diesel engine and the environment - dynamic positioning...

September 16-17, 2003Houston, Texas

Session Chair – Wayne Cole, Cole Engineering

ENVIRONMENT

The Diesel Engine and the Environment

David SteffensWartsila North America, Inc.

Introduction

The diesel engine and the environment - rules and regulations

- emission reduction technologies

Return to Session Directory

WFI-M MarineTypical composition of diesel engine exhaust gas

Nitrogen N2 : 76%Oxygen O2: 13%Carbon dioxide CO2: 5% Low due to high efficiencyWater H2O: 5%

Sulphur oxides SOX Fuel choice relatedCarbon monoxide CO Low due to good combustionHydrocarbons CXHy Low due to good combustionParticles Low at steady state operation

Influenced by fuel ash and sulphur content

Visible smoke FSN Low load related (<25% load)Nitrogen oxides NOX To be controlled

Together> 99.5%


Exhaust compounds and their environmental impactNOx:

– acid rain, acidification– ozone/smog formation in the lower atmosphere(potential damage on vegetation and human health)

Particulates:– some considered carcinogenic– blackening with soot

SOx:– acid rain, acidification– potential detrimental effect on human health

CO:– ozone/smog formation in the lower atmosphere

CO2:– the major greenhouse gas

Hydrocarbons: – ozone/smog formation in the lower atmosphere– some considered carcinogenic– contribute to the greenhouse effect


Annex VI to MARPOL 73/78

Applies to: Ships of 400 GRT or above,Platforms and Drilling Rigs

Enters into force: 12 month after the date on which not less than 15 states, constituting not less than 50% of the gross tonnage of the world’s merchant fleet, have signed the protocol

It is important to note that the NOx emission regulation is linked to the date, 1st of January 2000. Ships constructed after this date will be required retroactively to comply with these requirements when Annex VI enters into force.


IMO MEPC Proposal for Global Marine NOxLegislation

0

20

18

16

14

12

10

8500

NO

xem

issi

ons,

wei

ghte

d (g

/kW

h)

1000Rated engine speed (rpm)

ISO 8178 Test ProcedureReference Fuel: Marine Diesel Oil

1500 2000

NOx (g/kWh) = 17= 45 x rpm= 9.8 2000

130 rpm < 130

rpm >< rpm < 2000-0.2


Diesel NOX Formation

Thermal NOX formation (65-75%)

Nitrogen source: combustion air

Formation process: extremely complex including hundreds of different reactions

Strong temperature influence (exponential)


Thermal NOx Formation

02

4

68

1012

14

1618

20

400

200

600

800

1000

1200

1400

1600

1800

2000

2200

2400

Local Temperature (K)

Rel

ativ

e N

Ox

-Con

cent

ratio

n

NOx Equilibrium Concentration


Typical NOx-Emissions for Different Types of Engines

8

13

4

8

0.651.3

Typical NOx Emissions in g/kWh:

DieselLiquid Fuel

Gas Diesel

Lean BurnGas Engine


operating on MGO

0

2

4

6

8

10

12

14

Diesel engine withSelective Catalytic

Reduction

Aeroderivative gasturbine

Diesel engine withDirect Water

Injection

Diesel engine

NO

x g/

kWh

NOx emissions of different prime movers


Emission reduction

Technologies to reduce emissions:

• Primary Methods - During Combustion

• Secondary Methods - After Combustion


Primary NOx control - diesel engines

Available today - Combustion ModificationEmission rating

– Adjustment of fuel injection timing/TC specification– NOx reduction potential: 10 - 20 %– Simple and cheap– Increased fuel consumption and thermal load

Low NOx combustion– Rearranged diesel cycle– NOx reduction typically: 25 - 35 %– NOx well below the IMO limit– Unchanged or improved fuel consumption


Primary NOx control - diesel engines

Direct water injection– Humidification of the combustion process– NOx reduction typically: 50 - 60 %– Improved thermal load and engine cleanliness

Available today - Water Injection

Water-in-fuel emulsions– Humidification of the combustion process– NOx reduction potential typically: 20 %– Limitations

• emulsion stability• fuel injection system capacity• poor engine performance in “non-water” operational mode• cavitation risk in injection system


Low NOX Combustion Engine Design

Rearranged diesel cycle– Very late fuel injection start– Higher compression ratio– Early inlet valve closing (4-stroke)– Late exhaust closing (2-stroke)– Optimized combustion chamber– Optimized fuel injection pressure

Results– Lower combustion temperatures– Shorter duration at high temperatures

Conclusions– NOX reduction typically 25-35%– Unaffected fuel consumption


Low NOx Combustion

-90 -90-60 -60-30 -300 030 3060 6090 90120 120

Cyl

inde

r Pre

ssur

e

Cyl

inde

r Pre

ssur

e

Pressure riseinduced fromcombustion

Pressure riseinduced fromcombustion

Pressure riseinduced fromcompression

Pressure riseinduced fromcompression

Conventional DesignEngine Maximum Firing Pressure

Low NOx DesignEngine Maximum Firing Pressure

Application: All Fuel Types

TDC TDC


Implementation of Low NOx Combustion onWärtsilä Vasa 32b

100%

80%

100% 97%

Relative NOx Emissions Relative Spec. Fuel Cons.

Σ = 12WV32

Σ = 13.8WV32LN

Σ = 12WV32

Σ = 13.8WV32LN

Compr.Ratio


Features of fuel-water emulsionsDisadvantages

– Increased camshaft torque and cam load.– Full load of engine not possible at high water ratios due to

limitations in the fuel injection equipment.– Same nozzles not optimal for operation with and without

emulsion.– Negative impact on injection equipment reliability and

lifetime.– Increased fuel viscosity, higher preheating temperatures

needed.Advantages

– Improved low load smoke.– Lower NOx. The NOx limitation is limited to about 20%,

because unlimited water amounts cannot be kept in a stable emulsion.


FSNMEC Test on W6L46CR, Vaasa

2-19 December 2002INFLUENCE OF WATER EMULSION ON FSN

Standard Nozzle: 12x0.64x160°, Fuel: HFO

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0 10 20 30 40 50 60 70 80 90 100 110

Engine load [%]

W/F ratio = 0, without MECW/F ratio = 0, with MECW/F ratio = 0.1W/F ratio = 0.2W/F ratio = 0.3

FSN


NOx emissionsMEC Test on W6L46CR, Vaasa

2-19 December 2002INFLUENCE OF WATER EMULSION ON NOx EMISSIONS

Standard Nozzle: 12x0.64x160°, Fuel: HFOReference NOx: Without MEC

0.75

0.80

0.85

0.90

0.95

1.00

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

W/F ratio

100% load85% load75% load50% load

Rel

ativ

e N

O


The principle of Direct Water Injection


Direct Water Injection

Flow fuse

High pressurewater pump

Watertank

Water

Fuel

Water needle

Fuel needle

Solenoidvalve

Controlunit

T


Direct Water Injectiontypical water/fuel timing and duration


•CASS (Combustion Air Saturation System)

Emission Control Technologies - Tomorrow’s solutions

Future Technologies:


CASS

CASS

The hot air after the compressor is cooledto the saturation point by injecting watermist

After heating in the “charge air cooler” the mixture is again saturated by injecting ofmore water

Heating of the air by HT-water

Compressor “Intercooler”/heater

Receiver

Heat

Water injection

Water injection


Efficiency of humidification methods

Relative NOxformation

0.5 1.0 1.5 2.0

Direct Water Injection

Combustion Air Humidification

1.11.00.90.80.70.60.50.40.30.20.1

Water/Fuel flow ratio

W20

W32


Predicted NOx behavior with different control methods on Wärtsilä 46

NOx

5

10

15

50 100 150 200 250Water amount as % of fuel consumption

Fuel Water Emulsion

CASS

FWE + CASS


Secondary NOx control - diesel engines

Available today

Selective catalytic reduction (SCR)– NOx reduction typically: 85 - 95 %– Urea/water solution injected – Integrated part of the engine package– Exhaust temperature window 330 - 450 °C at HFO operation– Investment and operating costs relatively high

Compact SCR– Combined silencer and SCR unit– Minimized size


Principle of Selective Catalytic Reduction


SCR Reactions With Urea

Before Entering the Reactor:(NH2)2 CO + H2O 2 NH3 + CO2

In the Reactor:4 NO + 4 NH3 + O2 4 N2 + 6 H2O

6 NO2 + 8 NH3 7 N2 + 12 H2O


Retrofit of Compact SCR

Birka Princess at Lloyd Werft

SCR plants have been retrofitted in several passenger ships in existing engine casing = no lost space!

A Compact SCR occupies a little more space than a normal silencer which it replaces.


Particle Emissions– Particle emissions are seen as smoke– More prevalent at low loads and start-up

Smoke Reduction Methods– Common rail fuel injection

Smokeless Diesel Engine


Targets for the Smokeless Engine• No visible smoke at start-up• No visible smoke at any load• NOx emissions to be reduced• CO2 emissions to be reduced even lower by further

improvements in efficiency

Smokeless Diesel Engine


Conventional injectionsystem

Common Rail Injection

Fuel pressureproduced each time by the injection pump

Mechanical./hydrauliccontrol at the injectors

Constant fuelpressure

Electronic / hydrauliccontrol of injection

Conventional vs common rail fuel injection


WÄRTSILÄ COMMON RAIL SYSTEM


Common Rail advantages

• Smokeless operation at all loads and speeds.

• Smokeless start of the engine.

• Smokeless load pick-up ramps.

• NOx reduction down to 3…4 g/kWh with humidification possible without visible smoke.

• Improved total fuel economy.

• Flexibility for different fuels without hardware modifications (heavy fuel, diesel oil, gas turbine fuel, water-fuel emulsion).

• Improved safety and comfort because more engines can be kept running with still good fuel economy and no smoke.


Wärtsilä 46 Common Rail

FSN status at engine laboratory and delivery test run

Engine load (%)

Filte

r sm

oke

num

ber

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 10 20 30 40 50 60 70 80 90 100 110

**

** *

Best lab. results with modified piston shape

Conventional injection

THIS ISSMOKELESS

Production engines May 2002 and for upgrading


diesel engine and the environment - dynamic positioning...

Documents