Current Issue : April - June Volume : 2013 Issue Number : 2 Articles : 5 Articles
Two-dimensional kinetic simulation has been carried out to investigate the effects of repetition rate and pulse width of nanosecond\r\nrepetitively pulsed discharges on stabilizing premixed lean methane-air combustion. The repetition rate and pulse width are varied\r\nfrom 10 kHz to 50 kHz and from 9 ns to 2 ns while the total power is kept constant. The lower repetition rates provide larger\r\namounts of radicals such as O, H, and OH. However, the effect on stabilization is found to be the same for all of the tested\r\nrepetition rates. The shorter pulse width is found to favor the production of species in higher electronic states, but the varying\r\neffects on stabilization are also found to be small. Our results indicate that the total deposited power is the critical element that\r\ndetermines the extent of stabilization over this range of discharge properties studied....
This work aims at demonstrating the feasibility of replacing Indonesian coal (INC) with hydrothermally treated municipal solid\r\nwaste (MSWH) in cocombustion with high ash Indian coal (IC). The combustion efficiencies and emissions (CO, NO) of MSWH,\r\nINC and their blends with IC for a series of tests performed under a range of temperatures and air conditions were tested in a droptube\r\nreactor (DTR). The results showed the following. The combustion efficiency of IC was increased by blending both MSWH\r\nand INC and CO emission was reduced with increasing temperature. For NO emission, the blending of MSWH led to the increase\r\nof NO concentration whereas the effects of INC depended on the temperature. The combustion behaviors of IC-MSWH blend\r\nwere comparable to those of the IC-INC blend indicating it is possible for MSWH to become a good substitute for INC supporting\r\nIC combustion. Moreover, the CO emission fell while the NO emission rose with increasing excess air for IC-MSWH blend at\r\n900?C and the highest combustion efficiency was obtained at the excess air of 1.9. The existence of moisture in the cocombustion\r\nsystem of IC-MSWH blend could slightly improve the combustion efficiency, reduce CO, and increase NO....
Biomass, in form of residues and waste, can be used to produce energy with low environmental impact. It is important to use the\r\nfeedstock close to the places where waste are available, and with the shortest conversion pathway, to maximize the process efficiency.\r\nIn particular waste vegetable oil and the organic fraction of municipal solid waste represent a good source for fuel production in\r\nurban areas. Dual fuel engines could be taken into consideration for an efficient management of these wastes. In fact, the dual fuel\r\ntechnology can achieve overall efficiencies typical of diesel engines with a cleaner exhaust emission. In this paper the feasibility of\r\na cogeneration system fuelled with waste vegetable oil and biogas is discussed and the evaluation of performance and emissions\r\nis reported on the base of experimental activities on dual fuel heavy duty engine in comparison with diesel and spark ignition\r\nengines. The ratio of biogas potential from MSW and biodiesel potential from waste vegetable oil was estimated and it results\r\nsuitable for dual fuel fuelling. An electric power installation of 70kW every 10,000 people could be achieved....
Many practical combustion systems such as residential gas burners contain dense groupings or clusters of jet flames with\r\nsufficiently small spacing between them, which causes flame interaction. The interaction effect, due in part to Oxygen deficiency\r\nin the interstitial space between the flames, causes the spreading of flames, which may merge together to form larger group flames.\r\nThis interactive effect is studied analytically by revisiting the laminar isolated flame theory for 2D jets, for which similarity solutions\r\nare readily available in compressible form, and symmetrical interaction zones can be observed. Flame characteristics were studied\r\nby obtaining analytical expressions for flame specific parameters such as height and width, lift-off height and blow-off velocity, air\r\nentrainment and mixing layer growth. The theory for multiple interacting jets describes an approximate criterion for interburner\r\nspacing at which flame interaction and group flame formation are first observed. The analytical framework presented in this paper\r\npresented in this paper produced results which were compared with experimental measurements. The experimental apparatus\r\nallowed the interburner spacing to be varied from 7.87mm to 50.8 mm, and measurements of flame height, width, lift-off height\r\nand group-flame formation under interactive modes. Images of the evolving flow field were taken and Schlieren images of the\r\nmultiple 2D jets were also recorded using a digital camera....
The work presents the assessment of a low emissions premixer/swirl burner configuration utilizing lean stratified fuel preparation.\r\nAn axisymmetric, single- or double-cavity premixer, formed along one, two, or three concentric disks promotes propane-air\r\npremixing and supplies the combustion zone at the afterbody disk recirculation with a radial equivalence ratio gradient. The burner\r\nassemblies are operated with a swirl co-flow to study the interaction of the recirculating stratified flame with the surrounding\r\nswirl. A number of lean and ultra-lean flames operated either with a plane disk stabilizer or with one or two premixing cavity\r\narrangements were evaluated over a range of inlet mixture conditions. The influence of the variation of the imposed swirl was\r\nstudied for constant fuel injections.Measurements of turbulent velocities, temperatures, OH* chemiluminescence and gas analysis\r\nprovided information on the performance of each burner set up. Comparisons with Large Eddy Simulations, performed with\r\nan 11-step global chemistry, illustrated the flame front interaction with the vortex formation region under the influence of the\r\nvariable inlet mixture stratifications. The combined effort contributed to the identification of optimum configurations in terms\r\nof fuel consumption and pollutants emissions and to the delineation of important controlling parameters and limiting fuel-air\r\nmixing conditions....
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