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