energy consumption & power requirements of a vehicle
TRANSCRIPT
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Energy Consumption & Power Requirements of A Vehicle
P M V SubbaraoProfessor
Mechanical Engineering Department
Know the Requirements Before You develop an Engine…..
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Resistance Force : Ra
• The major components of the resisting forces to motion are comprised of :
• Aerodynamic loads (Faero) • Acceleration forces (Faccel = ma & I forces)• Gradeability requirements (Fgrade)• Chassis losses (Froll resist ).
grraero FFFmaF
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Aerodynamic Force : Flow Past A Bluff Body
Composed of:1. Turbulent air flow around vehicle body (85%)2. Friction of air over vehicle body (12%)3. Vehicle component resistance, from radiators and air
vents (3%)
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Aerodynamic Resistance on Vehicle
2
21 VPd
(Re)21 2 fAVFd
ACVF dd2
21
20, )()2.1(
21 VVACF ddesignd
VF = P designd ,
Dynamic Pressure:
Drag Force:
Aero Power
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Cd =
coefficient of drag
=
air density 1.2 kg/m3
A =
projected frontal area (m2)
f(Re)
= Reynolds number
v =
vehicle velocity (m/sec)
V0 =
head wind velocity)(862 0
2VV V A C )10 .(1 = P d-6
aero
P
= power (kw)
A = area (m2)V
= velocity (KpH)
V0 = headwind velocityCd
= drag coefficient
= 1.2 kg/m3
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Purpose, Shape & Drag
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Shape & Components of Drag
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Some examples of Cd:
• The typical modern automobile achieves a drag coefficient of between 0.30 and 0.35.
• SUVs, with their flatter shapes, typically achieve a Cd of 0.35–0.45. • Notably, certain cars can achieve figures of 0.25-0.30, although sometimes
designers deliberately increase drag in order to reduce lift.• 0.7 to 1.1 - typical values for a Formula 1 car (downforce settings change for
each circuit) • 0.7 - Caterham Seven • at least 0.6 - a typical truck • 0.57 - Hummer H2, 2003 • 0.51 - Citroën 2CV • over 0.5 - Dodge Viper • 0.44 - Toyota Truck, 1990-1995
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• 0.42 - Lamborghini Countach, 1974 • 0.42 - Triumph Spitfire Mk IV, 1971-1980 • 0.42 - Plymouth Duster, 1994 • 0.39 - Dodge Durango, 2004 • 0.39 - Triumph Spitfire, 1964-1970 • 0.38 - Volkswagen Beetle • 0.38 - Mazda Miata, 1989 • 0.374 - Ford Capri Mk III, 1978-1986 • 0.372 - Ferrari F50, 1996 • 0.36 - Eagle Talon, mid-1990s • 0.36 - Citroën DS, 1955 • 0.36 - Ferrari Testarossa, 1986 • 0.36 - Opel GT, 1969 • 0.36 - Honda Civic, 2001 • 0.36 - Citroën CX, 1974 (the car was named after the term for drag
coefficient) • 0.355 - NSU Ro 80, 1967
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• 0.34 - Ford Sierra, 1982 • 0.34 - Ferrari F40, 1987 • 0.34 - Chevrolet Caprice, 1994-1996 • 0.34 - Chevrolet Corvette Z06, 2006 • 0.338 - Chevrolet Camaro, 1995 • 0.33 - Dodge Charger, 2006 • 0.33 - Audi A3, 2006 • 0.33 - Subaru Impreza WRX STi, 2004 • 0.33 - Mazda RX-7 FC3C, 1987-91 • 0.33 - Citroen SM, 1970 • 0.32064 - Volkswagen GTI Mk V, 2006 (0.3216 with ground effects) • 0.32 - Toyota Celica,1995-2005 • 0.31 - Citroën AX, 1986 • 0.31 - Citroën GS, 1970 • 0.31 - Eagle Vision • 0.31 - Ford Falcon, 1995-1998 • 0.31 - Mazda RX-7 FC3S, 1986-91 • 0.31 - Renault 25, 1984 • 0.31 - Saab Sonett III, 1970 • 0.30 - Audi 100, 1983 • 0.30 - BMW E90, 2006 • 0.30 - Porsche 996, 1997 • 0.30 - Saab 92, 1947
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• 0.195 - General Motors EV1, 1996 • 0.19 - Alfa Romeo BAT Concept, 1953 • 0.19 - Dodge Intrepid ESX Concept , 1995 • 0.19 - Mercedes-Benz "Bionic Car" Concept, 2005 ([2]
mercedes_bionic.htm) (based on the boxfish) • 0.16 - Daihatsu UFEIII Concept, 2005 • 0.16 - General Motors Precept Concept, 2000 • 0.14 - Fiat Turbina Concept, 1954 • 0.137 - Ford Probe V prototype, 1985
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Rolling Resistance
Composed primarily of 1. Resistance from tire deformation (90%)2. Tire penetration and surface compression ( 4%)3. Tire slippage and air circulation around wheel ( 6%)4. Wide range of factors affect total rolling resistance5. Simplifying approximation:
WCF rrrr
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ROLLING RESISTANCE
V M C )10 (2.72 = P
V M C 36009.81 = P
rr3-
rr
rrrr
where:
P
= power (kW)
Crr
= coefficient of rolling resistance
M
= mass (kg)
V
= velocity (KpH)
Rolling resistance of a body is proportional to the weight ofthe body normal to surface of travel.
MgFrr
147101.0 VCrr
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Contact Type Crr
Steel wheel on rail 0.0002...0.0010
Car tire on road 0.010...0.035
Car tire energy safe 0.006...0.009
Tube 22mm, 8 bar 0.002
Race tyre 23 mm, 7 bar 0.003
Touring 32 mm, 5 bar 0.005
Tyre with leak protection 37 mm, 5 bar / 3 bar 0.007 / 0.01
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Rolling Resistance And Drag Forces Versus Velocity
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Grade Resistance
Composed of – Gravitational force acting on the vehicle
gg WF sin
gg tansin
gg WF tanGg tan
WGFg
For small angles,
θg W
θg
Fg
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Inertial or Transient Forces
• Transient forces are primarily comprised of acceleration related forces where a change in velocity is required.
• These include:• The rotational inertia requirements (FI ) and • the translational mass (Fma). • If rotational mass is added it adds not only rotational
inertia but also translational inertia.
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ra = k m = I =
dtd I = T
tire
vehiclewheelwheel
2wheeli
a r
k m = r
a k m = rT = F 2
tire
222
2tire
2
tire
ii
= angular acceleration k = radius of gyration t = time T = Torque
m = mass = ratio between rotating component and the tire
Transient Force due to Rotational Mass
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Therefore if the mass rotates on a vehicle which has translation,
a m + mr
k = F tr2tire
22
i t&r
m +
r
k m a + Slope% + C gm + V A C = F t2tire
22
rrrt2
dtire
2
Resistance power, Presistance V FP tireceresis tan
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P resi
stan
ce
Vehicle Speed
Power Demand Curve
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Gr F = T tiretire
PE
)( r G
RPM = hkm tirePE 377.0/
The Powering Engine Torque is:
The speed of the vehicle in km/h is:
rtire = Tire Rolling Radius (meters)
G = Numerical Ratio between P.E. and Tire
Ideal capacity of Powering Engine: kWNTP PEPE
600002
Ideal Engine Powering Torque
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Drive System Efficiency
• Drive train inefficiencies further reduce the power available to produce the tractive forces.
• These losses are typically a function of the system design and the torque being delivered through the system.
actual
PEdrivemech P
PEfficiencyMechanical
nredredreddrivemech ......21
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Actual Capacity of A Powering engine
kWNTPPmech
PE
mech
PEactual
600002
auxtyre
tyretyrePE PkWN
rFP
600002
Correction for Auxiliary power requirements:
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MATLAB for Vehicle Torque Requirement
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MATLAB Model for Transmission System
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MATLAB Model for Engine Performance
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Engine Characteristic Surface
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Requirements of Vehicle on Road & Engine Power
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Urban Driving Cycle
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Engine RPM during Urban Driving Cycle
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Engine Fuel Consumption During Urban Driving Cycle
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Inverse of Carnot’s Question
• How much fuel is required to generate required power?• Is it specific to the fuel?• A Thermodynamic model is required to predict the fuel
requirements.• Carnot Model• Otto Model• Diesel Model• A Geometric Model is required to implement the
thermodynamic model.