Systems Realization Laboratory How Does A Car Work? Chris Paredis G.W. Woodruff School of Mechanical...
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Systems Realization Laboratory How Does A Car Work? Chris Paredis G.W. Woodruff School of Mechanical Engineering Georgia Institute of Technology
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Transcript of Systems Realization Laboratory How Does A Car Work? Chris Paredis G.W. Woodruff School of Mechanical...
Systems Realization Laboratory
How Does A Car Work?
Chris Paredis
G.W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology
Systems Realization Laboratory
Learn More about Cars
The graphical material in this lecture is copied from www.howstuffworks.com
You can find much additional information at this web-site
Systems Realization Laboratory
Car Sub-Systems of Interest
Torque Converter
Engine
Transmission
Differential
Tires
CarBody
Systems Realization Laboratory
Engine
Systems Realization Laboratory
Four Cycles
Intake Compression Combustion Exhaust
Systems Realization Laboratory
Simplified Engine Model
1000 2000 3000 4000 5000 6000 7000 80000
50
100
150
200
250
300
350
400
450
Speed [RPM]P
ower
[kW
]
Engine Power as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
50
100
150
200
250
300
350
400
450
Speed [RPM]
Pow
er [
kW]
Engine Power as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
50
100
150
200
250
300
350
400
450
Speed [RPM]
Pow
er [
kW]
Engine Power as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
200
400
600
800
1000
1200
1400
Speed [RPM]
Tor
que
[Nm
]
Engine Torque as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
50
100
150
200
250
300
350
400
450
Speed [RPM]
Pow
er [
kW]
Engine Power as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
50
100
150
200
250
300
350
400
450
Speed [RPM]
Pow
er [
kW]
Engine Power as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
200
400
600
800
1000
1200
1400
Speed [RPM]
Tor
que
[Nm
]
Engine Torque as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
200
400
600
800
1000
1200
1400
Speed [RPM]
Tor
que
[Nm
]Engine Torque as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
200
400
600
800
1000
1200
1400
Speed [RPM]
Tor
que
[Nm
]
Engine Torque as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
200
400
600
800
1000
1200
1400
Speed [RPM]
Tor
que
[Nm
]
Engine Torque as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
1000 2000 3000 4000 5000 6000 7000 80000
200
400
600
800
1000
1200
1400
Speed [RPM]
Tor
que
[Nm
]
Engine Torque as a function of Engine Speed
Chevy 4-cyl 1.8LFord 6cyl 3LPorsche 8cyl 5.4L
( )f P
Use SI units! Torque in [Nm], velocity in [rad/s] and Power in [W]
Systems Realization Laboratory
Car Sub-Systems of Interest
Torque Converter
Engine
Transmission
Differential
Tires
CarBody
Systems Realization Laboratory
Torque Converter
Systems Realization Laboratory
Torque Converter
The model of a torque converter is fairly complex and highly nonlinearWe will not consider it in this class.
If you need it, it will be provided to you as a Matlab function.
Systems Realization Laboratory
Car Sub-Systems of Interest
Torque Converter
Engine
Transmission
Differential
Tires
CarBody
Systems Realization Laboratory
Transmission
Purpose: provide large power at all vehicle velocities
0 50 100 150 200 250 300 350 4000
50
100
150
200
250
Velocity [kmh]
Pow
er [
kW]
Power at the drive shaft for different gear ratios
Systems Realization Laboratory
Transmission
morecompact
sunplanet ring
Systems Realization Laboratory
Model of a Transmission
Assumptions:• No friction or other losses• No inertia
Reduces the rotational velocity:
Increases the torque
where n is the transmission ratio and subscript in refers to the shaft connected to the torque converter.
inout n
out in n
Systems Realization Laboratory
Car Sub-Systems of Interest
Torque Converter
Engine
Transmission
Differential
Tires
CarBody
Systems Realization Laboratory
Differential
Systems Realization Laboratory
Model of a Differential – Same as Transmission
Assumptions:• Car drives in a straight line• No friction or other losses; no inertia
Reduces the rotational velocity:
Increases the torque
where n is the transmission ratio and subscript in refers to the shaft connected to the transmission.
inout n
out in n
Systems Realization Laboratory
Model of a Wheel
Assumptions:• Car drives in a straight line• No slip; no tire deformation; no friction losses; no inertia
Converts rotational velocity into translational velocity:
Converts torque into force:
where R is the radius of the wheel.
car wheelv R
wheelcarF R
Systems Realization Laboratory
Model of the Car Body
Wind Resistance:
Gravitational Force:
Tire Resistance:
21( )
2drag d carF C A v
sin( )gravF mg
cos( )rolling rF mg
gravF
mg
rollingF
dragF
cos( )mg
Systems Realization Laboratory
Putting It All Together
1000 2000 3000 4000 5000 6000 7000 8000 9000 100000
50
100
150
200
250
300
engine speed in rpm
torq
ue
in [
Nm
]
Engine and Load Torques for a 10% Slope
engine torqueload torque (1st)load torque (2nd)load torque (3rd)load torque (4th)load torque (5th)
Systems Realization Laboratory
Examples of Other Models in Vehicle Design
Computational Fluid Dynamics
Noise, Vibration,and Harshness
Crash TestingThermalStress Analysis
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