Abstract
Air quality in urban areas is strongly influenced by exhaust emitted by the public transport fleet. The aim of this study was to analyze benefits in the fuel consumption, fuel costs and exhaust emissions when replacing baseline diesel fueled EURO III city buses by the compressed natural gas (CNG)-fueled EURO V buses and by hydraulic series hybrid diesel-fueled EURO V buses. Real-world measurements were performed on the regular bus route to access realistic energy consumption and exhaust emissions. Instantaneous gaseous emission (CO2, CO, NOx and THC) were measured together with the instantaneous PM10 mass emission. Innovativeness of the presented approach thus arises from the systematic comparison of different powertrain technologies under real-world drive cycles and measuring time traces of not only gaseous but also of PM10 mass emissions. Furthermore, lumped cycle averaged emissions are interpreted and explained by typical powertrain performance parameters and exhaust emission time traces. Cumulative results indicate that application of the CNG fueled buses does not necessary reduce CO2 emissions compared to diesel-fueled buses whereas reduction in fuel costs is evident. Additionally, it is shown that hybrid operation of the hydraulic series hybrid diesel-fueled bus resulted in higher fuel consumption due to poorly optimized hybrid topology and control strategy. Furthermore, analyses of the time traces point out inadequate lambda control of CNG-fueled buses and nucleation mode-based particle number emissions during deceleration.
Highlights
Road transport vehicles are still mainly powered by internal-combustion engines, which generally use fossil fuels and emit CO2, which is an important driver of climate change
PM10 results presented in this study are aligned in terms of PM heavy-duty emission relations heavy-duty diesel-powered vehicles, all equipped with diesel particle filter, and one10 between analyzed fuelsvehicle and emission standards with the results presented in the study where buses
Instantaneous gaseous and PM10 mass emissions as well as several powertrain parameters of three different buses applying different emission standards and fuels were measured in real-world conditions: conventional EURO III diesel bus, compressed natural gas (CNG)-powered EURO V bus and diesel-powered hydraulic series hybrid EURO V bus
Summary
Road transport vehicles are still mainly powered by internal-combustion engines, which generally use fossil fuels and emit CO2 , which is an important driver of climate change. Huge efforts were invested to reach five main climate change agreements: the United Nations Framework. Convention on Climate Change, 1992; the Kyoto Protocol, 1998; the Copenhagen Accord, 2009; the. Doha Amendment, 2012; the Paris Agreement, 2015. These agreements have been implemented by introducing green policies and actions in the transport sector, since transport is one of the major greenhouse gases emitters. As the majority of the public transport users are concentrated in cities, the harmful exhaust emissions of local buses have a considerable impact on human health. According to the Slovenian Environment Agency report [2], being in line with similar reports of other agencies, the impact of PM10 particles on health depends on their concentration and on the time of exposure. It is reported that long-term exposure to lower concentrations of PM10 has much greater impact than
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