Westport Awarded US$2.25 Million to Support Development of Next Generation Heavy-Duty LNG Fuel System
13 February 2008
Westport Innovations Inc. has been awarded US$2.25 million in funding from the California South Coast Air Quality Management District (SCAQMD), the California Energy Commission (CEC) and the Ports of Los Angeles and Long Beach.
The funding will support the development, demonstration, commercialization and certification of Westport’s heavy-duty LNG (liquefied natural gas) fuel system for the Cummins ISX to meet the US EPA 2010 NOx (0.2 g/bhp-hr NOx) emissions standard prior to 2010.
The Westport High Pressure Direct Injection (HPDI) system for heavy-duty trucks is currently certified by CARB and the US EPA to 0.8g/bhp-hr oxides of nitrogen (NOx) and 0.01g/bhp-hr Particulate Matter (PM). (Earlier post.) The HPDI system directly injects a small quantity of pilot diesel fuel into the engine cylinder to provide diesel-like compression ignition for natural gas.
Currently offered in the Kenworth T-800 and available for delivery, the 2007 Westport LNG system is available with 400 and 450 horsepower ratings and up to 1,750 lb-ft torque for heavy-duty port, goods distribution and other commercial truck applications. LNG fuel tanks can be configured to suit customer range requirements.
Based on the Cummins ISX diesel engine with cooled EGR, the LNG version of the engine offers the same horsepower, torque, and efficiency as the base diesel engine rating it is replacing.
Under the terms of the agreement, Westport will receive US$1.25 million from the SCAQMD, US$250,000 from each port and US$500,000 from the CEC.
Reducing NOx by a factor of 4 in such a short time is a tall order, but this is essentially a spark ignition engine running on LNG. It just uses diesel instead of a spark plug, because diesel can penetrate much deeper into the combustion chamber, which is relatively large on heavy-duty engines. Methane has a high octane rating, i.e. it is hard to ignite.
One option is more aggressive intercooling - even interchilling - of the fresh charge, provided there is no condensation or ice formation. This increases charge density and hence, oxygen mass as well as power. More power per combustion cycles means relatively less is lost to internal friction, so fuel economy goes up. Cool intake air also sharply reduces peak combustion temperatures and hence, NOx formation.
A second option is to replace diesel ignition with laser ignition. This technology is still stuck in the lab, but research by the TU Vienna, AVL List and others in Austria has proven its feasibility. The main issue is the high cost of the precision optics, given the harsh vibration environment of a combustion engine.
The third option is more effective exhaust gas aftertreatment. A three-way catalyst requires sufficient CO and HC to neutralize the NOx.
Posted by: Rafael Seidl | 13 February 2008 at 11:07 AM
Rafael:
Westport developed this technology (along with conventional NG lean-burn spark ignition engines) for over 15 years. It is not regular SI Otto engine. Compressed NG is injected near TDC, combustion is going in boundary layer while NG is mixing with air, there could be infinite excess of air compared to fuel, there are no port injection, mixed charge, fast combustion with risk of detonation, octane number limitation on compression ratio, throttling, etc. As such, it is classified as classic diesel engine, with ignition assist of pilot diesel oil injection. Engine could work on diesel fuel alone, or on any combination of 100-2% of power from diesel oil, the rest is NG.
For small engines they have prototypes with glow plug ignition assist without pilot diesel injection.
Posted by: Andrey | 13 February 2008 at 07:20 PM
@Andrey -
thanks for the additional info. Sounds to me like stratified NG injection, which should be very fuel efficient in part load because there is no need for throttling the intake. It's still a spark ignition engine when using the diesel to ignite NG, though mechanical considerations may indeed force the thermodynamic cycle to approximate the diesel cycle. When running on diesel only, it's a CI engine, so you really have both ignition concepts in a single design here.
The lean-burn concept does mean the NOx cannot be cleaned up with a three-way catalyst. SCR should work, but I'm not sure if that's the direction Westport will take.
Posted by: Rafael Seidl | 14 February 2008 at 03:46 AM