Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 5 Articles
The effects of postinjection with late partially premixed charge compression ignition (PCCI) were investigated with respect to\r\ndiesel exhaust gas conditioning and potential power production. Initial tests comparing postinjection application with PCCI to\r\nthat with conventional diesel high temperature combustion (HTC) indicated the existence of similar trends in terms of carbon\r\nmonoxide (CO), total unburned hydrocarbon (THC), oxides of nitrogen (NOx), and smoke emissions. However, postinjection in\r\nPCCI cycles exhibited lower NOx and smoke but higher CO and THC emissions.With PCCI operation, the use of postinjection\r\nshowed much weaker ability for raising the exhaust gas temperature compared to HTC. Additional PCCI investigations generally\r\nshowed increasing CO and THC, relatively constantNOx, and decreasing smoke emissions, as the postinjection was shifted further\r\nfrom top dead center (TDC). Decreasing the overall air-to-fuel ratio resulted in increased hydrogen content levels but at the cost\r\nof increased smoke, THC and CO emissions. The power production capabilities of early postinjection, combined with PCCI, were\r\ninvestigated and the results showed potential for early postinjection power production....
Canola methyl ester (CME) is a biofuel that is a renewable alternative energy resource and is produced by the transesterification\r\nof canola oil. The objective of this study was to document the effects of turbulence on the combustion characteristics of blends\r\nof CME and No 2 diesel fuel in a partially-premixed flame environment. The experiments were conducted with mixtures of prevaporized\r\nfuel and air at an initial equivalence ratio of 7 and three burner exit Reynolds numbers, 2700, 3600, and 4500. Three\r\nblends with 25, 50, and 75% volume concentration of CME were studied. The soot volume fraction was highest for the pure diesel\r\nflames and did not change significantly with Reynolds number due to themutually compensating effects of increased carbon input\r\nrate and increased air entrainment as the Reynolds number was increased. The global NOx emission index was highest and the\r\nCO emission index was the lowest for the pure CME flame, and varied non-monotonically with biofuel content in the blend The\r\nmean temperature and the NOx concentration at three-quarter flame height were generally correlated, indicating that the thermal\r\nmechanism of NOx formation was dominant in the turbulent biofuel flames also....
Numerical simulation can be key to the understanding of themultidimensional nature of transient detonation waves.However, the\r\naccurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes\r\na successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme\r\nand the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into themethod to allow\r\nfor embedded geometrically complex boundaries. Large-scale parallel simulations of unstable detonation structures of Chapman-\r\nJouguet detonations in low-pressure hydrogen-oxygen-argon mixtures demonstrate the efficiency of the described techniques in\r\npractice. In particular, computations of regular cellular structures in two and three space dimensions and their development under\r\ntransient conditions, that is, under diffraction and for propagation through bends are presented. Some of the observed patterns\r\nare classified by shock polar analysis, and a diagram of the transition boundaries between possible Mach reflection structures is\r\nconstructed....
Vortices are almost always present in the wildland fire environment and can sometimes interact with the fire in unpredictable ways,\r\ncausing extreme fire behavior and safety concerns. In this paper, the current state of knowledge of the interaction of wildland fire\r\nand vortices is examined and reviewed. A basic introduction to vorticity is given, and the two common vortex forms in wildland\r\nfire are analyzed: fire whirls and horizontal roll vortices. Attention is given to mechanisms of formation and growth and how this\r\ninformation can be used by firefighters....
The performance of a spark ignition engine is investigated under different values of ignition advance. A two-zone burnt/unburned\r\nmodel with the fuel burning rate described by aWiebe function is used formodeling in-cylinder combustion, and then experiments\r\nare carried out to validate the calculated data. By varying the ignition timing, the results of some characteristics such as power,\r\ntorque, thermal efficiency, pressure, and heat release are obtained and compared. The results show that optimal power and torque\r\nare achieved at 31?CA before top dead center, and performance is decreased if this ignition timing is changed. It is also shown that\r\nthe maximum thermal efficiency is accomplished when peak pressure occurs between 5 and 15?CA after top dead center....
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