Current Issue : April - June Volume : 2014 Issue Number : 2 Articles : 6 Articles
The biomass market has experienced an increase in development, leading to\r\nresearch and development efforts that are focused on determining optimal biofuel\r\ncombustion conditions. Biomass combustion is a complex process that involves divergent\r\nparameters and thus requires the use of advanced analysis methods. This study proposes\r\ncombining grey relational analysis (GRA) and error propagation theory (EPT) to select a\r\nbiofuel and its optimal combustion conditions. This research will study three biofuels that\r\nare currently used in a region of South Europe (Spain), and the most important variables\r\nthat affect combustion are the ignition front propagation speed and the highest temperature\r\nthat is reached at the fixed bed combustor. The results demonstrate that a combination of\r\nboth theories for the analysis of solid-state thermochemical phenomena enables a fast and\r\nsimple way of choosing the best configuration for each fuel....
This paper discusses the effect of ignition delay time in diesel engines on the formation of particulate matter, using fuel\r\nformulations with different sulfur concentrations from various sources. Our findings indicate that the cetane number has a\r\nsignificant influence on particulate matter emissions, especially in engines with mechanical fuel injection. The maximum pressure\r\nin the combustion chamber increases as the cetane number increases, favoring the increase in the cracking reactions of high\r\nmolecular weight fractions remaining in the liquid state and thus increasing the production of particulate matter. In certain\r\nconditions, this increase in pressure has a beneficial effect on the thermal efficiency of the cycle. Higher temperatures in the\r\ncombustion chamber augment the speed of oxidation, reducing unburned hydrocarbon emissions. The ignition delay time of fuel\r\nhas a strong effect on the formation of particulate matter and on the emission of unburned hydrocarbons....
Relevant to the self-propagating high-temperature synthesis (SHS) process, an analytical study has been conducted to investigate\r\nthe effects of electric field on the combustion behavior because the electric field is indispensable for systems with weak exothermic\r\nreactions to sustain flame propagation. In the present study, use has been made of the heterogeneous theory which can satisfactorily\r\naccount for the premixed mode of the bulk flame propagation supported by the nonpremixed mode of particle consumption. It has\r\nbeen confirmed that, even for the SHS flame propagation under electric field, being well recognized to be facilitated, there exists\r\na limit of flammability, due to heat loss, as is the case for the usual SHS flame propagation. Since the heat loss is closely related to\r\nthe representative sizes of particles and compacted specimen, this identification provides useful insight into manipulating the SHS\r\nflame propagation under electric field, by presenting appropriate combinations of those sizes. A fair degree of agreement has been\r\ndemonstrated through conducting an experimental comparison, as far as the trend and the approximate magnitude are concerned,\r\nsuggesting that an essential feature has been captured by the present study....
This study investigated the effects of high exhaust gas recirculation (EGR) rates\r\non dimethyl ether (DME) fuel combustion performance, exhaust emissions and particle\r\nemission characteristics in a small direct injection diesel engine under various injection\r\ntimings. To examine the effect of EGR and injection timings, the experiment was performed\r\nunder high EGR rates (0%, 30%, 50%) and injection timings were varied from 40�° before\r\ntop dead center (BTDC) to top dead center (TDC) of the crank angle to examine the effects\r\nof early injection of DME fuel. The combustion pressures and heat release rates for\r\ndifferent EGR rates followed similar trends. As the injection timing was advanced, the\r\nindicated mean effective pressure (IMEP) differed little in response to EGR rate in the\r\nrange from TDC to 25�° BTDC, and more for crank angles beyond 25�° BTDC. DME\r\ncombustion exhibited very little soot emission, but soot emission increased slightly with\r\nEGR rate. The use of high EGR during combustion produced very low NOx concentrations\r\nbut increased HC and CO emissions for advanced injection timings from 25�° BTDC to 40�°\r\nBTDC. The use of EGR increased both the emissions of total particle number and particle\r\nvolume over the whole range of the injection timings; for all cases, total particle volume\r\ndecreased as injection timing was advanced....
The study investigated the potential of water hyacinths and phytoplankton scum, an aquatic weed, as binder for production of fuel\r\nbriquettes. It also evaluated some physical and combustion characteristics. The water hyacinths were manually harvested, cleaned,\r\nsun-dried, and milled to particle sizes distribution ranging from <0.25 to 4.75mm using hammer mill.The water hyacinth grinds\r\nand binder (phytoplankton scum) at 10% (B1), 20% (B2), 30% (B3), 40% (B4), and 50% (B5) by weight of each feedstock were\r\nfed into a steel cylindrical die of dimension 14.3 cm height and 4.7 cm diameter and compressed by hydraulic press at pressure\r\n20MPa with dwell time of 45 seconds. Data were analysed using analysis of variance and descriptive statistics. Initial bulk density\r\nof uncompressed mixture of water hyacinth and phytoplankton scum at different binder levels varied between 113.86 �± 3.75 (B1) and\r\n156.93 �± 4.82 kg/m3 (B5). Compressed and relaxed densities of water hyacinth briquettes at different binder proportions showed\r\nsignificant difference ?? < 0.05. Durability of the briquettes improved with increased binder proportion. Phytoplankton scum\r\nimproved the mechanical handling characteristics of the briquettes. It could be concluded that production of water hyacinth\r\nbriquettes is feasible, cheaper, and environmentally friendly and that they compete favourably with other agricultural products....
Neem biodiesel is currently being explored as a future biofuel and was extracted\r\nchemically from the vegetable oil. Many of its properties are still under investigation and\r\nour aim was to study its noxious-gas emission profiles from blends with regular petroleum\r\ndiesel. The distinct advantage of a real-time study is acquisition of in situ data on the\r\ncombustion behavior of gas components with actual progression of time. Mixtures of neem\r\nbiodiesel and petroleum diesel corresponding to neem additives of 5%, 10%, 15% and 25%\r\nwere tested for combustion efficiency and emitted gases using a high-performance gas\r\nanalyzer. Our study, therefore, investigated the overall efficiency of the combustion\r\nprocess linked to emissions of the following gases: O2, CO2, NO, NOx and SO2. The results\r\nfor the 95/5% blend compared to the neat sample were most promising and showed no\r\nserious change in performance efficiency (<2%). NO/NOx emission trends displayed\r\nmaxima/minima, suggestive of interconvertible chemical reactivity. Declining CO and SO2\r\nemissions were consistent with rapid chemical conversion. The CO and SO2 concentrations\r\nfell well below the toxic atmospheric limits in less than 300 s. The results are generally\r\nencouraging for blends below 10%. The potential environmental impact of the study\r\nis discussed....
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