Direct injection natural gas engine with spark plug fuel injector Combustion, performance and emission characteristics offset between single-cylinder and production engines A s s i s t a n t P r o f e s s o r M e c h a n i c a l E n g i n e e r i n g Te c h n o l o g y D e p t. Ya n b u I n d u s t r i a l C o l l e g e C e n t e r o f Te c h n i c a l R e s e a r c h & I n n o v a t i o n R o y a l C o m m. o f Ya n b u C o l l e g e s & I n s t i t u t e S e n i o r L e c t u r e r D e p t. o f M e c h a n i c a l & M a t e r i a l s E n g r. A s s o c i a t e S e n i o r F e l l o w C e n t r e f o r A u t o m o t i v e R e s e a r c h N a t i o n a l U n i v e r s i t y o f M a l a y s i a
Presentation Overview Natural Gas Vehicles (NGV) Natural Gas Engines Direct injection CNG engines Spark Plug Fuel Injector Single-cylinder engine Multi-cylinder production engine Some comparisons and offsets Conclusion
Natural Gas Vehicles GLOBAL OVERVIEW & MALAYSIA S PERSPECTIVE
Quick facts and Statistics Compressed natural gas is the most widely used alternative fuels in internal combustion engines powering nearly 20 millions road vehicles worldwide. Interest in NG is mainly attributed to its price competitiveness 50% lower than gasoline (Heavily subsidized in many countries) NG engines produce cleaner emission, easily meeting most emission standards. Most NG vehicles are converted from gasoline or diesel either in bi-fuel (two separate fuel systems) dual-fuel (mix of fuel & NG) modes. Dedicated NG engines are still rare.
Benefits The advantages NGV can offer to vehicle owners include: Substantial savings (50%) in fuel cost Contributes to a cleaner environment Lower operating cost Extended travel range The world s cleanest internal combustion production line car is a dedicated NG engine the Honda Civic GX (US) produce exhaust emissions that are cleaner than the air going into the engine In a high pollution area The Civic can drive from the West Coast of the United States to the East Coast and emit less non-methane hydrocarbons than if you were to spill one teaspoon of petrol!
NGV in Malaysia NGV was originally introduced for taxicabs and airport limousines in 1998 Enviro 2000, predominantly in the cities PETRONAS - the only supplier of CNG 41% price hike on petrol and diesel starting in 2008-500% increase in the number of new CNG tanks installed. More than 50,000 NGV (0.25% of vehicles on road) in Malaysia with almost 200 refueling stations Proton and local distributor of locally assembled Hyundai cars offers new models with CNG kits. Conversion on both petrol or diesel and CNG with a cost varying between RM3,500 to RM5,000 for passenger cars
Government Incentives & Legislations NGV price is only 63.5 cent/liter equivalent of petrol. NGV conversion kits are exempted from import duty and sales tax. Reduction of road tax from existing levels: Monogas vehicle (NGV only) - 50% off Bi-fuel vehicle (Petrol & NGV) - 25% off Dual-fuel vehicle (Diesel & NGV) - 25% off CNG MYR0.11/km vs Gasoline MYR0.23/km (51% cheaper)
PROTON CNG-DI project (2002-2008) The national car manufacturer PROTON established a project to build a dedicated CNG DI car based on its first locally developed engine Campro. Involved 5 UNIVERSITIES, PETRONAS and ORBITAL (Air-assisted direct injector) Ptrns Orbital UKM UM UTP Protn UPM UiTM
Promising results [Source: Kalam & Masjuki (2011),Energy 36 p3563-3571] Comparable power to gasoline Significantly better fuel economy Lowest CO 2 & HC CO and NOx more stable over speed range
Alternative to dedicated CNG-DI engine The Proton project was a successful story but has not entered the final production stage due to economic and infrastructure barrier. Development works continues at slower rate (thermal management, refueling, fuel storage) Final production is hold till this date Buy new vs. convert the existing? consumer choice Why not develop conversion systems for CNG DI? Cheap Technically simpler New research idea!!!
Natural gas engines TECHNOLOGY & CHALLENGES
CNG engines basic comparison DUAL FUEL MANIFOLD INJECTION DIRECT INJECTION o Better mixing (homogeneous) o Volumetric loss o Easy and cheap conversion o Better mixture control stratified & homogeneous o Volumetric efficiency gain higher charge heating value o Requires cylinder head redesign
Natural Gas combustion properties PROPERTIES METHANE GASOLINE Enthalpy of reaction (lower heating value), MJ/kg 50.0 44.3 Specific gravity at 15 o C 0.424 0.72-0.78 Inhaled energy at stoichiometry, MJ/kmol 76.25 83.6 Laminar burning velocity, m/s 0.43 0.5 Octane number Main reason 120 90-100 Adiabatic flame temperature, K for power 2776 2895 Stoichiometry air-fuel ratio drop 17.2 14.7 Auto ignition temperature, o C 580 246-280 Minimum ignition energy, mj 0.28 0.30 Flammability limits in air (Equivalent ratio) 0.50-1.68 ~0.6-4.0 5-16% vol. fuel ~1-6% vol. fuel
Direct Injection CNG engines SOME CURRENT DEVELOPMENTS
Advantages & Challenges Higher volumetric efficiency - Increased charged heating value More precise fuel metering Possibility of throttle-less operation reduced pumping loss Homogeneous and stratified charge possibilities Spatial and temporal limitations Some reports on NOx & HC problems High injection pressure requires bigger fuel storage
Charge formation strategies Location-specific injection for ignition control Time-specific injection for charge spatial distribution
Spark plug fuel injector TECHNICAL SIMPLICITY OF CNG-DI CONVERSION
Spark Plug Fuel Injector http://gazeo.eu/technology/technology-and-maintenance/spfi-direct-natural-gasinjection,article,7626.html
Fuel arrival delay, milliseconds 4 th SAS-CI Annual Meeting, April 29 th 2014, KAUST, Thuwal, KSA Cylinder pressure, bar Preliminary investigations 6 5 4 SPFI Adjusted SPFI Projected trendline SPFI Projected trendline adjusted SPFI 20 18 16 14 Normal spark plug SPFI 10.5:1 initial compression setting 3 12 2 1 10 8 6 0 0 20 40 60 80 100 Injection pressure, bar Injection delay 4 2 0 0 90 180 270 360 450 540 630 720 Crank angle Reduced effective compression ratio due to fuel path volume in SPFI
PLIF imaging of gas jet Gas jet plume moves away from ignition point Wall impingement needed to send it back at the right location. Assistive piston crown geometry
Single-cylinder research engine INITIAL DEVELOPMENT OF SPFI
Ricardo E6 single-cylinder engine 10 Air in 17 12 23 15 Bore (mm) 76.2 Stroke (mm) 111.125 Methane 19 3 21 8 13 Exhaust gas 14 V Disp (liter) 0.507 CR 10.5 : 1 100bar CH4 20 7 11 9 24 4 25 2 16 IVO IVC 8 o BTDC 33 o ABDC 6 22 1 5 26 18 EVO 42 o BBDC EVC Thermal mgmt. 8 o ATDC Water cooled 1.RICARDO E6 ENGINE 2.ELECTRIC DYNAMOMETER 3.SPARK PLUG FUEL INJECTOR 4.FLYWHEEL 5.LOAD CELL 6.SLOTTED DISK 7.PHOTODIODE 8.SHAFT ENCODER 9.PRESSURE SENSOR 10.PRESSURE REGULATOR 11.THROTTLE VALVE 12.MOSFET 13.POWER SUPPLY UNIT 14. PULSE GENERATOR 15.CHARGE AMPLIFIER 16.DATA ACQUISITION UNIT 17.FUEL FLOW METER 18.MULTISLOPE MANOMETER 19.VISCOUS AIRFLOW METER 20.SPARK IGNITION UNIT 21.CAMSHAFT 22.CRANKSHAFT 23.OSCILLOSCOPE 24.LAMBDA SENSOR 25.LAMBDA METER 26.CAR BATTERY
Cylinder pressure, bar Experimental set up Flat cylinder head Flat-top piston crown CR 10.5:0 Swept volume 0.507 liter SPFI vertical inclination 45 o Shape factor (S/B) = 1.46 15 14 13 12 11 10 9 8 7 6 5 4 3 Motorised pressure of Ricardo E6, comp. Ratio 10.5:1, 1100 rpm with SPFI Cylinder pressure 60 bar inj duration 80 bar inj duraion 50 bar inj duration 80 bar injection pressure optimal calibration 50 & 60 bar injection pressure optimal calibration Inlet valve closes Ignition 2 1 0 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 Crank angle
Cylinder work, J Cylinder pressure analysis BT 3 MPa 6 Mpa 8 MPa OVPI SPFI DI (60bar injection) SPFI DI (80bar injection) 10 8 1100 RPM, Lambda 1.0, MBT OVPI SPFI DI (60bar injection) SPFI DI (80bar injection) Operation Open Valve PI SPFI DI SPFI DI 6 4 2 0 0 90 180 270 360 450 540 630 720-2 Injection pressure, MPa 3 6 8 MEP, kpa 660 620 600 Power, kw 3.0 2.9 2.8 η v, % 72.4 83.4 79.5 η f, indicated, % 27 22 22 SFC, g/kwh 267 330 323-4 -6 Crank angle 270 360 450 540 630 720 Crank angle
Mass burnt fraction 4 th SAS-CI Annual Meeting, April 29 th 2014, KAUST, Thuwal, KSA Mass burnt fraction Normalized mass burnt fraction Ignition timing effects Injection timing effects 1 1 0.9 1100 rpm, 60 bar injection, lambda 1.0 25 BTDC 0.9 1100 rpm, 60 bar injection, lambda 1.0 160 ATDC 0.8 20 BTDC 0.8 170 ATDC 0.7 30 BTDC 0.7 180 ATDC 190 ATDC 0.6 0.6 200 ATDC 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0 330 335 340 345 350 355 360 365 370 375 380 385 390 Crank angle 0 330 335 340 345 350 355 360 365 370 375 380 385 390 Crank angle
Performance summary Optimal setting for 1100 rpm, 6 MPa injection pressure: 25 o BTDC injection timing 190 o ATDC injection timing
Peak pressure, bar Combustion analysis 60 50 40 40 o BTDC DI 35 o BTDC DI 30 o BTDC DI 40 o BTDC PI 25 o BTDC DI 35 o BTDC PI 30 o BTDC PI Optimal DI performance 25 o BTDC PI Optimal PI performance 30 20 o BTDC PI 20 20 o BTDC DI 16 o BTDC PI 14 o BTDC PI 15 o BTDC DI 10 0 360 365 370 375 380 385 390 395 Location of peak pressure, o ATDC oin both PI and DI settings, optimal ignition timings at 25 o BTDC obest peak cylinder between 10 o and 18 o ATDC
Multi-cylinder production engine A STEP FORWARD
Cylinder arrangement Pent-roof cylinder head Flat-top piston crown CR 9.2:0 Swept volume 0.367 liter SPFI vertical inclination 45 o Shape factor (S/B) = 1.09
Operation & performance optimization MoTec ECU for precise engine control Detailed calibration for optimization Dewetron combustion analyzer
Power, torque & BMEP
In-cylinder pressure & Heat Release
Emissions 4 th SAS-CI Annual Meeting, April 29 th 2014, KAUST, Thuwal, KSA
Some comparison & offset NORMALIZED COMPARISON
Engine and performance comparison Column1 4G15 Ricardo E6 Type In-line OHV, SOHC OHV, SOHC Number of cylinders 4 1 Combustion chamber Pentroof type Disk-type Total displacement (cm3) 1468 507 Displacement/cylinder (cm3) 367 507 Cylinder bore (mm) 75.5 76.2 Piston stroke (mm) 82 111.125 Connecting rod (mm) 131 241.27 Firing order 1-3-4-2 1 Compression ratio 9.2 10.5 Number of intake valve/cylinder 2 1 Number of exhaust valve/cylinder 1 1 Intake valve open (IVO) o ATDC -15-3 Intake valve close (IVC) o ATDC 233 213 Intake valve opening length oca 398 390 Intake valve clearance (mm) 0.15 Exhaust valve open (EVO), o ATDC 483 528 Exhaust valve close (EVC), o ATDC 15 8 Exhaust valve opening length oca 252 200 Exhaust valve clearance (mm) 0.2 1 Cylinder 4 Cylinder kw/dm3 5.6 7.6 ROHR max [kg/m 3.CA] 69 49.4 P cyl,max MPa 3.8 5.63 Phasing angle [ o ATDC] 10 4 Ign. Delay [CA] 10 1 MBT spark [ o BTDC] 25 19 Injection [ o ATDC] 190 220
Power analysis Shifted optimal injection timing Ignition advanced is less in production engine (19 o vs. 25 o BTDC) More specific power in production engine (4 power pulse in one crank rotation) Shorter stroke better for mixing thus higher power
Conclusion LESSON LEARNED
SPFI is a technically simple and cost competitive conversion to CNG direct injection Optimal performance are very sensitive to operational parameters injection timing, injection timing and injection pressure Geometrical factor plays some role in offset performance between single cylinder engine and production engine cylinder shape, compression ratio, cam profile etc. Temporal and spatial limitations in DI operation leads to performance drop compared to port injection operation More detailed in-cylinder flow and reaction studies are required Emission levels easily satisfy current emission standards
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