Am Epistonlecture1

AME 436AME 436

Energy and PropulsionEnergy and Propulsion

Paul D. RonneyPaul D. RonneySpring 2006Spring 2006

AME 436AME 436

Energy and PropulsionEnergy and Propulsion

Lecture 1Lecture 1Introduction: engine types, Introduction: engine types,

basic principles, alternatives basic principles, alternatives to IC engines, history of IC to IC engines, history of IC

engines, review of engines, review of thermodynamicsthermodynamics

AME 436 - January 10, 2006AME 436 - January 10, 2006 33

Helpful handy hintsHelpful handy hints

Download lectures from website before Download lectures from website before classclass, print out and bring to class so you , print out and bring to class so you can annotate notescan annotate notes

If you don’t have Powerpoint, you can If you don’t have Powerpoint, you can download a download a free free powerpoint powerpoint viewerviewer from from Microsoft’s websiteMicrosoft’s website

… … but if you don’t have the full Powerpoint but if you don’t have the full Powerpoint and Excel, you won’t be able to open the and Excel, you won’t be able to open the imbedded Excel spreadsheetsimbedded Excel spreadsheets

Please ask questions in classPlease ask questions in class - the goal of - the goal of the lecture is to maintain a 2-way the lecture is to maintain a 2-way “Socratic” dialogue on the subject of the “Socratic” dialogue on the subject of the lecturelecture

Bringing your laptop and wireless cardsBringing your laptop and wireless cards allows you to download files from my allows you to download files from my website as necessarywebsite as necessary


AssignmentAssignment By Tuesday 1/17/06By Tuesday 1/17/06

Email your schedule to me (Email your schedule to me ([email protected]@usc.edu) ) so I can choose office hours (default so I can choose office hours (default value: 9 am - 12 am Thursdays)value: 9 am - 12 am Thursdays)

(Optional) email your picture to me so I (Optional) email your picture to me so I can start to identify youcan start to identify you


Nomenclature (summary for whole course)Nomenclature (summary for whole course)AA Cross-section area (mCross-section area (m22))AA** Throat area (mThroat area (m22))AAee Exit area (mExit area (m22))

ATDCATDC After Top Dead CenterAfter Top Dead CenterBB Transfer number for droplet burning (---)Transfer number for droplet burning (---)BMEPBMEP Brake Mean Effective Pressure (N/mBrake Mean Effective Pressure (N/m22))BSFCBSFC Brake Specific Fuel ConsumptionBrake Specific Fuel ConsumptionBSNOBSNOxx Brake Specific NOBrake Specific NOxx (g/kW-hr or kg/J) (similar definition with CO, UHC (g/kW-hr or kg/J) (similar definition with CO, UHC

emissions)emissions)BTDCBTDC Before Top Dead CenterBefore Top Dead Centercc Sound speed (m/s)Sound speed (m/s)CC Duct circumference (m)Duct circumference (m)CCDD Drag coefficient (---)Drag coefficient (---)

CCff Friction coefficient (---)Friction coefficient (---)

COCO Carbon monoxide (compound having 1 carbon and 1 oxygen atom)Carbon monoxide (compound having 1 carbon and 1 oxygen atom)CMCM Control MassControl MassCCPP Heat capacity at constant pressure (J/kgK)Heat capacity at constant pressure (J/kgK)

CCvv Heat capacity at constant volume (J/kgK)Heat capacity at constant volume (J/kgK)

CVCV Control VolumeControl VolumeDD Mass diffusivity (mMass diffusivity (m22/s)/s)DD Drag force (N)Drag force (N)DORFDORF Degree Of Reaction FreedomDegree Of Reaction FreedomEE Energy contained by a substance = U + KE + PE (J)Energy contained by a substance = U + KE + PE (J)EE Activation Energy (J/mole)Activation Energy (J/mole)ff Fuel mass fraction in mixture (---)Fuel mass fraction in mixture (---)FARFAR Fuel to air mass ratio (---)Fuel to air mass ratio (---)FMEPFMEP Friction Mean Effective Pressure (N/mFriction Mean Effective Pressure (N/m22))


Nomenclature (summary for whole course)Nomenclature (summary for whole course)gg Acceleration of gravity (m/sAcceleration of gravity (m/s22))gg Gibbs function Gibbs function h - Ts (J/kg) h - Ts (J/kg)HH Enthalpy Enthalpy U + PV (J) U + PV (J)hh Enthalpy per unit mass = u + Pv (J/kg)Enthalpy per unit mass = u + Pv (J/kg)hh Heat transfer coefficient (dimensionless value in AirCycles.xls Heat transfer coefficient (dimensionless value in AirCycles.xls

spreadsheets)spreadsheets)HH Heat transfer coefficient (usually W/mHeat transfer coefficient (usually W/m22K, dimensionless in K, dimensionless in

AirCycles.xls files)AirCycles.xls files)Enthalpy of chemical species i per mole = Enthalpy of chemical species i per mole =

(J/mole) (J/mole)Thermal enthalpy of chemical species i per mole (J/mole)Thermal enthalpy of chemical species i per mole (J/mole)

ICEICE Internal Combustion EngineInternal Combustion EngineIMEP IMEP Indicated Mean Effective Pressure (N/mIndicated Mean Effective Pressure (N/m22))ISFCISFC Indicated Specific Fuel ConsumptionIndicated Specific Fuel ConsumptionIISPSP Specific impulse (sec)Specific impulse (sec)

KKii Equlibrium constant of chemical species i (---)Equlibrium constant of chemical species i (---)

kk Thermal conductivity (W/mK)Thermal conductivity (W/mK)kk Reaction rate constant ([moles/mReaction rate constant ([moles/m33]]1-n1-n/sec) (n = order of reaction)/sec) (n = order of reaction)KK Droplet burning rate constant (mDroplet burning rate constant (m22/s)/s)KaKa Karlovitz number Karlovitz number 0.157 Re 0.157 ReLL

-1/2 -1/2 (u(u’’/S/SLL))22

KEKE Kinetic energy (J or J/kg)Kinetic energy (J or J/kg)LL Lift force (N)Lift force (N)LLff Jet flame lengthJet flame length

LLII Integral length scale of turbulence (m)Integral length scale of turbulence (m)

LOMALOMA Law Of Mass ActionLaw Of Mass Action

˜ h i

[ ˜ h (T) ˜ h 298]i ˜ h f ,io

[ ˜ h (T) ˜ h 298]i


Nomenclature (summary for whole course)Nomenclature (summary for whole course)

MMii Molecular weight of chemical species i (kg/mole)Molecular weight of chemical species i (kg/mole)

MM Mach number (---)Mach number (---)mm mass (kg)mass (kg)

Mass flow rate (kg/sec)Mass flow rate (kg/sec)Air mass flow rate (kg/s)Air mass flow rate (kg/s)Fuel mass flow rate (kg/s)Fuel mass flow rate (kg/s)

MEPMEP Mean Effective Pressure (N/mMean Effective Pressure (N/m22))nn Order of reaction (---)Order of reaction (---)nn Parameter in MEP definition (= 1 for 2-stroke engine, = 2 for 4-Parameter in MEP definition (= 1 for 2-stroke engine, = 2 for 4-

stroke)stroke)nnii Number of moles of chemical species iNumber of moles of chemical species i

NN Engine rotational speed (revolutions per second)Engine rotational speed (revolutions per second)NONO Nitric oxide (compound having 1 nitrogen atom and 1 oxygen atom)Nitric oxide (compound having 1 nitrogen atom and 1 oxygen atom)NONOxx Oxides of Nitrogen (any compound having nitrogen and oxygen atoms)Oxides of Nitrogen (any compound having nitrogen and oxygen atoms)

OO33 OzoneOzone

PP Pressure (N/mPressure (N/m22))PPaa Ambient pressure (N/mAmbient pressure (N/m22))

PPee Exit pressure (N/mExit pressure (N/m22))

PPrefref Reference pressure (101325 N/mReference pressure (101325 N/m22))

PPtt Stagnation pressure (N/mStagnation pressure (N/m22))

PEPE Potential Energy (J or J/kg)Potential Energy (J or J/kg)PMEPPMEP Pumping Mean Effective Pressure (N/mPumping Mean Effective Pressure (N/m22))QQ Heat transfer (J or J/kg)Heat transfer (J or J/kg)QdotQdot Heat transfer rate (Watts or Watts/kg)Heat transfer rate (Watts or Watts/kg)QQRR Fuel heating value (J/kg)Fuel heating value (J/kg)

Ý m

Ý m a

Ý m f



RR Gas constant = Gas constant = /M (J/kgK)/M (J/kgK)RR Flight vehicle range (m)Flight vehicle range (m)r or rr or rcc Compression ratio Compression ratio (V (Vcc+V+Vdd)/V)/Vcc (---) (---)

rree Expansion ratio (---)Expansion ratio (---)

ReReLL Reynolds number of turbulence Reynolds number of turbulence u’L u’LII// (---) (---)

Universal gas constant = 8.314 J/moleKUniversal gas constant = 8.314 J/moleKRPMRPM Revolutions Per Minute (1/min)Revolutions Per Minute (1/min)SS Entropy (J/K)Entropy (J/K)ss Entropy per unit mass (J/kgK)Entropy per unit mass (J/kgK)SSLL Laminar burning velocity (m/s)Laminar burning velocity (m/s)

SSTT Turbulent burning velocity (m/s)Turbulent burning velocity (m/s)

STST Specific ThrustSpecific ThrustTT Temperature (K)Temperature (K)TSFCTSFC Thrust Specific Fuel ConsumptionThrust Specific Fuel ConsumptionTTadad Adiabatic Flame Temperature (K)Adiabatic Flame Temperature (K)

TTtt Stagnation temperature (K)Stagnation temperature (K)

TTww Wall temperatureWall temperature

TT∞∞ Ambient Temperature (K)Ambient Temperature (K)

UU Internal energy (J)Internal energy (J)uu Internal energy per unit mass (J/kg)Internal energy per unit mass (J/kg)uuee Exit velocity (m/s)Exit velocity (m/s)

uu11 Flight velocity (m/s)Flight velocity (m/s)

u’u’ Turbulence intensity (m/s)Turbulence intensity (m/s)UHCUHC Unburned hydrocarbonsUnburned hydrocarbons



VV Volume (mVolume (m33))VVcc Clearance volume (mClearance volume (m33))

VVdd Displacment volume (mDisplacment volume (m33))

vv Specific volume = 1/Specific volume = 1/ (m (m33/kg)/kg)VV Velocity (m/s)Velocity (m/s)WW Work transfer (J or J/kg)Work transfer (J or J/kg)WdotWdot Work transfer rate (Watts or Watts/kg)Work transfer rate (Watts or Watts/kg)XXff Mole fraction fuel in mixture (---) Mole fraction fuel in mixture (---)

XXii Mole fraction of chemical species i (---)Mole fraction of chemical species i (---)

YYff Mass fraction of fuel in mixture (---)Mass fraction of fuel in mixture (---)

ZZ Pre-exponential factor in reaction rate expression Pre-exponential factor in reaction rate expression ([moles/m([moles/m33]]1-n1-nKK-a-a/s) (n = order of reaction)/s) (n = order of reaction)

zz Elevation (m)Elevation (m)


Nomenclature (summary for whole course)Nomenclature (summary for whole course)[ ][ ]ii Concentration of species i (moles/mConcentration of species i (moles/m33))

( )’( )’ Property of fan stream (prime superscript)Property of fan stream (prime superscript)( )( )** Property at reference state (M = 1 for all cases considered in this Property at reference state (M = 1 for all cases considered in this

course)course) Thermal diffusivity (mThermal diffusivity (m22/s)/s) Turbofan bypass ratio (ratio of fan to compressor air mass flow rates) (---)Turbofan bypass ratio (ratio of fan to compressor air mass flow rates) (---) Non-dimensional activation energy Non-dimensional activation energy E/ E/T (---)T (---) Cutoff ratio for Diesel cycleCutoff ratio for Diesel cycle Flame thickness (m)Flame thickness (m)

Enthalpy of formation of chemical species i at 298K and 1 atm (J/mole)Enthalpy of formation of chemical species i at 298K and 1 atm (J/mole)Entropy of chemical species i at temperature T and 1 atm (J/mole K)Entropy of chemical species i at temperature T and 1 atm (J/mole K)

Equivalence ratio (---)Equivalence ratio (---) Gas specific heat ratio Gas specific heat ratio C CPP/C/Cvv (---) (---)

Efficiency (thermal efficiency unless otherwise noted)Efficiency (thermal efficiency unless otherwise noted)bb Burner (combustor) efficiency for gas turbine engines (---)Burner (combustor) efficiency for gas turbine engines (---)

cc Compression efficiency for reciprocating engines (---)Compression efficiency for reciprocating engines (---)

cc Compressor efficiency for gas turbine engines (---)Compressor efficiency for gas turbine engines (---)

dd Diffuser efficiency for propulsion engines (---)Diffuser efficiency for propulsion engines (---)

ee Expansion efficiency for reciprocating engines (---)Expansion efficiency for reciprocating engines (---)fanfan Fan efficiency for propulsion engines (---) Fan efficiency for propulsion engines (---) nn Nozzle efficiency for propulsion engines (---)Nozzle efficiency for propulsion engines (---)

oo Overall efficiency (---)Overall efficiency (---)

pp Propulsive efficiency (---)Propulsive efficiency (---)

tt Turbine efficiency for gas turbine engines (---)Turbine efficiency for gas turbine engines (---)

thth Thermal efficiency (---)Thermal efficiency (---)

vv Volumetric efficiency for reciprocating engines (---)Volumetric efficiency for reciprocating engines (---)

˜ h f ,io

˜ s io(T)



Dynamic viscosity (kg/m s)Dynamic viscosity (kg/m s) Stoichiometric coefficient (---)Stoichiometric coefficient (---) Kinematic viscosity Kinematic viscosity // (m (m22/s)/s)ii Stagnation pressure ratio across component i (i = diffuser (d), Stagnation pressure ratio across component i (i = diffuser (d),

compressor (c), burner compressor (c), burner (b), turbine (t), afterburner (ab) (b), turbine (t), afterburner (ab) or nozzle (n)) or nozzle (n))

rr = P= P1t1t/P/P11 (“recovery pressure” ratio) = {1 + [( (“recovery pressure” ratio) = {1 + [(-1)/2]M-1)/2]M22}}/(/(-1)-1) if if = = constantconstant

Density (kg/mDensity (kg/m33)) Torque (N m)Torque (N m) = T= T4t4t/T/T11 (ratio of maximum allowable turbine inlet temperature to (ratio of maximum allowable turbine inlet temperature to

ambient temperature)ambient temperature)rr = T= T1t1t/T/T11 (“recovery temperature” ratio) = 1 + [( (“recovery temperature” ratio) = 1 + [(-1)/2]M-1)/2]M22 if if = constant = constant

Overall chemical reaction rate (1/s)Overall chemical reaction rate (1/s)


Outline of 1st lectureOutline of 1st lecture Introduction to internal combustion enginesIntroduction to internal combustion engines

ClassificationClassification Types of cycles - gas turbine, rocket, Types of cycles - gas turbine, rocket,

reciprocating piston gasoline/dieselreciprocating piston gasoline/diesel Why internal combustion engines? Why not Why internal combustion engines? Why not

something else?something else? History and evolutionHistory and evolution Things you need to understand before…Things you need to understand before…

Engineering scrutinyEngineering scrutiny Review of basic thermodynamicsReview of basic thermodynamics


Classification of ICEsClassification of ICEs

This course focuses on the design and This course focuses on the design and performance characteristics of performance characteristics of internal internal combustion engines (ICEs)combustion engines (ICEs) generally used for generally used for vehicle (car, aircraft, etc.) propulsionvehicle (car, aircraft, etc.) propulsion

Definition of an ICE: a Definition of an ICE: a heat engineheat engine in which in which the heat source is a the heat source is a combustible mixturecombustible mixture that that also serves as the working fluidalso serves as the working fluid

The working fluid in turn is used either toThe working fluid in turn is used either to Produce shaft work by pushing on a piston or Produce shaft work by pushing on a piston or

turbine blade that in turn drives a rotating shaft turbine blade that in turn drives a rotating shaft oror

Creates a high-momentum fluid that is used Creates a high-momentum fluid that is used directly for propulsive forcedirectly for propulsive force

By this definition, ICEs include gas By this definition, ICEs include gas turbines, supersonic propulsion engines, and turbines, supersonic propulsion engines, and chemical rockets (but rockets will not be chemical rockets (but rockets will not be discussed in this class, take ASTE 470; this discussed in this class, take ASTE 470; this course covers only course covers only airbreathingairbreathing ICEs) ICEs)


What is / is not an ICE?What is / is not an ICE?

ISIS Gasoline-fueled Gasoline-fueled reciprocating reciprocating piston enginepiston engine

Diesel-fueled Diesel-fueled reciprocating reciprocating piston enginepiston engine

Gas turbineGas turbine RocketRocket

IS NOTIS NOT Steam power plantSteam power plant Solar power plantSolar power plant Nuclear power Nuclear power plantplant


What is / is not an ICE?What is / is not an ICE?

TurboshaftAll shaft work to drive propeller,

generator, rotor (helicopter)

TurbofanPart shaft, part jet -"ducted propeller"

TurbojetAll jet except for work needed to

drive compressor

Gas TurbineUses compressor and turbine,

not piston-cylinder

RamjetNo compressor or turbine

Use high Mach no. ram effect for compression

Solid fuelFuel and oxidant are premixed

and put inside combustion chamber

Liquid fuelFuel and oxidant are initially separatedand pumped into combustion chamber

RocketCarries both fuel and oxidantJet power only, no shaft work

Steady

Two-strokeOne complete thermodynamic cycle

per revolution of engine

Four-strokeOne complete thermodynamic cycle

per two revolutions of engine

Premixed-chargeFuel and air are mixed before/during compression

Usually ignited with spark after compression

Two-strokeOne complete thermodynamic cycle

per revolution of engine

Four-strokeOne complete thermodynamic cycle

per two revolutions of engine

Non-premixed chargeOnly air is compressed,

fuel is injected into cylinder after compression

Non-steady

Internal Combustion Engines


Basic gas turbine cycleBasic gas turbine cycle


TurbofanTurbofan


Solid / liquid rocketsSolid / liquid rockets

SolidSolid LiquidLiquid


Reciprocating piston engines Reciprocating piston engines (gasoline/diesel)(gasoline/diesel)

http://www.howstuffworks.com


Premixed vs. non-premixed charge enginesPremixed vs. non-premixed charge engines

Flame front Fuel spray flame

Premixed charge (gasoline)

Non-premixed charge (Diesel)

Spark plug Fuel injector

Fuel + air mixture Air only


Largest internal combustion engineLargest internal combustion engine Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel (application: Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel (application:

large container ships)large container ships) Cylinder bore 38”, stroke 98”; 14 cylinder version: weight 2300 tonsCylinder bore 38”, stroke 98”; 14 cylinder version: weight 2300 tons; ;

length 89 feet; height 44 feet; max. power 108,920 hp @ 102 rpm; max. length 89 feet; height 44 feet; max. power 108,920 hp @ 102 rpm; max. torque 5,608,312 ft-lbf @ 102rpm; BMEP 18.5 atm - about righttorque 5,608,312 ft-lbf @ 102rpm; BMEP 18.5 atm - about right


Smallest internal combustion engineSmallest internal combustion engine Application: Application: model airplanesmodel airplanes

Weight: Weight: 0.49 oz.0.49 oz.Bore: Bore: 0.237” = 6.02 mm0.237” = 6.02 mmStroke: Stroke: 0.226” = 5.74 mm0.226” = 5.74 mmDisplacement: Displacement: 0.00997 in0.00997 in33

(0.163 cm(0.163 cm33))RPM: RPM: 30,00030,000Power:Power: 3 watts3 wattsIgnition: Glow plugBMEP: 0.36 atm (low!)

Typical fuel: castor oil (10 - 20%), nitromethane (0 - 50%), balance methanol

Poor performancePoor performance Low efficiency (< 5%)Low efficiency (< 5%) Emissions & noise unacceptable for indoor Emissions & noise unacceptable for indoor

applicationsapplications


Why internal combustion engines?Why internal combustion engines?

Alternatives - external combustion - "steam engine," Alternatives - external combustion - "steam engine," "Stirling cycle”"Stirling cycle”

Heat transfer, gasoline engineHeat transfer, gasoline engine Heat transfer per unit area (q/A) = k(dT/dx)Heat transfer per unit area (q/A) = k(dT/dx) Turbulent mixture inside engine: Turbulent mixture inside engine:

k ≈ 100 kk ≈ 100 kno turbulenceno turbulence ≈ 2.5 W/mK ≈ 2.5 W/mK dT/dx ≈ dT/dx ≈ T/T/x ≈ 1500K / 0.02 mx ≈ 1500K / 0.02 m q/A ≈ q/A ≈ 187,500 W/m187,500 W/m22

Combustion: q/A = Combustion: q/A = YYffQQRRSSTT = (10 kg/m = (10 kg/m33) x 0.067 x (4.5 ) x 0.067 x (4.5 x 10x 1077 J/kg) x 2 m/s = J/kg) x 2 m/s = 60.3 x 1060.3 x 1066 W/m W/m22 - - 321x higher!321x higher!

CONCLUSION: HEAT TRANSFER IS TOO SLOW!!!CONCLUSION: HEAT TRANSFER IS TOO SLOW!!! That’s why 10 Boeing 747 engines ≈ large (1 That’s why 10 Boeing 747 engines ≈ large (1

gigawatt) coal-fueled electric power plantgigawatt) coal-fueled electric power plant

k = gas thermal conductivity, T = temperature, x = k = gas thermal conductivity, T = temperature, x = distance,distance,

= density, Y= density, Yff = fuel mass fraction, Q = fuel mass fraction, QRR = fuel heating = fuel heating value, value, SSTT = turbulent flame speed in engine = turbulent flame speed in engine


Why internal combustion engines?Why internal combustion engines? Alternatives - electric vehiclesAlternatives - electric vehicles

Why not generate electricity in a large central Why not generate electricity in a large central power plant (power plant ( ≈ 40%), distribute to charge ≈ 40%), distribute to charge batteries to power electric motors (batteries to power electric motors ( ≈ 80%)? ≈ 80%)?

Car battery, lead acid: 100 amp-hours, 12 volts, Car battery, lead acid: 100 amp-hours, 12 volts, 20 kg; energy/mass = 100 A * 12 V * 3600 sec / 20 20 kg; energy/mass = 100 A * 12 V * 3600 sec / 20 kg = kg = 2 x 102 x 1055 J/kg J/kg

Gasoline (and other hydrocarbons): Gasoline (and other hydrocarbons): 4.5 x 104.5 x 1077 J/kg J/kg Batteries are heavy ≈ 1000 lbs/gal of gasoline Batteries are heavy ≈ 1000 lbs/gal of gasoline

equivalentequivalent Fuel cell systems better, but still nowhere near Fuel cell systems better, but still nowhere near

gasolinegasoline "Zero emissions" myth - EVs "Zero emissions" myth - EVs exportexport pollution pollution Environmental cost of battery materialsEnvironmental cost of battery materials Possible advantage: makes smaller, lighter, more Possible advantage: makes smaller, lighter, more

streamlined cars acceptable to consumersstreamlined cars acceptable to consumers Prediction: eventual conversion of electric Prediction: eventual conversion of electric

vehicles to gasoline power (>100 miles per gallon)vehicles to gasoline power (>100 miles per gallon)


““Zero emission” electric vehiclesZero emission” electric vehicles


Why internal combustion engines?Why internal combustion engines? Alternatives - solarAlternatives - solar

Arizona, high noon, mid summer: solar flux ≈ 1000 Arizona, high noon, mid summer: solar flux ≈ 1000 W/mW/m22

Gasoline engine, 20 mi/gal, 60 mi/hr, thermal power Gasoline engine, 20 mi/gal, 60 mi/hr, thermal power = (60 mi/hr / 20 mi/gal) x (6 lb/gal) x (kg / 2.2 = (60 mi/hr / 20 mi/gal) x (6 lb/gal) x (kg / 2.2 lb) x (4.5 x 10lb) x (4.5 x 1077 J/kg) x (hr / 3600 sec) = 102 kW J/kg) x (hr / 3600 sec) = 102 kW

Need ≈ 100 mNeed ≈ 100 m22 collector ≈ 32 ft x 32 ft - lots of collector ≈ 32 ft x 32 ft - lots of air drag, what about underpasses, nighttime, bad air drag, what about underpasses, nighttime, bad weather, northern/southern latitudes, etc.?weather, northern/southern latitudes, etc.?


Why internal combustion engines?Why internal combustion engines? Alternatives - nuclearAlternatives - nuclear

Who are we kidding ???Who are we kidding ??? Higher energy density thoughHigher energy density though

»UU235235 fission: 3.2 x 10 fission: 3.2 x 10-11-11J/atom * (6.02 x 10J/atom * (6.02 x 102323 atom / atom / 0.235 kg)0.235 kg) = = 8.2 x 108.2 x 101313 J/kg ≈ 2 million x hydrocarbons! J/kg ≈ 2 million x hydrocarbons!»Radioactive decay much less, but still much higher Radioactive decay much less, but still much higher

thanthanhydrocarbon fuelhydrocarbon fuel

Moral - hard to beat liquid-fueled internal Moral - hard to beat liquid-fueled internal combustion engines forcombustion engines for Power/weight & power/volume of enginePower/weight & power/volume of engine Energy/weight & energy/volume of liquid Energy/weight & energy/volume of liquid hydrocarbon fuelshydrocarbon fuels

Distribution & handling convenience of liquids Distribution & handling convenience of liquids Conclusion: IC engines are the worst form of Conclusion: IC engines are the worst form of

vehicle propulsion, except for all the other vehicle propulsion, except for all the other formsforms


History of automotive enginesHistory of automotive engines

1859 - Oil discovered in Pennsylvania1859 - Oil discovered in Pennsylvania 1876 - Premixed-charge 4-stroke engine - 1876 - Premixed-charge 4-stroke engine - OttoOtto 1st practical IC engine1st practical IC engine Power: 2 hp; Weight: 1250 poundsPower: 2 hp; Weight: 1250 pounds Comp. ratio = 4 (knock limited), 14% Comp. ratio = 4 (knock limited), 14%

efficiency (theory 38%)efficiency (theory 38%) Today CR = 8 (still knock limited), 30% Today CR = 8 (still knock limited), 30%

efficiency (theory 52%)efficiency (theory 52%) 1897 - Nonpremixed-charge engine - Diesel - 1897 - Nonpremixed-charge engine - Diesel - higher efficiency due tohigher efficiency due to Higher compression ratio (no knock problem)Higher compression ratio (no knock problem) No throttling loss - use fuel/air ratio to No throttling loss - use fuel/air ratio to

control powercontrol power


History and evolutionHistory and evolution 1923 - Tetraethyl lead - anti-knock 1923 - Tetraethyl lead - anti-knock additiveadditive Enable higher CR in Otto-type enginesEnable higher CR in Otto-type engines

1952 - A. J. Haagen-Smit1952 - A. J. Haagen-Smit NO + UHC + ONO + UHC + O22 + sunlight + sunlight

NONO22 + O + O33

(from exhaust) (from exhaust) (brown) (irritating) (brown) (irritating)

UHC = unburned hydrocarbonsUHC = unburned hydrocarbons 1960s - Emissions regulations1960s - Emissions regulations

Detroit won’t believe itDetroit won’t believe it Initial stop-gap measures - lean mixture, Initial stop-gap measures - lean mixture,

EGR, retard sparkEGR, retard spark Poor performance & fuel economyPoor performance & fuel economy

1973 & 1979 - The energy crises1973 & 1979 - The energy crises Detroit takes a bathDetroit takes a bath


History and evolutionHistory and evolution 1975 - Catalytic converters, unleaded fuel1975 - Catalytic converters, unleaded fuel

Detroit forced to buy technologyDetroit forced to buy technology More “aromatics” (e.g., benzene) in gasoline - high More “aromatics” (e.g., benzene) in gasoline - high

octane but carcinogenic, soot-producingoctane but carcinogenic, soot-producing 1980s - Microcomputer control of engines1980s - Microcomputer control of engines

Tailor operation for best emissions, efficiency, ...Tailor operation for best emissions, efficiency, ... 1990s - Reformulated gasoline1990s - Reformulated gasoline

Reduced need for aromatics, cleaner(?)Reduced need for aromatics, cleaner(?) ... but higher cost, lower miles per gallon... but higher cost, lower miles per gallon Now we find MTBE pollutes groundwater!!!Now we find MTBE pollutes groundwater!!! Alternative “oxygenated” fuel additive - ethanol - Alternative “oxygenated” fuel additive - ethanol -

very attractive to powerful senators from farm very attractive to powerful senators from farm statesstates

2000’s - hybrid vehicles2000’s - hybrid vehicles Use small gasoline engine operating at maximum power Use small gasoline engine operating at maximum power

(most efficient way to operate) or turned off if not (most efficient way to operate) or turned off if not neededneeded

Use generator/batteries/motors to make/store/use Use generator/batteries/motors to make/store/use surplus power from gasoline enginesurplus power from gasoline engine

More efficient, but much more equipment on board - More efficient, but much more equipment on board - not clear if fuel savings justify extra cost not clear if fuel savings justify extra cost


Things you need to understand before ...Things you need to understand before ...

……you invent the zero-emission, 100 mpg 1000 hp you invent the zero-emission, 100 mpg 1000 hp engine, revolutionize the automotive engine, revolutionize the automotive industry and shop for your retirement home industry and shop for your retirement home on the French Rivieraon the French Riviera

Room for improvement - factor of 2 in Room for improvement - factor of 2 in efficiencyefficiency Ideal Otto cycle engine with CR = 8: 52%Ideal Otto cycle engine with CR = 8: 52% Real engine: 25 - 30%Real engine: 25 - 30% Differences because ofDifferences because of

»Throttling losses Throttling losses »Heat lossesHeat losses»Friction lossesFriction losses»Slow burningSlow burning»Incomplete combustion is a very minor effectIncomplete combustion is a very minor effect



Room for improvement - infinite in Room for improvement - infinite in pollutantspollutants Pollutants are a Pollutants are a non-equilibriumnon-equilibrium effect effect

»Burn: Fuel + OBurn: Fuel + O22 + N + N22 H H22O + COO + CO22 + N + N22 + CO + + CO + UHC + NOUHC + NO

OK OK OK Bad OK OK OK Bad Bad Bad Bad Bad»Expand: CO + UHC + NO “frozen” at high Expand: CO + UHC + NO “frozen” at high

levelslevels»With slow expansion, no heat loss:With slow expansion, no heat loss:

CO + UHC + NO CO + UHC + NO H H22O + COO + CO22 + N + N22

...but how to slow the expansion and eliminate ...but how to slow the expansion and eliminate heat loss?heat loss?

Worst problems: cold start, transients, old Worst problems: cold start, transients, old or out-of-tune vehicles - 90% of pollution or out-of-tune vehicles - 90% of pollution generated by 10% of vehiclesgenerated by 10% of vehicles



Room for improvement - very little in powerRoom for improvement - very little in power IC engines are air processorsIC engines are air processors

»Fuel takes up little spaceFuel takes up little space»Air flow = powerAir flow = power»Limitation on air flow due toLimitation on air flow due to

•““Choked” flow past intake valvesChoked” flow past intake valves•Friction loss, mechanical strength - limits RPMFriction loss, mechanical strength - limits RPM•Slow burnSlow burn

Majority of power is used to overcome air Majority of power is used to overcome air resistanceresistance - smaller, more aerodynamic - smaller, more aerodynamic vehicles beneficialvehicles beneficial


““Engineering scrutiny” 1. Smoke testEngineering scrutiny” 1. Smoke test

Equivalent in building electronics: turn the Equivalent in building electronics: turn the power switch on and see if it smokespower switch on and see if it smokes

For analysis: For analysis: check the unitscheck the units - this will catch - this will catch 90% of your mistakes 90% of your mistakes

Example: I just derived the ideal gas law as Pv Example: I just derived the ideal gas law as Pv = R/T, obviously units are wrong= R/T, obviously units are wrong

Other rulesOther rules Anything inside a square root, cube root, etc. Anything inside a square root, cube root, etc.

must have units that is a square (e.g. mmust have units that is a square (e.g. m22/sec/sec22) or ) or cube, etc.cube, etc.

Anything inside a log, exponent, trigonometric Anything inside a log, exponent, trigonometric function, etc., must be dimensionlessfunction, etc., must be dimensionless

Any two quantities that are added together must Any two quantities that are added together must have the same unitshave the same units


““Engineering scrutiny” 2. Function testEngineering scrutiny” 2. Function test

Equivalent in building electronics: does the Equivalent in building electronics: does the device do what it was designed it to do, e.g. the device do what it was designed it to do, e.g. the red light blinks when I flip switch on, the bell red light blinks when I flip switch on, the bell rings when I push the button, etc.rings when I push the button, etc.

For analysis: does the result gives sensible For analysis: does the result gives sensible predictions?predictions?

Determine if sign (+ or -) of result is Determine if sign (+ or -) of result is reasonable, e.g. if predicted absolute temperature reasonable, e.g. if predicted absolute temperature is –72 K, obviously it’s wrongis –72 K, obviously it’s wrong

Determine whether what happens to y as x goes up Determine whether what happens to y as x goes up or down is reasonable or not. For example, in the or down is reasonable or not. For example, in the ideal gas law, Pv = RT:ideal gas law, Pv = RT: At fixed v, as T increases then P increases At fixed v, as T increases then P increases – reasonable– reasonable

At fixed T, as v increases then P decreases At fixed T, as v increases then P decreases – reasonable– reasonable

Etc.Etc.


““Engineering scrutiny” 2. Function testEngineering scrutiny” 2. Function test

Determine what happens in the limit where x goes Determine what happens in the limit where x goes to special values, e.g. 0, 1, ∞ as appropriateto special values, e.g. 0, 1, ∞ as appropriate

Example: entropy change (SExample: entropy change (S22 - S - S11) of an ideal gas) of an ideal gas

For TFor T22 = T = T11 and P and P22 = P = P11 (no change in state) then S (no change in state) then S22 – S– S11 = 0 or S = 0 or S22 = S = S11

Limit of SLimit of S22 = S = S11, the allowable changes in state , the allowable changes in state areare

which is the isentropic relation for ideal gas with which is the isentropic relation for ideal gas with constant specific heatsconstant specific heats

S2 S1 CP lnT2

T1

R ln

P2

P1

T2

T1

P2

P1

RCP

P2

P1

1


““Engineering scrutiny” 3. Performance testEngineering scrutiny” 3. Performance test

Equivalent in building electronics: how Equivalent in building electronics: how fast, how accurate, etc. is the devicefast, how accurate, etc. is the device

For analysis: how accurate is the result?For analysis: how accurate is the result? Need to compare result to something else, Need to compare result to something else, e.g. a “careful” experiment, more e.g. a “careful” experiment, more sophisticated analysis, trusted published sophisticated analysis, trusted published result, etc.result, etc.

Example, I derived the ideal gas law and Example, I derived the ideal gas law and predicted Pv = 7RT - passes smoke and predicted Pv = 7RT - passes smoke and function tests, but fails the performance function tests, but fails the performance test miserably (by a factor of 7)test miserably (by a factor of 7)


Review of thermodynamics (1)Review of thermodynamics (1)

Almost everything we do in this course will Almost everything we do in this course will be analyzed withbe analyzed with 1st Law of Thermodynamics (conservation 1st Law of Thermodynamics (conservation of energy) - “you can’t win”)of energy) - “you can’t win”)

2nd Law of Thermodynamics - “you can’t 2nd Law of Thermodynamics - “you can’t break even”)break even”)

Equation of state (usually ideal gas law) Equation of state (usually ideal gas law) - “you can’t even choose your poison”- “you can’t even choose your poison”

Conservation of massConservation of mass Conservation of momentumConservation of momentum


Review of thermodynamics (2)Review of thermodynamics (2)

1st Law of Thermodynamics 1st Law of Thermodynamics for a control massfor a control mass, , i.e. a fixed mass of material (but generally i.e. a fixed mass of material (but generally changing volume)changing volume)

dE = dE = Q - Q - WW E = energy contained by the mass - a E = energy contained by the mass - a propertyproperty of the of the

massmassQ = heat transfer Q = heat transfer to the massto the massW = work transfer W = work transfer to or from the mass (see below)to or from the mass (see below) Control mass form useful for fixed mass, e.g. gas Control mass form useful for fixed mass, e.g. gas

in a piston/cylinderin a piston/cylinder Each term has units of Each term has units of JoulesJoules Work transfer is generally defined as positive if Work transfer is generally defined as positive if

out of the control mass, in which case - sign out of the control mass, in which case - sign applies, i.e. applies, i.e. dE = dE = Q - Q - WW; If work is defined as ; If work is defined as positive into system then positive into system then dE = dE = Q + Q + WW

Heat and work are NOT properties of the mass, they Heat and work are NOT properties of the mass, they are are energy transfersenergy transfers to/from the mass; a mass does to/from the mass; a mass does notnot contain heat or work but it does contain contain heat or work but it does contain energy (E)energy (E)


Review of thermo (2) - heat & workReview of thermo (2) - heat & work

Heat and work transfer depend on the path, but the Heat and work transfer depend on the path, but the internal energy of a substance at a given state internal energy of a substance at a given state doesn’t depend on how you got to that state; for doesn’t depend on how you got to that state; for example, simple compressible substances exchange example, simple compressible substances exchange work with their surroundings according to work with their surroundings according to W = + W = + PdV (+ if work is defined as positive out of PdV (+ if work is defined as positive out of control mass)control mass)

For example in the figure below, paths A & B have For example in the figure below, paths A & B have different ∫ PdV and thus different work transfers, different ∫ PdV and thus different work transfers, even though the initial state 1 and final state 2 even though the initial state 1 and final state 2 are the same for bothare the same for bothP

V

1

2A

B


Review of thermo (3) - heat & workReview of thermo (3) - heat & work

What is the difference between heat and work? Why do What is the difference between heat and work? Why do we need to consider them separately?we need to consider them separately? Heat transfer is Heat transfer is disorganized disorganized energy transfer on the energy transfer on the

microscopic (molecular) scalemicroscopic (molecular) scale and has and has entropy transfer entropy transfer associated with itassociated with it

Work transfer is Work transfer is organized organized energy transfer which may be energy transfer which may be at either the microscopic scale or macroscopic scale and at either the microscopic scale or macroscopic scale and has has no entropy transferno entropy transfer associated with it associated with it

The energy of the substance (E) consists of The energy of the substance (E) consists of Macroscopic kinetic energy (KE = 1/2 mMacroscopic kinetic energy (KE = 1/2 mvv22)) Macroscopic potential energy (PE = mgz)Macroscopic potential energy (PE = mgz) Microscopic internal energy (U) (which consists of both Microscopic internal energy (U) (which consists of both

kinetic (thermal) and potential (chemical bonding) kinetic (thermal) and potential (chemical bonding) energy, but we lump them together since we can’t see it energy, but we lump them together since we can’t see it them separately, only their effect at macroscopic scalesthem separately, only their effect at macroscopic scales

If PE is due to elevation change (z) and work transfer If PE is due to elevation change (z) and work transfer is only PdV work, then the first law can be written asis only PdV work, then the first law can be written as

dU + mdU + mVVddVV + mgdz = + mgdz = Q - PdVQ - PdVVV = velocity, V = volume, m = mass, g = = velocity, V = volume, m = mass, g =

gravitygravity


Review of thermo (4) - types of energyReview of thermo (4) - types of energy

Potential energy (PE)

Kinetic energy (KE)

Macroscopic

Microscopic (U)Lump KE and PE together

Energy contained by a substance (E)

Heat transfer (Q)Disorganized

Has associated entropy transferMicroscopic only

Work transfer (W)Organized

Has NO associated entropy transferMicroscopic or macroscopic

Energy transfers to/from a substance

Energy


Review of thermo (5) - 1st law for CVReview of thermo (5) - 1st law for CV

1st Law of Thermodynamics 1st Law of Thermodynamics for a control volumefor a control volume, a fixed , a fixed volume in space that may have mass flowing in or out volume in space that may have mass flowing in or out (opposite of control mass, which has fixed mass but (opposite of control mass, which has fixed mass but possibly changing volume):possibly changing volume):

E = energy within control volume = U + KE + PE as beforeE = energy within control volume = U + KE + PE as before Qdot, Wdot = rates of heat & work transfer in or out Qdot, Wdot = rates of heat & work transfer in or out

(Watts)(Watts) Subscript “in” refers to conditions at inlet(s) of mass, Subscript “in” refers to conditions at inlet(s) of mass,

“out” to outlet(s) of mass“out” to outlet(s) of mass mdot = mass flow rate in or out of the control volumemdot = mass flow rate in or out of the control volume h h u + Pv = enthalpy u + Pv = enthalpy Note h, u & v are lower case, i.e. per unit mass; h = H/M, Note h, u & v are lower case, i.e. per unit mass; h = H/M,

u = U/M, V = v/M, etc.; upper case means total for all the u = U/M, V = v/M, etc.; upper case means total for all the mass (not per unit mass)mass (not per unit mass)

vv = velocity, thus = velocity, thus vv22/2 is the KE term/2 is the KE term g = acceleration of gravity, z = elevation at inlet or g = acceleration of gravity, z = elevation at inlet or

outlet, thus gz is the PE termoutlet, thus gz is the PE term Control volume form useful for fixed volume device, Control volume form useful for fixed volume device,

e.g. gas turbinee.g. gas turbine Most commonly written as a rate equation (as above)Most commonly written as a rate equation (as above)

)2()2(22

outout

outoutinin

inin gzvhmgzvhmWQdt

dE


Review of thermo (6) - 1st law for CVReview of thermo (6) - 1st law for CV Note that the Control Volume (CV) form of the 1st Note that the Control Volume (CV) form of the 1st

Law looks almost the same as the Control Mass (CM) Law looks almost the same as the Control Mass (CM) form with the addition of mdot*(h+form with the addition of mdot*(h+vv22/2+gz) terms /2+gz) terms that represent the flux of energy in/out of the CV that represent the flux of energy in/out of the CV that is carried with the mass flowing in/out of the that is carried with the mass flowing in/out of the CVCV

The only difference between the CV and CM forms that The only difference between the CV and CM forms that isn’t “obvious” is the replacement of u (internal isn’t “obvious” is the replacement of u (internal energy) with h = u + Pvenergy) with h = u + Pv

Where did the extra Pv terms come from? The Where did the extra Pv terms come from? The flow flow workwork needed to push mass into the CV or that you get needed to push mass into the CV or that you get back when mass leaves the CVback when mass leaves the CV


Review of thermo (7) - steady flowReview of thermo (7) - steady flow If the system is steady then If the system is steady then by definitionby definition

d[ ]/dt = 0 for all [d[ ]/dt = 0 for all [propertiesproperties], i.e. E], i.e. ECVCV, M, MCVCV, h, , h, v, zv, z

All All fluxesfluxes, i.e. Qdot, Wdot, mdot are constant , i.e. Qdot, Wdot, mdot are constant (not necessarily zero)(not necessarily zero)

Sum of mass flows in = sum of all mass flows out Sum of mass flows in = sum of all mass flows out (or mdot(or mdotinin = mdot = mdotoutout for a single-inlet, single- for a single-inlet, single-outlet system (if we didn’t have this condition outlet system (if we didn’t have this condition then the mass of the system, which is a property then the mass of the system, which is a property of the system, would not be constant)of the system, would not be constant)

In this case (In this case (steady-state, steady flowsteady-state, steady flow) the 1st ) the 1st Law for a CV isLaw for a CV is

0 Ý Q Ý W Ý m (hin hout ) v in2

2 vout2

2

(gzin gzout )


Review of thermo (8) - conservation of massReview of thermo (8) - conservation of mass

For a control massFor a control massm = mass of control mass = constant (wasn’t that m = mass of control mass = constant (wasn’t that easy?)easy?)

For a control volumeFor a control volume

(what accumulates = what goes in - what goes (what accumulates = what goes in - what goes out)out)

dmCV

dt Ý m i

all inlets

Ý m jall outlets


Review of thermodynamics (9) - 2nd lawReview of thermodynamics (9) - 2nd law

The 2nd Law of Thermdynamics statesThe 2nd Law of Thermdynamics statesThe entropy (S) of an isolated system always The entropy (S) of an isolated system always

increases or remains the sameincreases or remains the same By combining By combining

2nd law2nd law 1st Law1st Law State postulate - for a system of fixed chemical State postulate - for a system of fixed chemical

composition, 2 independent properties completely specify composition, 2 independent properties completely specify the state of the systemthe state of the system

The principle that entropy is a property of the system, The principle that entropy is a property of the system, so is additiveso is additive

“ “it can be shown” that it can be shown” that Tds = du + PdvTds = du + PdvTds = dh - vdPTds = dh - vdPThese are called the These are called the Gibbs equationsGibbs equations, which relate , which relate entropy to other thermodynamic properties (e.g. u, P, entropy to other thermodynamic properties (e.g. u, P, v, h, T)v, h, T)


Review of thermodynamics (10) - 2nd lawReview of thermodynamics (10) - 2nd law

From the Gibbs equations, “it can be shown” for a control From the Gibbs equations, “it can be shown” for a control massmass

= sign applies for a reversible (idealized; best possible) process= sign applies for a reversible (idealized; best possible) process> applies if irreversible (reality)> applies if irreversible (reality)T is the temperature on the control mass at the location where the T is the temperature on the control mass at the location where the

heat is transferred to/from the CMheat is transferred to/from the CM And for a control volumeAnd for a control volume

SSCVCV is the entropy of the control volume; if steady, dS is the entropy of the control volume; if steady, dSCVCV/dt = /dt = 00

These equations are the primary way we apply the 2nd law to These equations are the primary way we apply the 2nd law to the energy conversion systems discussed in this classthe energy conversion systems discussed in this class

Work doesn’t appear anywhere near the 2nd law - why? Work doesn’t appear anywhere near the 2nd law - why? Because there is NO entropy transfer associated with work Because there is NO entropy transfer associated with work transfer, whereas there IS entropy transfer associated with transfer, whereas there IS entropy transfer associated with heat transferheat transfer

dS Q

T

T

Qsmsm

dt

dSoutoutinin

CV


Review of thermo (11) - equations of stateReview of thermo (11) - equations of state

We’ll only consider 2 equations of state in this We’ll only consider 2 equations of state in this coursecourse Ideal gas - Ideal gas - P = P = RTRT (P = pressure, (P = pressure, = 1/v = density, T = 1/v = density, T

= temperature (absolute), R = gas constant = = temperature (absolute), R = gas constant = /M/Mmixmix, , = universal gas constant (8.314 J/mole-K), M= universal gas constant (8.314 J/mole-K), Mmixmix = = molecular weight of gas mixture)molecular weight of gas mixture)

Incompressible fluid - Incompressible fluid - = constant = constant Definition of specific heats (any substance)Definition of specific heats (any substance)

For ideal gases - h = h(T) and u = u(T) only (h and For ideal gases - h = h(T) and u = u(T) only (h and u depend only on temperature, not pressure, volume, u depend only on temperature, not pressure, volume, etc.), thus etc.), thus for ideal gasesfor ideal gases

From dh = CFrom dh = CPPdT, du = CdT, du = CvvdT, the Gibbs equations and dT, the Gibbs equations and P P = = RT RT we can show that (we can show that (again for an ideal gas onlyagain for an ideal gas only))

CP h

T

P

;CV u

T

V

; CP

CV

CP CV R

CP dh

dT;CV

du

dT;h u Pv u RT;

dh

dT

du

dT R

S2 S1 CP lnT2

T1

R ln

P2

P1

CV ln

T2

T1

R ln

V2

V1

CV ln

P2

P1

CP ln

V2

V1


Review of thermo (12) - isentropic relationsReview of thermo (12) - isentropic relations

Recall from the 2nd Law, Recall from the 2nd Law, dS ≥ dS ≥ Q/TQ/T If a process is reversible If a process is reversible dS = dS = Q/TQ/T, and if , and if

furthermore the process is adiabatic furthermore the process is adiabatic Q = 0 thus Q = 0 thus dS = dS = 00 or or SS22 - S - S11 = 0 = 0 ( (isentropic processisentropic process) then the ) then the previous relations for Sprevious relations for S22 - S - S11 can be written as can be written as

Isentropic processes are our favorite model for Isentropic processes are our favorite model for compression and expansion in enginescompression and expansion in engines

But remember these relations are valid But remember these relations are valid onlyonly for for Ideal gasIdeal gas Constant specific heats (CConstant specific heats (CPP, C, CVV) (note that since for an ) (note that since for an

ideal gas Cideal gas CPP = C = Cvv + R and R is a constant, if C + R and R is a constant, if CPP is is constant then Cconstant then Cvv is also and vice versa) is also and vice versa)

Reversible adiabatic (thus isentropic) processReversible adiabatic (thus isentropic) process(Still very useful despite all these restrictions…)(Still very useful despite all these restrictions…)

T2

T1

P2

P1

1

; T2

T1

v1

v2

1

; P2

P1

v1

v2

Am Epistonlecture1

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