Issue link: http://read.dmtmag.com/i/71813
prime time? N Industry begins to accept expensive natural gas engines running cheaper fuel, despite power and range tradeoffs. BY JACK ROBERTS atural gas as a fuel for internal combustion engines isn't a new idea. What is new is how fast it's penetrating new applications, including the heavy-duty truck market, in the wake of rising diesel prices. Interest in natural gas as a viable Class 8 fuel skyrocketed during the unprecedented 2007-08 fuel price spike. That brief affair ended as prices dropped when the subsequent recession hit. Today, interest is returning. The industry realizes that yesterday's lower fuel prices truly are a thing of the past, says Robert Carrick, vocational sales manager of natural gas for Freightliner. "Every time the prices retreat, they'll stay at a higher level instead of dropping all the way back down," Carrick says. Even if the natural gas infrastructure is lagging, competition is driving the heavy-duty truck marketplace, says Jonathan Burke, vice president of global market development for Westport. "We're seeing all of the major truck manufacturers step up and invest significant amounts of capital in making a huge range of new factory-built vehicles," Burke says. This is borne out by recent announcements from Volvo, Mack, Peterbilt, Kenworth, Navistar and Freightliner. All of these companies are investing heavily in natural gas technology and products. Freightliner recently completed a high-profile drive from San Diego to North Carolina in natural gas trucks fueled only at publicly available natural gas fueling stations. New engines are on rapid development tracks throughout the industry, but pull open the hood on a natural gas truck today, and odds are there's a red block sitting there. Cummins, through its Cummins- Westport joint venture, is the largest provider of natural gas heavy-duty engines in North America, with 8.9- liter and soon-to-be-released 12- and 15-liter offerings based on its own ISG diesel engine. Natural gas trucks are expensive, though they have a fast return on investment due to the decidedly lower cost of natural gas. A new natural gas truck can cost as much as $40,000 more in incremental upcharges than a comparable Class 8 diesel truck, says Greg Treinen, who works with alternative fuels for 3 types of gas engines Three versions of heavy-duty natural gas engine technologies are available or in development in North America. conventional manner: A fuel-air mixture entering the cylinder is ignited by a spark plug, providing lower compression ratios. 1 system in which diesel and natural gas are fumigated in the compression chamber and mixed with diesel fuel injected into the cylinder on a displacement ratio to ignite the mixture. While the power curve is close to 2 Navistar is working on a technology it calls Clean Air Power. It's a dual-fuel Cummins-Westport employs a spark-ignited engine, which works in a that of conventional all-diesel powertrains, there are weight and packaging issues since large amounts of two different fuel types have to be carried on the vehicle. This is an attractive option for fleets that have high-horsepower and torque requirements but still want to cut diesel fuel costs. big-bore 15-liter configuration based on the Cummins ISX diesel platform. The pure diesel combustion cycle uses a fuel injector in the cylinder. The engine looks exactly the same as a conventional diesel, but the injector sends diesel through one 3 Westport's high-pressure direct-injection (HPDI) engine is offered in a nozzle and natural gas through another. At the end of the compression stroke, the engine is compressing 100 percent air with the same compression ratio as a conventional diesel. At that point, a minuscule amount of diesel is injected to initiate combustion. Next, through the same injector but a different nozzle, the bulk shot of natural gas enters the chamber and is ignited in a process that uses about 95 percent natural gas and 5 percent diesel. In an on-road situation, that process could use even less diesel because the diesel injection is consistent. It goes in at the same rate all the time, so when under full power on the highway, the truck is using predominantly natural gas. JULY 2012 OVERDRIVE 45