Current Issue : January - March Volume : 2019 Issue Number : 1 Articles : 5 Articles
Compression ratio has very important influence on fuel economy, emission, and other performances of internal combustion\nengines. Application of variable compression ratio in diesel engines has a number of benefits, such as limiting maximal in cylinder\npressure and extended field of the optimal operating regime to the prime requirements: consumption, power, emission, noise, and\nmultifuel capability.Themanuscript presents also the patentedmechanismfor automatic change engine compression ratiowith twopiece\nconnecting rod. Beside experimental research,modeling of combustion process of diesel engine with direct injection has been\nperformed.The basic problem, selection of the parameters in double Vibe function used formodeling the diesel engine combustion\nprocess, also performed for different compression ratio values.The optimal compression ratio value was defined regardingminimal\nfuel consumption and exhaust emission. For this purpose the test bench in the Laboratory for Engines of the Faculty of Engineering,\nUniversity of Kragujevac, is brought into operation....
An investigation of ultralean stratified, disk stabilized, propane flames operated with acoustic modulation of the inlet velocity and\nfuel-air mixture profiles is presented. Transverse acoustic forcing was applied to the air, upstream of a double-cavity premixer\nsection, formed along three concentric disks, which fueled the stabilization region with a radial mixture gradient. Measurements\nand supporting Large Eddy Simulations with a nine-step mechanism for propane combustion were performed to evaluate variations\nin the ultralean flame characteristics under forced and unforced conditions.The effects of forcing on the heat release profiles and on\nthe interaction of the toroidal flame with the recirculation region are examined and discussed.The impact of the acoustic excitation\nof inlet conditions on the local extinction behavior is, also, assessed by monitoring a local stability criterion and by analyzing\nphase-resolved chemilumine scence images....
The combustion kinetic characteristics of wood powder and pelletwere investigated within thermogravimetric analyser (TGA) and\ntube furnace system. The kinetic parameters of these two different forms of woody fuel were measured and derived by double-stepand-\ndouble-equal and i so thermal method, respectively.The results showed that the combustion mechanisms of wood powder kept\nconsistent through the whole process, while the combustion mechanisms of wood pellet differed significantly between the volatile\nand char combustion stages.The most probable mechanism functions of the two different forms of woody fuel were not the same\ndue to the differences in internal heat and mass transfer properties. In addition, activation energy values varied from---mol--for wood powder to--mol--for wood pellet, while the preexponential factor value of wood powder---was far\ngreater than the one of the wood pellet---by seven orders of magnitude....
A 2D dynamicmodel for a bubbling fluidized bed (BFB) combustor has been developed for simulating the coal and biomass cofiring\nprocess under 21% O2/79% CO2 atmosphere in a 6 kWth bubbling fluidized bed, coupled with the Euler-Euler two-phase flow\nmodel. The kinetic theory of binary granular mixtures is employed for the solid phase in order to map the effect of particle size and\ndensity. The distribution of temperature, volume fraction, velocity, gas species concentration, and reaction rates are studied with\nnumerical calculations. The simulated temperature distribution along the height of the combustor and outlet gas concentrations\nshow good agreement with experimental data, validating the accuracy and reliability of the developed cofiring simulation model.\nAs indicated in the results, there are two high temperature zones in the combustor, which separately exist at the fuel inlet and dilute\nphase. The reaction rates are related to the species concentration and temperature.The higher concentration and temperature lead\nto the larger reaction rates. It can be seen that all of the homogeneous reaction rates are larger at the fuel inlet region because of\nrich O2 and volatiles. High mass fraction of volatile gas is found at the fuel inlet, and the main reburning gas at the dilute phase is\nCH4.The mass fraction distribution of CO is related to the volume fraction of fuel which is due to the fact that the source of CO\nis not only from the devolatilization but also from the gasification. On the basis of this theoretical study, a better understanding of\nflow and combustion characteristics in biomass and coal cofiring under oxy-fuel atmospheres could be achieved....
Theobjective of this work has been the synthesis of wollastonite by solution combustion method.Thenovelty of this work has been\nobtaining the crystalline phase without the need of thermal treatments after the synthesis. For this purpose, urea was used as fuel.\nCalcium nitrate was selected as a source of calcium and colloidal silica served as a source of silicon. The effect of the amount of fuel\non the combustion process was investigated. Temperature of the combustion reaction was followed by digital pyrometry. The\nobtained products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and specific surface area.\nThe results showed that the combustion synthesis provides nanostructured powders characterized by a high surface area. When\nexcess of urea was used, wollastonite-2M was obtained with a submicronic structure....
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