Awogbemi, O.; Kallon, D.V.V.; Onuh, E.I.; Aigbodion, V.S. An Overview of the Classification, Production and Utilization of Biofuels for Internal Combustion Engine Applications. Energies 2021, 14, 5687.
Awogbemi, Omojola, Daramy Vandi Von Kallon, Emmanuel Idoko Onuh, and Victor Sunday Aigbodion. 2021. "An Overview of the Classification, Production and Utilization of Biofuels for Internal Combustion Engine Applications" Energies 14, no. 18: 5687.
fuels and combustion sp sharma pdf 135
Maritime shipping is a key factor that enables the global economy, however the pressure it exerts on the environment is increasing rapidly. In order to reduce the emissions of harmful greenhouse gasses, the search is on for alternative fuels for the maritime shipping industry. In this work the usefulness of hydrogen and hydrogen carriers is being investigated as a fuel for sea going ships. Due to the low volumetric energy density of hydrogen under standard conditions, the need for efficient storage of this fuel is high. Key processes in the use of hydrogen are discussed, starting with the production of hydrogen from fossil and renewable sources. The focus of this review is different storage methods, and in this work we discuss the storage of hydrogen at high pressure, in liquefied form at cryogenic temperatures and bound to liquid or solid-state carriers. In this work a theoretical introduction to different hydrogen storage methods precedes an analysis of the energy-efficiency and practical storage density of the carriers. In the final section the major challenges and hurdles for the development of hydrogen storage for the maritime industry are discussed. The most likely challenges will be the development of a new bunkering infrastructure and suitable monitoring of the safety to ensure safe operation of these hydrogen carriers on board the ship.
We conclude that FCO models need to address the composite fuel consumption problem by extending models to include all the dimensions, i.e. aircraft technology & design, aviation operations & infrastructure, socioeconomic & policy measures, and alternative fuels & fuel properties. FCO models typically comprise all the four dimensions and this reality need to be taken into account in global FCO models. In addition, these models should have objectives or constraints to evaluate the aircraft sizes according to market structure, impact of various policy measures on fuel burn, and near term potential alternative fuel options in the global FCO problem. In the models reviewed, we evaluated that, only the few authors considered these factors. The literature identifies 98 decision variables affecting the fuel consumption related to various dimensions in air transport. So we can conclude that this analysis could represent the informational framework for FCO research in air transport.
Based on the literature review carried out and the nature of FCO research observed in air transport, we have introduced a classification scheme to systematically organize the published articles. From the literature survey of articles we have identified five dimensions (1) Aircraft technology & design (2) Aviation operations & infrastructure (3) Socioeconomic & policy measures (4) Aviation alternate fuels, affecting the fuel consumption in air transport. Figure 1 shows the Classification scheme based on the dimensions of FCO research in air transport. They were further classified from the four major dimensions into their respective decision variables. Hileman et al. [13] suggested the advance aircraft design, operational improvements, and alternative fuels for aviation emission reductions. The result of the study showed that the narrower body aircraft has the greatest potential for fuel burn reduction, but it would require the promotion of innovative aircraft design and extensive use of alternative fuels. Grote et al. [14] addressed the technological, operational, and policy measures for fuel burn reduction in civil aviation and the analysis of the study showed that some of the measures were directly implemented on the market because they directly reduce the fuel consumption and fuel cost, but some were not due to market constraints.
Sgouridis et al. [15] examined and evaluated the impact of the five policies for reducing emission of commercial aviation; technological efficiency improvement, operational efficiency improvement, use of alternative fuels, demand shift, and carbon pricing. Similarly the study of Lee & Mo [16]; Green [11]; Lee [3]; Janic [17] and Singh & Sharma [18] collectively identified the above mentioned dimensions of the FCO.
Today airlines operate in an increasingly competitive environment caused by the globalization of air transport network worldwide and therefore a necessary condition for airlines are commercially successful is the reduction of direct operating costs, which mainly depends on the technological & design characteristics of the aircraft used. Technology development is going on at a rapid rate and we can effectively make use of this technological revolution to reduce the fuel consumption of a commercial aircraft. Moreover the fuel consumption of air transport can be reduced through the variety of options such as increased aircraft efficiency, improved operations, use of alternate fuels, socioeconomic measures, and improved infrastructure, but most of the gain so far have been resulted from the aircraft technological improvement. Aircraft technological improvement mainly depends upon the three factors: structural weight, aircraft aerodynamics, and engine specific fuel efficiency [14]. Moreover the aircraft technological efficiency is described by three aircraft performance metrics: engine efficiencies are expressed in terms of thrust specific fuel consumption (TSFC), aerodynamic efficiencies are measured in terms of maximum lift over drag ratio (Lmax/D) and structural efficiency is quantified using operating empty weight (OEW) divided by maximum takeoff weight (MTOW) [19, 20]. Further, Graham et al. [21] have considered the classical range equation in order to understand how the aircraft technology affects the fuel burn. Fuel consumption per payload range of idealized cruise, keeping the aircraft operating parameters fixed are expressed in terms of aerodynamic efficiency, structural efficiency, engine efficiency, and calorific value of the fuel.
We conclude that FCO models need to address the composite fuel consumption problem by extending models to include all the dimensions, i.e. aircraft technology & design, aviation operations & infrastructure, socioeconomic & policy measures, and alternative fuels & fuel properties. FCO models typically comprise all the four dimensions and this reality need to be taken into account in global FCO models. In addition, these models should have objectives or constraints to evaluate the aircraft sizes according to market structure, impact of various policy measures on fuel burn, and near term potential alternative fuel options in the global FCO problem. In the models reviewed, we evaluated that, only the few authors considered these factors.
Wildfire smoke is complex physically and chemically, and its composition is determined by fuel type and combustion conditions [30, 83]. Wildfire smoke generally consists of coarse and fine PM, VOCs (e.g., aldehydes, n-alkanes), polycyclic aromatic hydrocarbons (PAHs), gases (e.g., CO, SO2, NO, NO2), and metals [155]. PM composition is a summation of the emitted mixture of compounds that is usually present as soot or oily substances high in elemental and organic carbon, and metallic compounds [155]. VOCs and gases are normally dispersed into the environment and they are able to react further photochemically to generate secondary organic aerosol (SOA), for example in situ ozone oxidation of alkanes in the ambient air, which can also be detrimental to human health [60, 113]. Clinical and toxicological studies offer a detailed opportunity to examine the chemical compositions of wood smoke, a major contributor of wildfire smoke, in a controlled experimental setting. The chemical composition of wood smoke in a laboratory setting is different from that of wildfire smoke in a natural environment where vegetation characteristics, combustion conditions, weather conditions, and the geographical area burnt are factors that add complexity relative to emissions from the combustion or pyrolysis of one or two types of wood in a controlled chamber environment. As summarized from these studies in Table 1, wood smoke, independently of fuel type and combustion conditions, is characterized by the presence of PM, gases, n-alkanes, PAHs, methoxyphenol compounds, levoglucosan, and metals species.
Epidemiological studies are also prone to exposure misclassification due to their dependence on the use of exposure data from air quality monitoring stations or satellite images [85]. The broad approach applies exposure data based on smoky days, smoky area, scale of burnt forests, or air pollutant levels for the entire region [48, 54, 118], but does not consider individual-specific differences such as activity level, time spent indoors versus outdoors, and wind direction changes that may drastically affect the actual concentration of wildfire smoke. Total suspended particle levels from a study on biomass smoke derived from agricultural combustion of sugar cane, for example, may not specify particulate size information that is toxicologically relevant [16]. It has been shown that the amount of wood combustion in a city does not necessarily guarantee that the measured PM10 levels are representative of wood smoke exposure [44, 135]. 2ff7e9595c
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