Group No 6Group Members

Ali Raza (bme-01083093)

Husnain shah (bme-01083079)

Waleed bin khalid (bme-01083071)

Shezad Yahiya (bme-01083090)

Multistage Air Compressor

What is a compressor?

An instrument or device for compressing (i.e. liquid , gas )A machine used to supply air or other gas at increased pressure, e.g., to power a gas turbine

Interesting Fact The original air compressor is the lung. When you take a deep breath to blow out your birthday candles, for example, you're increasing the pressure of the air in your lungs, which effectively is an air compressor containing pressurized air. You then use the force of the air in your lungs to blow out the flames of your birthday candles

What is the basic differencebetween Compressor & Blower??

The main difference is that blowers are used for the transportation of high volumes at low pressure whereas compressors are used for low volumes with high pressures

Types of compressor

Positive Displacement air compressor: In the positive-

displacement type, a given quantity of air or gas is trapped in a compression chamber and the volume it occupies is mechanically reduced, causing a corresponding rise in pressure prior to discharge. At constant speed, the air flow remains essentially constant with variations in discharge pressure.

Dynamic compressor:

Dynamic compressors impart velocity energy to continuously flowing air or gas by means of impellers rotating at very high speeds. The velocity energy is changed into pressure energy both by the impellers and the discharge volutes or diffusers. In the centrifugal-type dynamic compressors, the shape of the impeller blades determines the relationship between air flow and the

pressure (or head) generated.

Compressor Classification

Mainly compressor are classified on the basis of following points

a) By principle of operationb) By construction typec) By stagingd) By service dutye) Lubricated/ non lubricated

Working Principal Reciprocating compressor: An air compressor takes free air (air at 14.7 PSI actual) into an intake port, and using mechanical means (pistons, screws, rotary sliding vanes )pushes that air into a smaller area. As more and more air is pushed into the smaller area (the receiver or the air tank on a compressor) the pressure continues to increase inside that tank..

Working of Multi stage Reciprocating air compressor Pressurized air discharge of 1st cylinder is send to 2nd cylinder , where it gets more pressurized by the action of piston cylinder assembly. The process goes on until last cylinder has reached .At the end we will get our desired pressurized gas from the last cylinder.

Video.1

Working principle of multistage rotary air compressor

Two rotary screws entrap air in between the spaces of the screw. As the screw rotates along its axis the air begins to compress and exit through the outer end.

While air in case of multistage screw air compressor ,the compressed air of 1st stage is send as input of 2nd stage and this process goes on.

Video.2

Working principal of dynamic air compressor

A centrifugal /axial pump is a kinetic device. Liquid entering the pump receives kinetic energy from the rotating impeller. The centrifugal action of the impeller accelerates the liquid to a high velocity, transferring mechanical (rotational) energy to the air. That kinetic energy is available to the fluid to accomplish work.

Working of multistage dynamic air compressor

A centrifugal pump containing two or more impellers is called a multistage centrifugal pump. The impellers may be mounted on the same shaft or on different shafts.

If we need higher pressure at the outlet we can connect impellers in series.

If we need a higher flow output we can connect impellers in parallel.

All energy added to the fluid comes from the power of the electric or other motor force driving the impeller.

Video 3

Components of a Reciprocating Air Compressor

Frame/Crank casePistonCompression RingsConnecting rodCrank ShaftCylinder Head

Components of a dynamic Air Compressor

A simple centrifugal/axial compressor is comprised of the following 4 components

Inletimpeller/rotordiffusecollector

Advantages of Multi-stage compression:

The work done in compressing the air is reduced, thus power can be savedPrevents mechanical problems as the air temperature is controlledThe suction and delivery valves remain in cleaner condition as the

temperature and vaporization of lubricating oil is lessThe machine is smaller and better balancedEffects from moisture can be handled better, by draining at each stageCompression ratio at each stage is lower when compared to a single-stage

machineLight moving parts usually made of aluminum, thus less cost and better

maintenance

Applications: In  pipeline transport of purified natural gas to move the gas from the

production site to the consumer. 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 conditioning equipment s. In gas turbine systems to compress the intake combustion air. In pressurized aircraft to provide a breathable atmosphere of

higher than ambient pressure. in turbochargers and superchargers to increase the

performance of internal combustion engines by increasing mass flow.

in submarines , to store air for later use in displacing water from buoyancy chambers, for adjustment of depth.