Designing Efficient Engines: Strategies Based on Th d ... Presentations/Day 2... · Designing Efficient Engines: Strategies Based on Th d iThermodynamics Jerald A. Caton ... Engine

Designing Efficient Engines: Strategies Based Th d ion Thermodynamics

Jerald A. CatonTexas A&M UniversityCollege Station, TX

for

CRC Advanced Fuel & Engine Efficiency WorkshopCRC Advanced Fuel & Engine Efficiency Workshop

Hyatt Regency Baltimore Inner Harbor

Baltimore, MD

25 February 2014

Designing Efficient Engines: Strategies Based on ThermodynamicsThermodynamics

INTRODUCTION AND BACKGROUND

Insights from Thermodynamics

DESCRIPTION OF THE CYCLE SIMULATION

ENGINE AND OPERATING CONDITIONSENGINE AND OPERATING CONDITIONS

RESULTS AND DISCUSSION

Overall Results – Efficiencies

Parametric Results (extra)

Thermodynamics

Nit i O id R lt ( t )Nitric Oxide Results (extra)

Exergy Destruction (extra)

• SUMMARY AND CONCLUSIONS• SUMMARY AND CONCLUSIONS


-- Importance of Thermodynamics --

Often overlooked in discussions of engines Often overlooked in discussions of engines

Rich and long history related to engine developments

An IC engine is not a heat engine: not limited by Carnot efficiency

Combustion devices are subject to exergy destruction

IC engine design for high efficiency can be guided by g g g y g yunderstanding the thermodynamics

3


The importance of thermodynamics is demonstrated by comparing a conventional and high efficiency engine

Efficiency increases due to CR, lean operation and the use of EGR – what is the contribution of each?

What are the thermodynamic reasons for the increases of efficiency?increases of efficiency?

Not all items will be obvious or measureable.

THERMODYNAMIC ENGINE CYCLE SIMULATION

Features/Considerations:1. One common pressure2. Three gas temperatures3 Three volumes and masses

5

3. Three volumes and masses4. Separate heat transfer

PROCEDURES FOR SOLUTIONS

• ORDINARY DIFFERENTIAL EQUATIONSNUMERICAL TECHNIQUES EULERS• NUMERICAL TECHNIQUES: EULERS

• INITIAL CONDITIONS: T1, p1, Residual Fraction• BOUNDARY CONDITIONS: INLET & EXHAUST• SPECIFY SUBMODEL PARAMETERS:

- Thermodynamic properties (Heywood, 1988)- Heat transfer coefficient (Hohenberg, 1979; Chang et al., 2004)( g g )- Friction (Sandoval and Heywood, 2003)- Fuel mass rates- Flow rate parameters- Exergy and second law considerations- Nitric oxide kinetics (Dean and Bozzelli, 2000)- Other

6

SPECIFICATIONS FOR THE ENGINESPECIFICATIONS FOR THE ENGINE

PARAMETER VALUEEngine Automotive, V-8Bore/Stroke 102/88 mm (4.0/3.5 in)Displacement 5.7 liter (350 in3)bmep 900 kPaEngine speed 2000 rpmC b i i i MBTCombustion timing MBTGeometric compression ratio from 8:1 to 16:1Valve arrangement OHV 2 valves/cylinder

7

Valve arrangement OHV, 2 valves/cylinder

TWO ENGINE OPERATINGTWO ENGINE OPERATING CONDITIONS:

CONVENTIONAL CONVENTIONAL

HIGH EFFICIENCY

8

Operating Conditions

Parameter Conventional High Efficiencybmep (kPa) 900 900Speed (rpm) 2000 2000

CR 8 16burn 60° 30° 1 0 0 7 1.0 0.7

EGR (%) 0 45p (kPa) 92 170pinlet (kPa) 92 170pexh (kPa) 105 180

Timing MBT MBT

9

Timing MBT MBT

RESULTSRESULTS Overall efficiency gains

Comparison to experimentsp p

Contributions to efficiency increasey

Thermodynamic insightsy g

DESCRIPTION OF CASES– STRATEGY –

Add f t i ti l f hiAdd features in a sequential fashion

CASE DESCRIPTION1 CR = 8; b = 60o; φ= 1.0; EGR = 0%2 CR = 16; b = 60o; φ= 1.0; EGR = 0%3 CR = 16; b = 30o; φ= 1.0; EGR = 0%4 CR = 16; b = 30o; φ= 0.7; EGR = 0%5 CR = 16; b = 30o; φ= 0.7; EGR = 45%

Overall Efficiency (1/5)

Base60

bmep = 900 kPa2000 rpm

MBT Ti iPumpingLosses

60bmep = 900 kPa

2000 rpmMBT Ti i

PumpingLosses

cien

cy (%

)

50

55 MBT Timing

Gross IndicatedEfficiency

Losses

MechanicalFrictionci

ency

(%)

50

55 MBT Timing


Losses

MechanicalFriction

d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

ndic

ated

and

35

40

5%ndic

ated

and

35

40

5%In

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5In

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5

Case

1 2 3 4 5

Case

1 2 3 4 5


Base60



60



Increase CR to 16

cien

cy (%

)

50

55 MBT Timing


Losses


ency

(%)

50

55 MBT Timing


Losses

MechanicalFriction

d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

ndic

ated

and

35

40

5%ndic

ated

and

35

40

5%In

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5In

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5

Case

1 2 3 4 5

Case

1 2 3 4 5


Base60



Increase CR to 16

Short Burn Duration

cien

cy (%

)

50

55 MBT Timing


Losses

MechanicalFriction

d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

ndic

ated

an

35

40

5%1 2 3 4 5

I

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5

Case

1 2 3 4 5


Base60

bmep = 900 kPa2000 rpm Pumping

Losses

60bmep = 900 kPa

2000 rpm PumpingLosses

Increase CR to 16

Short Burn Duration

Lean Mixturecien

cy (%

)

50

55 MBT Timing


Losses


ency

(%)

50

55 MBT Timing


Losses

MechanicalFriction Lean Mixture

d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

ndic

ated

and

35

40

5%ndic

ated

and

35

40

5%1 2 3 4 5

I

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

51 2 3 4 5

I

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5

Case

1 2 3 4 5

Case

1 2 3 4 5


55

60


MBT TimingPumpingLosses

55

60


MBT TimingPumpingLosses

Base

cien

cy (%

)

50

55 MBT Timing

Gross IndicatedEfficiency Mechanical

Frictioncien

cy (%

)

50

55 MBT Timing

Gross IndicatedEfficiency Mechanical

Friction

Increase CR to 16

Short Burn Duration

Lean Mixture

d B

rake

Effi

45Net Indicated

EfficiencyBrake

Efficiency

Friction

d B

rake

Effi

45Net Indicated

EfficiencyBrake

Efficiency

Friction Lean Mixture

Add 45% EGR

Indi

cate

d an

35

40

5%Indi

cate

d an

35

40

5%1 2 3 4 5

I

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

51 2 3 4 5

I

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5

Case

1 2 3 4 5

Case

1 2 3 4 5

Overall Efficiency

Increase of indicated

60



60


MBT Ti iPumpingLosses indicated

efficiencies: 37% to 53.9% (x 1.46)

16.9% increasecien

cy (%

)

50

55 MBT Timing


Losses


ency

(%)

50

55 MBT Timing


Losses

MechanicalFriction 16.9% increase

Highest improvements from CR, lean and EGRd

Bra

ke E

ffic

45Net Indicated

EfficiencyBrake

Efficiency

Friction

= 16.9%d B

rake

Effi

c

45Net Indicated

EfficiencyBrake

Efficiency

Friction

= 16.9% CR, lean and EGR

Dilute operation requires higher inlet pressuresnd

icat

ed a

nd

35

40

5%

ndic

ated

and

35

40

5%

pressures

Brake values somewhat mitigated by

In

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5In

30

35

BAS

E

CR

= 1

6

b =

30o

=

0.7

EGR

= 4

5mitigated by increases of friction

Case

1 2 3 4 5

Case

1 2 3 4 5

Comparison to Experimental ResultsComparison to Experimental Results

Table 5. Comparisons to Results from [22]ITEM REFERENCE THIS WORKITEM REFERENCE

(Kokjohn et al. [22])

THIS WORK(High Eff

Case) B /St k ( ) 137/165 102/88Bore/Stroke (mm) 137/165 102/88Fuels Gasoline/Diesel Isooctane Inlet Pressure (kPa) 200 170 Geometric CR 16.1 16 EGR (%) 45.5 45 Equivalence Ratio 0.77 0.7qSpeed (rpm) 1300 2000 RESULTS: IMEP (kPa) 1100 1015IMEP

NET (kPa) 1100 1015

Net Ind Efficiency (%) 50 53.9 Peak Pressure (MPa) 12 12.0 Nitric Oxide (g/kW-h) 0.01 0.003

Effect of IndividualEffect of IndividualEngine Parametersg

(extra)

Thermodynamic Reasons forThermodynamic Reasons for Efficiency Increases

Energy Comparison

100

UnusedFuel

(0.7%)


100

UnusedFuel

(0.7%)


Gains in efficiency only partly due to%

) 80 (46.7%) (40.5%)

Net TransferOut Dueto Flows

%) 80 (46.7%) (40.5%)

Net TransferOut Dueto Flows

partly due to reduced heat losses – the rest is largely aN

ERG

Y (%

60(5.0%)

HeatT fN

ERG

Y (%

60(5.0%)

HeatT f is largely a

result of the increases of CR and ???

EN

20

40(15.6%)

TotalI di t d

Transfer = 16.9%EN

20

40(15.6%)

TotalI di t d

Transfer = 16.9%

1 20

20 (37.0%) (53.9%)IndicatedWork

C ti l Hi h Effi i1 20

20 (37.0%) (53.9%)IndicatedWork

C ti l Hi h Effi i1 2Conventional High Efficiency1 2Conventional High Efficiency

Heat Transfer Reductions77

Only a portion of the heat transfer reductions arebs

)

6

72000 rpm

bmep = 900 kPaMBT Timing, CR = 16

bs)

6

72000 rpm

bmep = 900 kPaMBT Timing, CR = 16

transfer reductions are converted to work

For these conditions, a 10 6% d ti f h tie

ncy

(%, a

b

4

5

ienc

y (%

, ab

4

5

10.6% reduction of heat losses increases the indicated thermal efficiency by 3 4% (abs)as

e of

Effi

c

2

3

rsion = 0.32

tm =

1.0

ase

of E

ffic

2

3

rsion = 0.32

tm =

1.0

efficiency by 3.4% (abs)

For different conditions, the factor of improvement

solu

te In

cre

0

1 Conversht

solu

te In

cre

0

1 Conversht

changes but is of the same order

Abs

2

-1 Decreasing htm

Abs

2

-1 Decreasing htm

Absolute Reduction of RHT (%, abs)

-4 -2 0 2 4 6 8 10 12 14 16-2

Absolute Reduction of RHT (%, abs)

-4 -2 0 2 4 6 8 10 12 14 16-2

Contributions to Efficiency Gains

Feature Incremental Gain of Indicated Efficiency

(%)

Relative Gain (%)

(%)Compression Ratio Increase 6.5 39Shorter Burn Duration 1.2 7Reduced Heat Transfer 3.4 20??? (by difference) 5.8 34Total 16.9% 100%

Ratio of Specific Heats1 351 35

Increased ratio of specific heats important )

1.35bmep = 900 kPa

2000 rpmMBT Timing4th Sequence)

1.35bmep = 900 kPa

2000 rpmMBT Timing4th Sequence

for conversion of thermal energy to work

Small increases yieldsion

str

oke)

1.305

Highsion

str

oke)

1.305

High Small increases yield large benefits

From simple “Otto” cycle may show that am

a (e

xpan

s

4

HighEGR

ma

(exp

ans

4

HighEGR

cycle, may show that a 5% increase of gamma results in about a 20% relative increase ofve

rage

Gam

1.25

1 3High

Leaner

vera

ge G

am

1.25

1 3High

Leaner

relative increase of efficiency (e.g., 30% to 36%)

Av

2

ShortBD

HighCRAv

2

ShortBD

HighCR

Net Indicated Efficiency (%)

35 40 45 50 55 601.20

Net Indicated Efficiency (%)

35 40 45 50 55 601.20

Contributions to Efficiency Gains

Feature Incremental Gain of Indicated Efficiency

(%)

Relative Gain (%)

(%)Compression Ratio Increase 6.5 39Shorter Burn Duration 1.2 7Reduced Heat Transfer 3.4 20Ratio of Specific Heats Increase 5.8 34Total 16.9% 100%

SUMMARY/CONCLUSIONS Completed a thermodynamic assessment of the

parametric changes for increased efficiency

Th i f i d The most important features are increased compression ratio, lean operation and EGR

R f th i CR d t Reasons for the gains are CR advantage, reduced heat losses and the increased ratio of specific heatsp

The role of increased ratio of specific heats is important and can account for 30% or more of pthe gains

Reducing heat losses even further can provide

27

additional gains and is thermodynamically favorable

28

Extra InformationExtra Information

29

Brief Discussion of ExergyBrief Discussion of Exergy

Energy and Exergy

100

UnusedFuel

(0.7%)

Destructiondue to

Inlet Mixing(0 9%)

Conventionalbmep = 900 kPa

2000 rpm = 1.0100

UnusedFuel

(0.7%)

Destructiondue to

Inlet Mixing(0 9%)

Conventionalbmep = 900 kPa

2000 rpm = 1.0

ERG

Y (%

)

80 (46.7%)

(0.9%)

Net TransferO t D

(20.4%)

CombustionDestroyed

ERG

Y (%

)

80 (46.7%)

(0.9%)

Net TransferO t D

(20.4%)

CombustionDestroyed

These results demonstrate the differences

Y O

R E

XE

60

(15 6%)

(28.9%)

Heat

Out Dueto Flows

Y O

R E

XE

60

(15 6%)

(28.9%)

Heat

Out Dueto Flows

differences between energy and exergy quantities

ENER

GY

20

40

(37 0%)

(15.6%) (13.0%)

Total

HeatTransfer

ENER

GY

20

40

(37 0%)

(15.6%) (13.0%)

Total

HeatTransfer

quantities

1 20

20 (37.0%) (36.2%)TotalIndicated

Work

EEnergy1 20

20 (37.0%) (36.2%)TotalIndicated

Work

EEnergy1 2ExergyEnergy1 2ExergyEnergy

Exergy Comparison

For high efficiency

100

UnusedFuel

(0.7%)

Destructiondue to

Inlet Mixing


100

UnusedFuel

(0.7%)

Destructiondue to

Inlet Mixing


engine, destruction of exergy i b t) 80

100

(24.0%)

Inlet Mixing(0.7%)

(20.4%) CombustionDestroyed

) 80

100

(24.0%)

Inlet Mixing(0.7%)

(20.4%) CombustionDestroyed

increases – but trade-offs are favorable for increasedXE

RG

Y (%

)

60(17.9%)

(28.9%)Net Transfer

Out Dueto Flows

(3.8%)

XER

GY

(%)

60(17.9%)

(28.9%)Net Transfer

Out Dueto Flows

(3.8%)increased thermal efficiencies

EX

40

(52 9%)

(13.0%)

(36 2%)Total

Indicated

HeatTransferEX

40

(52 9%)

(13.0%)

(36 2%)Total

Indicated

HeatTransfer

0

20 (52.9%)(36.2%) IndicatedWork

0

20 (52.9%)(36.2%) IndicatedWork

1 2High EfficiencyConventional1 2High EfficiencyConventional

Exergy Destruction

Increases of exergy d t ti l lst

ion

30

bmep = 900 kPa2000 rpmst

ion

30

bmep = 900 kPa2000 rpm destruction largely

due to dilution which results in lower combustionin

g C

ombu

srg

y) 25


ing

Com

bus

rgy) 25


lower combustion temperatures

truc

tion

Dur

(% fu

el e

xer

20truc

tion

Dur

(% fu

el e

xer

20

Exer

gy D

est

ASE

R =

16

b = 3

0o

= 0.

7

GR

= 4

5%

Exer

gy D

est

ASE

R =

16

b = 3

0o

= 0.

7

GR

= 4

5%Case

1 2 3 4 515 B

A C b ECase

1 2 3 4 515 B

A C b E

Brief Discussion of EmissionsBrief Discussion of Emissions

CO2 and NO Values1.21.2

y un

its)

0.8

1.0

29.2% reduction

y un

its)

0.8

1.0

29.2% reduction

CO

2 (a

rbitr

ary

0.4

0.6

CO

2 (a

rbitr

ary

0.4

0.6

Case

C

0.0

0.2

Conventional High EfficiencyCase

C

0.0

0.2

Conventional High Efficiency

15

20

15

20

Carbon Dioxide Estimates

O (g

/kW

-hr)

10

~100% reductionO (g

/kW

-hr)

10

~100% reductionN

0

5

C i l

N

0

5

C i lCase

Conventional High EfficiencyCase

Conventional High Efficiency

Nitric Oxide Estimates

Effect of Engine ParametersEffect of Engine Parameters

Equivalence Ratio5656

Lean operation provides efficiency gains54

56Net Indicated

Efficiency54

56Net Indicated

Efficiency

Gains are largely a result of reduced heat losses and higher gamma

lcy (%

)

50

52

HighEfficiency

CaseBrakecy

(%)

50

52

HighEfficiency

CaseBrake

values

Requires higher inlet pressuresal

Effi

cien

c

46

48Efficiency

al E

ffici

enc

46

48Efficiency

p

Brake values subject to higher frictionTh

erm

42

44Ther

m

42

44

Friction increases largely due to piston/rings/cylinder friction

40

42bmep = 900 kPa

EGR = 45%, b = 30o

2000 rpm, cr = 16MBT Timing

40

42bmep = 900 kPa

EGR = 45%, b = 30o


friction

Equivalence Ratio

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.338

Equivalence Ratio

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.338

Exhaust Gas Recirculation5656

EGR provides efficiency gains

54

55bmep = 900 kPa = 0.7, b = 30o


Net Indicated Efficiency54

55bmep = 900 kPa = 0.7, b = 30o


Net Indicated Efficiency

Gains are largely a result of reduced heat losses and higher gamma

lcy (%

)

52

53

cy (%

)

52

53

values

Requires higher inlet pressures

mal

Effi

cien

c

50

51High

EfficiencyCase

mal

Effi

cien

c

50

51High

EfficiencyCase

p

Brake values subject to higher friction

Ther

m

48

49

Brake Efficiency

Ther

m

48

49

Brake Efficiency

Friction increases largely due to piston/rings/cylinder friction

46

47

46

47

friction

EGR (%)

0 10 20 30 40 50 6045

EGR (%)

0 10 20 30 40 50 6045

Compression Ratio6060

Increased CR is a significant factor55

bmep = 900 kPa = 0.7, b = 30o

2000 rpm, EGR = 45%MBT Timing55

bmep = 900 kPa = 0.7, b = 30o

2000 rpm, EGR = 45%MBT Timing

A consequence of the mechanical advantage and the greater

i ticy (%

)

50

HighEfficiency

CaseNet Indicated Efficiency

Brakecy (%

)

50

HighEfficiency

CaseNet Indicated Efficiency

Brake expansion ratio

Due to high dilution, spark knock not

mal

Effi

cien

c

45

BrakeEfficiency

mal

Effi

cien

c

45

BrakeEfficiency

pexpected to be an issue

Ther

m

40Ther

m

40

3535

Compression Ratio

4 6 8 10 12 14 16 18 2030

Compression Ratio

4 6 8 10 12 14 16 18 2030

Burn Duration5656

Decreasing burn duration has a modest impact

54

55bmep = 900 kPa

= 0.7, EGR = 45%2000 rpm, cr = 16

MBT Timing


54

55bmep = 900 kPa

= 0.7, EGR = 45%2000 rpm, cr = 16

MBT Timing


impact

The improvement diminishes for shorter d tinc

y (%

)

52

53

Hi hncy

(%)

52

53

Hi h durations

The difference between 60° and 30° burn m

al E

ffici

en

50

51High

EfficiencyCase

mal

Effi

cien

50

51High

EfficiencyCase

duration is about a factor of 3.5 higher pressure rise rate

Ther

m

47

48

49Brake EfficiencyTh

erm

47

48

49Brake Efficiency

45

46

47

45

46

47

b (oCA)

0 10 20 30 40 50 6045

b (oCA)

0 10 20 30 40 50 6045

Combustion Timing5656

All previous results for MBT timing54

55bmep = 900 kPa = 0.7, b = 30o

2000 rpm, cr = 16Net Indicated Efficiency54

55bmep = 900 kPa = 0.7, b = 30o

2000 rpm, cr = 16Net Indicated Efficiency

cy (%

)

52

53

cy (%

)

52

53

mal

Effi

cien

50

51High

EfficiencyCase

mal

Effi

cien

50

51High

EfficiencyCase

Ther

m

48

49

Brake Efficiency

Ther

m

48

49

Brake Efficiency

46

47Brake Efficiency

Retard46

47Brake Efficiency

Retard

Relative Combustion Timing (oCA)

-10 0 1045

Relative Combustion Timing (oCA)

-10 0 1045

Table 3. Conventional Engine Item Value

UsedHow Obtained

Table 3. Conventional Engine Item Value

UsedHow Obtained

Used bmep = 900 kPa, CR = 8, EGR = 0%, MBT timing Equivalence Ratio 1.0 inputEngine Speed (rpm) 2000 input

Used bmep = 900 kPa, CR = 8, EGR = 0%, MBT timing Equivalence Ratio 1.0 inputEngine Speed (rpm) 2000 inputg p ( p ) pMech Frictional mep (kPa) 81.3 from algorithm [19]Inlet Pressure (kPa) 92.1 inputExhaust Pressure (kPa) 105.0 input

26 0 d i d f MBT

g p ( p ) pMech Frictional mep (kPa) 81.3 from algorithm [19]Inlet Pressure (kPa) 92.1 inputExhaust Pressure (kPa) 105.0 input

26 0 d i d f MBTStart of Combustion (bTDC) 26.0 determined for MBTCombustion Duration (CA) 60 inputCylinder Wall Temp (K) 450 inputHeat transfer correlation Hohenberg [20]

Start of Combustion (bTDC) 26.0 determined for MBTCombustion Duration (CA) 60 inputCylinder Wall Temp (K) 450 inputHeat transfer correlation Hohenberg [20]Heat transfer correlation Hohenberg [20] Gross Ind thermal eff (%) 37.63 outputNet Ind thermal eff (%) 36.98 output

Heat transfer correlation Hohenberg [20] Gross Ind thermal eff (%) 37.63 outputNet Ind thermal eff (%) 36.98 outputet d t e a e (%) 36 98 outputBrake thermal eff (%) 33.92 output Exergy destruction comb (%) 20.37 output

et d t e a e (%) 36 98 outputBrake thermal eff (%) 33.92 output Exergy destruction comb (%) 20.37 outputMax press rise rate (kPa/CA) 152 output

Max press rise rate (kPa/CA) 152 output

Table 4. High Efficiency Engine Item Value How Obtained Table 4. High Efficiency Engine

Item Value How Obtained Used

bmep = 900 kPa, CR = 16, EGR = 45%, MBT timing Equivalence Ratio 0.7 inputE i S d ( ) 2000 i t

Used bmep = 900 kPa, CR = 16, EGR = 45%, MBT timing Equivalence Ratio 0.7 inputE i S d ( ) 2000 i tEngine Speed (rpm) 2000 inputMech Frictional mep (kPa) 115.9 from algorithm [19]Inlet Pressure (kPa) 169.5 inputExhaust Pressure (kPa) 179 5 input

Engine Speed (rpm) 2000 inputMech Frictional mep (kPa) 115.9 from algorithm [19]Inlet Pressure (kPa) 169.5 inputExhaust Pressure (kPa) 179 5 inputExhaust Pressure (kPa) 179.5 inputStart of Combustion (bTDC) 13.5 determined for MBTCombustion Duration (CA) 30 inputCylinder Wall Temp (K) 450 input

Exhaust Pressure (kPa) 179.5 inputStart of Combustion (bTDC) 13.5 determined for MBTCombustion Duration (CA) 30 inputCylinder Wall Temp (K) 450 inputy p ( ) pHeat transfer correlation Chang et al. [21] Gross Ind thermal eff (%) 54.95 output

y p ( ) pHeat transfer correlation Chang et al. [21] Gross Ind thermal eff (%) 54.95 outputNet Ind thermal eff (%) 53.92 outputBrake thermal eff (%) 47.79 output Exergy destruction comb (%) 24 01 output

Net Ind thermal eff (%) 53.92 outputBrake thermal eff (%) 47.79 output Exergy destruction comb (%) 24 01 outputExergy destruction comb (%) 24.01 outputMax press rise rate (kPa/CA) 536 outputExergy destruction comb (%) 24.01 outputMax press rise rate (kPa/CA) 536 output

Heat Transfer Reductions

Only a portion of the heat transfer reductions are1.0

1.2

Net Ind Eff

1.0

1.2

Net Ind Eff

transfer reductions are converted to work

For these conditions, a 50% d ti f h t

0.8

1.0

CR = 16, b = 30o

CR = 8, b = 60o

0.8

1.0

CR = 16, b = 30o

CR = 8, b = 60o

50% reduction of heat losses increases the indicated thermal efficiency by a factor ofAc

tual

/Bas

e

0.6

Actu

al/B

ase

0.6

efficiency by a factor of about 1.05

For different conditions,

A

0.4B

ase

Cas

eA

0.4B

ase

Cas

e

the factor of improvement changes but is of the same order

0.2bmep = 900 kPa

2000 rpmMBT Timing

htm0.2bmep = 900 kPa

2000 rpmMBT Timing

htm

Relative Heat Transfer (compared to base)

0 20 40 60 80 100 1200.0

Relative Heat Transfer (compared to base)

0 20 40 60 80 100 1200.0

45

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