Current Issue : July - September Volume : 2016 Issue Number : 3 Articles : 4 Articles
To meet more stringent norms and standards concerning engine performances and emissions, engine manufacturers need to\ndevelop new technologies enhancing the nonpolluting properties of the fuels. In that sense, the testing and development of\nalternative fuels such as biodiesel are of great importance. Fuel testing is nowadays a matter of experimental and numerical work.\nResearches on diesel engine�s fuel involve the use of surrogates, for which the combustion mechanisms are well known and relatively\nsimilar to the investigated fuel. Biodiesel, due to its complex molecular configuration, is still the subject of numerous investigations\nin that area. This study presents the comparison of four biodiesel surrogates, methyl-butanoate, ethyl-butyrate, methyl-decanoate,\nand methyl-9-decenoate, in a 0D phenomenological combustion model. They were investigated for in-cylinder pressure, thermal\nefficiency, andNO...
In the present study, a semiempirical, zero-dimensional multizone model, developed by the authors, is implemented on two\nautomotive diesel engines, a heavy-duty truck engine and a light-duty passenger car engine with pilot fuel injection, for various\noperating conditions including variation of power/speed, EGR rate, fuel injection timing, fuel injection pressure, and boost pressure,\nto verify its capability for Nitric Oxide (NO) emission prediction.The model utilizes cylinder�s basic geometry and engine operating\ndata and measured cylinder pressure to estimate the apparent combustion rate which is then discretized into burning zones\naccording to the calculation step used. The requisite unburnt charge for the combustion in the zones is calculated using the\nzone equivalence ratio provided from a new empirical formula involving parameters derived from the processing of the measured\ncylinder pressure and typical engine operating parameters. For the calculation of NO formation, the extended Zeldovich mechanism\nis used. From this approach, the model is able to provide the evolution of NO formation inside each burned zone and, cumulatively,\nthe cylinder�s NO formation history. As proven from the investigation conducted herein, the proposed model adequately predicts\nNO emissions and NO trends when the engine settings vary,with low computational cost. These encourage its use for engine control\noptimization regarding NOx abatement and real-time/model-based NOx control applications....
mathematical analysis of laminar premixed spray flame propagation with heat loss is presented. The analysis makes use of a\ndistributed approximation of the Arrhenius exponential term in the reaction rate expression and leads to an implicit expression for\nthe laminar burning velocity dependent on the spray-related parameters for the fuel, gas-related parameters and the intensity of\nthe heat losses. It is shown that the initial droplet load, the value of the evaporation coefficient, and the initial size distribution are\nthe spray-related parameters which exert an influence on the onset of extinction. The combination of these parameters governs the\nmanner in which the spray heat loss is distributed spatially and it is this feature that is the main factor, when taken together with\nvolumetric heat loss, which determines the spray�s impact on flame propagation and extinction....
In order to compare solar-hydrogen and the most used fossil fuels, the evaluation of the ââ?¬Å?externalââ?¬Â costs related to their use is\nrequired. These costs involve the environmental damage produced by the combustion reactions, the health problems caused by air\npollution, the damage to land from fuel mining, and the environmental degradation linked to the global warming, the acid rains,\nand the water pollution. For each fuel, the global cost is determined as sum of the market price and of the correspondent external\ncosts. In order to obtain a quantitative comparison, the quality of the different combustion reactions and the efficiency of the\ntechnologies employed in the specific application sector have to be considered adequately. At this purpose, an entropic index that\nconsiders the degree of irreversibility produced during the combustion process and the degradation of surroundings is introduced.\nAdditionally, an environmental index that measures the pollutants released during the combustions is proposed.The combination\nof these indexes and the efficiency of the several technologies employed in four energy sectors have allowed the evaluation of the\ntotal costs, highlighting an economic scenario from which the real advantages concerning the exploitation of different energy carrier\nare determined....
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