CRC releases ACES Phase 2 final report
16 December 2013
The Coordinating Research Council (CRC) has released the final report from the Phase 2 of the ACES study that characterized emissions from new technology, emission controlled heavy-duty on-road diesel engines. The report provides emission results from three model year 2010 engines—utilizing urea-SCR aftertreatment—and compares them to emissions from the MY 2007 engines evaluated in ACES Phase 1 and MY 2004 engines without particulate filters.
For a number of the most important pollutants, emission levels from the tested 2010 engines were substantially lower than required by regulations. All criteria pollutant emissions were below the 2010 standard: CO was 97% lower than its 2010 limit, NMHC 99%, NOx 61% and PM 92%. The above reductions were measured over the regulatory, composite FTP test cycle.
The 2010 engine technology also demonstrated significant reductions relative to 2007 engines. Measurements over the 16 hour test cycle developed under the ACES study showed a 72% reduction for CO, 99.9% for NMHC, 71% for PM, and 94% for NOx. CO2 emissions and brake specific fuel consumption were reduced by 3% on the 2010 engines relative to 2007 engines. N2O emissions were higher for 2010 engines compared to 2007 technology engines, but they were still below the EPA 2014 N2O limit of 0.1 g/bhp-hr. The average N2O emissions for the three engines were 0.052, 0.054, and 0.11 g/bhp-hr.
A number of unregulated emissions were also measured in the study, including THC, CH4, NO, NO2, NH3, organic carbon (OC), elemental carbon (EC), PAH, nitro-PAH, oxy-PAH, alkanes, cyanide ions, carbonyls and speciated HCs. Dioxins, furans, and urea-related compounds were also measured over the 16-hour cycle.
NO2 emissions, an unregulated component of NOx, were reduced by 94%, while particulate number emissions were reduced by 72% relative to 2007 engines (16 hour test). Substantial reductions in other unregulated emission compounds (36%-99%) were observed relative to 2007 engines and even greater reductions (91%-100%) relative to 2004 engines. Of the urea-related compounds, only urea and cyanuric acid were detected in the range from 5-15 μg/bhp-hr. Ammonia slip emissions ranged from 0.12-1.37 ppm.
The observed reductions in PM (total mass, soot, and number) and unregulated emissions from 2007 to 2010 engines are likely due to differences in active DPF regeneration operation, concluded the report. The 2007 engines triggered multiple regeneration events during the 16 hour cycles, while the 2010 engines did not trigger any events. The improvement/reduction in regeneration was achieved through a combination of lower engine-out PM, increased passive regeneration and improved control strategies.
The ACES Phase 2 report describes work conducted by Dr. Imad Khalek and colleagues at Southwest Research Institute and Desert Research Institute. The ongoing Advanced Collaborative Emissions Study (ACES) is being undertaken by the Health Effects Institute (HEI) and the CRC, with support from the US EPA, California ARB, US DOE, EMA, API, and emission control manufacturers. Phase 3 of the study is looking into biological effects of emissions from new technology diesel engines
Source: HEI