Detailed Characterization of Gaseous Emissions from Advanced Internal Combustion Engines

With the advancement of engine technologies and combustion strategies, aftertreatment architectures are expected to evolve as they continue to be the primary emissions mitigation hardware. Some of the engine approaches offer unique challenges and benefits that are not well understood beyond criteria pollutant emissions. As such, there continues to be a need to quantify engine emissions characteristics in pursuit of catalyst technology development and the use of advanced simulation tools. The following study discusses results from an extensive engine emissions assessment for current state-of-the-art technology and novel combustion regimes. The engines tested include a Tier 4 final compliant 6.8 L John Deere PSS 6068 diesel engine, a modified 15 L diesel engine, and a dual fuel 13 L natural gas-diesel engine. The dual fuel engine could operate in conventional positive ignition mode (CDF) or low temperature reactivity-controlled compression ignition mode (RCCI). The selection considered engine technologies and calibrations intended for commercialization over the next decade. Emissions characterization involved operating the engines at various steady state speed and load conditions. Exhaust gas emission measurements and analysis included standard emissions characterization (e.g. HC, CO, NO_X) and hydrocarbon speciation techniques. Results indicated up to 90% lower NO_X emissions and favorable NO₂ to NO_X ratios from the RCCI engine. However, the dual fuel engine operated in either RCCI or CDF mode also generated the highest amounts of CH₄, which contributes to the overall greenhouse gas emissions. The baseline engine was observed to have the highest exhaust temperatures and would contribute to a more advantageous catalyst thermal environment. Overall, the results provide an engine emissions summary to consider aftertreatment solutions for future engine operating regimes.