Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 4 Articles
The work presents comparisons of the flame stabilization characteristics of axisymmetric disk and 2D slender bluff-body burner\r\nconfigurations, operating with inlet mixture stratification, under ultralean conditions.Adouble cavity propane air premixer formed\r\nalong three concentric disks, supplied with a radial equivalence ratio gradient the afterbody disk recirculation, where the first flame\r\nconfiguration is stabilized. Planar fuel injection along the center plane of the leading face of a slender square cylinder against the\r\napproach cross-flow results in a stratified flame configuration stabilized alongside the wake formation region in the second setup.\r\nMeasurements of velocities, temperatures, OH* and CH* chemiluminescence, local extinction criteria, and large-eddy simulations\r\nare employed to examine a range of ultralean and close to extinction flameconditions.Thevariations of the reacting front disposition\r\nwithin these diverse reacting wake topologies, the effect of the successive suppression of heat release on the near flame region\r\ncharacteristics, and the reemergence of large-scale vortical activity on approach to lean blowoff (LBO) are investigated. The crosscorrelation\r\nof the performance of these two popular flame holders that are at the opposite ends of current applications might\r\noffer helpful insights into more effective control measures for expanding the operational margin of a wider range of stabilization\r\nconfigurations....
The heat release process in a free volume combustion chamber and in porous reactors has been analyzed under Diesel engine-like\r\nconditions. The process has been investigated in a wide range of initial pressures and temperatures simulating engine conditions at\r\nthe moment when fuel injection starts. The resulting pressure history in both porous reactors and in free volumes significantly\r\ndepends on the initial pressure and temperature. At lower initial temperatures, the process in porous reactors is accelerated.\r\nCombustion in a porous reactor is characterized by heat accumulation in the solid phase of the porous structure and results in\r\nreduced pressure peaks and lowered combustion temperature.This depends on reactor heat capacity, pore density, specific surface\r\narea, pore structure, and heat transport properties. Characteristic modes of a heat release process in a two-dimensional field of\r\ninitial pressure and temperature have been selected. There are three characteristic regions represented by a single- and multistep\r\noxidation process (with two or three slopes in the reaction curve) and characteristic delay time distribution has been selected in five\r\ncharacteristic ranges. There is a clear qualitative similarity of characteristic modes of the heat release process in a free volume and\r\nin porous reactors. A quantitative influence of porous reactor features (heat capacity, pore density, pore structure, specific surface\r\narea, and fuel distribution in the reactor volume) has been clearly indicated....
Engine and car manufacturers are experiencing the demand concerning fuel efficiency and low emissions from both consumers\r\nand governments. Homogeneous charge compression ignition (HCCI) is an alternative combustion technology that is cleaner and\r\nmore efficient than the other types of combustion. Although the thermal efficiency andNO?? emission ofHCCI engine are greater in\r\ncomparison with traditional engines, HCCI combustion has several main difficulties such as controlling of ignition timing, limited\r\npower output, and weak cold-start capability. In this study a literature review on HCCI engine has been performed and HCCI\r\nchallenges and proposed solutions have been investigated from the point view of Ignition Timing that is the main problem of this\r\nengine. HCCI challenges are investigated by many IC engine researchers during the last decade, but practical solutions have not\r\nbeen presented for a fully HCCI engine. Some of the solutions are slow response time and some of them are technically difficult to\r\nimplement. So it seems that fully HCCI engine needs more investigation to meet its mass-production and the future research and\r\napplication should be considered as part of an effort to achieve low-temperature combustion in a wide range of operating conditions\r\nin an IC engine....
Thebasic problems of application of detonation process in propulsion systemswith impulse and continuous burning of combustible\r\nmixture are discussed.The results on propagation of detonation waves in supersonic flow are analyzed relatively to air-breathing\r\nengine. The experimental results are presented showing the basic possibility of creation of an engine with exterior detonation\r\nburning. The base results on optimization of initiation in impulse detonation engine are explained at the expense of spatial and\r\ntemporal redistribution of an energy, entered into a mixture. The method and technique for construction of highly effective\r\naccelerators for deflagration to detonation transition are discussed also....
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