Dual-fuel technology allows diesel engines to operate using both diesel fuel and natural gas. It can convert a diesel engine to run on dual-fuel with only minor modifications, allows the engine to still run on diesel if gas is unavailable, and is more efficient than spark-ignited gas engines. However, dual-fuel engines face technical challenges like methane slip and decreased efficiency at part loads due to the need for a throttle. Various systems exist for supplying the gas, including premixed and direct injection, with tradeoffs between emissions and performance. Suitable aftertreatment is also needed to meet emission standards while addressing issues like low exhaust temperatures.

1. Dual-fuel-tekniken
– hur fungerar den och vad har den att ge?
Per Stålhammar per.stalhammar@avl.com

2. What is AVL?
AVL
Powertrain
Engineering
n ts
me
passenger cars 2-wheelers racing
eg
rS AVL
me Advanced
sto
Engineering Simulation
cu
Technologies
al l
construction agriculture commercial vehicle
e rs
c ov
AVL Testing
AVL
Instrumentation
and Test Systems
locomotive marine power plants
per.stalhammar@avl.com 2

3. What is AVL Sweden?
MTC - Founded 1988
Independent Company 1998
In the AVL-group 2002
Acquired GMPT Södertälje 2008
Situated in Haninge, Södertälje
and Gothenburg
Center Of Expertice for alternative
fuels
Notified Technical Service
Accreditations
Japan TRIAS (2000)
ISO 17025 (2001)
ISO 9001 2000 (2001)
~ 200 Persons Employed
per.stalhammar@avl.com 3

4. Methane Engine Technologies
Different Technologies for different applications
SI (Spark Ignited) CI (Compression Ignited)
Stoichiometric Lean Burn
Bi-fuel Dedicated gas (mono-fuel)
Dual-fuel
per.stalhammar@avl.com 4

5. Why Dual Fuel?
Possible to convert Diesel engine to Duel Fuel
without major changes to base engine.
Possible to continue running on Diesel if gas is
not available.
Higher efficiency compared to spark ignited gas
engines.
Possible to convert the engine back to original
Diesel
No spark plugs

6. Dual Fuel - Diesel or Otto combustion?
Diesel Otto
No throttle Throttle to control A/F
Compression ignited Spark ignited
High compression ratio Knock limited compression ratio
Diffusion controlled Flame propagating controlled
combustion combustion
Dual Fuel (except DI gas)
Throttle to control A/F
Compression ignited
Knock limited compression ratio
Flame propagating controlled combustion
per.stalhammar@avl.com 6

7. Dual Fuel converted Diesel engine
(Typical retrofit solution)
Throttle Gas supply
per.stalhammar@avl.com 7

8. Dual Fuel converted Diesel engine
(Typical OEM solution for large engines)
Inlet manifold:
Turbocharger:
Throttle
- Compressor Bypass /
Gas piping
Waste-Gate / VTG
Cylinder head: - Re-specify
- Cylinder-individual gas
admission valves Piston:
- Pilot fuel injectors - Reduced
- Increased turbulence compression ratio
- Valve seat material - Bore increase
CR Pilot Diesel Injection: Liner:
- Electrically-driven HP Bore increase
Pumps
- Piping Camshaft:
Int. & exh. cam profile
Crank case:
- Safety relief valves for Engine Control System:
intake receiver - Gas operation
- Crankcase ventilation - Knock control
with gas detection - Wiring
sensor
per.stalhammar@avl.com 8

9. Technical challenges with Dual Fuel
Combustion chamber is not optimized for Otto
combustion leading to high levels of Methane slip
Throttle is needed, leading to decreased efficiency at
part load. (increased pumping losses)
Not possible/suitable to run gas at idle and low loads
Not possible to run gas at full load (knock limitations)
per.stalhammar@avl.com 9

10. Damages from knocking combustion
in a retrofit Dual Fuel engine
Before knocking After knocking
per.stalhammar@avl.com 10

11. Dual Fuel Technologies
Premixed gas system DI gas system
(Micro pilot ignition)
Picture Wärtsilä
per.stalhammar@avl.com 11

12. Dual Fuel Technologies
Premixed gas with DI gas with
diesel ignition diesel ignition
Generally higher levels of HC Generally higher NOx than premixed
(Methane) from crevices and flame depending on diffusion controlled
quenching. combustion.
Knock limited performance on gas. Better knock tolerance than premixed
Possible to run 100% Diesel mode Less HC from crevices
when gas is not available.
Limited performance on Diesel
Demand throttle which leads to poor
Generally more expensive than
part load efficiency
Premixed systems
More system suppliers than DI
per.stalhammar@avl.com 12

13. Dual Fuel Technologies
AVL pre-chamber system for large engines-ultra lean burn
per.stalhammar@avl.com 13

14. Aftertreatment systems for Dual Fuel
Challanges
High levels of unburnt methane
Low exhaust temperature
Cold start demands from EURO VI
After treatment system
Methane oxidation catalyst with high efficiency and
durability is needed from EURO III
SCR or DPF/POC is probably needed for EURO VI
(maybe also for EURO V)
per.stalhammar@avl.com 14

15. Dual Fuel Combustion
Dual fuel combustion properties
from R&D project in Sweden
Later
pilot injection
Earlier
pilot injection
per.stalhammar@avl.com 15

16. Dual Fuel system suppliers
Examples of Duel Fuel System Suppliers
Bosch
Clean Air Power
Hardstaff
Westport
per.stalhammar@avl.com 16

17. Dual Fuel system suppliers
Clean Air Power Secondary intercooler to
enable higher power without knock
Picture CAP

18. Dual Fuel system suppliers
Hardstaff OIGI Dual Fuel Technology (Oil Ignition Gas Injection)
2 injectors per cylinder –
reduced duty cycle
Injector layout to achieve
sequential operation
Point of injection close to each
inlet valve
Picture Hardstaff

19. Dual Fuel system suppliers
Hardstaff Dual Fuel Technology (aftertreatment )
Picture Hardstaff

20. Dual Fuel system suppliers
Westport HPDI Dual fuel system (High Pressure Direct gas Injection)
Picture Westport

21. Dual Fuel system suppliers
Westport HPDI Dual fuel system
Picture Hardstaff

22. Dual Fuel Technologies
Conclusions
Dual Fuel combustion is more complex than
conventional.
Dual Fuel enables new combustion strategies
Dual Fuel has not yet shown its full potential in truck
applications
Lack of legislation hamper further development
per.stalhammar@avl.com 22