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原文传递 Analyze Existing West LA Data set for On-Road Evaporative Emissions.

题名：	Analyze Existing West LA Data set for On-Road Evaporative Emissions.
作者：	Bishop, G.
关键词：	Remote sensing device, Emissions trends, On-road measurement, Vehicle emissions, Evaporative emissions, Fuel efficiency automobile test system (FEAT)
摘要：	U.S. vehicle fleet emissions have been on a steady decline since the early 90’s producing significant improvements in air quality. On-road vehicles can potentially emit carbon monoxide (CO), hydrocarbons (HC) and reactive nitrogen compounds from the tailpipe as well as nontailpipe (evaporative) HC emissions from the fuel tank and fuel delivery system. As mobile source emissions have decreased the relative contributions of tailpipe and evaporative emissions to the total have been studied and debated. Into the early 2000’s measurements and model predictions generally agreed that tailpipe emissions of HC constituted the majority of the mobile source HC emissions. As the total HC emissions have declined the fraction of the total predicted to be contributed by evaporative emissions have grown in the models; yet, analysis of ambient air measurements have disagreed over whether that is the case. In the spring of 2013 and 2015 the University of Denver collected on-road emission measurements of an in-use fleet that uses the La Brea Ave. and I-10 interchange in West Los Angeles as part of a California Air Resources Board sponsored project. This resulted in two data sets, the first collected between Saturday April 27 through Saturday May 4, 2013 with 33,807 attempted measurements and 27,247 valid and registration matched records. The second set was collected between Saturday March 28 and Friday April 3, 2015 with 27,413 attempted measurements and 22,124 valid and registration matched records. In addition to the fuel specific emission results for each vehicle, the high frequency data which consists of 50 individual voltages from each of the four infrared detectors and concentration data from the ultraviolet spectrometers collected at 100 Hz over the one half second emissions measurement, was also collected for each attempted measurement. These high frequency files contain millisecond level emissions absorption data for each channel and can be used to analyze the changes in an individual species emissions measurement as a function of time during each vehicles tailpipe test. The high frequency data files were screened for the presence of non-tailpipe hydrocarbons using an evaporative emissions index (EI23) developed by the Eastern Research Group (ERG) in cooperation with the Colorado Department of Public Health and Environment and several of FEAT’s additional quality assurance metrics (DeFries et al., 2012). The EI23 index is a method for categorizing the observed noise that exits in the linear least squares fit of supposed exhaust HC emissions for each vehicle. When a vehicle has more than one source of HC emissions there is the potential for this second source of HC to disrupt the correlation with the tailpipe CO2 emissions. The EI23 index is calculated using the results of the linear least squares fit to the HC to CO2 correlation graph. The residuals from the fit are then ordered from largest to smallest and the EI23 index is the 95th percentile.
报告类型：	科技报告