Quote:
Originally Posted by slowmover
I see dedicated CNG Class 8 tractors regularly now (big fleets; daycabs) and have talked with a few owner/operators with dual-fuel capability on oilfield trucks in TX and OK.
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I help manage the service department in what we shall call an undisclosed Paccar branded truck dealership. Wow...that narrows it down....
Anyway, we are a dealership for Westport GX 15L engines, as they are factory installed in our trucks. These engines are quite interesting, but unfortunately they quit production a few months ago. Westport is the research company that does much of the R&D for Cummins' natural gas engines, and they also developed their own system to run natural gas and diesel through a single injector per cylinder (direct injection) in a Cummins ISX 15L engine. They run on 95% natural gas/5% diesel. The diesel portion of the injector is the "spark plug" to initiate combustion (no actual spark plugs), and the natural gas portion of the injector provides the fuel volume for power delivery. They will not run on natural gas alone, so each truck has liquid natural gas tanks (120 gallons per side, vacuum insulated to hold -260F LNG), a small diesel tank and a DEF tank (urea for SCR catalyst/aftertreatment).
Westport's success vs spark plug ignited (normal) natural gas engines is that they are large (15L) and keep the high diesel compression ratio to maintain efficiency and diesel-like torque numbers - 485 HP and 1650 ft/lb.
http://www.cngva.org/media/4344/west...d_brochure.pdf