. FLUID ( F ast L ight '''U'''ser '''I'''nterface D esigner is a graphical editor that is used to produce FLTK Source code Liquid is one of the principal States of matter. A liquid is a Fluid that has the particles loose and can freely form a distinct surface at the boundaries of This page is about the physical properties of gas as a state of matter The vane geometry may be involute, archimedean spiral, or hybrid curves. In the Differential geometry of curves, an involute of a smooth Curve is another curve obtained by attaching an imaginary taut string to the given curve and tracing The Archimedean spiral (also known as the arithmetic spiral) is a Spiral named after the 3rd century BC Greek Mathematician [9][10][11] They operate more smoothly, quietly, and reliably than other types of compressors in the lower volume range.
Often, one of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and pumping or compressing pockets of fluid or gas between the scrolls.
Diaphragm compressors
A diaphragm compressor (also known as a membrane compressor) is a variant of the conventional reciprocating compressor. A diaphragm compressor is a variant of the classic Reciprocating compressor with backup and piston rings and rod seal The compression of gas occurs by the movement of a flexible membrane, instead of an intake element. The back and forth movement of the membrane is driven by a rod and a crankshaft mechanism. Only the membrane and the compressor box come in touch with the gas being compressed. [1]
Diaphragm compressors are used for hydrogen and compressed natural gas (CNG) as well as in a number of other applications. Compressed Natural Gas (CNG is a Fossil fuel substitute for Gasoline (petrol Diesel, or Propane Fuel.
The photograph included in this section depicts a three-stage diaphragm compressor used to compress hydrogen gas to 6,000 psi (41 MPa) for use in a prototype hydrogen and compressed natural gas (CNG) fueling station built in downtown Phoenix, Arizona by the Arizona Public Service company (an electric utilities company). Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Compressed Natural Gas (CNG is a Fossil fuel substitute for Gasoline (petrol Diesel, or Propane Fuel. Phoenix (ˈfiːˌnɪks O'odham Skikik, Yavapai Wasinka, Western Apache Fiinigis, Navajo Hoozdo, Arizona Public Service Company is the largest electric utility in Arizona and the principal subsidiary of publicly-traded S&P 500 member Pinnacle West Capital Reciprocating compressors were used to compress the natural gas. A reciprocating compressor is a compressor that uses Pistons driven by a Crankshaft to deliver gases at high pressure Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane,
The prototype alternative fueling station was built in compliance with all of the prevailing safety, environmental and building codes in Phoenix to demonstrate that such fueling stations could be built in urban areas. Alternative fuels, also known as non-conventional Fuels are any Materials or substances that can be used as a Fuel, other than conventional fuels
Temperature
Compression of a gas naturally increases its temperature. This articles outlines the historical development of the laws describing ideal gases Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature
In an attempt to model the compression of gas, there are two theoretical relationships between temperature and pressure in a volume of gas undergoing compression. Although neither of them model the real world exactly, each can be useful for analysis. A third method measures real-world results:
- Isothermal - This model assumes that the compressed gas remains at a constant temperature throughout the compression or expansion process. An isothermal process is a Thermodynamic process in which the Temperature of the System stays Constant: &Delta T = 0 In this cycle, internal energy is removed from the system as heat at the same rate that it is added by the mechanical work of compression. Isothermal compression or expansion more closely models real life when the compressor has a large heat exchanging surface, a small gas volume, or a long time scale (i. e. , a small power level). Compressors that utilize inter-stage cooling between compression stages come closest to achieving perfect isothermal compression. However, with practical devices perfect isothermal compression is not attainable. For example, unless you have an infinite number of compression stages with corresponding intercoolers, you will never achieve perfect isothermal compression.
- Adiabatic - This model assumes that no energy (heat) is transferred to or from the gas during the compression, and all supplied work is added to the internal energy of the gas, resulting in increases of temperature and pressure. This article covers adiabatic processes in Thermodynamics. For adiabatic processes in Quantum mechanics, see Adiabatic process (quantum mechanics Theoretical temperature rise is T2 = T1·Rc(k-1)/k, with T1 and T2 in degrees Rankine or kelvins, and k = ratio of specific heats (approximately 1. Rankine is a thermodynamic (absolute temperature scale named after the Scottish Engineer and Physicist William John Macquorn Rankine The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantity 4 for air). R is the compression ratio; being the absolute outlet pressure divided by the absolute inlet pressure. The rise in air and temperature ratio means compression does not follow a simple pressure to volume ratio. This is less efficient, but quick. Adiabatic compression or expansion more closely model real life when a compressor has good insulation, a large gas volume, or a short time scale (i. e. , a high power level). In practice there will always be a certain amount of heat flow out of the compressed gas. Thus, making a perfect adiabatic compressor would require perfect heat insulation of all parts of the machine. For example, even a bicycle tire pump's metal tube becomes hot as you compress the air to fill a tire.
- Polytropic - This model takes into account both a rise in temperature in the gas as well as some loss of energy (heat) to the compressor's components. A polytropic process is a Thermodynamic process that obeys the relation P V^n = C where P is pressure V is volume This assumes that heat may enter or leave the system, and that input shaft work can appear as both increased pressure (usually useful work) and increased temperature above adiabatic (usually losses due to cycle efficiency). Compression efficiency is then the ratio of temperature rise at theoretical 100 percent (adiabatic) vs. actual (polytropic).
In the case of the fire piston and the heat pump, people desire temperature change, and compressing gas is only a means to that end. A fire piston, sometimes called a fire syringe, is a device of ancient origin which is used to kindle fire A heat pump is a machine or device that moves Heat from one location (the 'source' to another location (the 'sink' or 'heat sink' using work.
Staged compression
Since compression generates heat, the compressed gas is to be cooled between stages making the compression less adiabatic and more isothermal. The inter-stage coolers cause condensation meaning water separators with drain valves are present. In the case of small reciprocating compressors, the compressor flywheel may drive a cooling fan that directs ambient air across the intercooler of a two or more stage compressor.
Because of mechanical limitations and to increase efficiency, most compressors utilize staged compression, usually with intercooling between stages. In the case of centrifugal compressors, commercial designs currently do not exceed more than a 3. 5 to 1 ratio in any one stage. Because rotary screw compressors can make use of cooling lubricant to remove the heat of compression, they very often exceed a 9 to 1 ratio. For instance, in a typical diving compressor the air is compressed in three stages. If each stage has a compression ratio of 7 to 1, the compressor can output 343 times atmospheric pressure (7 x 7 x 7 = 343 Atmospheres).
Prime movers
There are many options for the "prime mover" or motor which powers the compressor:
- gas turbines power the axial and centrifugal flow compressors that are part of jet engines
- steam turbines or water turbines are possible for large compressors
- electric motors are cheap and quiet for static compressors. A turbine is a rotary Engine that extracts Energy from a Fluid flow specific --->A jet engine is a Reaction engine that discharges a fast moving jet of Fluid to A steam turbine is a mechanical device that extracts Thermal energy from pressurized Steam, and converts it into useful mechanical work A water turbine is a rotary Engine that takes energy from moving water An electric motor uses Electrical energy to produce Mechanical energy. Small motors suitable for domestic electrical supplies use single phase alternating current. In electrical engineering single-phase electric power refers to the distribution of Alternating current Electric power using a system in which all the voltages of An alternating current ( AC) is an Electric current whose direction reverses cyclically as opposed to Direct current, whose direction remains constant Larger motors can only be used where an industrial electrical three phase alternating current supply is available. This article deals with the basic mathematics and principles of three-phase electricity
- diesel engines or petrol engines are suitable for portable compressors and support compressors used as superchargers from their own crankshaft power. A diesel engine is an Internal combustion engine which operates using the Diesel cycle (named after Dr A Petrol engine or Gasoline engine is an Internal combustion engine with spark-ignition designed to run on petrol ( Gasoline) and similar volatile A supercharger is an air compressor used for Forced induction of an Internal combustion engine. They use exhaust gas energy to power turbochargers
Applications
Gas compressors are used in various applications where either higher pressures or lower volumes of gas are needed:
- in pipeline transport of purified natural gas to move the gas from the production site to the consumer. A turbocharger, or turbo, is an air Compressor used for forced-induction of an Internal combustion engine. Pipeline transport is the transportation of goods through a pipe.
- in petroleum refineries, natural gas processing plants, petrochemical and chemical plants, and similar large industrial plants for compressing intermediate and end product gases.
- in refrigeration and air conditioner equipment to move heat from one place to another in refrigerant cycles: see Vapor-compression refrigeration. Refrigeration is the process of removing Heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable An air conditioner is an Appliance, System, or mechanism designed to extract Heat from an area via a Refrigeration cycle In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature A refrigerant is a compound used in a heat cycle that undergoes a Phase change from a Gas to a Liquid and back Vapor-compression refrigeration is one of the many Refrigeration cycles available for use
- in gas turbine systems to compress the intake combustion air
- in storing purified or manufactured gases in a small volume, high pressure cylinders for medical, welding and other uses. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of Medicine is the art and science of healing It encompasses a range of Health care practices evolved to maintain and restore Human Health by the Welding is a fabrication process that joins materials usually Metals or Thermoplastics by causing coalescence.
- in many various industrial, manufacturing and building processes to power all types of pneumatic tools. Pneumatic tools or air tools are Tools driven by gas usually Compressed air supplied by a Gas compressor.
- as a medium for transferring energy, such as to power pneumatic equipment. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός Pneumatics, Pressurized gas to affect mechanical motion Pneumatic power is used in Industry, where it is common to have factory units plumbed for Compressed
- in pressurised aircraft to provide a breathable atmosphere of higher than ambient pressure. Cabin pressurization is the active pumping of compressed Air into an Aircraft cabin when flying at altitude to maintain a safe and comfortable environment for crew
- in some types of jet engines (such as turbojets and turbofans) to provide the air required for combustion of the engine fuel. specific --->A jet engine is a Reaction engine that discharges a fast moving jet of Fluid to TurboJET (噴射飛航 is the brand name for the operations of the Hong Kong -based Shun Tak-China Travel Ship Management Limited (信德中旅船務管理有限公司 A turbofan is a type of Jet engine, similar to a Turbojet. It essentially consists of a Ducted fan with a smaller diameter turbojet engine The power to drive the combustion air compressor comes from the jet's own turbines. A turbine is a rotary Engine that extracts Energy from a Fluid flow
- in SCUBA diving, hyperbaric oxygen therapy and other life support devices to store breathing gas in a small volume such as in diving cylinders. Scuba diving is swimming underwater, or taking part in another activity while using a Scuba set. Hyperbaric medicine, also known as hyperbaric oxygen therapy (HBOT is the medical use of Oxygen at a higher than Atmospheric pressure. Air is the most common and only natural breathing gas. Other artificial gases either pure gases or mixtures of gases are used in breathing equipment and enclosed habitats such A diving cylinder, scuba tank or diving tank is used to store and transport high Pressure Breathing gas as a component of SCUBA (Self-Contained
- in submarines, to store air for later use in displacing water from buoyancy chambers, for adjustment of depth. A submarine is a Watercraft that can operate independently below water as distinct from a Submersible that has only limited underwater capability
- in turbochargers and superchargers to increase the performance of internal combustion engines by increasing mass flow. A turbocharger, or turbo, is an air Compressor used for forced-induction of an Internal combustion engine. A supercharger is an air compressor used for Forced induction of an Internal combustion engine. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a
- in rail and heavy road transport to provide compressed air for operation of rail vehicle brakes or road vehicle brakes and various other systems (doors, windscreen wipers, engine/gearbox control, etc). "Railroad" and "Railway" both redirect here For other uses see Railroad (disambiguation. Road transport ( British English) or road transportation ( American English) is Transport on Roads of passengers or goods Compressed air An air brake is a conveyance braking system applied by means of compressed air. Air brakes are used in Trucks Buses trailers, and Semi-trailers. A door is a panel or barrier usually hinged or sliding that is used to cover an opening in a Wall or partition going into a building or space A windscreen wiper ( windshield wiper in North America) is a device used to wipe Rain and dirt from a Windscreen. An engine is a mechanical device that produces some form of output from a given input
- in miscellaneous uses such as providing compressed air for filling pneumatic tires. This article is about tires used on road Vehicles including pneumatic tires and solid tires.
See also
References
- ^ a b c d e f Perry, R. Cabin pressurization is the active pumping of compressed Air into an Aircraft cabin when flying at altitude to maintain a safe and comfortable environment for crew A centrifugal fan (also squirrel-cage fan, as it looks like a Hamster wheel) is a mechanical device for moving Air or other Gases It has a Compressed air A Variable Speed Drive (VSD Air Compressor is an air compressor that takes advantage of Variable Speed Drive technology Hot air engine (historically simply 'air engine' or ' Caloric engine' is a catch-all term for any Heat engine which uses the expansion and contraction of A fire piston, sometimes called a fire syringe, is a device of ancient origin which is used to kindle fire A hydrogen compressor is a mechanical device that increases the pressure of Hydrogen by reducing its volume A liquid ring pump is a rotating positive displacement pump They are typically used as a Vacuum pump but can also be used as a Gas compressor. The Roots type Supercharger or Roots blower is a positive displacement pump which operates by pulling Air through a pair of meshing lobes not Pneumatic cylinders (sometimes known as air cylinders) are Mechanical devices which produce Force, often in combination with movement, and are Pneumatic tubes (or capsule pipelines; Lamson tubes) are systems in which cylindrical containers are propelled through a network of tubes by Pressurization generally refers to the application of Pressure in a given situation or environment and more specifically refers to the process by which Atmospheric pressure Vapor-compression refrigeration is one of the many Refrigeration cycles available for use H. and Green, D. W. (Editors) (2007). Perry's Chemical Engineers' Handbook, 8th Edition, McGraw Hill. Perry's Chemical Engineers' Handbook was first published in 1934 and the most current eighth edition was published in October 2007. ISBN 0-07-142294-3.
- ^ Dixon S. L. (1978). Fluid Mechanics, Thermodynamics of Turbomachinery, Third Edition, Pergamon Press. ISBN 0-08-022722-8.
- ^ Aungier, Ronald H. (2000). Centrifugal Compressors A Strategy for Aerodynamic design and Analysis. ASME Press. ISBN 0-7918-0093-8.
- ^ Bloch, H. P. and Hoefner, J. J. (1996). Reciprocating Compressors, Operation and Maintenance. Gulf Professional Publishing. ISBN 0-88415-525-0.
- ^ Reciprocating Compressor Basics Adam Davis, Noria Corporation, Machinery Lubrication, July 2005
- ^ Introduction to Industrial Compressed Air Systems
- ^ Screw Compressor Describes how screw compressors work and include photographs.
- ^ Technical Centre Discusses oil-flooded screw compressors including a complete system flow diagram
- ^ Tischer, J. , Utter, R: “Scroll Machine Using Discharge Pressure For Axial Sealing,” U. S. Patent 4522575, 1985.
- ^ Caillat, J. , Weatherston, R. , Bush, J: “Scroll-Type Machine With Axially Compliant Mounting,” U. S. Patent 4767293, 1988.
- ^ Richardson, Jr. , Hubert: “Scroll Compressor With Orbiting Scroll Member Biased By Oil Pressure,” U. S. Patent 4875838, 1989.
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