Impact of Driving Cycles on Greenhouse Gas (GHG) Emissions, Global Warming Potential (GWP) and Fuel Economy for SI Car Real World Driving

The transport sector is one of the major contributors to greenhouse gas emissions. This study investigated three greenhouse gases emitted from road transport: CO2, N2O and CH4 emissions as a function of engine warm up and driving cycles. Five different urban driving cycles were developed and used including free flow driving and congested driving. An in-vehicle FTIR (Fourier Transform Inferred) emission measurement system was installed on a EURO2 emission compliant SI (Spark Ignition) car for emissions measurement at a rate of 0.5 HZ under real world urban driving conditions. This emission measurement system was calibrated on a standard CVS (Constant Volume Sampling) measurement system and showed excellent agreement on CO2 measurement with CVS results. The N2O and CH4 measurement was calibrated using calibration gas in lab. A MAX710 real time in-vehicle fuel consumption measurement system was installed in the test vehicle and real time fuel consumption was then obtained. The temperatures across the TWC (Three Way Catalyst) and engine out exhaust gas lambda were measured. The GHG (greenhouse gas) mass emissions and consequent GWP (Global Warming Potential) for different urban diving conditions were analyzed and presented. The results provided a better understanding of traffic related greenhouse gas emission profile in urban area and will contribute to the control of climate change

A Quiet Area Accessibility Metric for the Southampton Urban Agglomeration

Thermal characteristics of SI engine exhaust during cold start and warm up period were investigated for different ambient temperatures (-2 to 32 °C). A Euro 1 emission compliance SI car was tested using a real world urban driving cycle to represent typical city driving patterns and simulate ECE15 urban driving cycle. The test car was equipped with 27 thermocouples along the engine and exhaust pipes so as to measure metal and exhaust gas temperatures along the engine, exhaust and catalyst. The characteristics of thermal properties of engine, exhaust system and catalyst were studied as a function of warm up time and ambient temperature. The temperature and time of the light-off of catalyst were investigated so as to evaluate the effect of thermal properties of the catalyst on emissions. The results show that the coolant water reached the full warm up about 5 minutes in summer and 9 minutes in winter after a cold start. Lubricating oil reached the full warm up in 10 minutes in summer and 14 minutes in winter after a cold start. The light-off time of TWC was about 3 minutes in summer and 6 minutes in winter in terms of catalyst substrate temperatures. The determination of catalyst light off has been studied and discussed in terms of catalyst substrate temperatures and gas temperatures. The ambient temperature had little influence on engine out exhaust gas temperatures. The heat loss from the engine out to the catalyst was at highest level in the first 5~6 minutes and after this point the heat available at the catalyst was relatively stable. The thermal properties of the engine and exhaust system had significant influence on emissions. The results indicate that in some urban driving conditions such as short journeys in cities especially under cold weather conditions, the function of catalysts for emission reductions is very limited

Study of the Emissions Generated at intersections for a SI Car Real World Urban Driving Conditions

A precision in-vehicle tail-pipe emission measurement system was installed in a EURO1 emissions compliant SI car and used to investigate the variability in tail-pipe emission generation at an urban traffic junction. Exhaust gas and skin temperatures were also measured along the exhaust pipe of the instrumented vehicle, so the thermal characteristics and the efficiency of the catalyst monitored could be included in the analysis. Different turning movements (driving patterns) at the priority T-junction were investigated such as straight, left and right turns with and without stops. The test car was hot stable running conditions before each test, thereby negating cold start effects. To demonstrate the influence of the junction on tail-pipe emissions and fuel consumption, distance based factors were determined that compared the intersection drive-through measurements with steady speed (state) runs. Fuel consumption was increased at intersections by a factor of 1.3~5.9. CO, THC and NOx emission were increased by a factor of 8~26, 6~21 and 2.5~10 respectively. Benzene emissions were also increased by a factor of 4~21. Through fine-scale analysis of real-world driving profiles and tail-pipe emissions, this research makes a contribution to our understanding of the variability in driving parameters and emission production in urban areas. The results of this study will be useful in advising the development of combined traffic/ emission models for urban areas and developing optimal traffic management strategies to minimise emissions