TECHNOLOGY FOCUSCould HEDGE be the Alternative
for Light-Duty Diesels? WAUKEGAN, IL (May 31, 2007) - For many automakers, light-duty diesel vehicles is the wave of the future in the United States. However, Ford and GM have stated publicly that they have no plans for production of light-duty diesel cars for the U.S. market, citing reasons such as the limited availability of diesel fuel at retail stations, high cost of diesel oxides of nitrogen (NOx) and particulate emissions controls, technician shortages and training, vehicle integration engineering and new manufacturing tooling requirements. In search for an alternative to diesel engines, a large industry group is financing development of new gasoline engine technology called the High-Efficiency Dilute Gasoline Engine (HEDGE) at Southwest Research Institute (SWRI), San Antonio. HEDGE technology employs very high exhaust gas recirculation (EGR) rates, turbocharging and high-energy ignition. A recent list of sponsors (both vehicle and supplier firms) includes Corning, Cummins, Hino (51 percent-owned by Toyota), Deere, Peugeot/Citroen, Volkswagen, Volvo, Renault, Ford, Nissan, Honda, Valeo, Honeywell, Federal-Mogul, Dynagen, IVECO, NGK, DaimlerChrysler and Lubrizol. "Fuel consumption less than 210 grams/kWh has been measured, along with brake thermal efficiency of over 40 percent, which puts the HEDGE system on a par with diesels for cars and light trucks."An alternative to take seriously According to Charles Roberts, manager of Advanced Combustion Emissions at SWRI, "dyno testing of a 4.5L four-cylinder experimental HEDGE system engine [a modified Deere diesel engine] has demonstrated diesel-competitive fuel efficiency at 18 bar Brake Mean Effective Pressure (BMEP) and at remarkably high 17:1 compression ratio with pump grade gasoline." However, he says, initial production HEDGE engines may have somewhat lower compression ratios until long-life experience is gained. "Good engine stability, including transient operation over typical test cycles such as the U.S. Federal Test Procedure, has been achieved," he adds. "Fuel consumption less than 210 grams/kWh has been measured, along with brake thermal efficiency of over 40 percent, which puts the HEDGE system on a par with diesels for cars and light trucks," says Roberts. Basic reasons for this are low pumping losses and high compression made possible by high EGR rates. Vehicle testing will begin late summer this year with a 3,000-pound passenger vehicle (104-inch wheelbase) powered by a modified HEDGE 2.4L engine that may be downsized later to 1.8L, Roberts says. This could put HEDGE dead center in a very large segment of the automobile market: The 4.5L four-cylinder engine is aimed at large passenger vehicles and light trucks. Consortium participation by diesel engine makers is said to reflect favorable outlook for robust HEDGE technology engines for light commercial markets at much lower cost than new emissions-controlled diesels. "HEDGE technology employs turbocharging with unusually high EGR rates for knock tolerance and low NOx emissions," says Roberts. "State-of-the-art ignition provides good EGR tolerance, which leads to engine-out NOx [levels that are] 10 to 100 times lower than diesels." The HEDGE technology is expected to use less-complex turbocharging systems than what will be needed by diesels.
for Light-Duty Diesels? WAUKEGAN, IL (May 31, 2007) - For many automakers, light-duty diesel vehicles is the wave of the future in the United States. However, Ford and GM have stated publicly that they have no plans for production of light-duty diesel cars for the U.S. market, citing reasons such as the limited availability of diesel fuel at retail stations, high cost of diesel oxides of nitrogen (NOx) and particulate emissions controls, technician shortages and training, vehicle integration engineering and new manufacturing tooling requirements. In search for an alternative to diesel engines, a large industry group is financing development of new gasoline engine technology called the High-Efficiency Dilute Gasoline Engine (HEDGE) at Southwest Research Institute (SWRI), San Antonio. HEDGE technology employs very high exhaust gas recirculation (EGR) rates, turbocharging and high-energy ignition. A recent list of sponsors (both vehicle and supplier firms) includes Corning, Cummins, Hino (51 percent-owned by Toyota), Deere, Peugeot/Citroen, Volkswagen, Volvo, Renault, Ford, Nissan, Honda, Valeo, Honeywell, Federal-Mogul, Dynagen, IVECO, NGK, DaimlerChrysler and Lubrizol. "Fuel consumption less than 210 grams/kWh has been measured, along with brake thermal efficiency of over 40 percent, which puts the HEDGE system on a par with diesels for cars and light trucks."An alternative to take seriously According to Charles Roberts, manager of Advanced Combustion Emissions at SWRI, "dyno testing of a 4.5L four-cylinder experimental HEDGE system engine [a modified Deere diesel engine] has demonstrated diesel-competitive fuel efficiency at 18 bar Brake Mean Effective Pressure (BMEP) and at remarkably high 17:1 compression ratio with pump grade gasoline." However, he says, initial production HEDGE engines may have somewhat lower compression ratios until long-life experience is gained. "Good engine stability, including transient operation over typical test cycles such as the U.S. Federal Test Procedure, has been achieved," he adds. "Fuel consumption less than 210 grams/kWh has been measured, along with brake thermal efficiency of over 40 percent, which puts the HEDGE system on a par with diesels for cars and light trucks," says Roberts. Basic reasons for this are low pumping losses and high compression made possible by high EGR rates. Vehicle testing will begin late summer this year with a 3,000-pound passenger vehicle (104-inch wheelbase) powered by a modified HEDGE 2.4L engine that may be downsized later to 1.8L, Roberts says. This could put HEDGE dead center in a very large segment of the automobile market: The 4.5L four-cylinder engine is aimed at large passenger vehicles and light trucks. Consortium participation by diesel engine makers is said to reflect favorable outlook for robust HEDGE technology engines for light commercial markets at much lower cost than new emissions-controlled diesels. "HEDGE technology employs turbocharging with unusually high EGR rates for knock tolerance and low NOx emissions," says Roberts. "State-of-the-art ignition provides good EGR tolerance, which leads to engine-out NOx [levels that are] 10 to 100 times lower than diesels." The HEDGE technology is expected to use less-complex turbocharging systems than what will be needed by diesels.
The HEDGE engine's hydrocarbon, carbon monoxide (CO) and NOx emissions are in the range of today's gasoline engines, says Roberts, and are controlled with "economic, off-the-shelf, three-way catalyst emissions controls." He stresses that "diesel-type exhaust NOx and particulate controls are not needed."
More in the works In addition to 4.5L and 2.4L four-cylinder engine development, further advanced ignition and control systems - as well as a single-cylinder engine experiment - are planned. Work on direct injection also has been initiated. Roberts explains that as work progresses at SWRI, "our consortium sponsor members are incorporating our findings into engines or components they are working on in parallel at their facilities aimed at their business objectives." One of the major economic advantages of the HEDGE technology is the low-cost, conventional low-pressure, port fuel injection vs. high-pressure diesel-type injection - although direct gasoline injection is also being explored. Another is in its conventional three-way catalyst emissions controls, rather than employing high-cost diesel particulate and NOx control systems. One European supplier has projected that diesel penetration of the European Union car market could decline from the current 50 percent level to 40 percent by 2020. Additional cost savings may also be realized through the engine's less-severe combustion characteristics compared to those that diesels must be built to tolerate - although this has yet to be fully explored. In addition, the HEDGE technology is expected to use less-complex turbocharging systems than what will be needed by diesels. Overall cost projections by SWRI favor HEDGE by up to several thousand dollars less than the new diesels. The long-held belief by many engine technologists that we would see the day when diesel and gasoline systems converge may indeed be near, if not actually here - thanks to broad consortium sponsorship by the industry and technical collaboration. While this is an interesting academic subject, in the broader picture, there are major questions attached to the HEDGE engine development, such as to what degree would European automakers begin to switch back from diesel to gasoline engine production? One European supplier has projected that diesel penetration of the European Union car market could decline from the current 50 percent level to 40 percent by 2020. However, rapid change in the diesel/gasoline engine mix - whether in Europe or the United States - is inhibited by the huge cost of petroleum refinery changes in the diesel/gasoline product mix. Reflecting on the GM and Ford positions on U.S. diesel cars, Marathon Oil Co. recently announced a $3.2 billion expansion of its Garryville, LA refinery that will result in a modest decrease in total refinery gasoline production from 66 percent to 60 percent and a small increase in diesel fuel production. Marathon says this reflects the expected improvements in gasoline engine efficiency and vehicle downsizing, and not a significant increase in diesel engine use.(Source: SWRI)
