Embed Size (px)
Citation preview
Phenomenological Modeling of Internal Combustion Engines
P M V SubbaraoProfessor
Mechanical Engineering Department
A method of inquiry based on the premise that reality consists of Processes
which are Understood with consciousnes
s ….
The First Step in Phenomenological Modeling of I.C. Engines
Understand the Vehicle Driving Cycle
High Way Driving Cycle
3
Urban Driving Cycle
The SECOND step
Develop Consciousness into the Engine Behaviour During a Driving Cycle
Urban Driving Cycle Vs Engine Speed
Global Phenomenological Model
Phenomenological Model for Transmission System
How to Develop a Phenomenological Model for Engine????
Is it OK to be satisfied with Otto cycle/Diesel Cycle/Dual Cycle ????
What does our consciousness say???
First Law for CV:Uniform State Uniform Flow
• Conservation of mass:
outinCV
inoutCV mm
dt
dmmm
dt
dm 0
• Conservation of energy:
Wdt
dEQ out
CVin
Properties of CV are variant:
Finite Duration process of Accumulation or/and depletion of mass of a CV.
Finite Duration Process of Heat Addition/removal / Work across surface of CV.More Complex Energy transaction processes.
Salient Features of CV @USUF Process
• Rate of mass inflow Rate mass outflow.
• The state of the mass crossing each of the areas of flow on the control surface is
• constant with time although the mass flow rates may be time varying.
• Rate of Work done is variant.
• Rate of Heat transfer is variant.
• Temporal Change of state or process is both for the CV and Flows!
• The incoming fluid changes its state from inlet(at one time t0) to exit (at time t0+t) condition.
• A CV with USUF process is approximates as a homogeneous but variant device.
• The importance of time is very high!
CV following A USUF Process for time t
• A change of state of a CV as USUF device are temporal.
• A total change in a CV over time t can be calculated using:
tt
t
outin
tt
t
CV dtmmdtdt
dm 0
0
0
0
tt
t
outinCVCV dtmmtmttm0
0
)( 00
Total change in mass of A CV during a time interval t
Total change in energy of A CV during a time interval Dt
dtWdtdtdt
dEdtdtQ
tt
t
tt
t
out
tt
t
CV
tt
t
in
tt
t
0
0
0
0
0
0
0
0
0
0
in
inin gzV
hm
2
2
out
outout gzV
hm
2
2
gz
VumE CVCV 2
2
All parameters mentioned above are perceived to be homogeneous and variant.
Instantaneous inflow rate of Methalpy:
Instantaneous outflow rate of Methalpy:
Instantaneous Energy of Substance present in CV
Integral Quantities over time t
dtQQtt
t
CV
0
0
dtWWtt
t
CV
0
0
dttt
t
inin
0
0
dttt
t
outout
0
0
Net Heat Transfer during finite time interval
Net Work Transfer during finite time interval
Total Methalpy Entered the CVduring finite time interval
Total Methalpy left the CV during finite time interval.
1
21
112
22
22 22
0
0
gZV
umgZV
umdtdt
dEtt
t
CV
First Law for A CV executing USUF for finite cycle time
First Law Analysis: USUF
Intake Process:
A I R
FUELA I R
SI Engine CI Engine
SI Engine
0)()(
tmtmdt
dmfuelair
CV
)()()()()(
tWtQthmthmdt
medCVCV
fuelairCV
CI Engine
0)(
tmdt
dmair
CV
)()()()(
tWtQthmdt
medCVCV
airCV
ptACtm Dair
)()(
Ideal Gas Equation for Intake Process
CVCVCVCV RTmVp
ptACtm Dair
)()(
First Law Analysis
Compression Process : USNF Transient Control Mass
Fuel/AirMixture
Air
SI Engine CI Engine
outinCV
inoutCV mm
dt
dmmm
dt
dm 0 Wdt
dEQ out
CVin
Compression Process
)()()()(
tWtQdt
med
dt
medCVCV
CV
fuelair
dt
tdVtptW CV
)()()(
atmcylCV TTtUAtQ
)()(
First Law Analysis: USUF
Combustion Process
Fuel injectedat 15o bTC
SI Engine CI Engine
Combustion Process
SI Engine
)()(
)()()( 1
tWtQdt
med
dt
med
dt
medCVCV
CV
j
n
jfuelair
CI Engine
0
)()()( 1
fuel
CV
j
n
jfuelair mdt
md
dt
md
dt
md
)()(
)()()( 1
tWtQhmdt
med
dt
med
dt
medCVCV
fuel
CV
j
n
jfuelair
First Law Analysis: USUF
Power Stroke:
PowerStroke
)()(
)(1 tWtQdt
emd
CVCV
CV
n
jjj
First Law Analysis: USUFExhaust Stroke:
0)(1
1
tmdt
mdn
jj
CV
n
jj
)()()(1
1 tWtQhtmdt
emd
CVCVj
n
jj
CV
n
jjj
The Important Cycle is Executed in CM Mode
)()()()(
tWtQdt
med
dt
medCVCV
CV
fuelair
)()(
)()()( 1
tWtQdt
med
dt
med
dt
medCVCV
CV
j
n
jfuelair
