Showing papers on "Ignition system published in 2018"

Combustion theory : the fundamental theory of chemically reacting flow systems

Abstract: * Summary of Relevant Aspects of Fluid Dynamics and Chemical Kinetics * Rankine-Hugoniot Relations * Diffusion Flames and Droplet Burning * Reactions in Flows with Negligible Molecular Transport * Theory of Laminar Flames * Detonation Phenomena * Combustion of Solid Propellants * Ignition, Extinction, and Flammability Limits * Combustion Instabilities * Theory of Turbulent Flames * Spray Combustion * Flame Attachment and Flame Spread

Application of hydrogen enriched natural gas in spark ignition IC engines: from fundamental fuel properties to engine performances and emissions

Abstract: This review offers a summary of the recent research progress on hydrogen enriched compressed natural gas (HCNG) engines. Spark ignition IC engines fueled by HCNG have been shown to be advantageous over traditional gasoline engines in terms of fuel efficiencies and pollutant emissions. Further taking into account the vast availability of natural gas and the renewability of hydrogen, HCNG is considered to be a promising alternative fuel for large-scale applications in spark ignition engines. The past decade has witnessed significant progress in the research and development of HCNG engines. In this work, we intend to provide a comprehensive survey of recent studies on the power, efficiency and combustion & emission characteristics of HCNG engines. Additionally, we also focus on correlating fuel properties with experimentally observed HCNG engine performances, providing fundamental insights in the effects of hydrogen addition on engine working processes. To reach this goal, the physicochemical properties of hydrogen and its mixture with natural gas were firstly analyzed, followed by the detailed presentation and analysis of notable experimental results on HCNG engine performances. Numerical models for HCNG engines, which serve as an efficient way for engine parameter optimization, were also discussed. Apart from HCNG, the usage of other hydrogen-enriched fuels, such as hydrogen-gasoline, hydrogen-diesel, biogas and hydrogen-ethanol/methanol in IC engines were also briefly discussed.

Assessment on the consequences of injection timing and injection pressure on combustion characteristics of sustainable biodiesel fuelled engine

Abstract: In the rapidly growing global energy consumption, diesel engines play the key role. Usage of diesel fuel contributes to harmful air pollution exhausted from combustion chamber. To overcome these serious issues, the biodiesel extracted from many feedstocks have been studied and implemented for the past few decades. The combustion characteristics of diesel are not same as the biodiesel blends due to the discrepancy in physio-chemical properties of biodiesel. Enormous studies have been focused on inadequate combustion profiles of biodiesel in compression ignition engines. This review paper analyzes the previous researches concerning the consequences of proposed effective strategies including the variation in engine operating parameters like fuel injection timing and injection pressure for enhancing combustion characteristics of biodiesel implementation. This study focuses its light on the advancement and retardation methods of injection timing and injection pressure to treat the engine combustion indicators such as in-cylinder pressure, peak cylinder pressure, heat release rate, ignition delay period and combustion duration, finally a comparative evaluation has been developed and the relevant reasons for the variation of combustion characteristics have been conversed. The review concludes that the advancement in injection timing and higher injection pressure are best in amplifying the combustion phenomena of biodiesel fuelling.

Characteristics of mass, heat and gaseous products during coal spontaneous combustion using TG/DSC–FTIR technology

Abstract: Spontaneous combustion, if not eradicated immediately, may lead to coal ignition and even a full-blown fire. An understanding of the characteristics of coal oxidation under various environmental conditions is conducive to the reveal of the mechanism and the prevention of coal spontaneous combustion. TG/DSC–FTIR coupling technology was employed to investigate the evolutions of coal mass, heat and gaseous products during coal spontaneous combustion. The experiments conclude that the mass loss rate in Combustion Stage was much higher than other stages and the major of coal mass (over 80%) was consumed at this stage. As the oxygen concentration decreased, the combustion of coal was evidently postponed and the exothermic region shifted to a higher temperature. Correspondingly, the temperatures at which productions of CO and CO2 reached to the maximum were deferred as well. Experimental results also indicated that heating rates behaved differently before and after the ignition temperature. The mass loss rates of coal were independent of heating rates before ignition temperatures but obviously expanded and moved to higher temperatures after exceeding the ignition temperature. Additionally, with the increase of the heating rates, the exothermic region shifted to higher temperatures and the release of CO and CO2 were delayed and reached to the maximum in a longer time.

Gasoline compression ignition approach to efficient, clean and affordable future engines:

Abstract: The worldwide demand for transport fuels will increase significantly but will still be met substantially (a share of around 90%) from petroleum-based fuels. This increase in demand will be significantly skewed towards commercial vehicles and hence towards diesel and jet fuels, leading to a probable surplus of lighter low-octane fuels. Current diesel engines are efficient but expensive and complicated because they try to reduce the nitrogen oxide and soot emissions simultaneously while using conventional diesel fuels which ignite very easily. Gasoline compression ignition engines can be run on gasoline-like fuels with a long ignition delay to make low-nitrogen-oxide low-soot combustion very much easier. Moreover, the research octane number of the optimum fuel for gasoline compression ignition engines is likely to be around 70 and hence the surplus low-octane components could be used without much further processing. Also, the final boiling point can be higher than those of current gasolines. The potential a...

High-Performance Indirect-Drive Cryogenic Implosions at High Adiabat on the National Ignition Facility

Abstract: To reach the pressures and densities required for ignition, it may be necessary to develop an approach to design that makes it easier for simulations to guide experiments. Here, we report on a new short-pulse inertial confinement fusion platform that is specifically designed to be more predictable. The platform has demonstrated 99%+0.5% laser coupling into the hohlraum, high implosion velocity (411 km/s), high hotspot pressure (220+60 Gbar), and high cold fuel areal density compression ratio (>400), while maintaining controlled implosion symmetry, providing a promising new physics platform to study ignition physics.

Energetic Performance of Optically Activated Aluminum/Graphene Oxide Composites

Abstract: Optical ignition of solid energetic materials, which can rapidly release heat, gas, and thrust, is still challenging due to the limited light absorption and high ignition energy of typical energetic materials (e.g., aluminum, Al). Here, we demonstrated that the optical ignition and combustion properties of micron-sized Al particles were greatly enhanced by adding only 20 wt % of graphene oxide (GO). These enhancements are attributed to the optically activated disproportionation and oxidation reactions of GO, which release heat to initiate the oxidization of Al by air and generate gaseous products to reduce the agglomeration of the composites and promote the pressure rise during combustion. More importantly, compared to conventional additives such as metal oxides nanoparticles (e.g., WO3 and Bi2O3), GO has much lower density and therefore could improve energetic properties without sacrificing Al content. The results from Xe flash ignition and laser-based excitation experiments demonstrate that GO is an eff...

Overview of the oxygenated fuels in spark ignition engine: Environmental and performance

Abstract: Oxygenated fuels such as alcohols and ethers have the potential to provide reliable sources, and environmentally friendly fuel to world's increasing future energy demands. Oxygenated fuels have a promised future since are renewable and produced from several sources, also can be produced locally. The first objective of this paper is to systematically review of oxygenated fuels including alcohol and ether regarding the production, environmental impacts and potential using as octane booster of gasoline that used in spark ignition SI) engine. Another objective of this paper is to review the effects of oxygenated fuels on performances and emissions characteristics of spark ignition engine. Alcohol and ether burn very cleanly than regular gasoline and produce lesser carbon monoxide (CO) and nitrogen oxides (NOx). Mainly the ether fuels (methyl tertiary butyl ether MTBE and Dimethyl Ether DME) are used as additives at low blending ratio to enhance the octane number and oxygen content of gasoline. Furthermore, alcohols and ethers have significant impacts on the environment, greenhouse gas and human health. In addition to this, application of oxygenated fuel on SI engines can decrease environmental pollution, strengthen agricultural economy and decrease gasoline fuel requirements. The increase in engine performance could be attained with an increased compression ratio along with the use of alcohol fuels which have a higher-octane value. Overall, oxygenated fuels have been found to be a very promising alternative fuel for SI engines, capable of providing high thermal efficiency, and lower NOx levels.

The effect of liquid target on a nonthermal plasma jet - Imaging, electric fields, visualization of gas flow and optical emission spectroscopy

Abstract: The article describes the complex study of the interaction of a helium plasma jet with distilled water and saline. The discharge development, spatial distribution of the excited species, electric field measurement results and the results of the Schlieren imaging are presented. The results of the experiments showed that the plasma-liquid interaction could be prolonged with the proper choice of the gas composition between the jet nozzle and the target. This depends on the gas flow and the target distance. Increased conductivity of the liquid does not affect the discharge properties significantly. An increase of the gas flow enables an extension of the plasma duration on the liquid surface up to 10 μs, but with a moderate electric field strength in the ionization wave. In contrast, there is a significant enhancement of the electric field on the liquid surface, up to 30 kV cm-1 for low flows, but with a shorter time of the overall plasma liquid interaction. Ignition of the plasma jet induces a gas flow modification and may cause turbulences in the gas flow. A significant influence of the plasma jet causing a mixing in the liquid is also recorded and it is found that the plasma jet ignition changes the direction of the liquid circulation.

An overview of the effects of fuel molecular structure on the combustion and emissions characteristics of compression ignition engines

Abstract: Future fuels for compression ignition engines will be required both to reduce the anthropogenic carbon dioxide emissions from fossil sources and to contribute to the reductions in the exhaust levels of pollutants, such as nitrogen oxides and particulate matter. Via various processes of biological, chemical and physical conversion, feedstocks such as lignocellulosic biomass and photosynthetic micro-organisms will yield a wide variety of potential fuel molecules. Furthermore, modification of the production processes may allow the targeted manufacture of fuels of specific molecular structure. This paper therefore presents an overview of the effects of fuel molecular structure on the combustion and emissions characteristics of compression ignition engines, highlighting in particular the submolecular features common to a variety of potential fuels. An increase in the straight-chain length of the alkyl moiety reduces the duration of ignition delay, and the introduction of double bonds or branching to an alkyl moiety both increase ignition delay. The movement of a double bond towards the centre of an alkyl chain, or the addition of oxygen to a molecule, can both increase and decrease the duration of ignition delay dependent on the overall fuel structure. Nitrogen oxide emissions are primarily influenced by the duration of fuel ignition delay, but in the case of hydrogen and methane pilot-ignited premixed combustion arise only at flame temperatures sufficiently high for thermal production. An increase in aromatic ring number and physical properties such as the fuel boiling point increase particulate matter emissions at constant combustion phasing.