Slide 1 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.
Slide 2Boyle’s Law
The pressure of a gas expanding at constant temperature varies inversely to the volume
or
(P1)(V1) = (P2)(V2) = (P3)(V3) = constant.
Slide 3Charles’ Law
The 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
or
V1 /V2 = T 1/T2
or
P 1/P2 = T 1/T2
Slide 4 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 becomes
Pv = RT
where the pressure and temperature are absolute values.
Slide 5Ideal Gas Constant Values
Slide 6Pressure – Volume Diagram
Slide 7Fluids
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
Slide 8Air Compressors
Types
Classifications
Components
Principles of Operation
Failure Mechanisms and Symptoms
Slide 9Air Compressors - Types
Rotary
Reciprocating
Centrifugal
Slide 10Air Compressors - Classifications
Pressure
Construction and Operation Features
Air Quality
Slide 11Air Compressors – Classifications - Pressure
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
Slide 12Air Compressors – Classifications Construction and Operation Features
Positive Displacement Type
Reciprocating
Rotary
Rotary Screw
Rotary Vane
Dynamic Type.
Centrifugal
Axial Flow
Blower
Article Source:
Slide 13Air Compressors - Components
Staging
Relief valve
Cooling water
Slide 14Air 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
Slide 15Air Compressor Failure Mechanisms and Symptoms
Power loss
Line ruptures
Air pressure reduction
Air operated component repositioning
Slide 16Diesel Engines
Principles of Operation
Main Structural Components
Main Moving Components
Accessories/ Support Systems
Failure Mechanisms and Symptoms
Slide 17Diesel Engine Principles of Operation
Internal Combustion
Compression ignition
Diesel Cycle
Slide 18Idealized Diesel Cycle
This is a p-V diagram for the ideal Diesel cycle; where p is pressure and v is specific volume. The ideal Diesel cycle follows the following four distinct processes (The color references refer to the color of the line on the diagram.):
•Process 1 to 2 is isentropic compression (blue)
•Process 2 to 3 is reversible constant pressure heating (red)
•Process 3 to 4 is isentropic expansion (yellow)
•Process 4 to 1 is reversible constant volume cooling (green)[1]
The Diesel is a heat engine: it converts heat into work. The isentropic processes are impermeable to heat: heat flows into the loop through the left expanding isobaric process and some of it flows back out through the right depressurizing process, and the heat that remains does the work.
•Work in (Win) is done by the piston compressing the working fluid
•Heat in (Qin) is done by the combustion of the fuel
•Work out (Wout) is done by the working fluid expanding on to the piston (this produces usable torque)
•Heat out (Qout) is done by venting the air
Slide 19Diesel Engine Main Structural Components
Frame
Block
Pedestal
Fuel distribution system
Slide 20Diesel Engine Main Moving Components
Pistons
Cylinders
Crankshaft
Bearings
Valves
Control air
Turbochargers
Slide 21Diesel Engine Accessories/ Support Systems
Air start
Cooling water
Lube oil
Electrical
Fuel oil distribution
Slide 22Diesel Engine Failure Mechanisms and Symptoms
Failure to start
Failure to reach operating speed
Failure to stop
Rough idling