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This article seeks to address aviation as an emerging biofuel consumer and to discuss sustainability issues and consequences for feedstock production concepts. Biojet fuels have been identified as a promising, readily deployable alternative to fossil‐based aviation fuels. At the same time they are highly criticised as their production may have negative social and environmental impacts. Therefore, the paper aims to identify major sustainability issues and assessment challenges and relate these to the production of biojet fuel feedstock.

Two plant oil production concepts are presented that address the sustainability issues discussed. Both concepts are being investigated within the research project “Platform for Sustainable Aviation Fuels”. A literature‐based overview of sustainability issues and assessment challenges is provided. Additionally, conceptual insights into new plant oil production concepts are presented.

The use of biojet fuels is often hailed as a strategy for the aviation industry to become more sustainable. However, biofuels are not necessarily sustainable and their potential to reduce GHG emissions is highly debated. Several unresolved sustainability issues are identified highlighting the need for improved assessment methods. Moreover, the two concepts presented have the potential to provide sustainably grown feedstock, but further empirical research is needed.

This article addresses researchers and practitioners by providing an overview of sustainability issues and assessment challenges related to biojet fuels. Consequences are identified for two plant oil feedstock concepts: catch cropping in temperate regions and silvopastoral systems in tropical and subtropical regions.

The purpose of this paper is to shed light on the biofuels debate in air transport.

The controversies about biofuels sustainability in general and research findings on biofuels are complemented by the specific circumstances the aviation industry encounters in its attempt to become more sustainable. The author's corporate affiliation allows for insights from an airline's perspective and experience with biojet fuel.

The paper highlights accountability and accounting advances required by the aviation industry as well as further stakeholders to safeguard sustainability of biofuels.

The paper provides a viewpoint taking account of research findings but written from a corporate perspective. The intention is not to provide a complete review of the growing academic literature in the biofuels field, nor to elaborate on the entire array of challenges in practice.

The paper integrates macro‐level societal limitations for sustainable biofuel feedstock production with micro and meso‐level corporate and industry perspectives on sustainable biofuels.

The purpose of this paper is to explore the scope of applications and benefits of sustainability accounting for the production and industrial use of biomass as an energy source and substitute for fossil‐fuel use. As environmental degradation and unacceptable social impacts not only increase from the production and use of fossil‐fuel based energy, but also from alternative energy sources, the monitoring, controlling and measuring of the (un‐)sustainability of alternative energy production and use emerges as an area in critical need of research.

The paper presents a review of the issues surrounding the accounting for the (un‐)sustainability of industrial biomass production and use, considering what biomass is, the current and forecast importance of industrial biomass, different approaches to its production, and the subsequent measurement and monitoring of its potential (un‐)sustainability.

The paper finds that it is insufficient to conclude in general terms, as is often done or assumed in policy documents and statements, that industrial production and use of biomass is sustainable (or unsustainable) and that accounting for biomass must recognise the broader ecological and social system of which the production and use form a part. A further finding of the paper is that from agricultural or industrial production of biomass through to consumption and industrial use of biomass, the accounting issues surrounding biomass production and use are essential to determining its (un‐)sustainability.

The paper provides an overview of the importance of and problems with the production of biomass for industrial use, and related sustainability issues. It discusses possibilities for and limitations of accounting to address these sustainability issues as well as the need for and the challenges in measuring the (un‐)sustainability of biomass production for industrial use and the accounting for sustainability improvements.

This study aims to introduce an approach to evaluate environmental impact of a piston-prop engine from the view point of life cycle assessment (LCA).

In the aviation industry, safety is an important issue. For reliable and safe flights, the maintenance of aerial vehicles and engines is mandatory. Additionally, regular and correct maintenance plays a key role in keeping efficiency at a high level. With this in mind, a LCA of a regular 50 hourly maintenance process of Cessna type training aircraft is conducted. During the assessment, the starting of the engine before maintenance, replacement of the oil filter, test procedure of the spark plugs, a compressor test, engine cleaning and engine starting following maintenance are taken into account.

At the end of the study, normalization and characterization values for the maintenance, electricity consumption during maintenance and used fuel are obtained.

Regarding the number of this type aircraft worldwide, the current study offers a valuable contribution to the literature. The authors also intend to introduce an approach which may be useful for the assessment of large body aircraft still in service.

The present paper is a pioneer for future applications of LCA methodology to piston-prop engines and training aircraft.

The purpose of this paper is to examine the effects of heat capacity and density of biofuels on aircraft engine performance indicated by thrust and fuel consumption.

The influence of heat capacity and density was examined by simulating biofuels in a two-spool high-bypass turbofan engine running at cruise condition using a Cranfield in-house engine performance computer tool (PYTHIA). The effect of heat capacity and density on engine performance was evaluated through a comparison between kerosene and biofuels. Two types of biofuels were considered: Jatropha Bio-synthetic Paraffinic Kerosene (JSPK) and Camelina Bio-synthetic Paraffinic Kerosene (CSPK).

Results show an increase in engine thrust and a reduction in fuel consumption as the percentage of biofuel in the kerosene/biofuel mixture increases. Besides a low heating value, an effect of heat capacity on increasing engine thrust and an effect of density on reducing engine fuel consumption are observed.

The utilisation of biofuel in aircraft engines may result in reducing over-dependency on crude oil.

This paper observes secondary factors (heat capacity and density) that may influence aircraft engine performance which should be taken into consideration when selecting new fuel for new engine designs.

Diesel has traditionally been considered the best-suited and most widely used fuel in various sectors, including manufacturing industries, power production, automobiles and transportation. However, with the ongoing crisis of fossil fuel inadequacy, the search for alternative fuels and their application in these sectors has become increasingly important. One particularly interesting and beneficial alternative fuel is biodiesel derived from bio sources.

In this research, an attempt was made to use biodiesel in an unconventional micro gas turbine engine. It will remove the concentric use of diesel engines for power production by improving fuel efficiency as well as increasing the power production rate. Before the fuel is used enormously, it has to be checked in many ways such as performance, emission and combustion analysis experimentally.

In this paper, a detailed experimental study was made for the use of Spirulina microalgae biodiesel in a micro gas turbine. A small-scale setup with the primary micro gas turbine and secondary instruments such as a data acquisition system and AVL gas analyser. The reason for selecting the third-generation microalgae is due to its high lipid and biodiesel production rate. For the conduction of experimental tests, certain conditions were followed in addition that the engine rotating rpm was varied from 4,000, 5,000 and 6,000 rpm. The favourable and predicted results were obtained with the use of microalgae biodiesel.

The performance and combustion results were not exactly equal or greater for biodiesel blends but close to the values of pure diesel; however, the reduction in the emission of CO was at the appreciable level for the used spirulina microalgae biodiesel. The emission of nitrogen oxides and carbon dioxide was a little higher than the use of pure diesel. This experimental analysis results proved that the use of spirulina microalgae biodiesel is both economical and effective replacement for fossil fuel.

The purpose of the study is to examine the influence of the corn biofuel on the Jet engine. Each tests were carried out in a small gas turbine setup. The performance characteristics of thrust, thrust-specific fuel consumption, exhaust gas temperature and emission characteristics of Carbon monoxide(CO), Carbon dioxide (CO₂), Oxygen (O₂), Unburned hydrocarbons (UHC) and Nitrogen of oxides (NO) emissions were measured and compared with Jet-A fuel to find the suitability of the biofuel used.

Upgrading and using biofuels in aviation sector have been emerging as a fruitful method to diminish the CO emission into the atmosphere. This research paper explores the possibility of using nanoparticles-enriched bio-oil as a fuel for jet engines. The biofuel taken is corn oil and the added nanoparticles are Al₂O₃.

The biofuel blends used are B0 (100% Jet-A fuel), B10 (10 % corn oil biofuel + 90% Jet-A fuel), B20 (20% corn oil biofuel + 80% Jet-A fuel) and B30 (30% corn oil biofuel + 70% Jet-A fuel). All fuel blends were mixed with the moderate dosage level of 30 ppm. All tests were conducted at different rpm as 50,000, 60,000, 70,000 and 80,000 rpm.

The results proved that within the lower limit, use of biofuel increased the performance characteristics and reduced the emission characteristics except the emission of NO. The moderate-level biofuel with Jet-A fuel showed the equally better performance to the neat Jet-A fuel.

This study aims to deal with the large eddy simulation (LES) of an ignition sequence and the resulting steady combustion in a swirl-stabilized liquid-fueled combustor. Particular attention is paid to the ease of handling the numerical tool, the accuracy of the results and the reasonable computational cost involved. The primary aim of the study is to appraise the ability of the newly developed computational fluid dynamics (CFD) methodology to retrieve the spark-based flame kernel initiation, its propagation until the full ignition of the combustion chamber, the flame stabilization and the combustion processes governing the steady combustion regime.

The CFD model consists of an LES-based spray module coupled to a subgrid-scale ignition model to capture the flame kernel initiation and the early stage of the flame kernel growth, and a combustion model based on the mixture fraction-progress variable formulation in the line of the flamelet generated manifold (FGM) method to retrieve the subsequent flame propagation and combustion properties. The LES-spray module is based on an Eulerian-Lagrangian approach and includes a fully two-way coupling at each time step to account for the interactions between the liquid and the gaseous phases. The Wall-Adapting Local Eddy-viscosity (WALE) model is used for the flow field while the eddy diffusivity model is used for the scalar fluxes. The fuel is liquid kerosene, injected in the form of a polydisperse spray of droplets. The spray dynamics are tracked using the Lagrangian procedure, and the phase transition of droplets is calculated using a non-equilibrium evaporation model. The oxidation mechanism of the Jet A-1 surrogate is described through a reduced reaction mechanism derived from a detailed mechanism using a species sensitivity method.

By comparing the numerical results with a set of published data for a swirl-stabilized spray flame, the proposed CFD methodology is found capable of capturing the whole spark-based ignition sequence in a liquid-fueled combustion chamber and the main flame characteristics in the steady combustion regime with reasonable computing costs.

The proposed CFD methodology simulates the whole ignition sequence, namely, the flame kernel initiation, its propagation to fully ignite the combustion chamber, and the global flame stabilization. Due to the lack of experimental ignition data on this liquid-fueled configuration, the ability of the proposed CFD methodology to accurately predict ignition timing was not quantitatively assessed. It would, therefore, be interesting to apply this CFD methodology to other configurations that have experimental ignition data, to quantitatively assess its ability to predict the ignition timing and the flame characteristics during the ignition sequence. Such further investigations will not only provide further validation of the proposed methodology but also will potentially identify its shortfalls for better improvement.

This CFD methodology is developed by customizing a commercial CFD code widely used in the industry. It is, therefore, directly applicable to practical configurations, and provides not only a relatively straightforward approach to predict an ignition sequence in liquid-fueled combustion chambers but also a robust way to predict the flame characteristics in the steady combustion regime as significant improvements are noticed on the prediction of slow species.

The incorporation of the subgrid ignition model paired with a combustion model based on tabulated chemistry allows reducing computational costs involved in the simulation of the ignition phase. The incorporation of the FGM-based tabulated chemistry provides a drastic reduction of computing resources with reasonable accuracy. The CFD methodology is developed using the platform of a commercial CFD code widely used in the industry for relatively straightforward applicability.

The purpose of this paper is to numerically investigate the three-dimensional (3D) reacting turbulent two-phase flow field of a scaled swirl-stabilized gas turbine combustor using the commercial computational fluid dynamic (CFD) software ANSYS FLUENT. The first scope of the study aims to explicitly compare the predictive capabilities of two turbulence models namely Unsteady Reynolds Averaged Navier-Stokes and Scale Adaptive Simulation for a reasonable trade-off between accuracy of results and global computational cost when applied to simulate swirl-stabilized spray combustion. The second scope of the study is to couple chemical reactions to the turbulent flow using a realistic chemistry model and also to model the local chemical non-equilibrium(NEQ) effects caused by turbulent strain such as flame stretching.

Standard Eulerian and Lagrangian formulations are used to describe both gaseous and liquid phases, respectively. The computing method includes a two-way coupling in which phase properties and spray source terms are interchanging between the two phases within each coupling time step. The fuel used is liquid jet-A1 which is injected in the form of a polydisperse spray and the droplet evaporation rate is calculated using the infinite conductivity model. One-component (n-decane) and two-component fuels (n-decane+toluene) are used as jet-A1 surrogates. The combustion model is based on the mean mixture fraction and its variance, and a presumed-probability density function is used to model turbulent-chemistry interactions. The instantaneous thermochemical state necessary for the chemistry tabulation is determined by using initially the equilibrium (EQ) assumption and thereafter, detailed NEQ calculations through the steady flamelets concept. The combustion chemistry of these surrogates is represented through a reduced chemical kinetic mechanism (CKM) comprising 1,045 reactions among 139 species, derived from the detailed jet-A1 surrogate model, JetSurf 2.0 using a sensitivity based method, Alternate Species Elimination.

Numerical results of the gas velocity, the gas temperature and the species molar fractions are compared with their experimental counterparts obtained from a steady state flame available in the literature. It is observed that, SAS coupled to the tabulated flamelet-based chemistry, predicts reasonably the main flame trends, while URANS even provided with the same combustion model and computing resources, leads to a poor prediction of the global flame trends, emphasizing the asset of a proper resolution when simulating spray flames.

The steady flamelet model even coupled with a robust turbulence model does not reproduce accurately the trend of species with slow oxidation kinetics such as CO and H2, because of the restrictiveness of the solutions space of flamelet equations and the assumption of unity Lewis for all species.

This work is adding a contribution for spray flame modeling and can be seen as an extension to the significant efforts for the modeling of gaseous flames using robust turbulence models coupled with the tabulated flamelet-based chemistry approach to considerably reduce computing cost. The exclusive use of a commercial CFD code widely used in the industry allows a direct application of this simulation approach to industrial configurations while keeping computing cost reasonable.

This study is useful to engineers interested in designing combustors of gas turbines and others combustion systems fed with liquid fuels.

This paper analyzed country-wise energy consumption, sources of emissions, and how it gets impacted by their socioeconomic development and provides a framework for integrated climate and development policy.

An analysis of energy supply, consumption and emissions across developed and developing economies using long-term empirical data.

The framework provided areas to be focused on reducing emissions during the economic and social development trajectory of nations.

It provides a holistic and integrated picture of the context of emissions that induced global warming and developmental challenges for different types of countries.

All nations must reduce fossil fuel consumption to reduce anthropogenic greenhouse gas (GHG) emissions to keep the planet's temperature rise within 1.5 degrees Celsius compared to the preindustrial period.

Sustainable/green technologies might need upfront investment to implement sustainable technologies.

The main contribution of this paper is to provide a long-term integrated perspective on energy demand and supply, emissions, and a framework for the formulation of an integrated climate and development policy.