Air compressor

An air compressor is a

• Internal combustion engine: Petrol, petrol without oil, diesel
• Electric: AC, DC

• Direct drive
• Belt drive

Compressors may be classified according to the pressure delivered:

• Low-pressure air compressors, which have a discharge pressure of 150 pounds per square inch (10 bar) or less^[2]
• Medium-pressure compressors which have a discharge pressure of 151 to 1,000 pounds per square inch (10.4 to 68.9 bar)^[2]
• High-pressure air compressors, which have a discharge pressure above 1,000 pounds per square inch (69 bar)^[2]

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

• Single-stage reciprocating compressor
• Multi-stage reciprocating compressor^[4]
• Single stage rotary-screw compressor
• Two-stage rotary screw compressor
• Rotary vane pump
• Scroll compressor
• Centrifugal (roto-dynamic or turbo) compressor
• Axial compressor, often used in jet engines.

• Another way of classification, is by lubrication type: oil lubricated and oil-free. The oil-less (or oil-free) system has more technical development such as they do not require oil for lubrication. oil-less air compressors are also lighter and more portable than oil-lubricated models but require more maintenance. On other side Oil-lubricated air compressors are the more traditional type of air compressor. They require oil to lubricate the motor which helps prolong the compressor's life. One of the benefits of oil-lubricated compressors is that they tend to be more durable and require less maintenance than oil-free compressors.[1]

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

• Piston-type air compressors, which compress air by pumping it through cylinders by reciprocating pistons. They use one-way valves to admit air into the cylinder on the induction stroke and prevent it from leaving by the same route, and out of the cylinder through the exhaust valve to the high pressure side on the compression stroke, again using a non-return valve to prevent it leaking back on the next induction stroke. Piston compressors can be single or multi-stage, and may also have one or more sets of cylinders in parallel (at the same pressure). Multi-stage compressors provide greater efficiency than their single-stage counterparts for high compression ratios, and generally use interstage cooling to improve efficiency.

The capacities for both single-stage and two-stage compressors are generally specified in

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]}

• Rotary screw compressors provide positive-displacement compression by matching two helical screws that, when turned, guide air into a chamber, whose volume is decreased as the screws turn. Rotary screw compressors can be single-stage or two-stage.^{[clarification needed]}
• Vane compressors: use a slotted rotor with varied blade placement^{[clarification needed]} to guide air into a chamber and compress the volume. This type of compressor delivers a fixed volume of air at high pressures.^{[clarification needed]}

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.

Due to

Air compressors have many uses, such as supplying clean high-pressure air to fill

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.

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]

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]}

• Vacuum pump
• Free-piston engine
• Gas compressor
• Pneumatics
• Gas cylinder
• "The Blue Air Compressor"

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