Air compressor

Last updated
Air compressor supplies air into a nail gun. AirCompressorHusky.JPG
Air compressor supplies air into a nail gun.

An air compressor is a machine that takes ambient air from the surroundings and discharges it at a higher pressure. It is an application of a gas compressor and a pneumatic device that converts mechanical power (from an electric motor, diesel or gasoline engine, etc.) into potential energy stored in compressed air, which has many uses. A common application is to compress air into a storage tank, for immediate or later use. When the delivery pressure reaches its set upper limit, the compressor is shut off, or the excess air is released through an overpressure valve. The compressed air is stored in the tank until it is needed. [1] The pressure energy provided by the compressed air can be used for a variety of applications such as pneumatic tools as it is released. When tank pressure reaches its lower limit, the air compressor turns on again and re-pressurizes the tank. A compressor is different from a pump because it works on a gas, while pumps work on a liquid.

Contents

Classification

Compressors may be classified according to the pressure delivered:

There are numerous methods of air compression, divided into either positive-displacement or roto-dynamic types. [3]

Positive displacement compressors

Positive-displacement compressors work by forcing air through a chamber whose volume is decreased to compress the air. Once the pressure is greater than the pressure outside the discharge valve, a port or valve opens and air is discharged into the outlet system from the compression chamber. [5] Common types of positive displacement compressors are

Technical illustration of a two-stage air compressor Two-Stage Air Compressor assembled on a vertical tank and equipped with a Joule-Thomson (JT) type refrigerated compressed air dryer.jpg
Technical illustration of a two-stage air compressor
Technical illustration of a portable single-stage air compressor Portable Single Stage Air Compressor.jpg
Technical illustration of a portable single-stage air compressor

The capacities for both single-stage and two-stage compressors are generally specified in Standard Cubic feet per Minute (SCFM) or litres per minute and pounds per square Inch (PSI) or bar. To a lesser extent, some compressors are rated in actual cubic feet per minute (ACFM).[ clarification needed ][ citation needed ] Still others are rated in cubic feet per minute (CFM).[ clarification needed ][ citation needed ] Using CFM alone to rate a compressor is ambiguous because it represents a flow rate without a pressure reference. i.e. 20 CFM at 60 PSI.

Single stage compressors usually fall into the fractional through 5 horsepower range.[ citation needed ] Two-stage compressors normally fall into the 5 through 30 horsepower range.[ citation needed ][ clarification needed ]

Roto-dynamic or turbo compressors

Roto-dynamic air compressors include centrifugal compressors where Rotating vanes impart kinetic energy to a gas and stationary passages convert velocity into a rise in pressure, and axial compressors, where rotor blades impart the kinetic energy and stator blades convert it to a rise in pressure.

Cooling

Due to adiabatic heating, air compressors require some method of disposing of waste heat. Generally this is some form of air- or water-cooling, although some (particularly rotary type) compressors may be cooled by oil (that is then in turn air- or water-cooled). [6] The atmospheric changes are also considered during cooling of compressors.[ clarification needed ] The type of cooling is determined by considering the factors such as inlet temperature, ambient temperature, power of the compressor and area of application. There is no single type of compressor that could be used for any application.

Applications

Portable diesel powered air compressor for powering tools, such as jackhammers CompAir Fahrbarer Kompressor Typ C38.jpg
Portable diesel powered air compressor for powering tools, such as jackhammers

Air compressors have many uses, such as supplying clean high-pressure air to fill gas cylinders, supplying clean moderate-pressure air to a submerged surface supplied air diver, supplying moderate-pressure clean air for driving some office and school building pneumatic HVAC control system valves, supplying a large amount of moderate-pressure air to power pneumatic tools, such as jackhammers, filling high pressure air tanks (HPA, air tank), for filling tires, and to produce large volumes of moderate-pressure air for large-scale industrial processes (such as oxidation for petroleum coking or cement plant bag house purge systems). [7]

Air compressors are also widely used in oil and gas, mining and drilling applications as the flushing medium, aerating muds in underbalanced drilling and in air pigging of pipelines.

Most air compressors either are reciprocating piston type, rotary vane or rotary screw. Centrifugal compressors are common in very large applications, while rotary screw, scroll, [8] and reciprocating air compressors are favored for small and medium-sized applications.

Power source

Air compressors are designed to utilize a variety of power sources. While direct drive gasoline or diesel-engines and electric motors are among the most popular, air compressors that utilize vehicle engines, power-take-off, or hydraulic ports are also commonly used in mobile applications. [9]

The power of a compressor is measured in HP (horsepower) and CFM (cubic feet per minute of intake air). [10] The volume of the pressure vessel and the stored pressure indicate the volume of compressed air (in reserve) available.

Gasoline and diesel-powered compressors are widely used in remote areas with problematic access to electricity. They are noisy and require ventilation for exhaust gases, particularly if the compressed air is to be used for a breathing air supply. Electric-powered compressors are widely used in production, workshops and garages with permanent access to electricity. Common workshop/garage compressors are 110-120 Volt or 230-240 Volt. Compressor tank shapes are: "pancake", "twin tank", "horizontal", and "vertical". Depending on a size and purpose compressors can be stationary or portable.

Maintenance

A small air compressor in use at a roadside tire repair shop in the village of Kodo, Niger Niger, Kodo (9), tire repair shop.jpg
A small air compressor in use at a roadside tire repair shop in the village of Kodo, Niger

To ensure all compressor types run efficiently with no leaks, it is necessary to perform routine maintenance. The cost of maintenance only accounts for 8% of the life cycle cost of owning an air compressor. [11]

Air compressor isentropic efficiency

According to CAGI air compressor performance verification data sheets, the higher the isentropic efficiency is, the better the energy saving is. The better air compressor isentropic efficiency has reached 95%. [12]

Approximately 70~80% of the air compressor's total lifetime cost is energy consumption, so using the high-efficiency air compressor is one of the energy-saving methods.[ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Pump</span> Device that imparts energy to the fluids by mechanical action

A pump is a device that moves fluids, or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy.

<span class="mw-page-title-main">Piston</span> Machine component used to compress or contain expanding fluids in a cylinder

A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder.

<span class="mw-page-title-main">Reciprocating engine</span> Engine utilising one or more reciprocating pistons

A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.

<span class="mw-page-title-main">Two-stroke engine</span> Internal combustion engine type

A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston during one power cycle, this power cycle being completed in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.

An air-start system is a power source used to provide the initial rotation to start large diesel engines and gas turbines.

<span class="mw-page-title-main">Brayton cycle</span> Thermodynamic cycle

The Brayton cycle, also known as the Joule cycle, is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. It is characterized by isentropic compression and expansion, and isobaric heat addition and rejection, though practical engines have adiabatic rather than isentropic steps.

<span class="mw-page-title-main">Compressed-air energy storage</span> Method for matching variable production with demand

Compressed-air energy storage (CAES) is a way to store energy for later use using compressed air. At a utility scale, energy generated during periods of low demand can be released during peak load periods.

<span class="mw-page-title-main">Compressor</span> Machine to increase pressure of gas by reducing its volume

A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.

<span class="mw-page-title-main">Diving air compressor</span> Machine used to compress breathing air for use by underwater divers

A diving air compressor is a breathing air compressor that can provide breathing air directly to a surface-supplied diver, or fill diving cylinders with high-pressure air pure enough to be used as a hyperbaric breathing gas. A low pressure diving air compressor usually has a delivery pressure of up to 30 bar, which is regulated to suit the depth of the dive. A high pressure diving compressor has a delivery pressure which is usually over 150 bar, and is commonly between 200 and 300 bar. The pressure is limited by an overpressure valve which may be adjustable.

<span class="mw-page-title-main">Reciprocating compressor</span> Device used to pump gases at high pressure

A reciprocating compressor or piston compressor is a positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases at high pressure. Pressures of up to 5,000 PSIG are commonly produced by multistage reciprocating compressors.

<span class="mw-page-title-main">Scroll compressor</span> Air compressor

A scroll compressor is a device for compressing air or refrigerant. It is used in air conditioning equipment, as an automobile supercharger and as a vacuum pump. Many residential central heat pump and air conditioning systems and a few automotive air conditioning systems employ a scroll compressor instead of the more traditional rotary, reciprocating, and wobble-plate compressors.

<span class="mw-page-title-main">Air pump</span> Pump for pushing air

An air pump is a pump for pushing air. Examples include a bicycle pump, pumps that are used to aerate an aquarium or a pond via an airstone; a gas compressor used to power a pneumatic tool, air horn or pipe organ; a bellows used to encourage a fire; a vacuum cleaner and a vacuum pump. All air pumps contain a part that moves which drives the flow of air. When the air gets moved, an area of low pressure gets created which fills up with more air.

<span class="mw-page-title-main">Axial piston pump</span>

An axial piston pump is a positive displacement pump that has a number of pistons in a circular array within a cylinder block.

<span class="mw-page-title-main">Rotary-screw compressor</span> Gas compressor using a rotary positive-displacement mechanism

A rotary-screw compressor is a type of gas compressor, such as an air compressor, that uses a rotary-type positive-displacement mechanism. These compressors are common in industrial applications and replace more traditional piston compressors where larger volumes of compressed gas are needed, e.g. for large refrigeration cycles such as chillers, or for compressed air systems to operate air-driven tools such as jackhammers and impact wrenches. For smaller rotor sizes the inherent leakage in the rotors becomes much more significant, leading to this type of mechanism being less suitable for smaller compressors than piston compressors.

<span class="mw-page-title-main">Vapor-compression refrigeration</span> Refrigeration process

Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services. Oil refineries, petrochemical and chemical processing plants, and natural gas processing plants are among the many types of industrial plants that often utilize large vapor-compression refrigeration systems. Cascade refrigeration systems may also be implemented using two compressors.

A hydrogen compressor is a device that increases the pressure of hydrogen by reducing its volume resulting in compressed hydrogen or liquid hydrogen.

Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.

<span class="mw-page-title-main">Booster pump</span> Machine to increase pressure of a fluid

A booster pump is a machine which increases the pressure of a fluid. It may be used with liquids or gases, and the construction details vary depending on the fluid. A gas booster is similar to a gas compressor, but generally a simpler mechanism which often has only a single stage of compression, and is used to increase pressure of a gas already above ambient pressure. Two-stage boosters are also made. Boosters may be used for increasing gas pressure, transferring high pressure gas, charging gas cylinders and scavenging.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.

Kirloskar Pneumatic Company Limited (KPCL) is one of the core Kirloskar Group companies and was founded in 1958 by Shantanurao Laxmanrao Kirloskar. The company offers engineering products and is represented by offices across the globe. KPCL serves major sectors like Oil and Gas, Steel, Cement, Food and Beverage, Railways, Defense and Marine. Their product range includes air compressors, air conditioning and refrigeration systems, process gas systems, vapour absorption chillers and industrial gearboxes.

References

  1. "How Do Air Compressors Work?". Popular Mechanics. 2015-03-18. Retrieved 2017-01-12.
  2. 1 2 3 "Classification of air compressors". www.tpub.com. Retrieved 2017-01-12.
  3. "Air Compressor Types and Controls". Natural Resources Canada. 4 February 2014.
  4. Davis, Jeff (2022-02-23). "What is a Two Stage Air Compressor – Air Compressor Insider" . Retrieved 2023-07-26.
  5. "Compressor Selection Basics: Positive Displacement versus Dynamic Compression" . Retrieved 2017-01-12 via The 5th Utility.
  6. "Types of Air Compressors". The Engineering ToolBox.
  7. "Applications for Compressors". www.industry.siemens.com. Retrieved 2017-01-12.
  8. Hislop, Reid. "Plug Power Places Large Production Order for Air Squared Compressors to be used in GenDrive Fuel Cell Units" (PDF). Plug Power. Retrieved 10 May 2019.
  9. "Easy Guide To Rotary Screw Air Compressors For Vehicles – By VMAC". VMAC. 2018-10-16. Retrieved 2018-10-30.
  10. "Evaluating True Horsepower and CFM Ratings of Air Compressors".
  11. "How Many Watts Does An Air Compressor Use".
  12. CAGI Performance Verification Data Sheets Archived 2022-01-21 at the Wayback Machine .