cummins emissions overview

7/31/2019 Cummins Emissions Overview

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CHOOSING THE RIGHT TECHNOLOGYMOBILE OFF-HIGHWAY EMISSIONS



Cummins Off-Highway Emissions Technology

Introduction

Cummins engines are designed to provide customers with the highest levels of reliability,

durability, performance and dependability at the lowest cost of operation. At the same

time, we are committed to meeting or exceeding clean air standards worldwide. This

document describes the technology options Cummins is exploring and developing to

meet emissions requirements for the off-highway market. It discusses several technologies

as well as their advantages and challenges.

Cummins has long been a pioneer in emissions research and development. We have

invested in critical technologies to achieve current and future emissions standards and

meet the needs of our customers. The emissions solutions we use today are the direct

result of a technology plan that was put in place in the early 1990s. It is a plan that will

carry us through 2015 and beyond. At the core of this technology road map is a strategic

decision not to limit ourselves to any one approach. Instead, we have decided to develop

the right technology for every application and market served. It stands to reason that

different operating conditions and economic factors can and will influence the technology

path most appropriate for each market. While developing multiple emissions solutions

requires a broader and deeper investment in Research and Development, we strongly

believe that it guarantees Cummins customers the optimum solution at the lowest

possible cost of operation.

MOBILE OFF-HIGHWAY EMISSIONS

1



A second, but no less important, part of our strategy has been to involve original equipment

manufacturers as early as possible in the development and integration process. This open

exchange of information and technology has been – and continues to be – instrumental in

developing solutions for the future.

Our objective is very clear. It is to deliver products that meet emissions standards with the

best reliability, durability, performance, fuel economy and the lowest cost of operation.

Cummins Strategy – The Right Technology Matters

Cummins is a

leading global

manufacturer

and supplier to

very diverse worldwide

markets and customers. As emissions

regulations are becoming more stringent worldwide,

there is a potential of affecting engine and equipment in terms of

both cost and performance. Cummins leadership in combustion research, fuel, air-handling,

aftertreatment and controls systems allows Cummins to achieve the goal of maximizing

customer value by providing the most appropriate emissions control solution integrated into

each equipment type and market. Cummins component technology companies, subsidiaries,

alliances and our relationships with universities and national laboratories uniquely position us


2



to design, manufacture and implement the best solutions for off-highway markets. Today and

in the future Cummins will continue to deliver power uniquely matched and integrated into every

application through advanced customer-engineering tools such as PowerMatch and Advisor.

Committed to Customer Needs

While we have taken measures to describe the emissions control technologies of today

and the future, our first commitment is to deliver great reliability, durability and cost-

effectiveness on all products. In each off-highway market, emissions control technologies

are matched to the product duty cycle and equipment design to deliver the best economic

benefit for the customer. We believe that our customers are best served by understanding

the emissions control technologies behind our products.

Off-Highway Emissions Technology

Evolution of Mobile Off-Highway Standards

The exhaust emissions from diesel engines

used in off-highway applications have

been regulated for only a few years. The

U.S. EPA/CARB first regulated on-highway

heavy-duty diesels in 1973. This was

followed with the introduction of

on-highway emissions legislation in Europe in 1990. In 1996, the first emissions regulations

went into effect for diesels used in mobile off-highway applications in the U.S. This was

mirrored three years later in Europe. Since then, the U.S. EPA and its counterparts in

3

U.S. Non-Road Emissions Standards



Europe and Japan have rapidly closed the gap between the on-highway and off-highway

emissions limits and implementation dates.

Several countries now regulate emissions of particulate matter (PM), oxides of nitrogen

(NOx), carbon monoxide (CO) and hydrocarbons (HC). As with on-highway diesel engines,

agencies have primarily focused on the reduction of PM and NOx, as CO and HC are

inherently low from diesel engines.

Recently proposed future off-highway regulations in Europe and the U.S. call for NOx and

PM levels 98% below unregulated levels beginning in 2011. As is planned for on-highway

diesel engines, the use of advanced aftertreatment devices will be required to achieve these

low-emissions levels off-highway.

While the gap between on- and off-highway emissions is closing, the effect dates for equivalent

off-highway emissions levels generally lag on-highway by a few years. Advanced research and

development in all markets and applications allows transfer of technology to design the right

emissions solution, bringing optimum value for the customer.

This simple technology chart illustrates the types of technology driven by on- and

off-highway emissions and how the off-highway implementation has followed the

on-highway segment.

Because of the global

nature of the off-highway

market, the move toward

harmonized emissions

levels is important to both


4

1 9 7 3

1 9 7 4

1 9 7 5

1 9 7 6

1 9 7

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1 9 7 8

1 9 7 9

1 9 8 0

1 9 8 1

1 9 8 2

1 9 8 3

1 9 8 4

1 9 8 5

1 9 8 6

1 9 8 7

1 9 8 8

1 9 8 9

1 9 9 0

1 9 9 1

1 9 9 2

1 9 9 3

1 9 9 4

1 9 9 5

1 9 9 6

1 9 9 7

1 9 9 8

1 9 9 9

2 0 0 0

2 0 0 1

2 0 0 2

2 0 0 3

2 0 0 4

2 0 0 5

2 0 0 6

2 0 0 7

2 0 0 8

2 0 0 9

2 0 1 0

2 0 1 1

2 0 1 2

2 0 1 3

2 0 1 4

2 0 1 5

Mechanical Mechanical

JWAC

Mech/Elect

CAC

Electronic

CAC

Electronic

CAC

Electronic

CAC

EGR

Elect

CAC

EGR

AT

Electronic

CAC

EGR

AT

Mechanical

JWAC

Mech/Elect

JWAC/CAC

Electronic

CAC

Elect

CAC

AT

Elect

CAC

ATEPA/CARB Off-Highway

EPA/CARB On-Highway

Emissions Technology

■ Fuel System/Controls (Mechanical or Electronic)

■ Charge Air Temperature Control (jacket-water aftercooled (JWAC)or air-to-air aftercooled (CAC)

■ EGR (Cooled EGR)

■ AT (Aftertreatment: NOx and/or PM)



engine and equipment manufacturers. As more countries begin to regulate off-highway diesel

emissions, industry organizations are emphasizing the need for harmonized standards.

Cummins takes a very active position working with emissions regulatory agencies worldwide

to help them understand the different needs of the on-highway and off-highway markets.

Emissions Standards Phased In by Power Category

Due to the broad power range, off-highway standards are phased in by power categories

(i.e., 100-174 hp [75-130 kW] and 174-750 hp [130-560 kW]). The U.S. EPA has set emissions

standards for all off-highway diesel engines regardless of their power output while Europe and

Japan do not regulate very small and very large engines (see the chart on pages 8 and 9). The

phase-in of new emissions levels (“tiers” as known in the U.S. or “stages” as they are called in

Europe) usually begins with engines in the power range of on-highway engines, 174-750 hp

(130-560 kW). These emissions levels are similar to those implemented a few years earlier for

on-highway engines.

Current Standards

Cummins has a broad product

line of certified off-highway diesel

engines providing power from

31-3500 hp (23-2611 kW). These

engines must meet all current

and future off-highway standards.

Today most engines must meet

the second tier or stage of emissions standards. Also, smaller and larger engines must

5

Cummins - Non-Road Engines (Industrial)



meet Tier 1 standards in the U.S. The phase-in of Tier 2 standards began in 2001. A close

examination of the chart on pages 8 and 9 reveals that current emissions levels are similar

in Europe, Japan and the U.S. While emissions levels are similar, various differences do

exist. For example, effect dates are different and emissions of NOx and HC are combined in

the U.S., but regulated separately in Europe and Japan. Unique standards and procedures

also exist for measuring smoke emissions during engine acceleration. Certification and

labeling requirements also vary. These differences cause additional work for manufacturers,

but the standards are close enough to permit the sale of common products in these

countries. This is important for both engine and equipment manufacturers.

Next-Generation Standards – Tier 3 and Stage IIIA

The third level of emissions standards will be phased in beginning as early as January 2005

in North America and January 2006 in Europe. As detailed in the chart on pages 8 and 9, the

standards are phased in between 2005 and 2008 depending on power category. Generally

these standards focus on the reduction of NOx. The NOx reduction will vary by power

category, but roughly a 40% reduction will be required from Tier 2 levels. PM levels will not

change in Europe and the U.S., but Japan will require varied amounts of PM reduction.

These unique PM standards may impact manufacturers’ ability to sell common products

for the Japanese market. Note that the

U.S. did not set Tier 3 standards for

very small and very large engines.

Engines greater than 750 hp (560 kW)

will need to meet Tier 2 standards in the

U.S. beginning in 2006.


6

Engine Emissions Evolution



Future Standards – Tier 4/Stage IIIB and Stage IV

The phase-in of aftertreatment-forcing standards will begin in 2011 in Europe and the U.S.

It is anticipated that Japan will also adopt similar standards in this time frame. A maximum

of 15-ppm sulfur content in diesel fuel will be regulated for these off-highway applications.

PM filters will be required for several power categories to meet the 0.02-g/kW-hr standard.

High-efficiency NOx aftertreatment will be required beginning in 2014 as the NOx standard

drops to 0.4-g/kW-hr. For the U.S. market, the phase-in of PM and NOx reductions in 2011

and 2014 will be similar to the 2007 and 2010 reductions in the on-highway market.

As stated earlier, the U.S. EPA did not set Tier 3 standards for very small and very large

engines, but they have established Tier 4 standards. For engines less than 50 hp (37 kW),

Tier 4 begins in 2008 and requires significant PM reductions. Interim Tier 4 standards

begin in 2011 for engines greater than 750 hp (560 kW). The interim Tier 4 standards for

these large engines are similar to the Tier 3 standards set for engines less than 750 hp

(560 kW). EPA has also established aftertreatment-forcing standards beginning in 2015 for

large engines used in mobile machines. For large engines used in portable power

generation applications, NOx aftertreatment will be required in 2011.

7



( 10.5 ) / 8.0 / 1.0

( 9.5 ) / 6.6 / 0.80

( 9.5 ) / 5.5 / 0.80

9.2 / – / – / – ( 6.6 ) / 5.

9.2 / 1.3 / 11.4 / 0.54 ( 6.6 ) / 3.

9.2 / 1.3 / 11.4 / 0.54 ( 6.4 ) / 3.5 / 0.20

9.2 / 1.3 / 11.4 / 0.54 ( 6.4 ) / 3.5 / 0.20

9.2 / 1.3 / 11.4 / 0.54

9.2 / – / – / –

9.2 / 1.3 / 5.0 / 0.70

9.2 / 1.3 / 5.0 / 0.54

8.0 / 1.5 / 5

6.0 / 1.0 / 3.5 / 0

9.2 / 1.3 / 6.5 / 0.85

12.4 / 2.4 / 5.7 --, for 7.5 - 14 kW, JIS 50% Smoke

10.5 / 1.9 / 5.7 --, for 15 - 29 kW, JIS 50% Smoke

9.2 / 1.3 / 5.0 --, Tier 1 standards are application-

specific and apply to engines 30 – 272 kW, JIS 50%

Smoke

U.S. EPAkW

0 - 7

8 - 18

19 - 36

37 - 55

56 - 74

75 - 129

130 - 224

225 - 449

450 - 560

>560

(HP)

(0 - 10)

(11 - 24)

(25 - 48)

(49 - 74)

(75 - 99)

(100 - 173)

(174 - 301)

(302 - 602)

(603 - 751)

(>751)

EUROPE

JAPAN (Tier 1 standards applicable by application. Tier 2 and Tier 3 applicable by power category.)

2000 2001 2002 20031996 1997 1998 1999

2000 2001 2002 20031996 1997 1998 1999

2000 2001 2002 20031996 1997 1998 1999kW (HP)

kW

18 - 36

37 - 55

56 - 74

75 - 129

130 - 560

(HP)

(24 - 48)

(49 - 74)

(75 - 99)

(100 - 173)

(174 - 751)

19 - 36 (25 - 48)

8 - 18 (11 - 24)

37 - 55 (49 - 74)

56 - 74 (75 - 99)

75 - 129 (100 - 173)

130 - 560 (174 - 751)

6.0

6.0

8.0


8

NOx/HC/CO/PM (g/kW-hr)(NOx+HC)/CO/PM (g/kW-hr)(Conversion: [g/kW-hr] x 0.7457 = g/bhp-hr)

The chart above is displayed for reference purposes only and does not depict the various options availableto engine and equipment manufacturers. See the appropriate regulations for specific details and optionsrelated to that region's emissions standards and implementation dates.



9

( 4.0 ) / 5.0 / 0.30

7.5 ) / 8.0 / 0.80

7.5 ) / 6.6 / 0.80

( 7.5 ) / 5.5 / 0.60

( 4.0 ) / 3.5 / 0.20

( 4.0 ) / 3.5 / 0.20

( 4.0 ) / 3.5 / 0.20

( 6.4 ) / 3.5 / 0.203.5 / 0.40 / 3.5 / 0.100.67 / 0.40 / 3.5 / 0.10*

3.5 / 0.19 / 3.5 / 0.040.67 / 0.40 / 3.5 / 0.03**

0.40 / 0.19 / 5.0 / 0.02

2.0 / 0.19 / 3.5 / 0.02 0.40 / 0.19 / 3.5 / 0.02

( 7.5 ) / 5.0 / 0.40( 4.7 ) / 5.0 / 0.30

( 4.7 ) / 5.0 / 0.403.4 / 0.19 / 5.0 / 0.02

( 7.5 ) / 6.6 / 0.40

( 7.5 ) / 5.5 / 0.30( 4.7 ) / 5.0 / 0.03

0.4 / 0.19 / 3.5 / 0.025

0.4 / 0.19 / 5.0 / 0.025

( 4.7 ) / 5.0 / 0.025

3.3 / 0.19 / 5.0 / 0.025

3.3 / 0.19 / 5.0 / 0.025

2.0 / 0.19 / 3.5 / 0.025

( 7.5 ) / 5.5 / 0.6

( 4.0 ) / 5.0 / 0.3

( 4.0 ) / 3.5 / 0.2

1.0 / 5.0 / 0.3

( 4.7 ) / 5.0 / 0.41.3 / 5.0 / 0.4

1.5 / 5.0 / 0.8, 40% Smoke

6.0 / 1.0 / 5.0 / 0.40, 40% Smoke

4.0 / 0.7 / 5.0 / 0.30, 35% Smoke

4.0 / 0.7 / 5.0 / 0.25, 30% Smoke

Tier 4 not yet proposed.

0.3, 40% Smoke

Tier 4 standards/dates not yet proposed.

0.2, 40%

1.3 / 5.0 / 0.4, 40% Smoke

0.8, 40% Smoke

3.6 / 0.4 / 5.0 / 0.20, 25% Smoke

3.6 / 0.4 / 3.5 / 0.17, 25% Smoke



2016 20172012 2013 2014 20152008 2009 2010 201105 2006 2007

2016 20172012 2013 2014 20152008 2009 2010 201105 2006 2007

2016 20172012 2013 2014 20152008 2009 2010 201105 2006 2007

Tier 4 FinalTier 4 InterimTier 3Tier 2Tier 1

Tier 4Tier 4Tier 3Tier 2Tier 1

Stage IVStage IIIBStage IIIAStage IIStage I

**Applies to portable power generation >1200 hp**Applies to portable power generation >751 hp



Fuel Standards – Tier 3/Stage IIIA-Tier 4/Stage IIIB and Stage IV

In meeting the new emissions requirements, diesel fuel is a critical part of the solution. The

sulfur level in diesel fuel for non-road engines in the U.S. will be lowered in two steps. First,

refiners will be required to reduce the sulfur level to 500-ppm maximum beginning in 2007.

In 2010 the sulfur in non-road diesel fuel must be further reduced to a maximum of 15-ppm.

The U.S. EPA has built in various flexibilities for refiners to ensure a smooth transition to

ultra-low sulfur fuel for the non-road market. These flexibilities will allow higher sulfur non-

road fuel to be sold beyond the effect dates listed above. However, because ultra-low sulfur

fuel is necessary for most aftertreatment technology, federal law will prohibit the use of

higher sulfur fuels in model year 2011 and later non-road engines.

Ultra-low sulfur fuel (15-ppm) has several beneficial effects. It inherently produces less PM

from combustion, so it is a PM control strategy for all in-use equipment. At Tier 4/Stage IV,

it enables advanced NOx aftertreatment technology. It also can have a positive effect on oil

drain intervals. With the fuel standards changing, there will be two fuels available in the

marketplace simultaneously, which will increase the risk of misfueling. Even at Tier 3/Stage IIIA,

sulfur levels above 500-ppm can be an issue with certain NOx-reduction solutions such as

cooled EGR. At Tier 4/Stage IV, most NOx aftertreatment will require ultra-low sulfur fuel

(15-ppm). Misfueling must be controlled to avoid aftertreatment issues/repair. NOx adsorbers

are not tolerant to fuel sulfur. SCR is tolerant of fuel sulfur.

PM aftertreatment (particulate filters) may not be permanently

damaged from misfueling, but the higher level of sulfur will

render the PM filter less effective and may not be emissions-

compliant due to the increased production of sulfates.


10



Lubricating Oil

Another important factor in meeting future emissions requirements is

the engine lubricating oil. New specifications are being developed to

be compatible with low-emissions solutions for Tier 4/Stage IV. The

primary focus will be to make the oils compatible with aftertreatment

devices. To enable Tier 4/Stage IV aftertreatment solutions, the

immediate requirement is to reduce ash and to extend maintenance intervals on the diesel

particulate filter while maintaining the important lubricating capability. It is likely today’s

on-highway API CI-4 or a future iteration of this oil will be used.

Tier 3/Stage IIIA NOx Emissions Reduction Options

The primary focus for the Tier 3/Stage IIIA standard is on NOx reduction. The NOx

standards for Tier 3/Stage IIIA off-highway emissions are listed in the chart on pages 8

and 9. The steady-state emissions test cycle remains unchanged for Tier 3/Stage IIIA.

Cummins has thoroughly examined all feasible

options to meet Tier 3/Stage IIIA standards,

and the best solution for our customers is

advanced combustion technology. The

following section explains the various reasons

why Cummins will not be using aftertreatment

or exhaust gas recirculation (EGR) in our

Tier 3/Stage IIIA engines.

11

Tier 3 Development:ISO 8178 8-Mode Test Cycle



NOx-Reduction Options for Tier 3/Stage IIIA:

■ Cooled EGR

■ Internal EGR

■ Advanced combustion

■ Aftertreatment

Cooled EGR

Cooled Exhaust Gas Recirculation (EGR) technology was introduced for U.S. on-highway

markets in 2002 to meet the 2.5-g/hp-hr NOx+NMHC EPA automotive standards. Cooled

EGR is a very effective NOx control. The EGR system takes a measured quantity of exhaust

gas, passes it through a cooler before mixing it with the incoming air charge to the cylinder.

The EGR reduces oxygen concentration in the combustion chamber by diluting the

incoming ambient air with exhaust gases. During combustion, the lower oxygen content

has the effect of reducing flame temperatures, which in turn reduces NOx since NOx

production is exponentially proportional to flame temperature.

In EGR engines, exhaust gases are cooled by engine coolant and additional combustion

air cooling is also needed which raises the total vehicle or equipment cooling system

requirement. For on-highway applications this is managed well with vehicle ram air and

slightly larger cooling packages. Where ram air is not available, increased cooling fan and

radiator/charge air packages are required to reject the additional heat (15%-25% higher

heat rejection). This may result in higher parasitic loads and increased cooling system

cost and noise levels.


12



Cooled-EGR solutions also increase

the demand on the air-handling

systems and typically result in a

slight power density reduction,

possibly eliminating the previously

offered highest ratings at the new

emissions levels. Low sulfur fuels

and proper oils released for on-

highway markets are also recommended. These fuels and oils are available and are

targeted for Tier 3 regulated areas. However, in unregulated areas, lower sulfur fuels and

proper lubrication oils may not be available.

Internal EGR or Un-Cooled EGR

As with cooled EGR, the EGR reduces oxygen concentration in the combustion chamber

by diluting the incoming ambient air with exhaust gases. During combustion, the lower

oxygen content has the effect of reducing flame temperatures, which in turn reduces

NOx production since NOx is exponentially proportional to flame temperature.

However, since the exhaust gas is quite hot when directly recirculated back into the

combustion chamber, the benefits are limited. The air/fuel ratios are also reduced,

resulting in increased smoke and fuel consumption. This technology will limit power

density and will likely be used only in low BMEP applications.

13

Cooled-EGR Schematic



NOx Aftertreatment

NOx aftertreatment will not be required at Tier 3/Stage IIIA. These options will be discussed

in detail at Tier 4/Stage IV.

Advanced Combustion

Critical elements of base engine design

to optimize combustion involve the

power cylinder, air-handling, fuel and

control systems. Cummins has made a

large investment in the development of

advanced combustion systems that

reduce engine-out emissions at the

source – inside the combustion chamber. The combustion system design process uses

detailed computer simulation of the combustion event, allowing engineers to study the

effects of changes to fuel injection system parameters and combustion chamber geometry.

This advanced design process accelerates the development process and has allowed

Cummins to attain low engine-out NOx and particulates.


14

Characteristics of Diesel Combustion



Cummins In-Cylinder Advanced Combustion Solution for Tier 3/Stage IIIA

Cummins knows combustion. Using analysis-led

design, engineers can model chemical reactions

anywhere in the cylinder at any time and optimize

the results by controlling or modifying critical

design parameters. We can analyze thousands

of combinations before committing to a design

and have developed great correlation between

analysis and empirical tests. This process has led

to defining the Tier 3/Stage IIIA solution for all

Cummins industrial products.

Cummins has been able to optimize the combustion system to meet the Tier 3/Stage IIIA

NOx levels without the need for emissions control devices such as EGR or oxidation catalysts.

In addition, the Cummins Tier 3/Stage IIIA advanced combustion solution provides a stable

equipment architecture through 2015 and beyond. The following Cummins products will

meet Tier 3/Stage IIIA emissions with minimal product changes from Tier 2.

QSK19 Minimal change from Tier 2 – add Common-Rail Fuel System

QSX No change from Tier 2 product

QSM No change from Tier 2 product

QSC, QSL No change due to emissions, but will transition to the latest platform/

technology with Common-Rail Fuel System

QSB No change due to emissions, but will transition to the latest platform/

technology with Common-Rail Fuel System

15



Fuel Systems

Fuel systems have been, and will

continue to be, a critical element in the

total emissions recipe. There are many

injection characteristics that must be balanced and tuned with all other critical engine

subsystems (base engine, air-handling, aftertreatment and controls). Clearly, electronic fuel

systems will be standard on most Tier 3/Stage IIIA solutions and will be required for Tier 4/

Stage IV. While there are many varieties and styles of fuel systems on the market today,

having full electronic control over fuel timing, quantity, pressure, delivery rate shape and the

number of injection events is a must for optimum emissions solutions and performance.

One such advanced system is the High-Pressure Common-Rail (HPCR) fuel system used

on the latest platforms of the QSB/QSC/QSL/QSK19. This system has full control over the

fuel injection event in relation to timing, quantity, pressure and number of injections.

Electronic Controls

The electronic control of engine systems is a critical element

in meeting emissions standards. More stringent emissions

regulations certainly require very precise control of engine, fuel,

air-handling and aftertreatment systems. Environmental factors

also need to be monitored to ensure that both engine power and

emissions levels remain as specified. At the same time, the extreme operating environments

in off-highway applications require a robust electronic system for reliable operation.


16

Common-Rail Fuel System



Cummins designs electronic control systems to meet the needs of individual applications in

the harshest environments. These designs have resulted in common architecture across all

Cummins electronic engines – small or large – in the area of control modules, software,

tools and sensors/harnesses. In addition, the systems are created to work seamlessly with

equipment electronics and provide operation data. Cummins has developed additional

electronic tools such as PowerMatch and Advisor to assist in equipment integration,

power optimization and diagnostics for all types of equipment and applications.

Tier 4/Stage IV Emissions Reduction Options

The final Tier 4/Stage IV emissions standards drive to very low NOx and PM limits. While

the primary focus for the Tier 3/Stage IIIA standard is on NOx reduction, the Tier 4/Stage IV

standard drives both NOx and PM down to levels that will likely require aftertreatment. Both

NOx and PM reduction technologies will be discussed.

NOx Reduction

The same NOx reduction technologies are considered for Tier 4/Stage IV as for Tier 3/

Stage IIIA with the addition of NOx aftertreatment. The following NOx aftertreatment

technologies are considered for Tier 4/Stage IV.

■ Selective Catalytic Reduction

■ NOx Adsorbers

■ Lean-NOx Catalysts

17



Selective Catalytic Reduction (SCR)

Selective Catalytic Reduction (SCR) systems use a chemical reductant, in this case urea,

which converts to ammonia in the exhaust stream and reacts with NOx over a catalyst to

form harmless nitrogen gas and water. Urea is a benign substance that is generally made

from natural gas and widely used in industry and agriculture. SCR systems are being

proposed today for mobile on-highway applications and are expected to be introduced in

Europe in October 2005. In an SCR system, the urea injection rate must be tightly controlled.

If the injection rate is too high, not all

of the ammonia will react with the

NOx, and some ammonia will “slip”

through the catalyst. If the rate is too

low, the desired NOx reduction will

not be achieved. Both situations are

undesirable and must be avoided.


18

Emissions Solutions for Tier 4 and Beyond

Selective Catalytic Reduction - SCR



The urea-SCR system basically consists of three elements:

■ Catalyst – The catalyst is mounted in the exhaust stream. It can be similar in

outward appearance to a muffler, but depending on NOx reduction required could

be marginally larger. It contains chemical compounds which, in the presence of

ammonia, help transform nitrogen oxides into harmless chemicals.

■ Urea – Urea quality and concentration in aqueous solution are important and must

be controlled and distributed properly. Urea is carried on board the equipment as a

water solution in a storage tank with a typical capacity of 5% of the diesel tank. The

storage tank is sized to minimize operator filling, but within packaging and weight

constraints of the equipment. The storage tank and urea injection system must be

protected from freezing or have a controlled heating system, since the urea-water

solution solidifies at approximately -11ºC.

■ Urea injection and control system – A sophisticated injection system and

controls (including NOx and urea quality sensors) are required to deliver a precise

amount of urea under all environmental conditions. The injection of urea has to be

carefully controlled so that the availability of ammonia is closely matched to the

amount of NOx being produced by the engine in real time.

How much urea does an SCR system use? For each 1-g/hp-hr reduction in NOx, an SCR

engine consumes urea at a rate of approximately 1.5% of the amount of fuel used.

Therefore, typical urea quantity will be 3%-8% of fuel used.

19



NOx Adsorbers

The NOx Adsorber Catalyst (NAC) is a new

technology developed in the late 1990s. The

NOx Adsorber Catalyst uses a combination of

base metal oxide and precious metal coatings to effect

control of NOx. The base metal component (for example, barium oxide) reacts with NOx

to form barium nitrate – effectively storing the NOx on the surface of the catalyst. When

the available storage sites are occupied, the catalyst is operated briefly under fuel-rich,

low-oxygen exhaust gas conditions. This releases

the NOx from the base metal storage sites

and allows it to be converted over the precious

metal components to nitrogen gas and water vapor.

Diesel engines normally operate with an excess ratio of air-to-fuel – “lean” operation.

Under lean operating conditions it is extremely difficult to control nitrogen oxides (NOx)

with a catalyst because of the excess of oxygen in the exhaust stream. Under lean

operating conditions, the NOx is simply stored in the catalyst. Regeneration is required to

release and convert the NOx to nitrogen gas. Regeneration of the NAC requires elimination

of all excess oxygen in the exhaust gas for a short period of time. This can be

accomplished by operating the engine rich, or by operating the exhaust flow through the

catalyst rich by injecting fuel prior to the NAC. Either way, the engine and catalyst must be

controlled as a system to determine exactly when regeneration is needed, and to control

the exhaust parameters during regeneration itself.


20



Sulfur poses challenges for NOx adsorbers. In

addition to storing NOx, the NAC will also store

sulfur, which reduces the capacity to store NOx.

Although 2011 and later model year non-road

engines must use ultra-low sulfur fuel (15-ppm),

sulfur at any level requires the engine design to provide for a periodic de-sulfation process –

a process to remove sulfur from the catalyst. This is similar to the NOx regeneration process,

but at higher temperatures. Obviously, additional regeneration events will also have a

negative impact on fuel economy. We expect NOx adsorbers to appear first in light-duty

automotive applications.

Lean-NOx Catalysts

A lean-NOx catalyst uses unburned hydrocarbons to reduce NOx over a catalyst. The

catalyst may contain precious metals such as platinum or other materials such as zeolite.

The successful operation of a lean-NOx catalyst requires continuous injection of fuel

upstream of the catalyst. The NOx conversion efficiency depends on many factors – but

typical values are 10%-25% in use over practical duty cycles. Both catalyst metals have

temperature range limitations that keep the conversion efficiencies lower than desired in

typical operation. Lean-NOx catalysts do not have adequate NOx reduction capability for

Tier 4 applications. However, lean-NOx catalysts are often an excellent option for retrofits.

They are relatively easy to install and integrate with existing engine and equipment systems.

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NOx Adsorber



NOx-Reduction Summary

In summary, key challenges for all NOx aftertreatment technologies (Cooled EGR, SCR,

NOx adsorber [NAC] and lean-NOx catalyst) include designing and developing integrated

systems to:

■ Be reliable and durable in all environmental conditions and applications.

■ Minimize packaging and weight.

■ Control emissions over the life of the product.

■ Minimize maintenance.

■ Be affordable in both initial price and operational costs.

PM Reduction

At Tier 4/Stage IIIB emissions standards, particulate emissions are 90% lower than the

Tier 3/Stage IIIA standards. While previous reductions in particulate matter emissions have

been achieved through engine combustion improvements, the stringent Tier 4/Stage IIIB

particulate standards require particulate aftertreatment. The active diesel particulate

filter (DPF) is the only current technical option for meeting the Tier 4/

Stage IIIB PM emissions standards. It is assumed that all engine

manufacturers will use this technology.

Active Diesel Particulate Filters (DPF)

In order to reach Tier 4/Stage IIIB particulate standards on all applications

and duty cycles, “active” diesel particulate filters are needed. Filtration of

exhaust gas to remove soot particles is accomplished using porous

ceramic media of cordierite or silicon carbide. A typical filter consists


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of an array of small channels that the

exhaust gas flows through. Adjacent

channels are plugged at opposite ends,

forcing the exhaust gas to flow through

the porous wall, capturing the soot

particles on the surface and inside pores

of the media. Soot accumulates in the

filter, and when sufficient heat is present a “regeneration” event occurs, oxidizing the soot

and cleaning the filter. The challenge of particulate filter design is to enable reliable and

consistent regeneration, so that soot is removed in all types of duty cycles. The use of this

“active” method involves monitoring the particulate filter backpressure and regeneration

events and managing the temperature entering the filter.

There are several methods to control or raise the exhaust temperature to “actively”

manage the DPF. The most promising methods for an active integrated system for

Tier 4/Stage IIIB are management of the engine combustion process in combination

with an additional oxidation catalyst. This will allow regeneration to take place under

low-ambient/low-load conditions when exhaust temperatures are low, and during normal

operation as well. EPA requirements state

that every engine has to achieve the required

reduction in every operating condition,

which is why active controls are needed.

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Active Particulate Filter



DPF Challenges

Maintenance may be required on diesel particulate filters. Metals in lubricant additives will

become ash and collect in the filter as oil is consumed and particulate matter is burned off

through regeneration. If this is the case, the ash must be cleaned from the filter or plugging

could occur. Fleetguard Emission Solutions has recently introduced its first commercial

cleaning system to the field for the automotive retrofit market. However, Cummins long-term

goal is to avoid this maintenance altogether.

Cummins is currently working with oil manufacturers on the development of low-ash oils

and to understand how different additive components may behave differently with regard to

filter plugging. If maintenance of the diesel particulate filter is required, we anticipate that it

will be at relatively high-hour intervals.

System Integration

Cummins remains focused on providing outstanding customer value, while meeting the

toughest emissions standards. Our Research and Development effort is the result of a

partnership between Cummins subsidiaries, such as Holset and Fleetguard, key suppliers

and customers. In addition, Cummins is deeply involved with our OEM partners and key

suppliers in the development and real-world testing of prototype equipment. This test

equipment is being put into service years in advance of the dates when EPA regulations

take effect. Cummins is positioned to provide turnkey solutions with advanced base

engines, controls, and packaging of the aftertreatment in the muffler.


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Meeting Tier 4/Stage IIIB Emissions – The Cummins Solution

The Cummins technology plan for off-highway applications at Tier 4/Stage IIIB

is straightforward:

■ Cummins has finalized the Tier 3/Stage IIIA technology and will utilize

those platforms for Tier 4/Stage IIIB.

■ Cummins has invested significantly in research and engineering efforts to

ensure that the proven products in operation today and at Tier 3/Stage IIIA

are the base platforms for Tier 4/Stage IIIB. To this end, we are working

hand-in-hand with our partner OEMs.

■ Cummins is the only engine manufacturer with wholly owned subsidiaries

providing technology for air-handling (Holset) and aftertreatment systems

(Fleetguard Emission Solutions).

■ In 2011, Cummins will use an active particulate filter to achieve the

Tier 4/Stage IIIB 90% reduction in particulate matter.

■ For very large engines above 751 hp (560 kW), Cummins will be prepared

to meet future emissions requirements.

The Right Technology Matters

The right technology does matter. That is why Cummins has invested in critical components

and subsystems across our entire product line. That is how we will continue to deliver

products that meet the demands of our customers at the lowest emissions levels.

Every hour. Every day. Every time.

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Glossary

Adsorber Catalyst An aftertreatment technology that uses a base metal oxide

and a precious metal compound as a catalyst to transform

NOx to nitrogen gas and H2O (water vapor).

Advisor A proactive tool for OEMs and technical support to select

and design installations that maximize engine to machine

performance for the end customer.

BMEP Brake Mean Effective Pressure. The average (mean) pressure

which, if imposed on the pistons evenly during each power

stroke, would produce the measured (brake) power output.

Common-Rail Fuel delivery system that maintains a high injection pressure

Fuel Injection regardless of engine speed, using high-pressure fuel stored

in a single “common” rail or tube that connects to every fuel

injector on the engine.

DPF Diesel Particulate Filter. Also known as a particulate “trap.”Captures particles of soot in a semi-porous medium as they

flow through the exhaust system. Available in “passive” or

“active” configurations. Active DPFs use a control system to

actively promote regeneration events.

EGR Exhaust Gas Recirculation. Technology that diverts a small

percentage of the exhaust gas back into the cylinder,

lowering combustion temperatures and reducing NOx.

EPA Environmental Protection Agency. Among many duties, the

U.S. government agency is responsible for governing heavy-

duty engine emissions.

Exhaust Any technology which treats emissions in the exhaust flow,

Aftertreatment as opposed to inside the power cylinder.


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Fleetguard A subsidiary of Cummins that is a world leader in theEmission Solutions development of advanced emissions and filtration

technology.

“Lean” Engine Using an air/fuel mixture with more air than fuel versus what

Operation would occur in a natural (stoichiometric) burning condition.

Lean-NOx Catalyst Uses platinum or zeolite as the reactant. Diesel fuel injected

upstream of the catalyst performs a similar function to urea

in an SCR system.

NAC NOx Adsorber Catalyst.

NMHC Non-Methane HydroCarbons. Primarily unburned fuel

in the exhaust stream.

NOx Nitrogen Oxides.

PM Particulate Matter, composed primarily of soot and other

combustion by-products.

PowerMatch A Calibration Delivery System allowing quick and easy

tailoring of electronic calibrations for a new application.

“Rich” Engine Using an air/fuel mixture with more fuel than air versus what

Operation would occur in a natural (stoichiometric) burning condition.

SCR Selective Catalytic Reduction. An aftertreatment technology

that uses a chemical reductant (urea) that is injected into the

exhaust stream where it transforms into ammonia and reacts

with NOx on a catalyst, converting the NOx to nitrogen and

water vapor.

Sulfur A natural element which has been linked to acid formation

both inside engines and in the atmosphere.

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Terms for U.S. EPA European Union Approximately Tier 1.....................Stage I

Equivalent Tier 2.....................Stage II

Standards Tier 3.....................Stage IIIA

Tier 4 - Interim.......Stage IIIB

Tier 4 - Final ..........Stage IV

ULSF Ultra-Low Sulfur Fuel. Diesel fuel which contains less

than 15 parts per million by volume of sulfur. Mandated

September 2010 for off-highway.

Urea A chemical usually made from natural gas, it is commonly

used in fertilizers. Urea breaks down into ammonia (NH4 )

and reacts with NOx in an SCR system.


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Cummins Inc.Box 3005Columbus, IN 47202-3005U.S.A.

Phone: 1-800-DIESELS (1-800-343-7357)

cummins emissions overview

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