Current Issue : October - December Volume : 2020 Issue Number : 4 Articles : 5 Articles
Fire extinguishing with the superior performance of fly ash composite colloid material is a cost-effective colloid fire prevention\ntechnology. In this paper, a new powder additive (suspending agent (XK-XJ) and gelling agent) was developed for the existing fire\nextinguishing technology of fly ash compound colloid. Tests show that the best additions to the fly ash slurry were 0.3% and\n0.1-0.3%, respectively. The grouting technical scheme of adding a suspending agent on the ground and gelling agent downhole\nwas proposed to solve the problems of solid material settlement and blockage in the long-distance pipeline transportation process.\nFinally, the optimized fly ash colloid fire prevention and extinguishing technology was successfully applied to the fire control\nengineering examples of close-range coal seam groups, and the rationality of the developed powder and its proportion was tested,\nand the feasibility in coal fire control was tested....
The new blended fuel (gasoline/hydrogenated catalytic biodiesel) is expected to address the cold start problem under low\ntemperature of gasoline compression ignition due to its excellent ignition performance. Additionally, its spray behavior as the\ncombustion boundary condition could have a direct impact on the characteristics of subsequent combustion. Therefore, the\nobjective of this study is to reveal the effects of hydrogenated catalytic biodiesel/gasoline on the spray characteristics under various\nambient conditions. As a significant index of spray characteristics, the spray penetration was achieved by applying Mie scattering\nmethods under nonevaporation and evaporation conditions on a constant volume combustion chamber. In addition, the experimental\nresults were compared against the calculated values of the models. As demonstrated by the results, a better spray\nperformance can be achieved by the blended fuel than diesel and hydrogenated catalytic biodiesel. In respect of spray penetration,\nthere is almost no difference among the three fuels under the ambient temperature of 323 K. Nevertheless, the blended fuel is lower\nthan that of hydrogenated catalytic biodiesel and diesel when the ambient temperature is 434 K and 523 K. Moreover, the blended\nfuel is the first to reach the stable state, and the hydrogenated catalytic biodiesel is earlier than diesel for the spray penetration.\nMeanwhile, the spray model is identified as suitable for the blended fuel....
Combustion instabilities in a small MMH/NTO liquid rocket engine used for satellite attitude and course control are numerically\ninvestigated. A three-dimensional Navier-Stokes code is developed to simulate two-phase spray combustion for cases with five\ndifferent droplet Sauter Mean Diameters. As the droplet size increases from 30 microns to 80 microns, pressure oscillations are\nstronger with larger amplitudes. But an increase of the droplet size in the range of 80 microns to 140 microns indicates a\nreduction in the amplitudes of pressure oscillations. This trend is the same as the Hewitt criterion. The first tangential (1T)\nmode and the first longitudinal (1L) mode self-excited combustion instabilities are captured in the 60-micron and 80-micron\ncases. Abrupt spikes occur in the mass fraction of MMH and coincide with abrupt spikes in the mass fraction of NTO at the\ndownstream regions just adjacent to the impinging points. Thus, local combustible high-dense mixtures are formed, which\nresult in quasiconstant volume combustion and abrupt pressure spikes. The propagation and reflection of pressure waves in\nthe chamber stimulate the combustion instability. When the droplet size is too small or too large, it is difficult to form local\nhigh-dense premixtures and combustion is stable in the chamber....
In order to reduce the nitrogen oxide emission of cement plant, the denitrification of decomposing furnace is studied in this paper.\nBased on Fluent software platform, the 2500 t/d new dry-process cement kiln decomposing furnace of a plant is modeled and\nsimulated by using air fractional combustion technology combined with selective noncatalytic reduction technology. The model\nand simulation methods are verified by the field test. The effects of the urea injection position and ammonia-nitrogen molar ratio\non NO, NH3, and denitrification efficiency are studied by numerical simulation. The results show that the optimal injection\nposition of the urea solution is 12 m, the optimal ammonia/nitrogen molar ratio is 1.8, and the optimal injection velocity of the\nurea solution is 40 m/s. The simulation results obtained under the optimal parameters are as follows: NO concentration is\n187.60 mg/m3, NH3 escape is 32.40 mg/m3, and denitrification efficiency is 74.75%....
Talc is a popular filler for the fabrication of plastic composites. The presence of talc helps improve mechanical, thermal, and flame\nresistance properties of the composite. In this work, we report the influence of a talc-filled plastic shell layer on thermal stability and\nfire flammability of the core-shell structured wood high-density polyethylene (HDPE) composites manufactured through\ncoextrusion. The result showed that morphological analysis of the char layer after combustion confirmed the formation of a\ncontinuous surface char layer with talc addition in the composites, helping block fire penetration and enhance overall fire\nresistance of the composites. The shell thickness averaged at......................
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