Emission Rates of Regulated Pollutants from Current Technology Heavy-Duty Diesel and Natural Gas Goods Movement Vehicles. Thiruvengadam, A.; Besch, M., C.; Thiruvengadam, P.; Pradhan, S.; Carder, D.; Kappanna, H.; Gautam, M.; Oshinuga, A.; Hogo, H.; and Miyasato, M.
Emission Rates of Regulated Pollutants from Current Technology Heavy-Duty Diesel and Natural Gas Goods Movement Vehicles [pdf]Paper  Emission Rates of Regulated Pollutants from Current Technology Heavy-Duty Diesel and Natural Gas Goods Movement Vehicles [link]Website  abstract   bibtex   
Chassis dynamometer emissions testing of 11 heavy-duty goods movement vehicles, including diesel, natural gas, and dual-fuel technology, compliant with US-EPA 2010 emissions standard were conducted. Results of the study show that three-way catalyst (TWC) equipped stoichiometric natural gas vehicles emit 96% lower NOx emissions as compared to selective catalytic reduction (SCR) equipped diesel vehicles. Characteristics of drayage truck vocation, represented by the near-dock and local drayage driving cycles, were linked to high NOx emissions from diesel vehicles equipped with a SCR. Exhaust gas temperatures below 250 °C, for more than 95% duration of the local and near-dock driving cycles, resulted in minimal SCR activity. The low percentage of activity SCR over the local and near-dock cycles contributed to a brake-specific NOx emissions that were 5−7 times higher than in-use certification limit. The study also illustrated the differences between emissions rate measured from chassis dynamometer testing and prediction from the EMFAC model. The results of the study emphasize the need for model inputs relative to SCR performance as a function of driving cycle and engine operation characteristics. ■ INTRODUCTION United States Environmental Protection Agency's (US-EPA) 2010 emissions standards for heavy-duty (HD) engines seek to reduce the oxides of nitrogen (NOx) and particulate matter (PM) emissions to near-zero levels. The current regulations stipulate the brake-specific NOx (bs-NOx) and PM (bs-PM) emissions from HD engines tested over the federal test procedure (FTP) engine dynamometer cycle to be at or below 0.20 and 0.01 g per brake-horsepower (g/bhp-hr), respectively. HD engine platforms compliant to current US-EPA standards can be broadly classified as (1) spark-ignited natural gas engines operating with a three-way catalyst (TWC); (2) dual-fuel (diesel/natural gas) engine operating with a diesel particulate filter (DPF) and selective catalytic reduction (SCR) aftertreat-ment system (ATS); (3) diesel engines with DPF and SCR ATS; (4) diesel engines with advanced exhaust gas recirculation (EGR), and equipped with only a DPF. With the promulgation of the US-EPA 2010 emissions standards, the majority of the HD diesel engine manufacturers have adopted SCR with aqueous urea injection (diesel exhaust fluid) as the choice ATS for tailpipe NOx abatement. Modern HD on-highway natural gas engines are designed to operate at stoichiometric air−fuel ratio, wherein theoretically a homogeneous mixture of chemically correct proportion of fuel and air is inducted by the engine to achieve complete combustion of fuel. Because of the high octane rating of natural gas, spark ignition is highly favored in internal combustion applications. TWC is a catalytic ATS that is capable of simultaneous emissions reduction of carbon monoxide (CO), hydrocarbons (HC), and NOx. TWC require engine operation close to stoichiometry to achieve over 90% reduction in tailpipe NOx. 1 Legacy natural gas engines operated as lean-burn technology (excess of air relative to stoichiometric condition) were equipped with a simple oxidation catalyst that served to control only emissions of CO and nonmethane hydrocarbon (NMHC). The older lean-burn technology contributed to NOx emissions similar in magnitude to legacy diesel engines while emitting orders of magnitude lower soot emissions. 2,3 A study by Yoon et al. compared transit bus emissions from old and newer technology natural gas transit buses. The study concluded that NOx emissions from a stoichiometric natural gas engine equipped with a TWC was over 90% lower than from lean-burn natural gas engines, while emissions of CO were three times higher. 4 Reactions in a TWC involve the simultaneous emissions reduction of CO and NOx under conditions of an oxygen-deficient exhaust resulting from
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 title = {Emission Rates of Regulated Pollutants from Current Technology Heavy-Duty Diesel and Natural Gas Goods Movement Vehicles},
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 abstract = {Chassis dynamometer emissions testing of 11 heavy-duty goods movement vehicles, including diesel, natural gas, and dual-fuel technology, compliant with US-EPA 2010 emissions standard were conducted. Results of the study show that three-way catalyst (TWC) equipped stoichiometric natural gas vehicles emit 96% lower NOx emissions as compared to selective catalytic reduction (SCR) equipped diesel vehicles. Characteristics of drayage truck vocation, represented by the near-dock and local drayage driving cycles, were linked to high NOx emissions from diesel vehicles equipped with a SCR. Exhaust gas temperatures below 250 °C, for more than 95% duration of the local and near-dock driving cycles, resulted in minimal SCR activity. The low percentage of activity SCR over the local and near-dock cycles contributed to a brake-specific NOx emissions that were 5−7 times higher than in-use certification limit. The study also illustrated the differences between emissions rate measured from chassis dynamometer testing and prediction from the EMFAC model. The results of the study emphasize the need for model inputs relative to SCR performance as a function of driving cycle and engine operation characteristics. ■ INTRODUCTION United States Environmental Protection Agency's (US-EPA) 2010 emissions standards for heavy-duty (HD) engines seek to reduce the oxides of nitrogen (NOx) and particulate matter (PM) emissions to near-zero levels. The current regulations stipulate the brake-specific NOx (bs-NOx) and PM (bs-PM) emissions from HD engines tested over the federal test procedure (FTP) engine dynamometer cycle to be at or below 0.20 and 0.01 g per brake-horsepower (g/bhp-hr), respectively. HD engine platforms compliant to current US-EPA standards can be broadly classified as (1) spark-ignited natural gas engines operating with a three-way catalyst (TWC); (2) dual-fuel (diesel/natural gas) engine operating with a diesel particulate filter (DPF) and selective catalytic reduction (SCR) aftertreat-ment system (ATS); (3) diesel engines with DPF and SCR ATS; (4) diesel engines with advanced exhaust gas recirculation (EGR), and equipped with only a DPF. With the promulgation of the US-EPA 2010 emissions standards, the majority of the HD diesel engine manufacturers have adopted SCR with aqueous urea injection (diesel exhaust fluid) as the choice ATS for tailpipe NOx abatement. Modern HD on-highway natural gas engines are designed to operate at stoichiometric air−fuel ratio, wherein theoretically a homogeneous mixture of chemically correct proportion of fuel and air is inducted by the engine to achieve complete combustion of fuel. Because of the high octane rating of natural gas, spark ignition is highly favored in internal combustion applications. TWC is a catalytic ATS that is capable of simultaneous emissions reduction of carbon monoxide (CO), hydrocarbons (HC), and NOx. TWC require engine operation close to stoichiometry to achieve over 90% reduction in tailpipe NOx. 1 Legacy natural gas engines operated as lean-burn technology (excess of air relative to stoichiometric condition) were equipped with a simple oxidation catalyst that served to control only emissions of CO and nonmethane hydrocarbon (NMHC). The older lean-burn technology contributed to NOx emissions similar in magnitude to legacy diesel engines while emitting orders of magnitude lower soot emissions. 2,3 A study by Yoon et al. compared transit bus emissions from old and newer technology natural gas transit buses. The study concluded that NOx emissions from a stoichiometric natural gas engine equipped with a TWC was over 90% lower than from lean-burn natural gas engines, while emissions of CO were three times higher. 4 Reactions in a TWC involve the simultaneous emissions reduction of CO and NOx under conditions of an oxygen-deficient exhaust resulting from},
 bibtype = {article},
 author = {Thiruvengadam, Arvind and Besch, Marc C and Thiruvengadam, Pragalath and Pradhan, Saroj and Carder, Daniel and Kappanna, Hemanth and Gautam, Mridul and Oshinuga, Adewale and Hogo, Henry and Miyasato, Matt}
}
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