Impact of Gaseous Fuels on Highly Dilute Engines, 03-R8124
Printer Friendly VersionPrincipal Investigators
Mark Walls
Dr. Terrence Alger
Dr. Michael Joo
Barrett Mangold
Inclusive Dates: 12/28/09 – 04/28/10
Background - SwRI has been successful in developing technology to improve gasoline spark-ignited engine emissions and performance through the HEDGE® (High Efficiency Dilute Gasoline Engine) concept. However, the novel technologies developed within the HEDGE consortium are not limited to gasoline combustion and should be explored on gaseous fuels considering the sharp increase of global demand for lower CO2 emissions. It is imperative that the engine community understand how these fuels will impact next-generation engine technologies, like those developed in HEDGE, as they come of age in an environment where gaseous fuel could become more prevalent. The impact was quantified in two categories: engine performance and exhaust emissions for part- and full-load conditions. There is a general lack of published literature investigating these topics on highly dilute stoichiometric engines.
Approach - The objective of this project was to use the HEDGE concept while operating on gasoline (baseline), natural gas and propane and to determine the effect of the alternative fuels on the fuel economy and emissions of a light-duty passenger car engine. Engine performance and exhaust emissions were identified on a Turbocharged 2.4L 4-cylinder PFI spark-ignited engine with a compression ratio of 9.5:1. This engine was installed in an engine test cell and outfitted with HEDGE-class hardware and control technologies, including an exhaust gas recirculation (EGR) cooler and a proprietary ignition system. For part- and full-load testing, all of the engine actuators were exercised to optimize the speed/load/fuel operating point. These test points were achieved by sweeping ignition timing, EGR rate, cam phasing, turbo geometry and EGR type (internal/external or mixed) until the best brake thermal efficiency was achieved.
Accomplishments - As expected, natural gas and propane operate very similar to gasoline during part-load operation. Part-load comparisons demonstrate the ability of all three fuels to operate at optimal combustion phasing from light to medium loads. The gaseous fuels overall showed a slightly lower brake thermal efficiency at lower loads, but, in turn, reduced emissions levels. Brake specific hydrocarbon, carbon monoxide and nitrous oxides engine emission levels were reduced by up to 50 percent, and CO2 by as much as 20 percent. The use of the HEDGE concept for mid- to full-load operation in conjunction with alternative fuels shows great promise in reducing overall emissions while simultaneously improving fuel economy. The engine is able to reach loads 25 percent higher than that of gasoline and maintain higher efficiency due to its ability to maintain optimal combustion phasing. Further improvements for gaseous fuels might be realized with an increase in compression ratio and turbocharger optimization.
