Global energy demand is increasing due to the population growth and industrialization. In order to fulfill the energy demand with considering global concern, it is necessary to find out alternative ...fuel sources. Biodiesel is one of the best choices because of its immense potential to be part of energy mix in the near future as well as the capability of reducing greenhouse gas emissions. This paper aims to provide information to the engineers, industrialists and researchers who are interested on biodiesel. The paper presents a comprehensive review on the impact of potential biodiesel feedstocks (edible and non-edible) on engine performance and exhaust emissions including details of engine and operating condition. A large number of literatures from highly rated journals in scientific indexes are reviewed including the most recent publications. Most of the authors showed that using biodiesel from various feedstocks in diesel engines slightly lowered brake power and brake thermal efficiency but increases BSFC than diesel fuel. It was also reported that biodiesel significantly reduced the PM, HC, CO and CO2 emissions but gives slightly higher NOx emissions. It was shown that NOx can be reduced by some approaches such as blending with additives and EGR technique. The study concluded that biodiesel can be used in compression ignition engine with no or minor engine modification. Finally biodiesel can be used as a substitute of diesel fuel to fulfill the energy demand, reduce dependency on fossil fuel as well as the exhaust emissions of the engine.
Increasing energy demand and environment concerns have prompted an evolution of alternative fuel sources. As an alternative fuel source, biodiesel is attractive because it reduces engine emissions. ...However, biodiesel produces higher NOx emissions compared to ordinary diesel fuel. Previous researches have established many factors that cause biodiesel to produce elevated NOx emissions. This study reviews the impacts of biodiesel combustion on NOx emissions and their reduction approaches in diesel engines. The first part of this study recaps the NOx formation mechanisms for understanding the kinetics behind the NOx forming reactions. The second part describes the factors affecting on NOx emissions. This paper established that higher NOx emissions are produced for biodiesel combustion which influenced by several factors such as physicochemical properties and molecular structure of biodiesel, adiabatic flame temperature, ignition delay time, injection timing and engine load conditions etc. The final section discusses on the reduction of NOx emissions from biodiesel fuelled engines for both pre and post combustion techniques. The results of reduction approaches of the NOx emissions implies, exhaust gas recirculation (EGR) and retarded injection timing are effective as well as low cost techniques than others. Between these two techniques, EGR reduces the NOx emissions at 5–25% EGR rate adequately in biofuelled engine by controlling oxygen content and combustion peak temperature with slightly decreasing HC and CO emissions. However this technique shows few penalties on smoke and PM emissions as well as brake specific fuel consumption if not perfectly optimized.
The stricter worldwide emission legislation and growing demands for lower fuel consumption and anthropogenic CO2 emission require significant efforts to improve combustion efficiency while satisfying ...the emission quality demands. Ethanol fuel combined with gasoline provides a particularly promising and, at the same time, a challenging approach. Ethanol is widely used as an alternative fuel or an effective additive of gasoline due to the advantage of its high octane number and its self-sustaining concept, which can be supplied regardless of the fossil fuel. As a result, vast study has been carried out to study its effects on engine performance and emission.
The first part of this article discusses prospect of fuel ethanol as a gasoline substitute. Then it discusses comparative physicochemical properties of ethanol and gasoline. The slight differences in properties between ethanol and gasoline fuels are enough to create considerable change to combustion system as well as behaviors of SI engines. These effects lead to several complex and interacting mechanisms, which make it difficult to identify the fundamentals of how ethanol affects NOx emission. After that, general NOx forming mechanisms are discussed to create a fundamental basis for further discussion. Finally, the article discusses different fuel composition, engine parameter and engine modification effects on NOx formation as well as mathematical approach for NOx prediction using ethanol.
The increase of energy demand coped with utilization of fossil resources have engendered serious environmental impact. The progressively stringent worldwide emission legislation and increasing ...greenhouse gas emission require significant research effort on alternative fuels. Therefore, biodiesels are becoming important increasingly due to its ease in adaptation, environmental benefits and prospect in energy security. Biodiesel derived from vegetable oils, waste cooking oils and animal fats are long chain fatty acid alkyl esters, which contains unsaturated portions that are susceptible to oxidation. Biodiesel oxidation is a complex process having a number of mechanisms involved. Autoxidation radical chain reactions are the primary cause of biodiesel degradation that leads to formation of hydroperoxide, which, after that decompose to form an array of secondary oxidation products like aldehydes, ketones, carboxylic acids, oligomers, gum, sediment etc. Antioxidants are often used to inhibit biodiesel oxidative degradation. The present review attempts to cover the inhibition action of natural and synthetic antioxidants, methods used to analyze biodiesel oxidation and their effect on biodiesel derived from various feedstocks. Phenolic antioxidants are more effective compared to amine antioxidants. Pyrogallol is found to be the most effective antioxidant to improve the oxidation stability in case of almost all biodiesels reviewed.
•Environmental benefits of JB blends were found but adverse impact on NOx.•Addition of 0.15% (m) DPPD in JB20, average reduction in NO up to 16.54%.•In some cases, engine power is reduced with DPPD ...additive.•Emissions of HC and CO for JB blends with DPPD were lower compared to diesel.•Addition of DPPD in JB blends reduction of EGT was found.
Energy requirements are increasing rapidly due to fast industrialization and the increased number of vehicles on the road. The use of biodiesel in diesel engines instead of diesel results in the proven reduction of harmful exhaust emissions. However, most researchers have reported that they produce higher NOx emissions compared to diesel, which is a deterrent to the expansion of the market for these fuels. Several proposed pathways try to account for NOx formation during the combustion process. Among them, the Fenimore mechanism explains that fuel radicals formed during the combustion process react with nitrogen from the air to form NOx. It could be proposed that if these radical reactions could be terminated, the NOx formation rate for biodiesel combustion would decrease. An experimental study was conducted on a four-cylinder diesel engine to evaluate the performance and emission characteristics of Jatropha biodiesel blends (JB5, JB10, JB15 and JB20) with and without the addition of N,N′-diphenyl-1,4-phenylenediamine (DPPD) antioxidant. For each tested fuel, the engine performance and emissions were measured at engine speeds 1000–4000rpm at an interval of 500rpm under the full throttle condition. The results showed that this antioxidant additive could reduce NOx emissions significantly with a slight penalty in terms of engine power and Brake Specific Fuel Consumption (BSFC) as well as CO and HC emissions. However, when compared to diesel combustion, the emissions of HC and CO with the addition of the DPPD additive were found to be nearly the same or lower. By the addition of 0.15% (m) DPPD additive in JB5, JB10, JB15 and JB20, the reduction in NOx emissions were 8.03%, 3.503%, 13.65% and 16.54% respectively, compared to biodiesel blends without the additive under the full throttle condition. Moreover, the addition of DPPD additive to all biodiesel blend samples reduced the exhaust gas temperature.
This paper reviews the literature available concerning the energy balance of internal combustion engines operating on alternative fuels. Global warming and energy crisis are among the most important ...issues that threaten the peaceful existence of the man-kind. More usage of alternative fuels and energy loss minimization from automotive engines can be an effective solution to this issue. The energy balance analysis gives useful information on the distribution of supplied fuel energy in the engine systems and identifies the avoidable losses of the real engine process with respect to ideal process. It is a very widely used tool, mostly used for the layout of the engine components. The basic energy balance theory has been discussed in details along with the variations in energy balance approaches and terms. The wall energy loss may vary to a great extent depending on the selection of heat transfer correlations. The theoretical energy balance also explored in this paper with help of thermodynamic models. There are some significant variations observed in energy balance when the engine operating fuel is changed and devices like turbocharger, supercharger etc. are used to boost the intake air pressure. The review extends to the energy balance study of low heat rejection engines (LHR) as well as the effects of engine variables and design factors on energy balance.
This study, as an observation, put its utmost effort to emphasize on the development of various physicochemical properties using multiple alcohols (C2 to C6) at different ratios compared to that of ...the conventional ethanol–gasoline blend. To optimize the properties of multiple alcohol–gasoline blends, properties of each fuel were measured first. An optimization tool of Microsoft Excel “Solver” was used for obtaining the optimum blend. Using optimizing tool, three optimum blend ratios were selected which possessed maximum heating value (MaxH), maximum research octane number (MaxR) and maximum petroleum displacement (MaxD). These blends were used for testing in a four cylinder gasoline engine at the wide open throttle condition with varying speeds and compared obtained outcomes with that of E15 (15% ethanol and 85% gasoline) as well as gasoline. Optimized blends have shown higher brake torque and brake thermal efficiency (BTE) but lower brake specific fuel consumption (BSFC) than E15. MaxR, MaxD and MaxH blends produced mean 4.4%, 1.8% and 0.4% increased BTE and mean 4.39%, 1.8% and 2.27% lower BSFC than that of E15. On the other hand, MaxR, MaxD, MaxH and E15 reduced 4.46%, 8.37%, 12.4% and 17.2%, mean CO emission and 4.5%, 11.81%, 8.19% and 16% mean HC emission respectively than that of gasoline. NOx emission of optimized blends was higher than gasoline. However, MaxR, MaxD, MaxH reduced 4%, 14.57% and 20.76% NOx than that of E15.
•Optimized C2–C6 alcohols–gasoline blends achieved better properties than E15.•Optimum blends improved BTE and torque and reduced BSFC than that of E15 fuel.•Compared to gasoline, optimum blends reduced CO and HC emission.•Optimum fuels reduced NOx emission than E15 fuel.
•Different NOx reduction technologies are discussed along with their implementation.•EGR rate up to 25% is feasible considering engine performance and other emissions.•ITR technology reduces NOx ...fairly but increases other emissions, it also reduces performance.•LTC reduces NOx and PM emissions simultaneously but increases HC and CO emissions.•Water injection and emulsion reduce NOx (up to 38%) and PM but increases HC and CO emissions.
Biodiesel fuels have the potential to become a reliable substitute for diesel which is used moderately to meet the current energy demands. This fuel can be produced from new or used vegetable oils, non-edible sources and animal fats, which are non-toxic, biodegradable and renewable. In spite of the many advantages of using biodiesel, most of the researchers have reported that they produce higher NOx emissions compared to diesel, which is a deterrent to the market expansion of these fuels. In this study, the different paths to reduce NOx emissions from diesel engines by applying several technologies, such as using additives into fuel, exhaust gas recirculation (EGR), water injection (WI), emulsion technology (ET), injection timing retardation (ITR), simultaneous technology (ST) and low temperature combustion (LTC) mode are reviewed briefly. The impacts of different NOx mitigation technologies on biodiesel-fueled diesel engine performance and emissions are also analyzed critically and different methods of their implementation are shown. This paper also provides a comparison of different NOx mitigation technologies based on previous articles related to this topic. From this comparative study, it was found that the average reduction of NOx emissions by using additives, EGR, WI & ET, ITR, ST and LTC are in the ranges 4–45%, 26–84%, 10–38%, 9.77–37%, 22–95% and 66–93% respectively, compared to biodiesel combustion without applying technologies. However, the average reduction of NOx emissions by using those technologies for biodiesel are reasonable, 36–46%, 3–34%, 21–37%, 33–92% and 8.68–70% respectively, when compared to diesel. The results of this paper show that using new NOx mitigation technology, such as LTC, is more efficient and promising than the others because of its having the capability to reduce both NOx and particulate matter (PM) emissions simultaneously without significant penalties with regard to engine performance. However, applying this technology has increased CO and HC emissions in several cases due to the reduction in their oxidation rates in the combustion chamber.
The present work reports the theoretical investigation of the scattering of electrons and positrons by the ethane (C2H6) molecule over the energy range 1 eV–1 MeV. The investigation was carried out ...by taking into account the screening correction arising from a semiclassical analysis of the atomic geometrical overlapping of the scattering observables calculated in the independent atom approximation. The study is presented through the calculations of a broad spectrum of observable quantities, namely differential, integrated elastic, momentum transfer, viscosity, inelastic, grand total, and total ionization cross-sections and the Sherman functions. A comparative study was carried out between scattering observables for electron impact with those for positron impact to exhibit the similarity and dissimilarity arising out of the difference of the collisions of impinging projectiles with the target. Partial-wave decomposition of the scattering states within the Dirac relativistic framework employing a free-atom complex optical model potential was used to calculate the corresponding observable quantities of the constituent atoms. The results, calculated using our recipe, were compared with the experimental and theoretical works available in the literature. The Sherman function for a e±–C2H6 scattering system is presented for the first time in the literature. The addition of the screening correction to the independent atom approximation method was found to substantially reduce the scattering cross-sections, particularly at forward angles for lower incident energies.
Greenhouse gas emitted by the transport sector around the world is a serious issue of concern. To minimize such emission the automobile engineers have been working relentlessly. Researchers have been ...trying hard to switch fossil fuel to alternative fuels and attempting to various driving strategies to make traffic flow smooth and to reduce traffic congestion and emission of greenhouse gas. Automobile emits a massive amount of pollutants such as Carbon Monoxide (CO), hydrocarbons (HC), carbon dioxide (CO2), particulate matter (PM), and oxides of nitrogen (NO x). Intelligent transport system (ITS) technologies can be implemented to lower pollutant emissions and reduction of fuel consumption. This paper investigates the ITS techniques and technologies for the reduction of fuel consumption and minimization of the exhaust pollutant. It highlights the environmental impact of the ITS application to provide the state-of-art green solution. A case study also advocates that ITS technology reduces fuel consumption and exhaust pollutant in the urban environment.
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