On-board gaseous emissions of LPG taxis and estimation of taxi fleet emissions.

Instantaneous CO, NO, and HC emissions and exhaust flow rates from four LPG taxis, which adhered to Euro 2-4 emission standards, were measured using a sophisticated portable emission measurement system (PEMS). Instantaneous air/fuel ratios, emission rates, and emission factors at different operating modes were derived to explore the emission characteristics of these four taxis. Results show that gaseous emissions from these four taxis exceed emission standards, due to extended vehicle use and poor maintenance. NO emissions from newer taxis are lower whilst CO and HC emissions of the Euro 4 taxi are similar to those of Euro 2 taxis during idling and low speed travel. The taxis emit lower amounts of gaseous pollutants whilst idling and emit the highest amounts of CO and NO whilst accelerating. Large fluctuations in air/fuel ratios can be observed from the Euro 4 taxi during idling, indicating a malfunction of fuel supply control to the engine. Such fluctuations are not observed from the other taxis. This shows that a Euro 4 taxi is not necessarily cleaner than a Euro 3 taxi. Emission factors derived from on-board measurements are applied to estimate gaseous emissions from the taxi fleet; these results show that emissions are higher during peak hour traffic conditions. An estimate of the taxi fleet's emissions whilst the older taxis are replaced is also calculated. It can be seen that faster replacement of older taxis can lead to reductions in gaseous emissions from the taxi fleet. This study shows that the PEMS is an adequate tool for measuring emissions from LPG vehicles and that there is an urgent need to enforce emission standards on taxis. This study also shows that on-board measurements should be incorporated in the estimation of emissions from other vehicle types. This would result in better emission estimations under local traffic conditions.

[1]  Y. Ko,et al.  Characterization of large fleets of vehicle exhaust emissions in middle Taiwan by remote sensing. , 2006, The Science of the total environment.

[2]  Gordon E. Andrews,et al.  Comparisons of the Exhaust Emissions for Different Generations of SI Cars under Real World Urban Driving Conditions , 2008 .

[3]  Joda Wormhoudt,et al.  Real-time measurements of nitrogen oxide emissions from in-use New York City transit buses using a chase vehicle. , 2005, Environmental science & technology.

[4]  Norbert V. Heeb,et al.  Correlation of hydrogen, ammonia and nitrogen monoxide (nitric oxide) emissions of gasoline-fueled Euro-3 passenger cars at transient driving , 2006 .

[5]  M. A. Ceviz,et al.  Cyclic variations on LPG and gasoline-fuelled lean burn SI engine , 2006 .

[6]  David R. Cocker,et al.  Emission rates of regulated pollutants from on-road heavy-duty diesel vehicles , 2006 .

[7]  Tiago L. Farias,et al.  Evaluation of SI engine exhaust gas emissions upstream and downstream of the catalytic converter , 2006 .

[8]  Tord Kjellstrom,et al.  Spatial analysis of annual air pollution exposure and mortality. , 2003, The Science of the total environment.

[9]  Andrew J. Kean,et al.  Effects of vehicle speed and engine load on motor vehicle emissions. , 2003, Environmental science & technology.

[10]  H. Frey,et al.  Quantification of Highway Vehicle Emissions Hot Spots Based upon On-Board Measurements , 2004, Journal of the Air & Waste Management Association.

[11]  Zhiliang Yao,et al.  High-resolution vehicular emission inventory using a link-based method: a case study of light-duty vehicles in Beijing. , 2009, Environmental science & technology.

[12]  Li Li,et al.  On-road emission characteristics of heavy-duty diesel vehicles in Shanghai , 2007 .

[13]  J. Park,et al.  Mercury emissions from automobiles using gasoline, diesel, and LPG , 2007 .

[14]  Mark Allen Dearth,et al.  SemtechD: The Chassis Roll Evaluation of a Commercial Portable Emission Measurement System (PEMS) , 2005 .

[15]  David C. Carslaw,et al.  Investigating the potential importance of primary NO2 emissions in a street canyon , 2004 .

[16]  Britt A. Holmén,et al.  Characterizing the Effects of Driver Variability on Real-World Vehicle Emissions , 1998 .

[17]  Christopher A. Laroo,et al.  On-road comparison of a portable emission measurement system with a mobile reference laboratory for a heavy-duty diesel vehicle , 2009 .

[18]  John B. Heywood,et al.  Internal combustion engine fundamentals , 1988 .

[19]  M. Nieuwenhuijsen,et al.  Personal exposures to VOC in the upper end of the distribution - Relationships to indoor, outdoor and workplace concentrations , 2005 .

[20]  Gordon E. Andrews,et al.  Impact of Traffic Conditions and Road Geometry on Real World Urban Emissions Using a SI Car , 2007 .

[21]  Patrick Debal,et al.  Comparison of on-road emissions with emissions measured on chassis dynamometer test cycles , 2006 .

[22]  Kyoungho Ahn,et al.  COMPARATIVE FIELD EVALUATION OF VEHICLE CRUISE SPEED AND ACCELERATION LEVEL IMPACTS ON HOT STABILIZED EMISSIONS , 2005 .

[23]  J Wayne Miller,et al.  Emission rates of particulate matter and elemental and organic carbon from in-use diesel engines. , 2004, Environmental science & technology.

[24]  Prashant Kumar,et al.  Real world driving cycle for motorcycles in Edinburgh , 2009 .

[25]  M. David Checkel,et al.  Emission Factors Analysis for Multiple Vehicles Using an On-Board, In-Use Emissions Measurement System , 2007 .

[26]  Tat Leung Chan,et al.  On-road remote sensing of liquefied petroleum gas (LPG) vehicle emissions measurement and emission factors estimation , 2007 .

[27]  Hsi-Hsien Yang,et al.  Comparative study of regulated and unregulated air pollutant emissions before and after conversion of automobiles from gasoline power to liquefied petroleum gas/gasoline dual-fuel retrofits. , 2007, Environmental science & technology.