Showing papers on "Combustion published in 2015"

Global vulnerability of peatlands to fire and carbon loss

Abstract: The amount of carbon stored in peats exceeds that stored in vegetation A synthesis of the literature suggests that smouldering fires in peatlands could become more common as the climate warms, and release old carbon to the air Globally, the amount of carbon stored in peats exceeds that stored in vegetation and is similar in size to the current atmospheric carbon pool Fire is a threat to many peat-rich biomes and has the potential to disturb these carbon stocks Peat fires are dominated by smouldering combustion, which is ignited more readily than flaming combustion and can persist in wet conditions In undisturbed peatlands, most of the peat carbon stock typically is protected from smouldering, and resistance to fire has led to a build-up of peat carbon storage in boreal and tropical regions over long timescales But drying as a result of climate change and human activity lowers the water table in peatlands and increases the frequency and extent of peat fires The combustion of deep peat affects older soil carbon that has not been part of the active carbon cycle for centuries to millennia, and thus will dictate the importance of peat fire emissions to the carbon cycle and feedbacks to the climate

Gas sensing using porous materials for automotive applications

Abstract: Improvements in the efficiency of combustion within a vehicle can lead to reductions in the emission of harmful pollutants and increased fuel efficiency. Gas sensors have a role to play in this process, since they can provide real time feedback to vehicular fuel and emissions management systems as well as reducing the discrepancy between emissions observed in factory tests and ‘real world’ scenarios. In this review we survey the current state-of-the-art in using porous materials for sensing the gases relevant to automotive emissions. Two broad classes of porous material – zeolites and metal–organic frameworks (MOFs) – are introduced, and their potential for gas sensing is discussed. The adsorptive, spectroscopic and electronic techniques for sensing gases using porous materials are summarised. Examples of the use of zeolites and MOFs in the sensing of water vapour, oxygen, NOx, carbon monoxide and carbon dioxide, hydrocarbons and volatile organic compounds, ammonia, hydrogen sulfide, sulfur dioxide and hydrogen are then detailed. Both types of porous material (zeolites and MOFs) reveal great promise for the fabrication of sensors for exhaust gases and vapours due to high selectivity and sensitivity. The size and shape selectivity of the zeolite and MOF materials are controlled by variation of pore dimensions, chemical composition (hydrophilicity/hydrophobicity), crystal size and orientation, thus enabling detection and differentiation between different gases and vapours.

A review of the combustion and emissions properties of advanced transportation biofuels and their impact on existing and future engines

Abstract: The fundamental combustion and emissions properties of advanced biofuels are reviewed, and their impact on engine performance is discussed, in order to guide the selection of optimal conversion routes for obtaining desired fuel combustion properties. Advanced biofuels from second- and third-generation feedstocks can result in significantly reduced life-cycle greenhouse-gas emissions, compared to traditional fossil fuels or first-generation biofuels from food-based feedstocks. These advanced biofuels include alcohols, biodiesel, or synthetic hydrocarbons obtained either from hydrotreatment of oxygenated biofuels or from Fischer–Tropsch synthesis. The engine performance and exhaust pollutant emissions of advanced biofuels are linked to their fundamental combustion properties, which can be modeled using combustion chemical-kinetic mechanisms and surrogate fuel blends. In general, first-generation or advanced biofuels perform well in existing combustion engines, either as blend additives with petro-fuels or as pure “drop-in” replacements. Generally, oxygenated biofuels produce lower intrinsic nitric-oxide and soot emissions than hydrocarbon fuels in fundamental experiments, but engine-test results can be complicated by multiple factors. In order to reduce engine emissions and improve fuel efficiency, several novel technologies, including engines and fuel cells, are being developed. The future fuel requirements for a selection of such novel power-generation technologies, along with their potential performance improvements over existing technologies, are discussed. The trend in the biofuels and transportation industries appears to be moving towards drop-in fuels that require little changes in vehicle or fueling infrastructure, but this comes at a cost of reduced life-cycle efficiencies for the overall alternative-fuel production and utilization system. In the future, fuel-flexible, high-efficiency, and ultra-low-emissions heat-engine and fuel-cell technologies promise to enable consumers to switch to the lowest-cost and cleanest fuel available in their market at any given time. This would also enable society as a whole to maximize its global level of transportation activity, while maintaining urban air quality, within an energy- and carbon-constrained world.

An overview of methanol as an internal combustion engine fuel

Abstract: Methanol is an alternative, renewable, environmentally and economically attractive fuel; it is considered to be one of the most favorable fuels for conventional fossil-based fuels. Methanol has been recently used as an alternative to conventional fuels for internal combustion (IC) engines in order to satisfy some environmental and economical concerns. Because of a number of relatively large research projects that have been ongoing recently, much progress has been made that is worth reporting. This paper systematically describes the methanol productions, including the productions from coal, natural gas, coke-oven gas, hydrogen, biomass etc. It introduces the potentials of methanol as a renewable resource taking into account the world supply and demand, economic benefits and the effects on human health and the environment. Thirteen methods of application such as methanol/gasoline, methanol/diesel blends which can be used on the IC engines are summarized. Finally, this paper puts forward some new suggestions on the weakness in the researches of methanol engine.

Solution combustion synthesis of metal oxide nanomaterials for energy storage and conversion

Abstract: The design and synthesis of metal oxide nanomaterials is one of the key steps for achieving highly efficient energy conversion and storage on an industrial scale. Solution combustion synthesis (SCS) is a time- and energy-saving method as compared with other routes, especially for the preparation of complex oxides which can be easily adapted for scale-up applications. This review summarizes the synthesis of various metal oxide nanomaterials and their applications for energy conversion and storage, including lithium-ion batteries, supercapacitors, hydrogen and methane production, fuel cells and solar cells. In particular, some novel concepts such as reverse support combustion, self-combustion of ionic liquids, and creation of oxygen vacancies are presented. SCS has some unique advantages such as its capability for in situ doping of oxides and construction of heterojunctions. The well-developed porosity and large specific surface area caused by gas evolution during the combustion process endow the resulting materials with exceptional properties. The relationship between the structural properties of the metal oxides studied and their performance is discussed. Finally, the conclusions and perspectives are briefly presented.

Conversion of the greenhouse gas CO2 to the fuel gas CO via the Boudouard reaction: A review

Abstract: The remediation of carbon dioxide emitted into the atmosphere has become the topic of the day due to the enormous contribution of CO 2 to the devastating global warming. The Boudouard reaction, in which solid carbon (char) reacts with CO 2 to produce carbon monoxide (CO 2 (g)+C(s)↔CO (g)), is a straightforward route for the CO 2 emission mitigation. Through this reaction, the CO 2 coming from variety of combustion plants, including exhaust/flue gas and synthesis gas, can be upgraded to the fuel gas, CO. This work presents a review on the CO 2 gasification of char, from coal, biomass, municipal solid wastes, sewage sludge or any co-utilized blend of them, to produce CO through the Boudouard reaction. An outline of the most effective parameters on the char gasification rate is presented. The parameters which affect the char reactivity are reviewed as those related to the char and its structural features (surface area and porosity, active sites, mineral content, structural evolution of char during gasification, pyrolysis condition and carbon source) and operation parameters (use of catalyst, gasification temperature, gasification pressure and CO 2 partial pressure, char particle size and gasification heat source). The kinetics of the char gasification reaction is studied and several theoretical or semi-empirical kinetic models used to interpret the reaction rate data and calculation of kinetic parameters, specifically activation energy, are reviewed and discussed.

Combustion of Nano Aluminum Particles (Review)

Abstract: Nano aluminum particles have received considerable attention in the combustion community; their physicochemical properties are quite favorable as compared with those of their micron-sized counterparts. The present work provides a comprehensive review of recent advances in the field of combustion of nano aluminum particles. The effect of the Knudsen number on heat and mass transfer properties of particles is first examined. Deficiencies of the currently available continuum models for combustion of nano aluminum particles are highlighted. Key physicochemical processes of particle combustion are identified and their respective time scales are compared to determine the combustion mechanisms for different particle sizes and pressures. Experimental data from several sources are gathered to elucidate the effect of the particle size on the flame temperature of aluminum particles. The flame structure and the combustion modes of aluminum particles are examined for wide ranges of pressures, particle sizes, and oxidizers. Key mechanisms that dictate the combustion behaviors are discussed. Measured burning times of nano aluminum particles are surveyed. The effects of the pressure, temperature, particle size, and type and concentration of the oxidizer on the burning time are discussed. A new correlation for the burning time of nano aluminum particles is established. Major outstanding issues to be addressed in the future work are identified.

Recent Advances in Catalysts for Methane Combustion

Abstract: This invited review highlights recent progress in the various classes of heterogeneous catalysts for methane combustion. These combustion catalysts provide a high-efficiency, clean energy source for natural gas vehicles and power plants. This review examines bimetallic systems, and a variety of oxides including single metal oxides, perovskites, spinels, and hexaaluminates. Noble metal mixed oxides exhibit superior catalytic activity due material-specific supports, additives, preparation methods, poisoning, regeneration and surface structure. Kinetic aspects, mechanisms, and the latest studies concerning density functional theory modelling are discussed in conjunction with particle oxidation/reduction mechanisms. The extensive background knowledge on the methane combustion reaction provided by this review provides guidance for researchers with interests ranging from the field of heterogeneous catalysis to the engineering of new high performance materials in environmental and chemical engineering.

Applications of Ni3Al Based Intermetallic Alloys—Current Stage and Potential Perceptivities

Abstract: The paper presents an overview of current and prospective applications of Ni3Al based intermetallic alloys—modern engineering materials with special properties that are potentially useful for both structural and functional purposes. The bulk components manufactured from these materials are intended mainly for forging dies, furnace assembly, turbocharger components, valves, and piston head of internal combustion engines. The Ni3Al based alloys produced by a directional solidification are also considered as a material for the fabrication of jet engine turbine blades. Moreover, development of composite materials with Ni3Al based alloys as a matrix hardened by, e.g., TiC, ZrO2, WC, SiC and graphene, is also reported. Due to special physical and chemical properties; it is expected that these materials in the form of thin foils and strips should make a significant contribution to the production of high tech devices, e.g., Micro Electro-Mechanical Systems (MEMS) or Microtechnology-based Energy and Chemical Systems (MECS); as well as heat exchangers; microreactors; micro-actuators; components of combustion chambers and gasket of rocket and jet engines as well components of high specific strength systems. Additionally, their catalytic properties may find an application in catalytic converters, air purification systems from chemical and biological toxic agents or in a hydrogen “production” by a decomposition of hydrocarbons.

Chemical kinetic and combustion characteristics of transportation fuels

Abstract: Internal combustion engines running on liquid fuels will remain the dominant prime movers for road and air transportation for decades, probably for most of this century. The world’s appetite for liquid transportation fuels derived from petroleum and other fossil resources is already immense, will grow, will at some future time become economically unsustainable, and will become infeasible only in the very long term. The ongoing process of augmenting and eventually replacing petroleum-derived fuels with liquid alternative fuels must necessarily involve approaches that result in comparatively much lower net carbon cycle emissions from the transportation sector, most likely through a combination of carbon sequestration and renewable fuel production. The successful growth and establishment of a sustainable, profitable alternative fuels industry will be best facilitated by approaches that integrate alternative products into petroleum-derived fuel streams (i.e., gasolines, diesel, and jet fuels) and consider synergistic evolution of and integration with prevailing refining and liquid fuel distribution infrastructures. The emergence of low temperature combustion strategies, particularly those implementing dual fuel methods to achieve Reaction Controlled Compression Ignition (RCCI), offers the potential to significantly improve operating efficiency and reduce emissions with minimal aftertreatment. For all advanced combustion engine technologies, but especially for RCCI, a clear understanding of fuel property influences on combustion behaviors will be important to achieving projected engine performance and emissions. To achieve the benefits projected by emerging engine technologies, the properties of petroleum-derived fuels themselves must be modified over time, but the effects of blending candidate alternative fuels with these conventional fuels must also be understood. Predicting the coupled physical and chemical property effects of real fuels on energy conversion system performance and emissions is a daunting problem, even for petroleum-derived real fuels, since each is composed of several hundred to thousands of individual chemical species typically belonging to one of a few organic classes (e.g., n-paraffins, iso-paraffins, cyclo-paraffins, olefins, aromatics). For specific combustion applications, it is often the global combustion response to variations in the composition of fuel mixtures – inclusive of those occurring by blending petroleum-derived fuel with alternative fuel candidates – that is of interest for fuel property optimization. This paper presents an overview of tools used for evaluating and emulating combustion-relevant properties of real fuels and alternative fuel candidates. New analytical and statistical methods can provide important insights as to how the ensembles of distinct molecular structures found in a given fuel mixture contribute to the physical and chemical kinetic properties that govern its combustion in energy conversion processes. Such tools can in turn assist in screening candidate alternative fuels for more detailed study.