Assessment of air quality has been traditionally conducted by ground based monitoring, and more recently by manned aircrafts and satellites. However, performing fast, comprehensive data collection ...near pollution sources is not always feasible due to the complexity of sites, moving sources or physical barriers. Small Unmanned Aerial Vehicles (UAVs) equipped with different sensors have been introduced for in-situ air quality monitoring, as they can offer new approaches and research opportunities in air pollution and emission monitoring, as well as for studying atmospheric trends, such as climate change, while ensuring urban and industrial air safety. The aims of this review were to: (1) compile information on the use of UAVs for air quality studies; and (2) assess their benefits and range of applications. An extensive literature review was conducted using three bibliographic databases (Scopus, Web of Knowledge, Google Scholar) and a total of 60 papers was found. This relatively small number of papers implies that the field is still in its early stages of development. We concluded that, while the potential of UAVs for air quality research has been established, several challenges still need to be addressed, including: the flight endurance, payload capacity, sensor dimensions/accuracy, and sensitivity. However, the challenges are not simply technological, in fact, policy and regulations, which differ between countries, represent the greatest challenge to facilitating the wider use of UAVs in atmospheric research.
•Oxygen ratio was used instead of the equivalence ratio.•Oxygen ratio decreases with engine load, but increases with engine speed.•IMEP, BMEP, friction power, CO2, HC, PM and PN decreased with ...oxygenated fuels.•BSFC, BTE and NOx increased with oxygenated fuels.•Accumulation mode count median diameter decreased with oxygenated fuels.
This study investigates the effect of oxygenated fuels on engine performance and exhaust emission under a custom cycle using a fully instrumented 6-cylinder turbocharged diesel engine with a common rail injection system. A range of oxygenated fuels based on waste cooking biodiesel with triacetin as an oxygenated additive were studied. The oxygen ratio was used instead of the equivalence ratio, or air to fuel ratio, to better explain the phenomena observed during combustion. It was found that the increased oxygen ratio was associated with an increase in the friction mean effective pressure, brake specific fuel consumption, CO, HC and PN. On the other hand, mechanical efficiency, brake thermal efficiency, CO2, NOx and PM decreased with oxygen ratio. Increasing the oxygen content of the fuel was associated with a decrease in indicated power, brake power, indicated mean effective pressure, brake mean effective pressure, friction power, blow-by, CO2, CO (at higher loads), HC, PM and PN. On the other hand, the brake specific fuel consumption, brake thermal efficiency and NOx increased by using the oxygenated fuels. Also, by increasing the oxygen content, the accumulation mode count median diameter moved toward the smaller particle sizes. In addition to the oxygen content of fuel, the other physical and chemical properties of the fuels were used to interpret the behavior of the engine.
ABSTRACT
Particulate matter (PM) emissions involve a complex mixture of solid and liquid particles suspended in a gas, where it is noted that PM emissions from diesel engines are a major contributor ...to the ambient air pollution problem. While epidemiological studies have shown a link between increased ambient PM emissions and respiratory morbidity and mortality, studies of this design are not able to identify the PM constituents responsible for driving adverse respiratory health effects. This review explores in detail the physico‐chemical properties of diesel PM (DPM) and identifies the constituents of this pollution source that are responsible for the development of respiratory disease. In particular, this review shows that the DPM surface area and adsorbed organic compounds play a significant role in manifesting chemical and cellular processes that if sustained can lead to the development of adverse respiratory health effects. The mechanisms of injury involved included inflammation, innate and acquired immunity, and oxidative stress. Understanding the mechanisms of lung injury from DPM will enhance efforts to protect at‐risk individuals from the harmful respiratory effects of air pollutants.
The current work is an experimental investigation to examine the influence of biodiesel derived from waste cooking oil on engine performance and exhaust emissions. Experiments were conducted with ...three biodiesel blends at 20%, 40%, and 60% (by volume). A petroleum diesel fuel was used as a reference fuel. The primary purpose of this study was to observe both particulate matter (PM) and particle number (PN) emissions for the three biodiesel blends. Furthermore, the blow-by emissions of the biodiesel blends were also studied. All measurements were conducted in a six-cylinder turbocharged diesel engine with a high-pressure common rail injection system in compliance with a 13-Mode European Stationary Cycle (ESC).
•Compared to the reference diesel, all biodiesel blends:•Showed no significant changes in engine performance.•Indicated substantial reductions in both particulate matter and number emissions.•Reduced carbon monoxide and total unburned hydrocarbon emissions.•Produced minimal increase in nitrogen oxides emissions.
In the transportation sector, the share of biofuels such as biodiesel is increasing and it is known that such fuels significantly affect NOx emissions. In addition to NOx emission from diesel ...engines, which is a significant challenge to vehicle manufacturers in the most recent emissions regulation (Euro 6.2), this study investigates NO2 which is a toxic emission that is currently unregulated but is a focus to be regulated in the next regulation (Euro 7). This manuscript studies how the increasing share of biofuels affects the NO2, NOx, and NO2/NOx ratio during cold-start (in which the after-treatment systems are not well-effective and mostly happens in urban areas). Using a turbocharged cummins diesel engine (with common-rail system) fueled with diesel and biofuel derived from coconut (10 and 20% blending ratio), this study divides the engine warm-up period into 7 stages and investigates official cold- and hot-operation periods in addition to some intermediate stages that are not defined as cold in the regulation and also cannot be considered as hot-operation. Engine coolant, lubricating oil and exhaust temperatures, injection timing, cylinder pressure, and rate of heat release data were used to explain the observed trends. Results showed that cold-operation NOx, NO2, and NO2/NOx ratio were 31–60%, 1.14–2.42 times, and 3–8% higher than the hot-operation, respectively. In most stages, NO2 and the NO2/NOx ratio with diesel had the lowest value and they increased with an increase of biofuel in the blend. An injection strategy change significantly shifted the in-cylinder pressure and heat release diagrams, aligned with the sudden NOx drop during the engine warm-up. The adverse effect of cold-operation on NOx emissions increased with increasing biofuel share.
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•Cold-operation NOx was 31–60% higher than hot-operation with different fuels.•Cold-operation adverse effect on NOx was more with biofuel.•Cold-operation NO2 was 1.15–2.42 times higher than hot-operation with all fuels.•Cold-operation NO2/NOx was 3–8% higher than hot-operation with different fuels.•NO2/NOX ratio was 13–17% during cold-operation and 5–13% during hot-operation.
•A comprehensive study on engine performance and emissions with n-butanol-diesel blends was conducted.•n-Butanol blends indicated insignificant changes in engine performance.•Much lower UBHC ...emissions with increase in blow-by and NOx emissions were observed with n-butanol blends.•Substantial reductions in both PM and PN emissions were observed with n-butanol blends.
This paper presents a comprehensive study of a wide range of engine performance parameters, including: indicated torque (IT), indicated power (IP), indicated mean effective pressure (IMEP) and indicated specific fuel consumption (ISFC). Further, the combustion parameters measured include: start of injection timing, in-cylinder peak pressure, boost pressure and rate of maximum pressure rise. Resultant emission parameters investigated include: exhaust blow by, unburned hydrocarbon (UBHC), oxides of nitrogen (NOx), particulate matter (PM), particle number (PN) and particle size distribution (PSD). Normal butanol (n-butanol) was chosen to blend with a reference diesel fuel. The experiment was conducted using a 6-cylinder, turbocharged common rail diesel engine in accordance with the 13-Mode European Stationary Cycle (ESC). Considering limits of solubility of n-butanol in reference diesel, a maximum of 30% n-butanol was blended with 70% reference diesel. Three different butanol blends having 10% butanol with 90% reference diesel, 20% butanol with 80% reference diesel and 30% butanol with 70% reference diesel (the blending percentages were on a volume basis) were prepared. The engine experimental results show that without considerably deteriorating engine performance, most of the emissions were significantly reduced with the butanol blends compared to those of the reference diesel.
•Diesel was blended with 1% and 5% waste lubricating oil.•During cold start, NOx emissions were higher than hot start.•During cold start, NOx increased as the engine warmed up.•NOx emissions had a ...direct correlation with maximum rate of pressure rise.•NOx emissions had an inverse correlation with maximum in-cylinder pressure.
NOx emissions from diesel engines are a concern from both environmental and health perspectives. Recently this attention has targeted cold-start emissions highlighting that emission after-treatment systems are not effective in this period. Using a 6-cylinder, turbocharged, common-rail diesel engine, the current research investigates NOx emissions during cold-start using different engine performance parameters. In addition, it studies the influence of waste lubricating oil on NOx emissions introducing it as a fuel additive (1 and 5% by volume). To interpret the NOx formation, this study evaluates different parameters: exhaust gas temperature, engine oil temperature, engine coolant temperature, start of injection/combustion, in-cylinder pressure, heat release rate, maximum in-cylinder pressure and maximum rate of pressure rise. This study clarified how cold-start NOx increases as the engine is warming up while in general cold-start NOx is higher than hot-start. Results showed that in comparison with warmed up condition, during cold-start NOx, maximum in-cylinder pressure and maximum rate of pressure rise were higher; while start of injection, start of combustion and ignition delay were lower. During cold-start increased engine temperature was associated with decreasing maximum rate of pressure rise and peak apparent heat release rate. During cold-start NOx increased with temperature and it dropped sharply due to the delayed start of injection. This study also showed that using waste lubricating oil decreased NOx and maximum rate of pressure rise; and increased maximum in-cylinder pressure. NOx had a direct correlation with the maximum rate of pressure rise; and an inverse correlation with the maximum in-cylinder pressure.
The disposal of waste rubber and scrap tyres is a significant issue globally; disposal into stockpiles and landfill poses a serious threat to the environment, in addition to creating ecological ...problems. Fuel production from tyre waste could form part of the solution to this global issue. Therefore, this paper studies the potential of fuels derived from waste tyres as alternatives to diesel. Production methods and the influence of reactor operating parameters (such as reactor temperature and catalyst type) on oil yield are outlined. These have a major effect on the performance and emission characteristics of diesel engines when using tyre derived fuels. In general, tyre derived fuels increase the brake specific fuel consumption and decrease the brake thermal efficiency. The majority of studies indicate that NOx emissions increase with waste tyre derived fuels; however, a few studies have reported the opposite trend. A similar increasing trend has been observed for CO and CO
emissions. Although most studies reported an increase in HC emission owing to lower cetane number and higher density, some studies have reported reduced HC emissions. It has been found that the higher aromatic content in such fuels can lead to increased particulate matter emissions.
Rising pollution levels resulting from vehicular emissions and the depletion of petroleum-based fuels have left mankind in pursuit of alternatives. There are stringent regulations around the world to ...control the particulate matter (PM) emissions from internal combustion engines. To this end, researchers have been exploring different measures to reduce PM emissions such as using modern combustion techniques, after-treatment systems such as diesel particulate filter (DPF) and gasoline particulate filter (GPF), and alternative fuels. Alternative fuels such as biodiesel (derived from edible, nonedible, and waste resources), alcohol fuels (ethanol, n-butanol, and n-pentanol), and fuel additives have been investigated over the last decade. PM characterization and toxicity analysis is still growing as researchers are developing methodologies to reduce particle emissions using various approaches such as fuel modification and after-treatment devices. To address these aspects, this review paper studies the PM characteristics, health issues, PM physical and chemical properties, and the effect of alternative fuels such as biodiesel, alcohol fuels, and oxygenated additives on PM emissions from diesel engines. In addition, the correlation between physical and chemical properties of alternate fuels and the characteristics of PM emissions is explored.
•Custom test was designed to study the engine performance during cold-start.•Oxygenated fuels had higher indicated torque during hot-start transient modes.•Oxygenated fuels had lower indicated torque ...during cold-start transient modes.•Oxygenated fuels had higher max in-cylinder pressure at hot-start transient modes.•Oxygenated fuels had lower max in-cylinder pressure at cold-start transient modes.
Using a six-cylinder turbocharged common rail compression ignition engine, this study investigated the effect of oxygenated fuels on transient and steady-state performance. This paper considers the effect of oxygenated fuels on both cold- and hot-start operation. A range of fuel oxygen contents between 0% and 13.57% was derived from diesel, waste cooking biodiesel and two other blends, containing triacetin as a fuel additive. A custom test was designed to investigate engine performance parameters using acceleration, load increase and steady-state modes of operation. For each fuel, the cold-start test was conducted after an overnight engine-off time. In this study, different parameters related to engine performance were studied, such as engine coolant and lubricant temperatures and their rise rate, boost pressure, injected fuel, turbocharger lag, engine speed and torque, start of injection, maximum in-cylinder pressure, maximum rate of pressure rise, cyclic variability, FMEP, mechanical and thermal efficiencies, and BSFC. In comparison with hot-start, the cold-start results indicated a higher injected fuel, indicated torque, maximum in-cylinder pressure, maximum rate of pressure rise, FMEP, BSFC and CoV of IMEP, and a lower SOI, ME and BTE. During cold-start, using oxygenated fuels, instead of diesel, resulted in a lower rate of lubricant temperature rise and a higher BSFC, while decreasing the FMEP. Using oxygenated fuels, instead of diesel, during the idle and transient modes resulted in lower indicated torque and maximum in-cylinder pressure under cold-start whilst, under hot-start, it resulted in higher indicated torque and maximum in-cylinder pressure, because during hot-start, the fuel oxygen is significantly influential in torque build-up during turbocharger lag. While, during cold-start there are some other influential factors. In addition, oxygenated fuels—compared to diesel—experienced higher CoV of IMEP during cold-start while, during hot-start, they had lower values.
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