1-1%20Simnick,%20Jim%20-%20Presentation%20AVFL%20Combustion%20Symposium,%202-2014%20Simnick.pdf

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CRC Study on Octane Number and

Engine Efficiency – Literature Review

February 25, 2014

Baltimore, MD

-. . ,

Delivered by James Simnick, Co-Chair CRC Performance

Committee

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2/17

Outline• Basis for the study

• Study objectives• -

• Selected Results• n ngs or na ura y asp ra e eng nes

• Findings for turbocharged/boosted

engines

• Data a s and R&D recommendations

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3/17

Basis for the CRC Stud

• CRC Performance Committee has an Octane Group

• c ane group s ocus s on om us on

• Combustion R&D, especially SI octane, now has much

+

• Octane Group wanted to know what is current published

technology & data gaps?• Prepared a RFP and solicited bidders, Phases1 - 5

• Contracted to H-D Systems, Dr. K.G. Duleep

• u y ava a e v a www.crcao.org we s e, u ca onsof “Performance Committee”

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4/17

Study Objectives

• Define relationship between octane and engine

e c ency

• Start with comprehensive literature search for

technical papers

• Phase 1 : gathered 250 papers based on titleand abstract, distill to 45 relevant papers.

• 10 papers directly examined the relationship

between efficiency and octane number.

• Then interviews with OEM’s

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5/17

Analysis issues• No simple relationship linking compression ratio (CR) and

en ine efficienc

• Engine octane requirement is also affected by:• engine design

• engine calibration (AF ratio and spark timing)

• fuel composition.• n ur oc arge oos e eng nes:

• octane may benefit torque and power more than engine thermalefficiency

• “complicating” parameters

• E.g. downsize the engine!

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6/17

Analysis Findings

• Literature review suggested engine OR differed by:

– Fuel management (Injection system PFI or DI), and

– Air management (aspirated or turbocharged/boosted).

,

– Fuel Research Octane Number (RON),

– Sensitivity (ROM – MON)

– Latent heat of evaporation (LHE)

• OEM’s recommended:

– Focus on the engine studies,

– Too many uncontrolled parameters in vehicle studies.

– o con en a a a was use n e ana ys s.

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Study methodolog

• H-D Systems utilized a 2 stage model

• rs , n o eng ne erma e c ency,

• Second, link CR and other variables to fuel octane, sensitivity

and LHE.

• Focus on WOT/low RPM (


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Indicated Effic iency vs. CR at 1500 RPM

40.00%

41.00%

38.00%

39.00%

i e n c y

37.00%

.

I n d

i c a t e d E f f i c

86mm bore

35.00%

36.00%68.25 mm bore

34.00%

7 8 9 10 11 12 13 14 15 16 17

Compression Ratio

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EFFECT OF CR ON TORQUE

120

110

A T K L S A

105

L I Z E D

T O R Q U E

DI 114RON

PFI 114RON

95

100

N O R M A

DI 90RON

PFI 90RON

90

10 11 12 13 14 15 16

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10/17

OCTANE NUMBER vs. KLSA

105

110

100

E R

OI

RON

95

O C T

A N E N U M B

MON

Linear (OI)

Linear (RON)

85

90

80

-4 -2 0 2 4 6 8 10 12

KLSA at 1200 RPM, DEGREES

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11/17

NIMEP vs. Spark Timing

1

0.9

N I M E P

N o r m a l i z e d

0.8

0.7

0 5 10 15 20 25 30

Spark Retard from MBT, deg

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12/17

TORQUE vs. RPM WITH DIFFERENT FUELTURBOCHARGED PFI ENGINE CR = 9.5

300

325

275

92.5 RON

225 T O R Q U E N -

.

98.3 RON

106.5 RON

200

150

0 1000 2000 3000 4000 5000 6000

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SEPARATION OF CHARGE COOLING AND OCTANEEFFECTS ON KNOCK LIMIT

40

45

30

35

20

25

N E T

I M E P ,

B A R

E0

E50, UFI

E50, D!

arge

Cooling

E50,PFI

E50,DI

10

15Octane

Improvement

0

5

0 5 10 15 20 25 30 35

CRANK ANGLE AT 50% MASS BURN, ATDC

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14/17

Findings for Naturally Aspirated Engines• Benefits from increased octane apparent

• a one point increase in CR,• or a spark advance increment of 5 to 8 degrees.

non-linear and depend on the (CR) starting point.

• The benefits are:• Lowest for small bore engines relative to medium or large bore

• For a medium bore engine at 10 CR, a 4 to 5 octane point can

allow a 2% improvement in thermal efficiency.

• output increases with increased CR.

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Findings for Turbocharged/Boosted Engines Turbocharged engines have:

So octane number response is dependent upon the operatingcondition.

- ,

Octane increase can improve torque and efficiency (approx.

1%). –

Ethanol blending can provide large benefits:

In turbo/boosted DI engines

Cooling power associated with ethanol’s high LHE Ethanol’s combustion properties

But need to address com atibilit .

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Data Gaps and Research Suggestions Available public data on the influence of fuel octane number

allow a robust numerical estimate of the benefits for allengine types and operating conditions.

a a s par cu ar y m e on mo ern - ur oc arge

engines and on new emerging designs like sequential turbo

DI engines that can offer high torque even at low RPM, aswell as on small bore size turbo-engines.

A large amount of data is available at manufacturers that is

currently not in the public domain. The development of a data

base with manufacturer co-operation can allow more detailedand specific analysis of all parameters affecting the octane to

efficienc relationshi .

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Research Suggestions (cont’d.)• Controlled testing of modern DI-Turbo engines of

emerging in the market can provide a forward look of theeffects of octane number in the coming decades.

• The effects of high volumetric content ethanol blends like

E30 or E50 on optimized turbo-DI engine performance

.

• Data from European auto-manufacturer studies that are

unpublished may provide some early insight into

structuring such public studies.

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