cng engine technology for passenger cars_dr hubert friedl

AVL ITC 24.4.2007, Advanced CNG Engine Technology Page 1

Entwicklungstrends Entwicklungstrends OttomotorOttomotorDaimlerChryslerDaimlerChrysler, Stuttgart 20.April 2004, Stuttgart 20.April 2004

AVL ITC, Technical Seminar

24. April 2007 Dr. Hubert FRIEDL

HighlyHighly AdvancedAdvanced CNG CNG EngineEngineTechnology Technology forfor PassengerPassenger Cars Cars

HigherHigher FuelFuel EfficiencyEfficiency and and lowerlower EmissionsEmissions


1. Market Trends1. Market Trends

2. Configurations of CNG SI2. Configurations of CNG SI--EnginesEngines

Turbo Charged BiTurbo Charged Bi--FuelFuel Mono Fuel CNG Direct InjectionMono Fuel CNG Direct Injection

3. Conclusion and Outlook3. Conclusion and Outlook

Content of Presentation


1.Market Trends


VolvoBMW

MercedesAudi

MazdaNissan

KiaHyundai

HondaSuzukiToyota

VWOpel

SkodaFord

PeugeotSeat

RenaultCitroen

Fiat

European European COCO22

Fleet Fleet DataData200520052012 2012

COCO22 LegislationLegislation as Technology Driver as Technology Driver forfor all all PassengerPassenger Car Brands in EuropeCar Brands in Europe

100 110 120 130 140 150 160 170 180 190 200

COCO22[g/km][g/km]

Extreme pressureto invest into high efficient powertraintechnology as well as to promotealternative fuels

EUROPE


VolvoBMW

MercedesAudi

MazdaNissan

KiaHyundai

HondaSuzukiToyota

VWOpel

SkodaFord

PeugeotSeat

RenaultCitroen

Fiat

European European COCO22

Fleet Fleet DataData200520052012 2012

100 110 120 130 140 150 160 170 180 190 200

COCO22[g/km][g/km]Super / Super / TurboTurbo--

ChargingCharging

CylinderCylinderDeactivationDeactivation

Variable Variable Charge MotionCharge Motion

GDIGDIStratifiedStratified

Variable Variable ValveValveActuationActuation

ControlledControlledAutoAuto--IgnitionIgnition

ReducedReducedparasiticparasiticlosseslosses

ImprovedImprovedenergyenergy

managemanage--mentment

EnergyEnergyrecoveryrecovery

Start / Start / StopStop

HybridHybrid--izationization

Alternative Alternative FuelsFuels

Technologies Technologies forfor GasolineGasoline EnginesEngines to to complycomply withwith forthcomingforthcoming CO2 CO2 TargetsTargets


Global PC and LD Vehicle Production by Propulsion Technology

15

30

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1995 2000 2005 2010 2015

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DIESEL CHARGEDDIESEL NACNG/LPG/

ALCOHOL/FLEX FUEL

ALTERNATIVE FUELS

GASOLINE GDI

HYBRID

GASOLINE PFIGASOLINE Charged

Source: Global Insight

GasolineGasoline

DieselDiesel

20072007

GDIGDI

chargedcharged

Alternative Alternative FuelsFuels::CNG, EthanolCNG, Ethanol


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100%

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H2/ElectricHybridFlexFuel,Alcohol

CNG/LPGDiesel

Gasoline

Global Vehicle Production by Propulsion Technology

Source: Global Insight, AVL


2. Configurations for CNG SI-Engines


Diesel Gaso- Metha- Etha- LPG CNG DMEline nol nol

Chemical Formula (-) C15H28 C7H15 CH3OH C2H5OH C3H9 CH4 C2H6OMolecular Weight (-) 208 99 32 46 45 16 46Carbon Content (%m) 86.1 84.9 37.5 52.2 80.0 75.0 52.2Hydrogen Content (%m) 13.9 15.1 12.5 13.0 20.0 25.0 13.0Oxygen Content (%m) 0 0 50.0 34.8 0 0 34.8Density Liquid at 20 (kg/l) 0.840 0.740 0.795 0.790 0.540 - 0.668Lower Heating Value (MJ/kg) 42.7 42.5 19.7 26.8 46.0 47.7 28.4Heat of Evaporation (kJ/MJ) 6.0 8.0 56.4 33.8 8.6 - 14.4Octane Rating RON (-) - 95 >110 >100 100 130 -Cetane Number CN (-) 45-55 - - - - - >55CO2 Emission (g/MJ) 74.2 73.3 70.0 71.5 63.8 57.7 67.5

LPG: Liquified Petroleum mGas (50%mass C3H8 + 50% C4H10)

CNG: Compressed Natural Gas (mainly Methane CH4)

DME: Dimethylether

Properties of Fuels

Properties of CNG Properties of CNG most attractive most attractive for SIfor SI--Engines !Engines !


High knock resistance of CNG (RON 120-140) allows high compression ratio, but this leads to higher combustion pressure and higher mechanical loads

Higher ignition energy and different ignition timing compared toliquid fuels

CNG lacks cooling effect unlike other liquid fuels, but due to higher compression ratio the exhaust temperatures are lower

As CNG is gaseous and combustion is without soot formation, special attention has to paid for valve seat material

Max torque with CNG occurs very close to =1 and enrichment / leaning leads to drop in torque

Power drop in CNG 10 ~ 12 % (due to lower volumetric efficiency) Lean burn power drop 20 ~ 30% (partially compensated by turbocharging)

CNG in Combustion Process


Bi Bi fuelfuel

(Petrol or Gas)(Petrol or Gas)

Stoichiometric Stoichiometric ( ( == 1)1)

SI Spark IgnitionSI Spark Ignition

Lean burn ( Lean burn ( > 1)> 1)

Mono fuel Mono fuel

(Optimized for gas)(Optimized for gas)

Most common solutionMost common solution

Development Paths for CNG SI-Engines

Potential for higher Potential for higher fuel efficiencyfuel efficiency

Turbo ChargingTurbo Charging


Bi-Fuel vs. Dedicated Mono-Fuel CNG Engines

High compression ratio CH4 optimized catalyst CH4 optimized lambda control CH4 tolerant O2 sensors One set of fuel injectors Pressure regulator instead of

fuel pump

Monofuel PC gas engines

Knock limited CR (for gasoline) is compromising thermal efficiency

Gasoline optimized catalyst Lambda control optimized for

gasoline

Cold start usually with gasoline Two sets of fuel injectors and dual

tank infrastructure required

Bi-fuel PC gas engines


2.1 Turbo Charged Bi-Fuel Application


Development Tasks: Integration of CNG fuel system adapt mechanical system for specific

requirement when running engine with CNG (e.g. valve seat rings)

Key Tasks and Challenges for Turbo-charging Bi-Fuel CNG Engine

Challenges: provide similar power and torque for

CNG as with gasoline fuel

Fulfill stringent emission standards (ULEV, Euro 5) even maintaining with gasoline dedicated exhaust aftertreatment


BOSCH Natural Gas System (BiBOSCH Natural Gas System (Bi--Fuel)Fuel)

Source: Robert BOSCH GmbH, GS/EVP


Integration of CNG Fuel System to Engine

A combined CNG / gasoline fuel rail was designed for optimized packaging


Full Load Performance of 2.0L Turbo Engine CNG compared to Gasoline Fuel

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CNG Torque [Nm]

Gasoline Torque [Nm]

CNG Power [kW]

Gasoline Power[kW]

Low end torque is lower onCNG compared to Gasoline.

CNG calibrated to 125kWGasoline std calibration 135kW


TEMPERATURES, PRESSURESCNG compered with gasoline at full load

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Full Load Conditions of 2.0L Turbo Engine CNG compared to Gasoline Fuel

Gasoline P Plenum

CNG P PlenumGasoline Cat 1 endCNG Cat 1 end

Catalyst Temperature Limit 950 C


Measures to reduce Exhaust Temperatures Measures to reduce Exhaust Temperatures with Turbowith Turbo--charged CNG Enginescharged CNG Engines

Integrated Exhaust ManifoldIntegrated Exhaust Manifold

Water Cooled Turbine


Slightly reduced power (7,5%) in CNG operation with 2.0L engine due to compromised layout for gasoline

Equalizing of performance gap to gasoline fuel operation feasible with higher compression ratio and further secondary measures (integrated exhaust manifold, cooled turbine)

Euro 5/ULEV Emission limits achieved in CNG operation due to optimized catalyst design and by calibrating lambda control as well as transient A/F control.

Results for Turbo charged Bi-FuelCNG Application Project


2.2 Mono Fuel CNG Direct Injection


Key Features of CNG Direct Injection Combustion System Application

Engine Capacity 450 ccm/cylinder

Compression ratio: 1:13

Injector: AVL proprietary DMI-Injector (Piezo Injector as Option)

CNG System Feed Pressure: 12 bar

Standard CNG pressure regulator and CNG system components as commercially available

Operation with homogeneous (=1) and stratified lean (>1) air/fuel ratio

Such dedicated system is able Such dedicated system is able to utilize the full potential and to utilize the full potential and advantages of CNG Fuel ! advantages of CNG Fuel !


CNG-supply

CNG / Mixture chamber (for pure CNGoperation and DMI operation)

Nozzle (different geometries)

HP-oil supply

solenoid valve

Actuation piston

Lift adjustment (0.6 and 0.3mm variant)

Oil leakage draining

CNG - DI Injector for combustion development(AVL Research Injector, no series product)



Principle of stratified CNG-DI Combustion Process

TDC

Swirl charge motion of intake air supports stratification of mixture cloud

[m2/s2]0.0 100

Turbulent Kinetic Energy

20 CA bTDC20 CA bTDC

CFD simulation shows toroidal rotation of mixture cloud


Central Injector Position, spark plug close to injector tip

Piston Bowl design for Wall-guided Mixture Formation

High turbulence due to gas-jet


CNG - DI Combustion CFD Simulation

CFD- Simulation for mixture formation in stratified and homogeneous operation (2000rpm / 3bar IMEP)

5 DEG CRA bTDC

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Homogeneous early injection, A/F 1.0Stratified late injection, A/F 2.6Spark Plug


2000rpm / 3bar imep - isfc [g/kWh]

MFB 50% [deg CA aTDC]SO

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CA bT

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isfc - OPT:SOI.....63 deg CA bTDCEGR...20 %MAP...810 mbarIGN....19 deg CA bTDC

Restrictions:CoV < 3 %isNOx < 3 g/kWh

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Stratified CNG-DI: Very stable Operation (Part Load Optimisation with DoE)


Combustion simulation with different operation strategies in part load

The 3D-CFD combustion simulation shows the same tendency regarding combustion speed as the measurements. Due to the turbulence introduced by the DI-gas-jet the combustion speed increases significantly with late injection.

Heat release curves for different combustion strategies(CFD Simulation)

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Homogeneous early - CFD Simulation

Homogeneous late - CFD Simulation

Stratified lean - CFD Simulation

Heat release curves for different combustion strategies(Measurement)

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Homogeneous early - Measurement

Homogeneous late - Measurement

Stratified lean - Measurement

Homogeneous early

Homogeneous late

Stratified lean

Flamefront 20deg CA after Ignition

CNG - DI Combustion CFD Simulation


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Combustion Efficiency CO2 Emission

Homogeneous Gasoline DI

Homogeneous CNG DI

Stratified lean with EGRCNG DI

-40%-25%

Part Load: 2000 rpm3 bar IMEP

Improvement Potential for CNG Direct Injectioncompared to stoichiometric homogeneous GDI


Part load:Part load: The CNG The CNG -- DI combustion system shows 25% better efficiency DI combustion system shows 25% better efficiency

compared with homogeneous compared with homogeneous stoichiometricstoichiometric combustioncombustion Compared to homogeneous Compared to homogeneous stoichiometricstoichiometric combustion with combustion with

gasoline a CO2 reduction of more than 40% is possible due to gasoline a CO2 reduction of more than 40% is possible due to beneficial H/C ratio of CNGbeneficial H/C ratio of CNG

Full Load:Full Load: Reduced volumetric efficiency as it is known from manifold gas Reduced volumetric efficiency as it is known from manifold gas

injection can be fully compensated by late direct injection (aftinjection can be fully compensated by late direct injection (after er intake closing), which results in +12% charge mass in cylinderintake closing), which results in +12% charge mass in cylinder No necessity for spark retardation due to high knock resistance No necessity for spark retardation due to high knock resistance

of CNG, possibility to use a CR of 13, which gives 13% higher of CNG, possibility to use a CR of 13, which gives 13% higher efficiency in low end WOT compared to gasoline operationefficiency in low end WOT compared to gasoline operation Together with the beneficial H/C ratio of CNG also at full load Together with the beneficial H/C ratio of CNG also at full load a a

CO2 advantage of more than 30% is possibleCO2 advantage of more than 30% is possible

Results Achieved for CNG Direct Injection


3. Conclusion and Outlook


CNG is highly attractive fuel for vehicles and will become more CNG is highly attractive fuel for vehicles and will become more important due to the demand of CO2 reduction and have less important due to the demand of CO2 reduction and have less dependency on crude oildependency on crude oil

BiBi--fuel vehicles represent a short term solution to introduce fuel vehicles represent a short term solution to introduce CNG into the market on bigger scaleCNG into the market on bigger scale

CNG in combination with turbo charging reduces power gap CNG in combination with turbo charging reduces power gap compared to gasoline operation by achieving better volumetric compared to gasoline operation by achieving better volumetric efficiency, and turbo charging opens door for downsizing and efficiency, and turbo charging opens door for downsizing and achieving higher fuel efficiencyachieving higher fuel efficiency

New monoNew mono--fuel systems and technologies (e.g. Direct Injection) fuel systems and technologies (e.g. Direct Injection) are under development to utilize even more advantages of CNG are under development to utilize even more advantages of CNG operation for passenger cars in near futureoperation for passenger cars in near future

Conclusion and Outlook


ThankThank youyou veryvery muchmuchforfor youryour kindkind attentionattention !!


Abbreviations (1/2)

A/F Air-/Fuel Ratio of Mixture (Lambda)

CA Crank Angle

BMEP Brake Mean Effective Pressure

CNG Compressed natural Gas

CR Compression Ratio

DI Direct Injection

DeNOx Nitrogen oxide reducing catalyst

DMI Direct Mixture Injection (Air + Fuel pre-mixed)

DoE Design of Experiments

EGR Exhaust Gas Recirculation

EURO5 European Emission Limit Stage 5

FE Fuel Economy

FTP Federal Test Procedure (USA)

GDI Gasoline Direct Injection


Gen.1 Generation 1 (first development stage of engine technology)

HSDI High Speed Direct Injection (Diesel)

IMEP Indicated Mean Effective Pressure

LDV Light Duty Vehicle

LPG Liquified Petrol Gas

NA Naturally Aspirated

NEDC New European Driving Cycle

PC Passenger Cars

PFI Port Fuel Injection

ROW Rest of the World

SI Spark Ignition

SULEV Super Ultra Low Emission Vehicle

TWC 3-Way Catalyst

ULEV Ultra Low Emission Vehicle

Abbreviations (2/2)


Global PC and LD Vehicle Production by Propulsion TechnologyGlobal Vehicle Production by Propulsion TechnologyCNG in Combustion ProcessAbbreviations (1/2)Abbreviations (2/2)

cng engine technology for passenger cars_dr hubert friedl

Documents

cng sienginesavl itc

configurations of cng

technology driver forfor

avlavl itc

ethanolavl itc

market trendsavl itc

global pc

market trends1