PATHWAYS TO REDUCTION OF CO2 EMISSIONS FROM … · amount of combustion energy for conversion to...

PATHWAYS TO REDUCTION OF CO2 EMISSIONS FROM COMBUSTION

ENGINES

Alok Warey, Ph.D.

OUTLINE

Part 1: Technology Screening to meet 2025 CO2

Emissions Regulations (Co-PI) – On-going

Part 2: Fundamental Exhaust Gas Recirculation

(EGR) Cooler Fouling and Mitigation Study (PI) -

Completed

Quick overview of other projects

OBJECTIVE

Explore diesel engine technology combinations

that meet 2025 CO2 regulations consistent with

future emissions standards

Remain cost competitive

METHODOLOGY

CO2 emissions estimated for different diesel engine technologies over

the New European Driving Cycle (NEDC) and the Worldwide

Harmonized Light Vehicles Test Procedure (WLTP)

1-D Engine Model Vehicle Model

+

CO2 (g/km)

DIESEL ADVANTAGE OVER GASOLINE

Data from EPA show approximately

30% reduction in gallons/100 miles for

diesel (approx. 40% higher MPG)

Why is a diesel engine more efficient

that a conventional gasoline engine?

Common answers:

No throttling losses

Higher compression ratio

These are contributors, but the lean

combustion process of the diesel

engine is the main factor leading to

efficiency gain

Source: Light-Duty Automotive Technology,

Carbon Dioxide Emissions, and Fuel Economy

Trends: 1975 Through 2012, EPA, 2013

LEAN COMBUSTION

Increased dilution improves

indicated fuel conversion efficiency

by lowering temperatures and

increasing gamma (ratio of specific

heats).

Switching from exhaust dilution to

air dilution improves indicated fuel

conversion efficiency by increasing

gamma.

Increased dilution improves the

indicated efficiency by lowering

temperatures and decreasing heat

losses.

Source: Foster, Combustion Engines Efficiency

Colloquium, DOE 2010

Compression Ratio (CR)

ηig

LOW HEAT REJECTION

In-cylinder heat losses in modern diesel engines constitute a

significant part of thermodynamics losses.

Engine efficiency can be increased by retaining a greater

amount of combustion energy for conversion to mechanical

work.

Sensitivity studies show that, provided heat losses could be

minimized, there is potential for significant fuel consumption

improvement.

Several pathways to achieve low heat rejection.

BASELINE DIESEL vs LEAN LOW HEAT REJECTION (LLHR) ENGINE

FUEL ENERGY BREAKDOWN

Combined pumping and friction torques are comparable

Boosting system for lean combustion adds more pumping torque

Due to leaner combustion and higher effective expansion ratio the LLHR engine is more efficient

Centroid of heat release closer to TDC for similar peak cylinder pressure and cylinder temperatures

Lower energy in the exhaust

Brake

Exhaust

Friction Pumping

Heat Transfer

166 Nm/35 kW 75 Nm/15 kw 25 Nm/5 kW

Baseline LLHR Engine Baseline LLHR Engine Baseline LLHR Engine

CO2 EMISSIONS

0.90 0.92

0

0.2

0.4

0.6

0.8

1

1.2

BASELINE Diesel Lean Combustion + Low Heat Rejection [LLHR]

No

rmal

ize

d C

O2

Emis

sio

ns

NEDC WLTP

SUMMARY

Developing robust, cost-effective, lean combustion and low heat rejection

diesel engines will be challenging but the fuel economy benefits are

significant.

Challenges for engine optimization:

• Robust combustion control over all operating conditions

• Robust emissions control over all operating conditions

• Good fuel consumption under real world driving conditions

• Low combustion noise

• Exhaust temperature

This will require a coordinated effort between air handling, combustion,

aftertreatment and controls – a system optimization approach.

In order for this to work effectively it is important to focus research on

fundamental insights that have long-term value critical to achieving upper-

bound efficiency and lower-bound emissions.

OUTLINE





Completed


EXHAUST GAS RECIRCULATION (EGR) COOLERS

EGR coolers are compact heat

exchangers used on all modern

diesel engines to cool exhaust

gasses that are re-circulated into the

combustion chamber.

Exhaust gas recirculation is used to

control NOx (oxides of nitrogen)

emissions that result from diesel

combustion.

Advanced diesel combustion

strategies to improve fuel economy

rely on cooled exhaust gas

recirculation (EGR).

EGR COOLER FOULING

Fouling of exhaust gas re-circulation (EGR)

coolers can result in significant deterioration of

the cooler effectiveness and increased

pressure drop across the cooler.

EGR cooler fouling can adversely affect the

combustion process, engine durability and

emissions.

Complicated flow physics with multiple soot

particle deposition and removal mechanisms.

Hydrocarbon and water condensation in

addition to soot deposition.

Goal of this research was to develop a

fundamental understanding of EGR cooler

fouling mechanisms and demonstrate novel

concepts to mitigate fouling and regenerate

fouled EGR coolers. Source: SAE 2010-01-1211

DIESEL EXHAUST PARTICLE EMISSIONS

Source: David Kittelson, University of Minnesota

EXPERIMENTAL SETUP

Intake Flow

Exhaust Flow

Exhaust Gas Analyzers

W/Heated Lines

DMS500

Switching Valves

Temperature / Pressure

EGR Valve Intake Throttle Valve

Turbocharger

EGR Bypass Valve

Compressor

CO2Analyzer

(EGR Flow)

Flow Meter

Clean Air (EGR Flowrate )

EGR Cooler

Heated/ Dilution Line

Temperature / Pressure

Engine Test Stand

at GM R&D

Single Rectangular Channel

EGR Cooler

Removable

Fouling Plates

EXPERIMENTAL SETUP

Lab Reactor – University of Stuttgart

Soot

Generator

Species Injection

Ports

Furnace

Emissions

Sampling

EGR

Cooler

EGR

Cooler

Bypass

Exhaust

Hood

THERMOPHORESIS

* Thermophoresis = Particle transport due to temperature difference (ΔT)

GM Proprietary

PSR Lab – Diesel Engine Systems Group

Thermophoresis* is the dominant mechanism for particle deposition in

EGR coolers.

Fouling will always occur as a result of the temperature difference,

which is necessary for heat exchanger operation.

1.E-13

1.E-12

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 100 200 300 400 500

Dep

osit

ion

velo

cit

ies (

m/s

)

Particle diameter (nm)

Thermophoresis

Diffusion

Turbulent Impaction

Gravitational Drift Left: ΔT ~ 0 °C Right: ΔT ~ 300°C

(Isothermal) (Thermophoresis)

0.0E+00

2.0E+07

4.0E+07

6.0E+07

8.0E+07

1.0E+08

1.2E+08

1.4E+08

1 10 100 1000

Pa

rtic

le C

on

ce

ntr

ati

on

[#

/cm

3]

Particle Diameter [nm]

25 °C 90 °C

EGR Cooler Outlet: 25 °C Coolant Temp.

90 °C Coolant Temp.

EGR Cooler Inlet

THERMOPHORESIS

0

5

10

15

20

25

30

35

40

45

50

0 20 40 60 80 100

So

ot

Dep

os

itio

n R

ate

[m

g/h

r]

EGR Cooler Coolant Temperature (°C)

Soot Deposition Rate

Accumulation Mode Particles

GM Proprietary


Particle measurements upstream and downstream of the EGR cooler

also show evidence of thermophoresis.

Soot deposition rate due to thermophoresis increases with decrease

in coolant temperature.

Bika, A.S., Warey, A., Long, D., Balestrino, S., and Szymkowicz, P.G., “Characterization of Soot Deposition and Particle Nucleation in Exhaust Gas Recirculation

Coolers”, Aerosol Science and Technology, 46(12): 1328-1336, 2012.

PARTICLE REMOVAL

GM Proprietary


Increasing wall shear stress due to gas velocity appears to be effective in

preventing dry soot accumulation on the cooler walls.

However, typical gas velocities through the EGR cooler are considerably

lower than 30 m/s for reasons of excessive pressure drop.

It is impractical to generate the high gas velocities necessary for deposit

removal through the cooler of a conventional diesel engine.

Abd-Elhady, M. S., Zornek, T., Malayeri, M. R., Balestrino, S., Szymkowicz, P. G., & Müller-Steinhagen, H., “Influence of Gas Velocity on Particulate Fouling of Exhaust

Gas Recirculation Coolers”, International Journal of Heat and Mass Transfer, 54(4): 838-846, 2011

30 m/s 70 m/s 120 m/s

EGR coolers typically

operate below 30 m/s

PARTICLE FORMATION

GM Proprietary


As the coolant temperature is decreased below 45 °C, nucleation mode

particle concentration begins to increase downstream of the cooler. This

trend is continued as the coolant temperature is decreased further.

Condensation of hydrocarbons occurs not only on the cooler walls but also in

the bulk gas.

0.0E+00

1.0E+07

2.0E+07

3.0E+07

4.0E+07

5.0E+07

6.0E+07

7.0E+07

8.0E+07

1 10 100 1000

Pa

rtic

le C

on

ce

ntr

ati

on

[#

/cm

3]

Diameter [nm]

Avg. Upstream 25C Downstream 30C Downstream 35C Downstream 40C Downstream 45C Downstream 50C Downstream Increasing

nucleation

mode with

decreasing

coolant temp.

EGR Cooler Outlet:







EGR Cooler Inlet

Bika, A.S., Warey, A., Long, D., Balestrino, S., and Szymkowicz, P.G., “Characterization of Soot Deposition and Particle Nucleation in Exhaust Gas Recirculation Coolers”, Aerosol Science

and Technology, 46(12): 1328-1336, 2012.

Warey, A., Bika, A.S., Long, D., Balestrino, S., and Szymkowicz, P.G., “Visualization and Analysis of Condensation in Exhaust Gas Recirculation Coolers”, SAE Paper 2013-01-0540.

EFFECT OF HYDROCARBON (HC) CONDENSATION

GM Proprietary


Significant changes in deposit morphology were observed due to

hydrocarbon condensation.

Condensed HC’s in the EGR cooler diffuse through the deposit layer and stay

near the cold wall. Cold wall inhibits evaporation of condensed HC’s.

Bika, A., Warey, A., Long, D., Balestrino, S., & Szymkowicz, P., “An Investigation of Diesel EGR Cooler Fouling And Effectiveness Recovery”, SAE 2013-01-0533

Tin = 215 °C FSN = 2.0

THC = 40 ppm C3

Flow: 200 SLPM

Exposure : 2 hours

Tcoolant: 25 C

Tin = 215 °C

FSN = 2.0

THC = 250 ppm C3

Flow: 200 SLPM

Exposure : 2 hours

Tcoolant: 25 C

Inlet Outlet

DEPOSIT ANALYSIS

GM Proprietary


Heavier hydrocarbons in diesel fuel tend to condense at coolant/wall

temperatures typically encountered in EGR coolers.

Deposit created at:

TGas = 215 °C Coolant = 25 °C

FSN = 2.0

THC = 250 ppm C3

(Post Injection)

Flow: 200 SLPM

Exposure : 2 hours

EFFECT OF WATER VAPOR CONDENSATION

GM Proprietary


Inlet Outlet

After Exposure to Water Vapor Condensation

Prior to Water Vapor Condensation

Tin = 215 °C FSN = 2.0

THC = 40 ppm C3

Flow = 200 SLPM

Exposure = 2 hours Coolant = 100 °C

Tin = 145 °C FSN = 0.3

THC = 65 ppm C3

Flow = 200 SLPM

Exposure = 30 min Coolant = 10 °C

Warey, A., Bika, A.S., Long, D., West, D., Balestrino, S., and Szymkowicz, P.G., “Influence of Water Vapor Condensation on Exhaust Gas Recirculation Cooler

Fouling”, International Journal of Heat and Mass Transfer, 65: 807-816, 2013.


GM Proprietary

PSR Lab – Diesel Engine Systems Group Warey, A., Bika, A.S., Long, D., West, D., Balestrino, S., and Szymkowicz, P.G., “Influence of Water Vapor Condensation on Exhaust Gas Recirculation Cooler


0

100

200

300

400

500

600

700

800

900

0 10 20 30 40 50 60 70 80 90 100

Ma

ss

Co

nd

en

sa

tio

n F

lux

of

Wa

ter

Va

po

r (m

g/m

2s

)

Coolant Temperature (°C)

Water Vapor

Removal Mechanism

METAL PLATE METAL PLATE METAL PLATE METAL PLATE METAL PLATE

2.) H2O Vapor Diffuses

Through Soot Layer

3.) H2O Droplet Disrupts

Soot Adhesive Force 4.) Reduced Adhesive

Force Enables Removal

5.) Clean Cooler

Plate

1.) Soot Deposited

by Thermophoresis

Soot Particles/Layer are Hydrophobic


GM Proprietary


Hydrophilic Deposit

METAL PLATE

METAL PLATE

Soot +HC

Droplet Forms/mixes on HC Surface

METAL PLATE

METAL PLATE

Dry Soot

Vapor Diffuses Through voids

METAL PLATE METAL PLATE

Clean Plate

HC’s fill voids

Possible Lacquer

Formation

Droplet Forms on

Metal Surface

Soot + HC yields Hydrophilic deposit

Condensation of water vapor

occurs on the surface of

hydrophilic deposits (not below)

and is unlikely to remove

deposits.

Hydrophobic Deposit

Warey, A., Bika, A.S., Long, D., West, D., Balestrino, S., and Szymkowicz, P.G., “Influence of Water Vapor Condensation on Exhaust Gas Recirculation Cooler


EFFECT OF OXIDATION CATALYST (OC)

GM Proprietary

PSR Lab – Diesel Engine Systems Group Warey, A., Bika, A.S., Vassallo, A., Balestrino, S., and Szymkowicz, P.G., “Combination of pre-EGR Cooler Oxidation Catalyst and Water Vapor

Condensation to Mitigate Fouling”, SAE International Journal of Engines, 7(1): 2014.

Specifications

Diameter mm 45

Length mm 120

Cell Density cpsi 200 LS

Volume L 0.19

Washcoat g/ft3 67.5 g/ft3 Pt / 22.5 g/ft3 Pd

0

10

20

30

40

50

60

70

80

90

100

0 100 200 300 400 500 600 HC

Eff

icie

ncy

(%

) &

HC

Slip

(p

pm

C3)

HC Concentration (ppm C3)

HC Slip (ppm C3) HC Conversion Eff (%)

HC Conversion Efficiency

0.0E+00

2.0E+07

4.0E+07

6.0E+07

8.0E+07

1.0E+08

1.2E+08

1.4E+08

1.6E+08

1 10 100 1000

dN

/dlo

gDp

(#/

cm3)

Diameter (nm)

Active OC Upstream

Active OC Downstream

Inactive OC Upstream

Inactive OC Downstream

No significant loss of particles from active or inactive catalysts

Particle Size Distribution

Two Catalysts:

Active (Washcoat)

Inactive (NO Washcoat)

EGR Cooler OC


GM Proprietary


0

20

40

60

80

100

120

140

Active OC Inactive OC

De

po

sit

Mas

s (m

g)

Engine Out - Soot + HC + H2O

After Vacuum Oven (2 hrs) - Mostly Soot

38%

49%

0

20

40

60

80

100

120

140


De

po

sit

Mas

s (m

g)

Engine Out - Soot + HC + H2O After Vacuum Oven (2 hrs) - Mostly Soot

50 C Coolant Temperature 25 C Coolant Temperature

37%

53%

An oxidation catalyst upstream of the EGR cooler results in lower

accumulated deposit mass.

Warey, A., Bika, A.S., Vassallo, A., Balestrino, S., and Szymkowicz, P.G., “Combination of pre-EGR Cooler Oxidation Catalyst and Water Vapor


EFFECT OF OXIDATION CATALYST (OC) + WATER VAPOR CONDENSATION

GM Proprietary


Exposure to water vapor condensation in addition to the oxidation

catalyst results in significant removal of deposit mass.

50 C Coolant Temperature 25 C Coolant Temperature

34.8

68.4

14.5

29.5

0

20

40

60

80

100

120

140


De

po

sit

Mas

s (m

g)

Engine Out - Soot + HC + H2O After Exp. to Water Cond. and Vac Oven - Residual Deposit

22.5

97.5

5.3

49.6

0

20

40

60

80

100

120

140


De

po

sit

Mas

s (m

g)

Engine Out - Soot + HC + H2O After Exp. to Water Cond. and Vac Oven - Residual Deposit




GM Proprietary


Saturation Ratio:

Pv (T) : Partial pressure of the condensing species

Psat (T) : Saturation pressure of the condensing species

Condensation typically occurs at SR > 1.0

)(

)(

TP

TPSR

sat

v

• EGR Coolant Temperature: 50 C

• Engine-out THC: 250 ppm C3

• 100% of the exhaust HC are

assumed to be n-hexadecane

(C16H34)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0% 20% 40% 60% 80% 100%

HC

Sat

ura

tio

n R

atio

in

EG

R C

oo

ler

[-]

Catalyst HC Conversion Efficiency (%)

NO Condensation

Condensation



1D FOULING MODEL

0.0E+00

2.0E+07

4.0E+07

6.0E+07

8.0E+07

1.0E+08

1.2E+08

1.4E+08

1.6E+08

1 10 100 1000

dN

/dlo

gD

p (

#/c

m3)

Diameter (nm)

Upstream Downstream: DMS500 Downstream: Model

Coolant Temperature: 50 °C

Flow direction

L

Do

x

r To(t) Co(t)

yHCo(t)

Tw (t)

Tm (x,t), Um (x,t), Cm (x,t)

Inlet (0m) Outlet (0.2m)

Warey, A., Balestrino, S., Szymkowicz, P.G., and Malayeri, M.R., “A One Dimensional Model for Particulate Deposition and Hydrocarbon Condensation in Exhaust

Gas Recirculation Coolers”, Aerosol Science and Technology, 46 (2):198–213, 2012.

1D FOULING MODEL

Warey, A., Balestrino, S., Szymkowicz, P.G., and Malayeri, M.R., “A One Dimensional Model for Particulate Deposition and Hydrocarbon Condensation in Exhaust

Gas Recirculation Coolers”, Aerosol Science and Technology, 46 (2):198–213, 2012.

EGR COOLER FOULING SUMMARY

Thermophoresis is the dominant mechanism for particle deposition in EGR

coolers.

Particulate fouling can be avoided if the gas velocity through the EGR cooler

is above a critical flow velocity.

Hydrocarbon condensation has the strongest influence on deposit

morphology changing it from a dry porous layer to sludge or lacquer like

deposit.

Significant removal of accumulated deposit mass was observed by using an

oxidation catalyst in combination with exposure to water vapor condensation.

Based on the findings in this study on-board “cleaning” or regeneration of the

EGR cooler by exposure to water vapor condensation does seem feasible.

OUTLINE





Completed


OTHER PROJECTS

Fuel Effects on Low Temperature Premixed Compression Ignition

(PCI) Combustion in a Light-Duty Diesel Engine

Characterization of Particulate Matter (PM) Emissions from a 2007

Emissions Level Heavy-Duty Diesel Engine

Development of an Electronic Sensor for Engine Exhaust Particulate

Measurements – Doctoral Dissertation

Effects of In−Cylinder Wall Wetting on Size and Mass of Particulate

Matter Emissions in Direct Injection Spark Ignition Engines– Masters

Thesis

Guest Graduate – Argonne National Laboratory

o Used laser scattering to measure the time resolved size distribution and mass of

particulate matter (PM) emissions from a direct-injection gasoline engine

Thank You

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PATHWAYS TO REDUCTION OF CO2 EMISSIONS FROM … · amount of combustion energy for conversion to...

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