Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 6 Articles
Concentrated animal feeding operations such as dairies produce a large amount of manure, termed as dairy biomass (DB), which\r\ncould serve as renewable feedstock for thermal gasification. DB is a low-quality fuel compared to fossil fuels, and hence the product\r\ngases have lower heat content; however, the quality of gases can be improved by blending with coals. This paper deals with air-steam\r\nfixed-bed counterflow gasification of dairy biomass-Wyoming coal blend (DBWC). The effects of equivalence ratio (1.6 < F < 6.4)\r\nand steam-to-fuel ratio (0.4 < S : F < 0.8) on peak temperatures, gas composition, gross heating value of the products, and energy\r\nrecovery are presented. According to experimental results, increasing F and (S : F) ratios decreases the peak temperature and\r\nincreases the H2 and CO2 production, while CO production decreases. On the other hand, the concentrations of CH4 and C2H6\r\nwere lower compared to those of other gases and almost not affected by F....
A 28-species reduced chemistry mechanism for Dimethyl Ether (DME) combustion is developed on the basis of a recent detailed\r\nmechanism by Zhao et al. (2008). The construction of reduced chemistry was carried out with automatic algorithms incorporating\r\nnewly developed strategies. The performance of the reduced mechanism is assessed over a wide range of combustion conditions\r\nanticipated to occur in future advanced piston internal combustion engines, such as HCCI, SAHCCI, and PCCI. Overall, the\r\nreduced chemistry gives results in good agreement with those from the detailed mechanism for all the combustion modes tested.\r\nWhile the detailed mechanism by Zhao et al. (2008) shows reasonable agreement with the shock tube autoignition delay data, the\r\ndetailed mechanism requires further improvement in order to better predict HCCI combustion under engine conditions....
The effects of turbulent Reynolds number on the statistical behaviour of the displacement speed have been studied using\r\nthree-dimensional Direct Numerical Simulation of statistically planar turbulent premixed flames. The probability of finding\r\nnegative values of the displacement speed is found to increase with increasing turbulent Reynolds number when the Damk�¨ohler\r\nnumber is held constant. It has been shown that the statistical behaviour of the Surface Density Function, and its strain rate\r\nand curvature dependence, plays a key role in determining the response of the different components of displacement speed.\r\nIncreasing the turbulent Reynolds number is shown to reduce the strength of the correlations between tangential strain rate\r\nand dilatation rate with curvature, although the qualitative nature of the correlations remains unaffected. The dependence\r\nof displacement speed on strain rate and curvature is found to weaken with increasing turbulent Reynolds number when\r\neither Damk�¨ohler or Karlovitz number is held constant, but the qualitative nature of the correlation remains unaltered. The\r\nimplications of turbulent Reynolds number effects in the context of Flame Surface Density (FSD) modelling have also been\r\naddressed, with emphasis on the influence of displacement speed on the curvature and propagation terms in the FSD balance\r\nequation....
The quasi-steady model of the combustion of a fuel droplet has been modified. The approach involved the modification of the\r\nquasi-steady model to reflect the difference in constant properties across the flame front. New methods for accurately estimating\r\ngas constants and for estimating Lewis number are presented. The proposed theoretical model provides results that correlate\r\nfavorably with published experimental results. The proposed theoretical model also eliminates the need for unguided adjustment\r\nof thermal constants or the complex analysis of the variation of thermal properties with temperature and can serve as a basis for\r\nanalysis of other combustion conditions like droplets cloud and convective and high-pressure conditions....
The production of biodiesel has notably increased over the past decade. Currently, plant oil is the main feedstock for biodiesel production,\r\nbut, due to concerns related to the competition with food production, alternative oil feedstocks have to be found. Oleaginous\r\nyeasts are known to produce high amounts of lipids, but no integrated process from microbial fermentation to final biodiesel\r\nproduction has reached commercial realization yet due to economic constraints. Therefore, growth and lipid production of\r\nred yeast Rhodotorula glutinis was tested on low-cost substrates, namely, wastewaters from potato, fruit juice, and lettuce processing.\r\nAdditionally, the production of carotenoids as high-value by-products was examined. All evaluated wastewaters met the\r\ngeneral criteria for microbial lipid production. However, no significant increase in lipid content was observed, probably due to lack\r\nof available carbon in wastewaters from fruit juice and lettuce processing, and excess of available nitrogen in potato processing\r\nwastewater, respectively. During growth on wastewaters from fruit juice and lettuce processing the carotenoid content increased significantly\r\nin the first 48 hours. The relations between carbon content, nitrogen content, and carotenoid production need to be further\r\nassessed. For economic viability, lipid and carotenoid production needs to be increased significantly. The screening of feedstocks\r\nshould be extended to other wastewaters....
The stability limits of a jet flame can play an important role in the design of burners and combustors. This study details an\r\nexperiment conducted to determine the liftoff and blowout velocities of oblique-angle methane jet flames under various air coflow\r\nvelocities. A nozzle was mounted on a telescoping boom to allow for an adjustable burner angle relative to a vertical coflow. Twentyfour\r\nflow configurations were established using six burner nozzle angles and four coflow velocities. Measurements of the fuel\r\nsupply velocity during liftoff and blowout were compared against two parameters: nozzle angle and coflow velocity. The resulting\r\ncorrelations indicated that flames at more oblique angles have a greater upper stability limit and were more resistant to changes\r\nin coflow velocity. This behavior occurs due to a lower effective coflow velocity at angles more oblique to the coflow direction.\r\nAdditionally, stability limits were determined for flames in crossflow and mild counterflow configurations, and a relationship\r\nbetween the liftoff and blowout velocities was observed. For flames in crossflow and counterflow, the stability limits are higher.\r\nFurther studies may include more angle and coflow combinations, as well as the effect of diluents or different fuel types....
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