power engg. air compressors

Mech_intBy Avinash Sir

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Which?

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Pressure Ratio

Ratio of absolute discharge press. / absolute inlet pressure

Compressor capacity

It is the quantity of actual free air delivered by the compressor

Free air delivered(FAD)

It is the volume of air actually delivered under the conditions of temperature and pressure existing at the compressor intake.

Swept volume

It is the volume swept by the recip. compressor piston during suction or delivery stroke

Pneumatics, the use of pressurized gases to do work. See compressed air energy storage.

Vehicular transportation using a compressed air vehicle

Energy storage

Scuba diving, to inflate buoyancy devices.

Cooling using a vortex tube.

Gas dusters for cleaning electronic components that cannot be cleaned with water.

Railway braking systems

Road vehicle braking systems

Diesel engine cranking

Paintball ammunition propulsion

Airsoft ammunition propulsion

Air tools

Cleaning the insides of electronics

SINGLE STAGE

One suction and one delivery

MULTI STAGE

One actual suction and multiple sub suctions and sub-deliveries

SINGLE ACTING

One piston delivers from only one side

DOUBLE ACTING

Piston delivers from both sides

Construction

Volumetric efficiency

1. Depends on clearance(IP)2. Piston ring leakage3. Speed of compressor(IP)4. Fresh air coming in contact with hot wall

expands and decreases Vol. Eff.

Isothermal efficiency

Mechanical eff. = IP / SP

Vol. eff. Increases

Power IP decreases

Uniform torque and flywheel size reduced

Max. temp reduced so less lubrication

Reduced leakage loss due to reduced pressure difference across piston and valves

Reduced wt. of cylinders.

Screw compressors Positive displacement compressors

Driver and driven rotor (sometimes only one rotor)

Air is sucked form one side and compressed in the variable space between the rotors both axially and radially

Advantages:

1. High volumetric eff.

2. Uniform and continuous flow

3. Perfect balancing due to pure rotary motion

Same as screw compressor

Both rotors have mating geometric profiles

Air is compresses in the variable space in the mating of the blowers

Spring fitted vanes to vary the space between the vanes

The rotor is fitted eccentrically to obtain the variable area

Reversibly and irreversibly compressed

Low speeds are suitable