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Further Analysis of Otto’s Ideal Model
P M V SubbaraoProfessor
Mechanical Engineering Department
Deeper understanding of Issues related t Practicablity
…
Ideal Otto Cycle
Net cycle work:
43214321 uumuumWWW
Analysis of Otto Cycle
1
11 rOttoth
1
3
4
4
31
1
2
1
1
2
v
v
T
Tr
v
v
T
T
2
11T
TOttoth
Clue to Achieve Higher Efficiency
r
Ottoth
Hardware Feasibility of Otto Cycle
Net cycle work:OttothinQW
1
11 r
QW in
Piston Displacement volume21 VV
1
21 1
V
VV
rV
111
Work done per unit piston displacement volume:
1121
11
1
rr
r
V
Q
VV
Win
Measure of Size & Feasibility
1121
11
1
rr
r
V
Q
VV
Win
P
V2 V1
Qin Wcycle
1
2
3
4
AIR
The net cycle work of an engine can be increased by either: i) Increasing the r (12’)
P
V2 V1
Qin Wcycle
1
2
3
4
Factors Affecting Work per Cycle
(i)
2’
3’C (ii)
4’’
3’’
ii) Increase Qin (23”)
4’C
1121
11
1
rr
r
V
Q
VV
Win
SI Engine for Propulsion
Thermo-chemical Feasibility
Fuel/AirMixture
CompressionStroke
Engine Damage From Severe KnockDamage to the engine is caused by a combination of high temperature and high pressure.
Piston Piston crown
Cylinder head gasket Aluminum cylinder head
Critical Compression Ratio
Formula Name Critical rCH4 Methane 12.6C3H8 Propane 12.2C8H18 Isooctane 7.3
History of Wildfires
18253,000,000 acres
Miramichi Fire
New Brunswick
Killed 160 people.
1853482,000 acres
Yaquina Fire
Oregon
18651,000,000 acres
Silverton Fire
OregonWorst recorded fire in state's history.[8]
1870964,000 acres
Saguenay Fire
Quebec
18711,200,000 acres
Peshtigo Fire
Wisconsin
Killed over 1,700 people and has distinction of the conflagration that caused the most deaths by fire in United States history. It was overshadowed by the Great Chicago Fire that occurred on the same day.
Generalized Flammability Map
Design Constraints: Flammability Characteristics
Mixture Temperature
a
f
m
m
Stoichiometric Line
Flammable Vapour
Sp
on
tan
eo
us
Ign
itio
n
Lean Mixture Line
Rich Mixture
Flam
mab
le m
ist
Flash Point
Burning Impossible
Spontaneous (Auto) Ignition Temperature of Fules
Fuel SIT, C
Petrol 246 -- 280
Diesel 210
Kerosene 295
Natural Gas 580
Hydrogen 500
Iso-Octane 447
Iso-Butane 462
Rudolf Christian Karl Diesel
• Diesel published a treatise entitled, Theory and Construction of a Rational Heat-engine to Replace the Steam Engine and Combustion Engines Known Today.
• This formed the basis for his work on and invention of, the diesel engine.
• In his engine, fuel was injected at the end of compression and the fuel was ignited by the high temperature resulting from compression.
A brief history of the diesel engine
• 1897 -- Diesel built the first diesel engine at the Augsburg Maschinenfabrik .
• 1898 -- Rudolph Diesel, filed a patent application
• The single cylinder engine was used to power stationary machinery.
• It weighed five tonnes and produced 20 hp at 172 rpm!
• The engine operated at 26.2% efficiency, a very significant improvement on the 20% achieved by the best gasoline engines of the time.
• 1922 Benz introduces a 2-cylinder, 30 hp 800 rpm tractor engine.
• 1924 Benz introduces a 4-cylinder, 50 hp 1000 rpm truck engine.
• 1960- 1970 Peugeot introduces the 404 Diesel followed by the 504 Diesel and the 204 Diesel, the first diesel-powered compact car
Displacement Work Devices : Compression Ignition Engine
A I R
IntakeStroke
PowerStroke
Air
CompressionStroke
CombustionProducts
ExhaustStroke
Air
CompressionProcess
ExpansionProcess
BC
Qout
Const volume heat rejection
Process
Qin
Const pressure heat addition
Process
Ideal Diesel Cycle