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Understanding Compression Processes in Fluid Mechanics

Learn about applying ideal gas laws to solve for pressure, temperature, or volume, effects of pressure changes on confined fluids, types of air compressors and diesel engines, and failure mechanisms.

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Understanding Compression Processes in Fluid Mechanics

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  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.

  2. Boyle’s Law The pressure of a gas expanding at constant temperature varies inversely to the volume or (P1)(V1) = (P2)(V2) = (P3)(V3) = constant.

  3. Charles’ 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

  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.

  5. Ideal Gas Constant Values

  6. Pressure – Volume Diagram

  7. 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

  8. Air Compressors • Types • Classifications • Components • Principles of Operation • Failure Mechanisms and Symptoms

  9. Air Compressors - Types • Rotary • Reciprocating • Centrifugal

  10. Air Compressors - Classifications • Pressure • Construction and Operation Features • Air Quality

  11. 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

  12. Air Compressors – ClassificationsConstruction and Operation Features • Positive DisplacementType • Reciprocating • Rotary • Rotary Screw • Rotary Vane • DynamicType. • Centrifugal • Axial Flow • Blower Article Source: http://EzineArticles.com/1098992

  13. Air Compressors - Components • Staging • Relief valve • Cooling water

  14. 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

  15. Air Compressor Failure Mechanisms and Symptoms • Power loss • Line ruptures • Air pressure reduction • Air operated component repositioning

  16. Diesel Engines • Principles of Operation • Main Structural Components • Main Moving Components • Accessories/ Support Systems • Failure Mechanisms and Symptoms

  17. Diesel Engine Principles of Operation • Internal Combustion • Compression ignition • Diesel Cycle

  18. Idealized Diesel Cycle

  19. Diesel Engine Main Structural Components • Frame • Block • Pedestal • Fuel distribution system

  20. Diesel Engine Main Moving Components • Pistons • Cylinders • Crankshaft • Bearings • Valves • Control air • Turbochargers

  21. Diesel Engine Accessories/ Support Systems • Air start • Cooling water • Lube oil • Electrical • Fuel oil distribution

  22. Diesel Engine Failure Mechanisms and Symptoms • Failure to start • Failure to reach operating speed • Failure to stop • Rough idling

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