2012 02-12 emet135 week 2 presentation

REVIEW

Fluid Power System Functions and Components

Fluid power systems perform Fluid power systems perform five functions during operation:five functions during operation: Energy conversionEnergy conversion

Power unit groupPower unit group Fluid distributionFluid distribution

Conductors groupConductors group Fluid controlFluid control

Control valves groupControl valves group Work performanceWork performance

Actuators groupActuators group Fluid maintenanceFluid maintenance

Fluid Maintenance groupFluid Maintenance group

CHAPTER 3CHAPTER 3

Basic Physical Principles and Basic Physical Principles and

Applications of Fluid Power Applications of Fluid Power SystemsSystems

© Permission granted to reproduce for educational purposes only

This Lesson Discusses The Basic Physical Properties Followed By Fluid Power

System

This lesson follows Chapter 3 in the Fluid Power book by James R. Daines


ObjectivesObjectives

Nature of electricity and the basic methods used Nature of electricity and the basic methods used for electrical measurement.for electrical measurement.

Operation of basic electrical circuits.Operation of basic electrical circuits.

Characteristics associated with the fluids used in Characteristics associated with the fluids used in fluid power systems.fluid power systems.


ObjectivesObjectives

Design and operation of the six basic machines.Design and operation of the six basic machines.

Factors that affect energy in fluid power systems.Factors that affect energy in fluid power systems.

Potential power of a fluid power system is Potential power of a fluid power system is established.established.

Nature of heat and how it is measured in fluid Nature of heat and how it is measured in fluid power systems.power systems.


Simple MachinesSimple Machines

A picture of the machines that exist in our society A picture of the machines that exist in our society today.today.



The machines shown in the last slide are The machines shown in the last slide are complex in nature, but all machines fall complex in nature, but all machines fall into the category of six basic types of into the category of six basic types of machines:machines: LeverLever Inclined planeInclined plane WedgeWedge ScrewScrew PulleyPulley Wheel and axleWheel and axle



LeversLevers



Inclined planeInclined plane WedgeWedge

Photo courtesy of handiramp.com



ScrewScrew



PulleyPulley

Dynamic Graphics© Permission granted to reproduce for educational purposes only


Wheel and axleWheel and axle

Creatas


BRANCHES OF MECHANICS TO SHOW HOW BRANCHES OF MECHANICS TO SHOW HOW FLUIDS INTERTWINES WITH THE OTHER FLUIDS INTERTWINES WITH THE OTHER

BRANCHESBRANCHES

S ta tics D yn am ics

R ig id B od ies(Th in g s th a t d o n o t ch an g e sh ap e)

D eform ab le B od ies(Th in g s th a t d o ch an g e sh ap e)

In com p ress ib le C om p ress ib le

F lu id s

M ech an icsTyp e tit le h ere


Basic Principles of Basic Principles of MechanicsMechanics

Work, energy, torque, or power describe the Work, energy, torque, or power describe the specified forces exerted while moving fixed specified forces exerted while moving fixed distances in given periods of time.distances in given periods of time.

Fluid power systems are required to do thisFluid power systems are required to do this


Energy is the capacity to do workEnergy is the capacity to do work

Force is the overall effort needed to produce, Force is the overall effort needed to produce, change, or stop motionchange, or stop motion

Pressure is force exerted over a unit areaPressure is force exerted over a unit area


Basic Principles of Basic Principles of MechanicsMechanics

WorkWork Movement of a force through a specified distance.Movement of a force through a specified distance.

W = F x d W = F x d units are ft lb, Joulesunits are ft lb, Joules Thermal energy Btu or caloriesThermal energy Btu or calories Electrical energy kWhElectrical energy kWh

EnergyEnergy Ability to perform useful work. Ability to perform useful work.

Stored energy is called potential energyStored energy is called potential energy Motion energy is called kinetic energy units are ft lb, JoulesMotion energy is called kinetic energy units are ft lb, Joules Thermal energy Btu or caloriesThermal energy Btu or calories Electrical energy kWhElectrical energy kWh


Work and EnergyWork and Energy

StrokeStroke Force applied through a selected distance.Force applied through a selected distance.

PowerPower Rate which work is doneRate which work is done Mechanical is measured in horsepower, electrical Mechanical is measured in horsepower, electrical

power in kWpower in kW


Work, Energy and PowerWork, Energy and Power

Torque or momentTorque or moment Ability of a force to cause rotation about a particular axisAbility of a force to cause rotation about a particular axis Force times Distance (F x d)Force times Distance (F x d) Units are lb ft and N mUnits are lb ft and N m Examples are torque wrenches and torque multipliersExamples are torque wrenches and torque multipliers


TorqueTorque

Mechanical advantageMechanical advantage relationship between the effort put into a relationship between the effort put into a

machine and the resistance overcomemachine and the resistance overcome

Mechanical efficiencyMechanical efficiency comparison of the work input and work comparison of the work input and work

output of a machineoutput of a machine Calculated by dividing the work output of Calculated by dividing the work output of

the machine by the work inputthe machine by the work input Expressed as a percentage and is always Expressed as a percentage and is always

less than 100% due to lossesless than 100% due to losses


Mechanical Mechanical MeasurementsMeasurements

ThermodynamicsThermodynamics the science dealing with the properties of matter the science dealing with the properties of matter

related to heat and the conversion of energy from related to heat and the conversion of energy from one form to anotherone form to another

Heat Heat generated when you have a pressure drop but no generated when you have a pressure drop but no

work donework done Type of kinetic energyType of kinetic energy Measured in British thermal units (Btu) or caloriesMeasured in British thermal units (Btu) or calories


Principles of Heat Principles of Heat TransferTransfer

TemperatureTemperature the rate of molecular movement within a the rate of molecular movement within a

substancesubstance measured in degreesmeasured in degrees

Fahrenheit scale (United States)Fahrenheit scale (United States) Celsius scale (everywhere else)Celsius scale (everywhere else) Rankine scale (often used in scientific and Rankine scale (often used in scientific and

engineering calculations)engineering calculations) Kelvin scale (often used in scientific and Kelvin scale (often used in scientific and

engineering calculations)engineering calculations)



Sensible heat Sensible heat Feeling of Feeling of ““hothot”” or or ““coldcold”” that can be measured using a that can be measured using a

thermometerthermometer

Latent heat Latent heat heat needed to change the state of a substance without heat needed to change the state of a substance without

changing its temperaturechanging its temperature Examples are ice converted to water and water converted Examples are ice converted to water and water converted

to steamto steam



Heat may be moved using three modes of transferHeat may be moved using three modes of transfer:: ConductionConduction ConvectionConvection

Using physical means to transfer heat energyUsing physical means to transfer heat energy RadiationRadiation

Transfers heat by electromagnetic raysTransfers heat by electromagnetic rays



An atom is the smallest identifiable part of an elementAn atom is the smallest identifiable part of an element

Composed of:Composed of: Electrons (–) Neutrons (+)Neutrons (+) Protons (no charge)Protons (no charge)


Electricity and MagnetismElectricity and Magnetism

An atom is the smallest identifiable part of an An atom is the smallest identifiable part of an elementelement Composed of:Composed of:

Electrons (–) Neutrons (+)Neutrons (+) Protons (no charge)Protons (no charge)

Electrical flowElectrical flow occurs when electrons leave outer orbital paths and move occurs when electrons leave outer orbital paths and move

other free electrons through the substance along with themother free electrons through the substance along with them

MagnetismMagnetism ability of a material to attract ironability of a material to attract iron Think of how a magnet attracts objects containing ironThink of how a magnet attracts objects containing iron



Electrical current is used to magnetize iron and iron alloysElectrical current is used to magnetize iron and iron alloys

http://www.youtube.com/watch?v=l9MF7dp6MbY&NR=1&feature=fvwp





Electricity may be produced using the lines of force that Electricity may be produced using the lines of force that surround a magnetsurround a magnet When an electrical conductor cuts these magnetic lines of When an electrical conductor cuts these magnetic lines of

force, electricity is producedforce, electricity is produced Electrical output is dependent on the number of lines cut and Electrical output is dependent on the number of lines cut and

the speed with which they are cutthe speed with which they are cut This is called This is called electromagnetic inductionelectromagnetic induction



Electricity flowing in a conductor involves:Electricity flowing in a conductor involves: Electrical current (amperage)Electrical current (amperage) Potential (voltage)Potential (voltage) Resistance (ohms)Resistance (ohms)

Ohm’s Law is the relationship between these Ohm’s Law is the relationship between these elements elements Amperage = Volts Amperage = Volts Ohms Ohms

I = E I = E R R



Types of current flow used in electrical circuitsTypes of current flow used in electrical circuits Direct current (dc)Direct current (dc)

Electrons flow in one direction only Electrons flow in one direction only Alternating current (ac) Alternating current (ac)

Electrons flow first in one direction, stop, and then reverse their Electrons flow first in one direction, stop, and then reverse their direction of flowdirection of flow



Electrical circuits are made up of four basic Electrical circuits are made up of four basic elementselements ConductorsConductors Control devicesControl devices Loading devicesLoading devices Electrical energy sourceElectrical energy source

Electrical circuits may be connected using either a Electrical circuits may be connected using either a series or parallel formatseries or parallel format



Series circuitSeries circuit

all loads are on a single current flow pathall loads are on a single current flow path

If one load is shorted, all current flow stopsIf one load is shorted, all current flow stops



Parallel circuitParallel circuit All loads have an individual current flow path for each All loads have an individual current flow path for each

one one If one load is shorted, current flow continues to all If one load is shorted, current flow continues to all

the other loadsthe other loads



FluidFluid Liquids and gases are both considered fluidsLiquids and gases are both considered fluids Each substance is able to flow and each can adjust its Each substance is able to flow and each can adjust its

shape to fit the container in which it is heldshape to fit the container in which it is held


General Characteristics of General Characteristics of FluidsFluids

MoleculesMolecules Small particles that bond in such a way to give material Small particles that bond in such a way to give material

distinctive characteristics.distinctive characteristics. SolidSolid

Molecules are bonded in a rigid lattice, maintaining shapeMolecules are bonded in a rigid lattice, maintaining shape LiquidLiquid

Molecules that conform to the shape of their container, thus Molecules that conform to the shape of their container, thus do not maintain shape.do not maintain shape.

Volume is constantVolume is constant Act similar to a solidAct similar to a solid

GasGas Molecules that conform to the shape of their container, thus Molecules that conform to the shape of their container, thus

do not maintain shape.do not maintain shape. Expand to fill volume of container placed inExpand to fill volume of container placed in


Fluid NatureFluid Nature

Specific weightSpecific weight weight of a specified volume of a substance at a given weight of a specified volume of a substance at a given

temperature and pressuretemperature and pressure

Specific gravity Specific gravity comparison of the weight of a substance to the weight of comparison of the weight of a substance to the weight of

an equal volume of wateran equal volume of water Float tube hydrometer is used to measure thisFloat tube hydrometer is used to measure this


Fluid PropertiesFluid Properties

Force applied to a fluid divided by the area of the Force applied to a fluid divided by the area of the fluidfluid

P=F/AP=F/A Units are psi, psf, N/m squared, PaUnits are psi, psf, N/m squared, Pa


PressurePressure

Gauge pressureGauge pressure Absolute pressureAbsolute pressure VacuumVacuum HeadHead AtmosphereAtmosphere


Pressure Measurement Pressure Measurement Scales for FluidsScales for Fluids

Gage Pressure Measured relative to atmosphere Psig, psi

Absolute Pressure Measured relative to a perfect vacuum

Psi(abs), psia


Pressure Measurement in Pressure Measurement in FluidsFluids

At normal atmospheric pressure:At normal atmospheric pressure: If gauge scale reads 0 psi, then absolute scale reads If gauge scale reads 0 psi, then absolute scale reads

14.7 psi14.7 psi



Barometer Instrument that measures atmospheric pressure Standard piece of meteorological data used by weather

forecasters to predict the future



Perfect vacuumPerfect vacuum Lowest possible pressure attained in natureLowest possible pressure attained in nature Absolute – psiaAbsolute – psia Gauge – psigGauge – psig

Head Pressure from the weight of a fluid at it’s base



Manometer U-tube containing some liquid such as water, oil, or

mercury that is immiscible with the fluid whose pressure is being measured.

Measures pressure at a certain point Blood pressure example



Pascal’s PrinciplePascal’s Principle

Pressure applied to a confined fluid is transmitted in Pressure applied to a confined fluid is transmitted in all directions to every portion of the fluidall directions to every portion of the fluid

Reaction of confined molecules to an applied loadReaction of confined molecules to an applied load Describes fluid in static systemsDescribes fluid in static systems Neglects pressure variations within a fluid that may Neglects pressure variations within a fluid that may

be caused by the weights of standing columns of fluidbe caused by the weights of standing columns of fluid Valid for both liquids and gases, even though there Valid for both liquids and gases, even though there

are different compressibility and temperature factors are different compressibility and temperature factors to a gasto a gas© Permission granted to reproduce for educational purposes only

BernoulliBernoulli’’s Theorems Theorem

In a volume of flowing fluid, total energy is In a volume of flowing fluid, total energy is the same at every point in its path of flowthe same at every point in its path of flow

Simply put, when the fluid speed Simply put, when the fluid speed increases, the pressure decreasesincreases, the pressure decreases


Gas Reactions to Pressure and Gas Reactions to Pressure and TemperatureTemperature

Ideal gas lawsIdeal gas laws used in pneumatic systemsused in pneumatic systems relate how real gases react to pressure, temperature, and relate how real gases react to pressure, temperature, and

volume changesvolume changes BoyleBoyle’’s laws law

constant temperatureconstant temperature CharlesCharles’’ law law

constant pressureconstant pressure Gay-LussacGay-Lussac’’s laws law

constant volume constant volume General gas law General gas law

Combination of all threeCombination of all three


Compression ratio ratio of initial to final volumes v1/v2 example is internal combustion engines

Ratio of compression ratio of final pressure to initial pressure p2/p1 example is compressors


Gas Reactions to Pressure and Gas Reactions to Pressure and TemperatureTemperature

Properties of Gases

Raising temperature of gas increases velocity, internal energy, and volume of molecules higher viscosity of gas due to increase rate of interaction

between molecules

Raising temperature of a liquid decreases viscosity


Week 2 Lab Assignment1. Build a basic hydraulic and pneumatic circuit from Week 1

using Automation Studio software in Lab.

Graded Lab Assignment

Week 2 Homework Assignment

In Lab Manual, do for homework grade:

1. Chapter 3 Key Terms Sheets

2. Chapter 3 Quiz

Graded Homework Assignment

2012 02-12 emet135 week 2 presentation

Engineering

Transcript of 2012 02-12 emet135 week 2 presentation