What is Compressed Air?

PrintEmailSave

Main Image: 

Compressed air is air which is kept under a certain pressure, usually greater than that of the atmosphere. In Europe 10 % of all electricity used by industry is used to produce compressed air. This amounts to 80 terawatt hours per year. Air that is held inside one of several types of special containers at a decreased volume is known as compressed air. In other words, it is the air which has been reduced in volume and increased in pressure. Compressed air is a well-known type of power since it is clean, easy to use, and easy to transport. It is also safe because air is not highly explosive in the same way that an energy source like gasoline can be. It is also readily available, since the air already surrounds us and needs only to be compressed in order to be ready to use.

How to compress air?

In order to compress air, its pressure inside the container should be at a higher pressure than that of the atmospheric air outside of it. It can be contained in many different forms while having a number of uses, many within the different industries that subsist nowadays. Compressed air can be used to power machines, pneumatic tools, the use of pressurized gases to do work, engines, and more, including power drills, liquid sprayers, machine presses, vehicle engines, and many others. One more chief use for compressed air is in the tanks of scuba divers, which must be safe, clean and reliable. Air is held under pressure in a tank to be breathed by underwater divers. A tank of compressed air is part of a diver's scuba (self-contained underwater breathing apparatus) gear.

How is atmospheric air compressed?

A pretty straightforward way of compressing air that is taken from the atmosphere within a smaller volume is by using a hand pump. In order to understand the working of a hand pump, one can take a look at a simple bicycle pump, which takes air and pumps it into a bike tire when a person constantly pushes a hand or foot pedal. Air enters the pump once the pedal is compressed, through an intake and is “pushed” into the bike tire by means of a plunger (used to unclog drains and plumbing of toilets, bathtubs, and sinks) within the pump casing. Once the air has entered the tire, it formally is called “compressed air”, and the more air that enters the tire results in higher air pressure within the volume of the tire. Air pressure, also known as atmospheric pressure, refers to the weight of the Earth's atmosphere pressing down on everything at the surface. Apparently, if the air pressure of a bike tire becomes too high, the tire will ultimately pop. Therefore, filling a bike tire with a mechanical air compressor, is usually not preferred since it has the capability of pushing much higher volumes of air into a tire, can, or tank at much faster speeds. Mechanical compressors can run on several principles by using pistons, rotary screws or centrifuges. They are used to fill vehicle tires, without doubt, but are also used to reload the compressed air tanks and cylinders that will be used for several other purposes.

What is an example of compressed air?

The most common type of a compressed air tank is a very simple spray can with a release trigger, which can be used to clean hard-to-reach dusty areas such as the inside of a computer. Basically, the airflow of larger tanks that activates machinery is controlled by the machines itself, and in most of the cases, the tanks or cylinders that hold the compressed air have been designed to work with only one specific machine. Most types of machinery, on the other hand, make use of a generic hookup that can be attached to a standard air tank for power as the compressed air is released.

What are the types of Air compressors?

There are three fundamental types of air compressors:

• 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 achieves this by a piston within a cylinder as the compressing and displacing element. The reciprocating air compressor is ‘single acting’ when the compressing is achieved 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. Fundamentally, 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 essentially oil cooled (with air cooled or water cooled oil coolers) where the oil seals the internal clearances. The working parts never experience extreme operating temperatures, since the cooling takes place right inside the compressor. As a result, the rotary compressor 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 achieved 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 provides the same flexibility as oil flooded rotaries when oil free air is required.

• Centrifugal Compressors: The centrifugal air compressor is dynamic compressor which depends on transfer of energy from a rotating impeller (The rotating part of a centrifugal pump, compressor, or other machine designed to move a fluid by rotation) 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 (fixed aero foils that direct air, gas, or water into the moving blades of a turbine or into or around bends in ducts with minimum loss of energy) is the usual 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.

Can a car run on compressed air?

Yes, it is possible. If we compress the air using an air compressor and fill a compressed-air tank in the car, and the car could run off of it. An engine which is very similar to a steam engine (using pressurized air instead of pressurized steam) can be used to convert the compressed air to rotational energy. Large quantity of compressed air is required to ride a car to longer distances. A compressed air car would generate no pollution while driving.

What are the Uses of compressed air?

Compressed air is regarded as the fourth utility, after electricity, natural gas, and water. But per unit energy delivered, compressed air is more expensive than the other three utilities. They can be used for:

• Cooling using a vortex tube. The vortex tube is a mechanical device that separates a compressed gas into hot and cold streams.
• Gas dusters for cleaning electronic components that cannot be cleaned with water. Gas duster, also known as canned air, is a product used to clean electronic equipment and other sensitive devices that cannot be cleaned using water.
• In Railway braking systems. On railcars, an air brake is a conveyance braking system actuated by compressed air. Modern trains rely upon a fail-safe air brake system
• Paintball ammunition propulsion. Paintball is a sport.
• Air soft ammunition propulsion. Air soft is a recreational activity
• Air tools are tools driven by gas, usually compressed air supplied by a gas compressor.

Related Videos: 

Related Images: