Lesson 9COMPRESSION PROCESSES

• Apply the ideal gas laws to SOLVE for the unknown pressure, temperature, or volume.

• DESCRIBE when a fluid may be considered to be incompressible.

• CALCULATE the work done in constant pressure and constant volume processes.

• DESCRIBE the effects of pressure changes on confined fluids.

• DESCRIBE the effects of temperature changes on confined fluids.

Boyle’s LawThe pressure of a gas expanding at constant

temperature varies inversely to the volume

or

(P1)(V1) = (P2)(V2) = (P3)(V3) = constant.

Charles’ LawThe pressure of a gas varies directly with temperature when

the volume is held constant, and the volume varies directly with temperature when the pressure is held constant

orV1 /V2 = T 1/T2

or

P 1/P2 = T 1/T2

Ideal Gas Law

Combination of Charles' and Boyle's Laws gives

P v /T = constant

This is the ideal gas constant and is designated by R

The ideal gas equation becomesPv = RT

where the pressure and temperature are absolute values.

Ideal Gas Constant Values

Pressure – Volume Diagram

Fluids• Any substance that conforms to the shape of its container. It may be either a

liquid or a gas.

• Compressibility– Liquid – Incompressible– Gas – Compressible

• Constant Pressure Process– W1-2 = P(ΔV)

• Constant Volume Process– W1-2 = V(ΔP)– W1-2 = mv(ΔP)

• Effects of Pressure and Temperature changes on Fluid Properties

Air Compressors

• Types

• Classifications

• Components

• Principles of Operation

• Failure Mechanisms and Symptoms

Air Compressors - Types

• Rotary

• Reciprocating

• Centrifugal

Air Compressors - Classifications• Pressure

• Construction and Operation Features

• Air Quality

Air Compressors – ClassificationsPressure

• Low-pressure air compressors (LPACs) - discharge pressure of 150 psi or less

• Medium-pressure compressors - discharge pressure of 151 psi to 1,000 psi

• High-pressure air compressors (HPACs) - discharge pressure above 1,000 psi

Air Compressors – ClassificationsConstruction and Operation Features

• Positive Displacement Type– Reciprocating– Rotary

• Rotary Screw• Rotary Vane

• Dynamic Type.– Centrifugal– Axial Flow– Blower

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Air Compressors - Components

• Staging

• Relief valve

• Cooling water

Air Compressors – Principles of Operation• Two primary components

– Compressing mechanism - helps in compressing atmospheric air by using energy from the power source.• piston, • rotating impeller• vane

– Power source. – electric motor– other energy sources.

• Atmospheric air is drawn in through an intake valve• More and more air is pulled inside a limited space mechanically by means of the compressing

mechanism• Amount of air is increased in the constant volume receiver or storage tank, pressure is raised

automatically. • When pressure increases to the maximum pressure setting in the receiver or tank, the pressure switch

shuts off the intake of air in the compressor. • When the compressed air is used, the pressure level falls. • As the pressure drops to a low pressure setting, the pressure switch is turned on, thus allowing the

intake of atmospheric air. • Cycle continues

Air Compressor Failure Mechanisms and Symptoms

• Power loss

• Line ruptures

• Air pressure reduction

• Air operated component repositioning

Diesel Engines• Principles of Operation

• Main Structural Components

• Main Moving Components

• Accessories/ Support Systems

• Failure Mechanisms and Symptoms

Diesel Engine Principles of Operation

• Internal Combustion

• Compression ignition

• Diesel Cycle

Idealized Diesel Cycle

Diesel Engine Main Structural Components

• Frame

• Block

• Pedestal

• Fuel distribution system

Diesel Engine Main Moving Components

• Pistons• Cylinders• Crankshaft• Bearings• Valves• Control air• Turbochargers

Diesel Engine Accessories/ Support Systems

• Air start

• Cooling water

• Lube oil

• Electrical

• Fuel oil distribution

Diesel Engine Failure Mechanisms and Symptoms

• Failure to start

• Failure to reach operating speed

• Failure to stop

• Rough idling