System Level 1-D Analysis of an Air-System for a Heavy-Duty Gasoline

Compression Ignition Engine

*PRAVEEN KUMAR, YU ZHANG, MICHAEL TRAVER

ARAMCO SERVICES COMPANY, ARAMCO RESEARCH CENTER–DETROIT

JOHN P. WATSON

BORGWARNER TURBO SYSTEMS

GT CONFERENCENovember 4-5, 2019 │ Plymouth, MI, USA

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Motivation

Experimental Baseline

Methodology for GCI System development

Air-System Configurations

Results/Discussions

Presentation Outline

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Motivation Future Demand

• Stringent criteria pollutants emissions regulations

• Global economic growth drives increase in commercial demand

ExxonMobil 2017 Outlook for Energy: A View to 2040

Total cost of ownership pressures will make gasoline range fuels attractive

Cummins Atlantic LLC

On-road HD

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EG

R C

oo

ler

IAT

EGR Valve

Exhaust

Restriction

Valve

CA

C

Exhaust

Intake

Displacement Volume 14.9 L

Number of Cylinders 6

Bore 137 mm

Stroke 169 mm

Compression Ratio 18.9, variants at 17.3 & 15.7

Diesel Fuel System 2500 bar common-rail

Air System single-stage VGT

high pressure cooled EGR loop

charge air cooler

Engine Ratings 450 hp @ 1800 rpm

1750 lb-ft @ 1000 rpm

• Modern heavy duty highway diesel engine that can be installed in all major truck brands – non-

road variant also available

Aramco purchased a 2013MY Cummins ISX 15L 450hp engine as a research test bed

Low NOx GCI Test Engine

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• Estimated energy distribution for the stock engine operation.

• Stock engine-out NOx target ~ 3-4 g/kWh

A well matched air-system managed the pumping losses within 1.5-4.5%.

Baseline GT-Power simulated ULSD CR17.3 perfromance

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Low NOx GCI System Targets & Methodology

GT-Power 1-D engine model & 3-D CFD model close-coupling for system design analysis.

RON80 CR16.5

HP-EGR Out

Temp (C)

LP-EGR

Out Temp (C)

CAC Out

Temp (C)

Intake

Man Temp (C)

110-130 70-80 45-46 65-70

RON80 CR16.5

A100 B25 B50 B75 C100

IntMan P

(bar)3.56 1.48 2.42 3.16 3.67

EGR +Res

(%)36.8 43.2 43.6 39.4 37.7

EO NOx

(g/kWh)1.5 1.0 1.0 1.5 1.5

ULSD CR 17.3

A100 B25 B50 B75 C100

IntMan P

(bar)2.9 1.2 1.9 2.5 2.4

EGR

(%)19.1 26.4 24.9 22.5 21.6

EO NOx

(g/kWh)3.9 4.0 3.7 3.9 3.4

Ref: *SAE 2018-01-0226

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Low NOx GCI Combustion Behavior Matching (IMT 65-70C)

Reasonable matching of ICP and HRR profiles between 3-D and 1-D models.

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Low NOx GCI Multiple Air Path Configurations

Multiple air system configurations evaluated.

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Air Systems Configuration I : 1-Stage VGT HPEGR

RON80 CR16.5

HP-EGR Out Temp (C)

LP-EGR Out Temp (C)

CAC Out Temp (C)

Intake Man Temp (C)

110-130 70-80 45-46 65-70

1-Stage VGT Turbine.

1. Simplistic solution.

2. Three different compressor maps.

3. Variable geometry turbine provide superior control

features.

(I) 1-Stage VGT, HP Loop EGR

Same configuration as production engine.

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High pumping losses

1-Stage + HPEGR Stock Turbocharger

Insufficient pressure ratio range for the stock turbine to deliver the desired boost.

BCs not met

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1-Stage + HPEGR BS1 w/ HPEGR

The boosting system satisfactorily delivers the air-thermal BCs.

Combined turbocharger efficiency ~55% through mid-high load operations except C100.

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Air Systems Configuration III : 1-Stage (WG) LPEGR

(III) 1-Stage WG, LP Loop EGR

EGR flow controlled by back-pressure valve (BPV).

CAC

Mixer

HPC TWG

LP-EGR

BPV

IAT

RON80 CR16.5

HP-EGR Out Temp (C)

LP-EGR Out Temp (C)

CAC Out Temp (C)

Intake Man Temp (C)

110-130 70-80 45-46 65-70

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BS3 w/ LPEGR

Combined turbocharger efficiency ~50-55%.

Strictly LPEGR flow incurred much higher pumping losses.

High pumping losses

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Low Pressure EGR challenges (Test cell)

1. Test cell capability allowed to target 70-80C. (Cooling Tower)

2. On vehicle LPEGR either cooled by Air-Air, Coolant-Air or a separate circuit.

A sensitivity study conducted to understand the impact of LPEGR cooler Out T impact on the production BW 1-Stage DLEGR turbocharger matching.

(IV) 1-Stage, Dual Loop EGR

In a hybrid EGR configuration, low pressure EGR may allow efficiency benefits with the

turbine.

Air Systems Configuration IV : 1-Stage DLEGR

RON80 CR16.5

HP-EGR Out Temp

(C)

LP-EGR Out

Temp (C)

CAC Out

Temp (C)

Intake Man

Temp (C)

110-130 70-80 45-46 65-70

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1-Stage DLEGR HP-Prop% Sweep

A100

B50

B25

C100

Inflection point: Dependent on boundary conditions

LP EGR portion assisted boosting system to meet the BCs targets.

HP-Portion (%) HP-Portion (%) HP-Portion (%)HP-Portion (%)

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BS4 w/ DLEGR

Combined turbocharger efficiency surpassed ~60%.

Brake efficiency closer to stock ULSD @ CR 17.3 operation.

A100

(HP-Prop 41%)

B75

(HP-Prop 60%)

B50

(HP-Prop 53%)

C100

(HP-Prop 98%)

B25

(HP-Prop 69%)

Best pumping #s from a 1-Stage turbocharger

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BS4 system with combined turbocharger efficiency ~60% using a DLEGR system displayed

superior performance.

Pumping Losses All 5 Configurations

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GT-Power based 1-D and 3-D CFD coupled methodology for boosting system

evaluations.

1-Stage HPEGR Configuration

Very high combined turbocharger efficiency desired for HPEGR only configurations.

1-Stage LPEGR Configuration

System incurred terribly high pumping losses due to the LPEGR configuration.

1-Stage DLEGR Configuration

With a waste-gated option and appropriate EGR split strategy, combined turbocharger

efficiency stretched to 60%.

Stock boost option performed with DLEGR reasonable.

HD-GCI Conclusions

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Acknowledgements

• David Branyon, Staff Engineer, Powertrain Design, SwRI.

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Thank you for your attention

Praveen Kumar, Ph.D.

Research Scientist – Commercial

Transport Fuels Research

Aramco Services Company

Fuel Technology

Aramco Research Center – Detroit

Tel.: +1 (248) 896-3873

Email:

Praveen.Kumar@aramcoservices.com