Fluid Mechanics: Principles and Applications
Fluid Mechanics
Tire circuits and hydraulic circuits are fluid circuits. Like electrical circuits, they are subject to a set of basic physical laws and principles, whose study is known as fluid mechanics.
Key Concepts in Fluid Mechanics
- Atmospheric Pressure: The pressure exerted by the atmospheric air on bodies immersed in it.
- Pascal’s Principle: Pressure applied to a fluid confined in a vessel is transmitted equally and acts in all directions.
Fundamental Laws of Perfect Gases
- Boyle’s Law: If the temperature of a gas remains constant, changes in volume are inversely proportional to changes in pressure.
- Gay-Lussac’s Law: If the gas pressure remains constant, the ratio of volume to temperature is constant (V/T = constant).
Properties of Liquids
The essential properties of liquids are:
- Fluency: The ability of a liquid to flow.
- Viscosity: The resistance of a liquid’s molecules to move over each other.
- Incompressibility: Liquids are difficult to compress; their volume changes very little under pressure.
- Flow Regime: Affects the type of fluency; it can be laminar or turbulent.
Pneumatic Circuits
Compressed air is used in various applications, including:
- Air cleaning systems
- Pressure-based painting
- Portable tools
- Modification of paths in conveyor belts
- Elevation of bodies
- Subjection of parts
- Verification systems
- Braking movements
- Opening and closing doors
Components of a Pneumatic Circuit
- Compressed Air Generator: Compresses atmospheric air to the required pressure.
- Pneumatic Actuators or Motors: Transform air pressure into useful mechanical work.
- Pipes and Ducts: Channel the air.
- Control Elements: Guarantee supply security and proper system control.
Types of Compressors
- Alternative (Reciprocating): Most widespread; a piston compresses air.
- Rotary: Provide a constant airflow and have lower noise levels.
Actuators
Actuators convert the potential energy of compressed air into mechanical energy.
- Cylinders: Produce straight-line movements; the most commonly used actuators.
- Engines: Produce circular motion from compressed air.
Types of Cylinders
- Single-Acting Cylinder: Acts when compressed air enters one end and returns to its rest position via a spring when the pressure stops. Consider these factors:
- Frictional force loss is approximately 10%.
- The safety margin is approximately 30%.
- Double-Acting Cylinder: Both the output and input of the cylinder rod are powered by air pressure.
Control Valves
Control valves can be operated in several ways:
- Manual Override: Like a switch or a button.
- Mechanical Drive: A contact mechanism activates the valve.
- Pneumatic: Air pressure controls the valve.
- Electric Drive: An electric signal pilots a power distributor.
Hydraulic Circuits
Fundamentals
Pneumatics has limitations in power and precision of movement. Hydraulics offers advantages in these areas.
Applications of Hydraulics
- Machine Tools: Machining movements, workholding, grinding table movements.
- Vehicles: Brakes, automatic transmissions, lifting and tilting of loads.
- Presses: Component compression, fastening, separation movements.
- Construction Machinery: Pressing, clamping, lifting, and cargo handling systems.
- Planes: Retractable landing gear, movement of rudders, ailerons, and flaps.
- Cranes and Robotic Arms: Lifting, transportation, and cargo handling.