Diesel engines from land vehicles are among the primary drivers of air pollution in Thailand, with relatively high emission rates due to incomplete combustion, resulting in risks to health and the environment. The exhaust emissions from diesel engines that mainly impact human health consist of nitrogen oxides (NOx), hydrocarbons (HCs), carbon monoxide (CO), and particulate matter (PMs). A method or technology for eliminating damaging exhaust emissions from diesel engines is an after-treatment system. In other terms, it is a device that cleans exhaust gases so that engines can fulfill pollution standards.
Thailand mostly uses crude palm oil (CPO) to create biodiesel, while other vegetable oils such as refined bleached, deodorized palm oil, and palm stearin are also used. Thai manufacturers use two chemical procedures to create pure biodiesel (B100): acid-esterification and transesterification using methanol. Unprocessed materials are turned into ethyl ester or methyl ester, which also have qualities comparable to standard mineral diesel, using alcohol-based chemical processing. Biodiesel is thought to be very suitable for diesel engines, with analysis revealing several advantages, including improved combustion characteristics (higher cetane number), the absence of aromatic and sulfuric components, environmental sustainability, biodegradability, and lower greenhouse emissions when compared to diesel fuel. [1]. Because its combustion characteristics are basically equivalent to that of common diesel, biodiesel may be used in diesel engines without needing additional changes to the engine components. In 1912, Rudolf Diesel invented biodiesel fuel and decided that the use of vegetable oil would be preferred in the future [2].
Particulate matter (PM) is a byproduct of the compression ignition engine that is created by incomplete combustion and is generally composed of adsorbed carbonaceous compounds and hydrocarbons. Engine load, speed, fuel characteristics, fuel injection variables, and lubricant type are all elements that might affect the physical and chemical properties of PM. The production of secondary pollution is caused by the oxidation of primary pollution by air oxidants and dilution, whereas primary pollution can be influenced by a range of atmospheric and climatic conditions. Secondary pollutants like PM and volatile organic compounds (VOCs) are created when oxidized volatile organic compounds, nucleated semi-volatiles, or oxidized primary PM condense on particles. Particles are frequently divided into four groups in terms of legislation and common public usage: PM0.1, PM1, PM2.5, and PM10, which represent particles with sizes less than 0.1, 1.25, and 10 µm, respectively. These size classes are commonly used in air quality standards and public health studies [3–4]. Particulate matter from biomass source materials like sugarcane leaves and forest leaves has been studied for its structure and oxidation kinetics. With some metallic ash still present, the oxidation of unburned hydrocarbon and the PM oxidation process was completed at between 250 and 650 degrees Celsius [5]. Further research into the physical properties of PM from gasoline and diesel direct injection engines revealed that gasoline PMs had the largest interlayer spacing and the shortest carbon fringe, which led to a higher rate of soot oxidation than diesel PMs [6]. In this study, a range of ways for reducing PM and controlling emissions by combining biodiesel fuels and various after-treatment systems will be investigated.
The greatest way to increase engine performance and minimize exhaust emissions is to install after-treatment equipment. Selective catalytic reduction (SCR), diesel particulate filter (DPF), low NOx trap (LNT), and diesel oxidation catalyst (DOC are a few technologies that are used to reduce diesel engine emissions. To reduce the amount of HC and CO emissions from the exhaust, a DOC is put on the exhaust line of a diesel engine. By oxidizing HC and CO using a platinum-based catalyst, which raises the exit temperature, the DOC reduces the amount of HC and CO emissions from the exhaust. A DOC is frequently located in front of a DPF in a vehicle's exhaust manifold because the temperature increases it provides are beneficial to the DPF's active regeneration [7–8]. The partial-flow diesel particulate filter (P-DPF), which will be employed together with DOC in this study, combines the qualities of a flow-through material combined with those of a wall flow filter to capture some, but not all, of the engine exhaust soot. This reduces PM without clogging the filter. However, a unique foil and metal fleece filter material is used, combining the benefits of a flow-through structure with the ability to collect soot. The P-DPF project's objective was to develop an affordable PM reduction system that could reduce PM by more than 50% and HC/CO by more than 60% in a prototype, simple-to-maintain package [9].
The emissions of light-duty vehicles (LDVs) are tested and validated using a variety of techniques, including approval tests and several operation cycles. LDVs are certified in Europe using the new European driving cycle (NEDC), despite the fact that it has drawn flak for not accurately simulating actual driving scenarios. Despite this, the NEDC is used as the benchmark for emissions standards for Euro 3 and newer LDVs throughout Europe [10]. Thus, this experiment was measured under the NEDC to monitor in-use qualities in terms of engine performance, and quantities of pollutants emitted from the vehicle, and evaluate the success of each countermeasure to control and reduce emissions emitted from vehicles.
Nonetheless, several researchers have focused on fuel economy, exhaust emissions, and particulate matter. Incomplete combustion of fuels has the potential to affect human health and the environment, which is a flaw shown by soot analysis and vehicle exhaust emissions. In spite of that, the objective of this study will focus on the three different fuels (B10, B20, and B100) and combinations of catalyst-coated DOC and P-DPF to investigate the effects of engine performance, diesel emissions, soot emissions, soot nanostructure, and soot morphology. This study employed a real pickup vehicle with a 2.5-liter direct injection diesel engine running under the NEDC to study the real-time driving conditions of urban driving cycles (UDCs) and extra-urban driving cycles (EUDC).