Michael DeakinTÜV Rheinland Indonesia

Vehicle Development Towards Pollution Management2019-03-29

Pollution Management

� What are we managing, and why?

� Regulatory controls & progress in Europe

� Technology for conventional powertrains

� The direction of engine development

� Electric and hydrogen-fueled propulsion

� Short and long-term solutions

3/29/20192

Regulated Pollutants

� Carbon Monoxide (CO): − Readily displaces oxygen in the blood and also has cumulative effects

− Caused by incomplete oxidation of carbon in the fuel

− Easy to control – needs only further oxidation in the exhaust stream

� Hydrocarbons (THC, HC, NMHC): − Total and non-methane are separately regulated since methane is not considered harmful

− Caused by incomplete combustion of fuel and lubricating oil

− Easy to control with oxidation catalyst

� Nitrous Oxides (NOx): − Predominantly NO and NO2, responsible for respiratory complaints and acid rain formation

− Caused by dissociation and recombination of nitrogen and oxygen from the induction air, under high combustion temperatures and pressures.

3/29/20193

HC and NOx combine to generate photochemical smog

Regulated Pollutants

� Particulates:− A complex blend of carbon, organic compounds and incombustible matter

which varies according to operating conditions− Ash from inorganic matter, soot, sulphates and unburnt/partially burnt hydrocarbons

− Heavily influenced by fuel quality and mixture formation

− Composition changes in the exhaust as volatile fractions condense around a solid nucleus

− Typically, 90% of the mass is from particles >10nm, yet 90% of the quantityare <2.5nm− Different measurement techniques for particulate mass and particulate number are

sensitive to different size distribution of particles.

− Accurate direct measurement of particulate mass by weighing becomes increasingly difficult as the limits and sample mass get smaller

� Ammonia (NH3)− As a pollutant: A by-product of 3-way catalysts, particularly at low temperature

− Deliberate addition to enable aftertreatment systems to function

3/29/20194

Carbon Dioxide

� Unregulated pollutant, but the effects of CO2 on global warming are a significant driver of new technology.

� European Commission reports that 12% of CO2 generation in the Union is from vehicles

� Most Member States employ some kind of taxation principle based either on CO2 emission or fuel consumption− Used as a driver to motivate the population in to newer, more efficient vehicles

� European fleet average in 2017 was 118.5g/km in 2017, against a target of 130g/km− 22% reduction since 2010

� 2021 fleet average target is reduced to 95g/km

� Increasing complexity of engine and emissions management systems tend to have an adverse effect on CO2 emissions

3/29/20195

EU Regulatory Progress – Passenger Cars

Euro 1 Euro 2 Euro 3 Euro 4 Euro 5 Euro 6 Euro 6d

1990 1995 2000 2005 2010 2015 2020

SI CI SI CI SI CI SI CI SI CI SI CI SI CI

Euro 1 2.72 2.72 0.97 0.97 0.14

Euro 2 2.2 1 0.5 0.7 0.08

Euro 3 2.3 0.66 0.2 0.15 0.5 0.56 0.05

Euro 4 1 0.5 0.1 0.08 0.25 0.3 0.025

Euro 5 1 0.5 0.1 0.068 0.06 0.18 0.23 0.0045 0.0045 6E^11

Euro 6 1 0.5 0.1 0.068 0.06 0.08 0.17 0.0045 0.0045 6E^12 6E^11

Euro 6d 1 0.5 0.1 0.068 0.06 0.08 0.17 0.0045 0.0045 6E^11 6E^11

SI = Spark Ignition

CI = Compression Ignition

PNCO THC NMHC NOx THC+NOx PM

THAILAND

Limits in g/km

!

EU regulatory progress – Heavy Duty Engines

� Ammonia limit introduced at Euro 6

� Testing and enforcement has been adapted and improved for Euro 6:− Transient test cycles for certification values− ‘Not to Exceed’ limits on randomly generated cycle− Real Driving Emission (PEMS) testing on public

highway.− In-Service conformity testing− On-board diagnostic testing

� The forces for change in the EU are different to those in Asia− NOx emission is critical in the EU− PM/PN dominates in SE Asia

Thailand

How to tackle exhaust pollution?

In order of complexity……

1. Less vehicle usage = less pollution and less CO2 emission.

2. More efficient drivetrains

3. Alternative or better refined fuels

4. Cleaner combustion

5. Better aftertreatment

6. No combustion –> switch to electric vehicles

The most appealing for our environment

Attractive, but not the most practical option

� Focus on items 2 to 5

3/29/20198

2. Drivetrain Improvements – Engine Development

� Benefits are principally lower CO2 emissions, but lighter loads also impact on other pollutants.

� Evolution, not revolution− Does not require radical re-design or costly additional parts -> Often a win-win situation

� Can be applied to any engine type

� Examples− Idle stop & cylinder deactivation > Savings depend upon traffic condition

− Low friction coatings on piston rings and skirts > 2-5%

− Honing patterns on cylinder walls > 1%

− Reduced tension on shaft seals > 0.3%

− Lower viscosity lubricants > 0.5%

− Electrically driven oil / coolant / auxiliary pumps with operation matched to actual demand > Variable gains

− Intelligent transmission – Optimises engine performance to road conditions and driver demand >1.5%

3/29/20199

2. The Cost of Technology (Petrol engine car - per vehicle)

Minimizing engine friction $50

Stop-start $500

Mild hybrid $1500

Lean-burn GDI engine$2500

Plug-in hybrid $5000

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2. Turbo Compounding

� Electrical− Secondary turbine connected to a generator to provide

additional electrical energy for vehicle systems

− Used in Formula 1 - in conjunction with regenerative braking can give power unit efficiency in excess of 50%

− Turbo can also be electrically driven to eliminate lag

� Mechanical− Secondary exhaust turbine is mechanically connected to the

engine crankshaft

− Direct impact on engine power output

− Better suited to commercial vehicles

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3-5. Pollution Control Stages

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Fuel

Air

Mixture Formation Combustion Aftertreatment

EGR

3. Fuel Quality

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� Global availability of low-sulphur fuel in 2018

� Thailand has made better progress than her neighbours, but more improvement is desirable

Euro IV 50ppm

3. Alternative Fuels & Fuel Additives

� CNG:

− Widely used in commercial vehicles

− Abundant as a fossil fuel, easy to obtain from refinery by-products or bio sources

� LPG:

− Commonly used in taxis and light-duty applications, including industrial

− Can be derived from a greater number of sources than petrol/diesel

� Low refinement cost

� Energy density is lower than liquid fuels

3/29/201914

Smaller, more volatile fraction

hydrocarbons, are inherently cleaner

burning and contain less sulphur

3. Alternative Fuels & Fuel Additives

� Biodiesel/Bioethanol: − Either as a percentage in fossil-based fuels, or as a whole fuel

− Generally has lower sulphur content than fossil fuels, but otherwise has not been shown to significantly affect emission performance in real-world situations

− Only viable in regions where using biomass for fuel does not impact on food resource.

� Fuel ether additives:− Oxygenated fuel additive, assists in the oxidation of CO and HC

− Raises fuel octane rating, allowing higher compression ratios

� Fuel-borne catalysts:− Compounds of iron, cerium or platinum

− Do not affect combustion, but reduce the temperatures required for soot regeneration in exhaust particulate filter systems

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4. Fuel Management & Mixture Formation

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� Port injection (Spark ignition)− Emission related variables are injector positioning and timing with respect to valve opening− Mechanisms are well understood and unlikely to change significantly− Significant advances in inlet port design to improve gas flow within the cylinder− Bore/stroke ratios optimized for fastest flame propagation− Economical to manufacture!

� Direct injection (Compression and spark ignition)− Particulate and HC emission are heavily influenced by injector nozzle design− Small injector orifices less reliable in service− Practical limitations to maximum fuel pressure

4. Air Management:

� Turbocharging:− Energy recovery from waste exhaust gas raises the overall efficiency of the powertrain

− Allows for excess air conditions which can be utilized either for optimizing power output or for emission control

− Smaller power unit may be used

� Supercharging:− Provides excess air for emissions and power, but does not recover waste heat energy

− Electric supercharging – variable boost at any engine speed (needs >12v supply)

− Turbo/supercharger combinations

� Ozone Seeding:− Ozone generator located in the air manifold/ports

− Useful in assisting the low-load operation of homogenous charge compression ignition (HCCI) engines

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4. Exhaust Gas Recirculation (EGR)

� Used as a NOx control measure in all diesel engines and some gasoline engines

� Exhaust gas acts as a diluent and restricts the amount of free oxygen available for combustion, lowering peak combustion pressure

� EGR reduces peak combustion temperatures as exhaust gas has a higher specific heat capacity than air.

� Typically, 5-30% EGR is used, depending upon the engine load.

� Was used historically in lean-burn petrol engines and is now seen again in GDI applications

3/29/201918

4. Exhaust Gas Recirculation (EGR)

� Too much EGR− Limits soot oxidation, leading to high particulate emission

− Reduces thermal efficiency

− Recirculation of particulates can lead to engine wear

� Current designs incorporate high and low pressure circuits, EGR coolers and, in some applications, also a separate particulate filter

� EGR also used to control mixture temperature through selective use of cooled/uncooled gas flows− Hot EGR used at low to medium loads and during engine warm-up

− Cold EGR gives better NOx reduction

� EGR found to increase NO2/NOx ratio which assists both DPF and SCR performance

3/29/201919

4. Engine Cycles – By Tradition

� Spark ignition:− Mixture formation outside of the combustion chamber

− Spark initiates a single flame front which propogates rapidly through a homogenous fuel/air charge

− HC & CO emissions are generated by incomplete combustion or poor mixture formation

� Compression ignition:− Mixture formed inside the combustion chamber by high-

pressure direct injection

− Fuel/air charge ignites spontaneously leading to high peak pressure

− Combustion is inherently high pressure and temperature, which favours NOx formation

− PM generated by non-homogenous nature of the charge, can be overcome by very lean operation

3/29/201920

4. The New Generation – Somewhere in Between

� Homogenous charge compression ignition (HCCI)− (Volatile) fuel mixture is homogenous

− No ‘flame front’, no unburnt fuel > low HC and CO

− combustion temperature is significantly lowered > low NOx

− Lean operation > Low soot generation

− Almost perfect in terms of emission control

− Cylinder temperature is critical - only controllable over a very small range of operating conditions, so not well suited to on-road applications

3/29/201921

4. The New Generation – Somewhere in Between

� Premixed charge compression ignition (PCCI)− HCCI, but leaning towards diesel operation

− Fuel injection begins during the induction cycle, allowing for an almost homogenous mixture

− Phasing of the final injection ‘pip’ can be timed to control ignition of the whole mixture

− Small flame front rapidly propagates and increases compression sufficiently to ignite the homogenous mixture

3/29/201922

4. The New Generation – Somewhere in Between

� Spark controlled compression ignition− HCCI, but leaning towards gasoline operation

− Secondary injection creates a rich mixture zone around the spark plug

− Spark initiates the flame front creating an ‘air piston’, and pressure rise ignites homogenous charge

− Can operate in different modes, from normal spark ignition through to full HCCI

− Variable fuel/air mixtures: Lean (as low as 29:1) for light load fuel economy, stoichiometric for normal running and rich (or additional secondary injection) for power and aftertreatment regeneration

− Systems are complex and include new components such as in-cylinder temperature and pressure monitoring

3/29/201923

4. Modified Engine Cycles

� Variable compression− Modification of engine stroke or connecting rod effective length

− Compression ratio can be optimized whilst driving for efficiency or clean running

� Variable valve timing/lift− Atkinson/Miller/Budack cycles – Compression ratio not the same as expansion ratio, higher efficiency and

lower NOx

� Six-stroke cycle− Compression ignition – two combustion cycles in three revolutions

− Allows further oxidation of soot particles

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4. Gasoline Direct Injection –A case study of technology advancing faster than legislation

� GDI first introduced to the market in 1997

� Characterised by higher compression ratios and higher efficiency

� Current systems have varying levels of complexity− Direct injection only or direct + port injection

� GDI engines potentially generate similar PM and PN emissions to compression ignition engines, yet not regulated until Euro 5!

3/29/201925

12+ Years!

5. Exhaust Aftertreatment – 3-Way Catalyst

� Application: Spark ignition only

� Very little substantial design change since their introduction− Introduction of cold ambient emission testing forced a move towards

close-coupled cat’s, or a combination of close-coupled and under-floor

− Different monolith: Metal foil or ceramic honeycomb

� Must operate within a close margin of stoichiometric, so do not permit lean-burn engine operation

� Todays catalysts are designed using computational fluid dynamics techniques to improve flow distribution across the bed− Variations in cell density across the monolith allows for greater

efficiency and less volume

� Manufactures balance the precious metal (Pt, Pd, Rh) content in the washcoat according to global precious metal markets, with little change to efficiency.

3/29/201926

#1 Pt/Rh -reduces

NOx

#2 Pt/Pd -oxidisesCO & HC

5. Exhaust Aftertreatment - Lean NOx trap

� Application: All lean-burn engine types

� Similar in construction to a 3-way catalyst, but the function is store NOx emissions during lean-burn operation

� LNT’s can be effective from cold-start

� Regeneration is achieved by running the engine momentarily with a conventional stoichiometric and homogenous air/fuel mixture, then adding extra fuel to create a mixture rich in CO and HC.

� Not so efficient across the whole range of driving conditions

� Require periodical de-sulfurization cycles to remove SO3 contamination:

− Rich operation for several minutes

− Raises bed temperatures to 650-750ºC

− Degrades overall fuel efficiency

3/29/201927

5. Exhaust Aftertreatment – Oxidation Catalysts (DOC/POC)

� Application: Compression ignition (DOC), gasoline direct injection (POC)

� A flow-through type monolith which resembles the three-way catalytic converter

� Different catalyst composition (Pt/Pd) to optimize activity under lean conditions

� In diesels: − Acts on HC and CO, and also SOF component of particulate emissions which arise from unburnt fuel

− Oxidation of NO to NO2 is useful for the passive regeneration of particulate filters and improves performance of SCR systems further downstream.

� In GDI: − Acts to oxidise particulates, but with quite low efficiency (45%)

� Problems with sulphur:− Oxidation of sulphur dioxide forms sulphate particles, which contribute significantly to the overall amount

of particulate matter generated by an engine

− Like the LNT, Pt/Pd oxidation catalysts are poisoned by sulphur and lose efficiency

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5. Exhaust Aftertreatment –Particulate Filters (GPF/DPF)

� Application: Compression ignition and gasoline direct injection

� Wall-flow type is highly effective, >90% efficiency (including PM2.5).

� Flow through only 45-50% efficient

� Periodical (active) regeneration type…..− Additional fuel injected into exhaust /DOC to heat the

filter > 600ºC

− Post-injection or secondary exhaust injector

− Direct impact on fuel economy!

� Or continuous (passive) regeneration…..− Substrate is catalysed

− Oxidising agent is NO2 which is generated by an upstream oxidation catalyst

− Reaction temperature is much lower >260ºC

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5. Exhaust Aftertreatment - Particulate Filters

� Particulate filters are established technology used across many different industrial, transport and non-road applications

� Advances in design include:− Segmented construction: Prevents thermal cracking and permits varying

cell density across the filter

− Asymmetric casing, wider inlet than outlet improves efficiency

− No washcoat - catalyst incorporated within the cell matrix

− Different geometry for inlet/outlet cell to increase filtration area – increases soot loading by up to 50% for the same back-pressure

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5. Exhaust Aftertreatment – Filter Regeneration & Practical Issues

� Filter regeneration requires certain operating conditions which are not always achievable in the real world – excessive back-pressure and engine malfunctions are not uncommon!

� Both passive and actively regenerating filters require differential pressure monitoring and soot estimation algorithms in the aftertreatment management systems

� Not all PM can be burned off, oil combustion and inorganic matter in fuel creates ash which reduces filtration efficiency

� Sulphur poising of catalysed filters

� Issues with current technology using post-injection or secondary injection: − B20 does not burn as effectively over DOC, requiring more fuel to regenerate DPF

− Direct waste of fuel

− During regeneration, emissions often exceed limit values

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5. Exhaust Aftertreatment – Filter Regeneration

� Solutions?− Move the filter as close as possible to the engine to retain as much heat as possible

− Turbo by-pass − Exhaust stream is hotter and more energetic

− Electrically heated filter− Regeneration can be independent of engine running conditions

− Heater can be upstream or incorporated in the filter substrate

− Microwave heated filter

− Soot is highly absorbent of microwave energy

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5. Exhaust Aftertreatment – Retro-Fitting DPF’s on Commercial Vehicles

� Successful in Europe prior to the introduction of Euro 4 (heavy duty) as a short-term solution

� Reliant on low-sulphur fuels to prevent sulphate particle accumulation in the filter

� Government sponsored schemes (and tax benefits) reduced the cost burden on operators

� When combined with a DOC, catalysed ‘flow-through’ type is self cleaning and zero maintenance

� Wall-flow DPF can be used, but on-board regeneration mechanisms add cost and complexity− Stand-alone exhaust fuel injector

− Electrical heater

− Fuel-borne catalyst

� Most types can be removed for cleaning

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5. Exhaust Aftertreatment – Selective Catalytic Reduction (SCR)

� Application: Compression ignition engines and GDI

� ‘Selective’ in that it targets only NOx emission

� DEF (Adblue) 30-33% aqueous urea solution injected into mixing chamber ahead of the SCR, hydrolyses to ammonia gas in the hot exhaust stream

� Catalytic action is provided by vanadium, copper or zeolite depending upon the design temperature of the exhaust stream

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5. Exhaust Aftertreatment – Selective Catalytic Reduction (SCR)

� SCR technology alone can achieve NOx reduction of 90 percent, potentially rendering EGR and LNT technology redundant − In practice, EGR will remain as it has other attributes in controlling combustion

− SCR is robust enough to allow the engine calibration to be tuned towards maximum efficiency in the knowledge that NOx can be removed later

� To be most effective, urea dosing is quite aggressive:− Leads to excess ammonia in the exhaust stream.

− Heavy duty applications: DEF consumption is 4-8% of fuel consumption

− Passenger cars are typically 0.1-0.2% of fuel consumption

� Driver inducement for urea dosing system faults – 1st stage warning, 2nd stage power limitation, 3rd stage ‘creep mode’

� Unlike most aftertreatments, SCR is relatively unaffected by sulphur poisoning, however, it can get ‘plugged’ by ammonium sulphate deposits

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5. Exhaust Aftertreatment – Ammonia Slip Catalyst (ASC)

� Application: Clean-up stage for SCR and sometimes LNT

� SCR is most effective with ‘rich’ ammonia:NOx ratio of 1:2

� ASC Oxidises any ammonia remaining in the exhaust stream

� A balancing act – ASC’s must operate in a manner which is selective to the oxidation of ammonia without regenerating NO. − Pt catalyst, low temperature

� In some instances, ASC can be part of a dual-layer SCR, although this configuration is less efficient and more difficult to control

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5. Aftertreatment Packaging

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� Aftertreatment components can be packaged in a variety of ways− Available space

− Thermal management

� Integration of ATS’s

GDI example: Diesel example:

Aftertreatment Management & On-Board Diagnostics

� Complexity and balance of different pollution control mechanisms requires advanced control and monitoring:

� Example: Euro 6 Compression ignition with EGR+DOC+DPF+SCR+ASC

Additional equipment required (over and above Euro 4 vehicle);− Sensors for:

− O2, Combined NOX/O2 sensor (SCR upstream/downstream), particulates

− Exhaust temperature in 5 locations: manifold, DOC upstream, DPF upstream/downstream, SCR upstream

− Exhaust pressure in 3 locations: manifold, DPF upstream/downstream

− Exhaust fuel injector (DOC upstream)

− Urea injection system (Separate dosing control unit, injector, tank, line pressure & temperature monitoring, urea quality sensor, pump)

− EGR high/low pressure circuit with cooler, diverter valves, pressure and temperature sensing

� Failure or blockage in any system can result in high emissions, so all are monitored by OBD for continuity, plausibility and functionality

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Hybrid Drivetrains

� Mild hybrid:− Electric motor(s) used to supplement conventional drivetrain

� Full hybrid:− Vehicle may be propelled either by the engine, the electric traction motor or a varying combination of both

� In both cases, there is no direct contribution to emission reduction. The benefits come from regenerative braking and the opportunity to use more fuel-efficient modes of engine operation.

� Range extender:− Powertrain is essentially that of an electric vehicle with an on-board engine driven generator for re-

charging the traction battery.

− The generator engine can be optimized to operate under fixed conditions

− Alternative engines/fuels can be adopted (Free piston engines, Sterling engines, gas turbines)

− Subject to normal emission limits

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Pure Electric Vehicles

� Shifting the pollution issue− PM emissions from conventional power stations create the same issues as vehicle emissions

− Nobody wants nuclear power

− Green alternatives are not sufficient to replace nuclear and thermal power stations

� Energy density of batteries limits range and performance

� Availability of power supply for recharging:− Not everybody has access to overnight charging

− Fast charging points are still significantly slower than refilling a fuel tank

� Pollution is generated away from major urban areas, so effects on health are reduced

� The benefits of pure EV are more universally suited to 2-wheelers at this point in time

3/29/201940

Hydrogen and Fuel Cells

� Hydrogen infrastructure needed to support technology

� Energy density is lower than liquid fuels - storage is not so convenient

� Hydrogen as a fuel for spark-ignition engine:− Generates only water and NOx (and a trace of HC from engine

lubricants).

− Not suitable for all engines

� Fuel cells− Require high purity gas

− Zero pollution

− Performance is equivalent to conventional combustion engine or hybrid vehicle

− Range limited only by fuel storage capacity

− Expensive

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What direction to take?

� Short Term:− GDI, HCCI and its derivatives will become mainstream for light-duty

− DPF/SCR+EGR combinations will be the accepted norm for compression ignition, although LNT will be used for lighter duty vehicles

− Development of alternative catalyst washcoats which are less dependent on precious metals

− Greater dependency on electrically driven subsystems – maybe 48V?

− Euro 6 and currently available technology can go a long way to improving air quality

� Long Term:− Hybrids with automated electric-only modes for high pollution areas

− Telemetry linking on-board emission monitoring to enforcement authorities and/or service centres

− Adaptive powertrain operating modes to suit location and demand

− Drive-by roadside emission testing to identify the worst polluters (already in use in HK and EU)

− Light-duty emission limits for ammonia

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Closing Thoughts - Driving Changes

� In a growing market (Thailand: 5%/year), the growth of the vehicle pool will offset advances made in emission reduction− Technology must be adopted more rapidly to realize an actual reduction in air pollution levels

� Change requires the coming together of several factors:− Availability of technology

− Health concerns

− Political willpower

− Public pressure (air quality, global warming)

− Availability of suitable fuels – SULPHUR CONTENT

− Cost of implementation

� Economies of scale

− Developing nations should benefit more quickly from the advances made in other markets

3/29/201943

Michael.Deakin@tuv.com

Thank You For Your Kind Attention