Changes In Combustion Process Research Articles

Numerical Study of Ignition and Combustion of Hydrogen-Enriched Methane in a Sequential Combustor

Ignition and combustion behavior in the second stage of a sequential combustor are investigated numerically at atmospheric pressure for pure CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{CH}}_{4}$$\\end{document} fueling and for two CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{CH}}_{4}$$\\end{document}-H2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{H}}_{2}$$\\end{document} fuel blends in 24:1 and 49:1 mass ratios , respectively, using Large Eddy Simulation (LES). Pure CH4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{CH}}_{4}$$\\end{document} fueling results in a turbulent propagating flame anchored by the hot gas recirculation zones developed near the inlet of the sequential combustion chamber. As the H2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{H}}_{2}$$\\end{document} content increases, the combustion process changes drastically, with multiple auto-ignition kernels produced upstream of the main flame brush. Analysis of the explosive modes indicates that, for the highest H2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{H}}_{2}$$\\end{document} amount investigated, flame stabilization in the combustion chamber is strongly supported by auto-ignition chemistry. The analysis of fuel decomposition pathways highlights that radicals advected from the first stage flame, in particular OH, induce a rapid fuel decomposition and cause the reactivity enhancement that leads to auto-ignition upstream of the sequential flame. This behavior is promoted by the relatively large mass fraction of OH radicals found in the flow reaching the second stage, which is approximately one order of magnitude greater than it would be at chemical equilibrium. The importance of the out-of-equilibrium vitiated air on the ignition behavior is proven via an additional LES that features weak auto-ignition kernel formation when equilibrium is artificially imposed. It is therefore concluded that parameters affecting the relaxation towards chemical equilibrium of the vitiated flow can have an important influence on the operability of sequential combustors fueled with varying fractions of H2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{H}}_{2}$$\\end{document} blending.

Influence of Air Infiltration on Combustion Process Changes in a Rotary Tilting Furnace

Air infiltration into the combustion chambers of industrial furnaces is an unwanted phenomenon causing loss of thermal efficiency, fuel consumption increase, and the subsequent increase in operating costs. In this study, a novel design for a rotary tilting furnace door with improved construction features is proposed and tested experimentally in a laboratory-scale furnace, aimed at air infiltration rate reduction by decreasing the gap width between the static furnace door and the rotating body. Temperatures in the combustion chamber and oxygen content in the dry flue gas were measured to document changes in the combustion process with the varying gap width. Volumetric flow values of infiltrating air calculated based on measured data agree well with results of numerical simulations performed in ANSYS and with the reference calculation procedure used in relevant literature. An achievable air infiltration reduction of up to 50% translates into fuel savings of around 1.79 to 12% of total natural gas consumption of the laboratory-scale furnace. The average natural gas consumption increase of around 1.6% due to air infiltration into industrial-scale furnaces can thus likewise be halved, representing fuel savings of almost 0.3 m3 per ton of charge.

Biomass based oil and hydrogen co-combustion in the compression ignition engine

Paper presents results from investigation focused on combustion progress of biomass based oil assisted with hydrogen in the internal combustion compression ignition (CI) engine. Hydrogen was added at amounts in the range from 0 to 40% by energy. The main target of this analysis was to determine impact of hydrogen on the following: combustion phases, smoke opacity and toxic emissions in the compression ignition engine. Literature review shows hydrogen can cause significant changes in combustion process even if it is added in small amounts. In this manuscript, investigation was carried out on a test bench consisted of a single cylinder compression ignition engine with common rail injection system. Hydrogen was injected into the intake manifold, where it created homogeneous mixture with air. Tests were performed at both fixed and optimal injection timings at full engine load. Results from experiments show that increasing amounts of hydrogen into the engine contribute to shorten ignition delay time that also affect main combustion phase. Additionally, it implicates heat release rate and toxic emissions (THC, CO, NOx). Moreover, decrease in smoke (mainly soot) in the exhaust gases was observed with increase of hydrogen amounts to the engine.

Rapid compression machine studies on ignition delay changes in a methyl butanoate/n-heptane mixture by hydrogen addition

The use of alternative energy is increasing with the concerns about global warming and the dwindling reserves of fossil fuels. Biodiesel and hydrogen are promising alternative fuels, and engine research has investigated the use of biodiesel/hydrogen mixtures. However, no study has examined the chemical kinetics of biodiesel and hydrogen mixtures. This study investigated the effects of hydrogen on the ignition delay of a methyl butanoate/n-heptane mixture. An experiment was conducted using a rapid compression machine (RCM) at 15 bar while varying the temperature (716–858 K) and hydrogen fraction in the fuel mixture (0, 25, 50, and 75%), and a numerical analysis was performed using CHEMKIN-PRO software to understand how the combustion process changes. The experimental and numerical analyses showed that, with hydrogen addition, the ignition delay increased.

Performance and emission characteristics of a low heat rejection engine using Nerium biodiesel and its blends

In the present study, the surface of cylinder head, piston, exhaust and inlet valves of a four stroke direct injection and single cylinder diesel engine has been coated with partially stabilised zirconia (PSZ) by the plasma spray method. The coated engine was tested with the neat diesel and methyl ester of neat Nerium oil. The performance and emission results were compared with the uncoated engine fuelled with diesel and methyl ester of Nerium oil (MEON). Specific fuel consumption of the PSZ-coated engine was lower at all loads, because of the insulation effect of coating and changes in combustion process due to coating. The brake thermal efficiency of PSZ-coated engine fuelled with MEON is 3.8% higher than uncoated engine fuelled with MEON. The emission for the PSZ-coated engine with diesel was improved compared with uncoated engine except NOx.

An experimental apparatus for testing biodiesels based on a CFR engine—setup and validation with different methyl ester blends

ABSTRACTA cooperative fuel research (CFR) engine was modified and instrumented in order to control operating conditions and to measure engine parameters and in-cylinder pressure diagrams. Aiming at the comparison of different alternative fuels, an experimental procedure was defined, including cetane number (CN) evaluation and the definition of engine operating quantities in different working points, for fixed levels of compression ratio (CR) and injection advance. An investigation was made considering several blends of methyl-esters of rapeseed oil (RME) and of a mix of vegetable oils (VOME) with conventional diesel oil. The defined experimental procedure was applied to assess CN, engine brake thermal efficiency (bte) and exhaust emissions. Results show that the biodiesel content has a positive influence on soot emissions, with strong reduction, while thermal efficiency and NOX emissions are negatively affected, which can be justified taking into account fuel properties and changes in combustion process. As observed outcomes are generally in line with those presented in literature, the facility proved to be a suitable tool for basic investigations on alternative fuels to be used in specific applications.