Combustion channel

Daou, J. and Matalon, M., Influence of conductive heat-losses on the propagation of premixed flames in channels, Combust. Flame, 128 321, 2002. 

The relation A, fc-1 means that the cell shape depends on a only, and not on the wavelength. In order to compare this result with the channel combustion problem, we assume that k = 1, and then obtain the amplitude of the curved flame corresponding to the channel width 2ir. 

Channel black n. Form of carbon black made from natural gas by the channel combustion process. The gas is burned with insufficient air in jets, and the flames are allowed to impinge on a cool, channeled metallic surface. The deposited carbon is then scraped from the channel after a certain period of burning. Because of air pollution control requirements, this type of black has been almost completely replaced by Furnace Black in the USA. 

Pizza G, Prouzakis CE, MantzarasJ, Tomboulides AG, Boulouchos K Dynamics ofpre-mixed hydrogen/air flames in mesoscale channels. Combust Flame 155 2—20, 2008b. 

The lack of a detailed surface reaction mechanism for propane/air combustion on platinum necessitated the use of a global-step reaction model in this work. Secondary hetero-Zhomogeneous chemistry interactions are not taken into account this way (such as the homogeneous conversion of C3Hg to CO and the subsequent conversion of the latter to CO2 on the catalytic surface) a closer-to-reahty description of the in-channel combustion processes in catalytic microreactors is thus not possible. While the impact of such a simplification in cases where total oxidation of the fuel is required is minimal, this does not hold true in catalytic partial oxidation applications. Therein, a detailed surface chemistry description would be necessary. 

WulffProcess. The regenerative technique is best exemplified by the Wulff process, Hcensed by Union Carbide Corp. The furnace consists basically of two masses of high purity alumina refractory tile having cylindrical channels for gas flow and separated by a central combustion space as shown in Figure 10. Its cychc operation has four distinct steps, each of approximately 1 min in duration, the sequence being pyrolysis and heat in one direction followed by pyrolysis and heat in the other direction. Continuity of output is achieved by paired installations. 

At the high temperatures found in MHD combustors, nitrogen oxides, NO, are formed primarily by gas-phase reactions, rather than from fuel-bound nitrogen. The principal constituent is nitric oxide [10102-43-9] NO, and the amount formed is generally limited by kinetics. Equilibrium values are reached only at very high temperatures. NO decomposes as the gas cools, at a rate which decreases with temperature. If the combustion gas cools too rapidly after the MHD channel the NO has insufficient time to decompose and excessive amounts can be released to the atmosphere. Below about 1800 K there is essentially no thermal decomposition of NO. 

The oil-fiimace process, based on the partial combustion of Hquid aromatic residual hydrocarbons, was first introduced in the United States at the end of World War II. It rapidly displaced the then dominant channel (impingement) and gas-furnace processes because it gave improved yields and better product quahties. It was also independent of the geographical source of raw materials, a limitation on the channel process and other processes dependent on natural gas, making possible the worldwide location of manufacturing closer to the tire customers. Environmentally it favored elimination of particulate air pollution and was more versatile than all other competing processes. 

Several investigations were performed in channels (Table 4.5). In experiments in which the channel was completely confined, flame speed enhancements were similar to those observed in tubes. In experiments in which channels were open on top, thus allowing combustion products to vent, far lower flame speeds were measured. Partially opening one side of a channel permitted varying degrees of confinement. 

TABLE 4.5. Overview of Test Results on Deflagrative Combustion of Fuel-Air Clouds in Channels... 

Elsworth et al. (1983) report experiments performed in an open-topped channel 52 m long x 5 m high whose width was variable from 1 to 3 m. Experiments were performed with propane, both premixed as vapor and after a realistic spill of liquid within the channel. In some of the premixed combustion tests, baffles 1-2 m high were inserted into the bottom of the channel. Ignition of the propane-air mixtures revealed typical flame speeds of 4 m/s for the spill tests, and maximum flame speeds of 12.3 m/s in the premixed combustion tests. Pressure transducers recorded strong oscillations, but no quasi-static ovetpressure. 

The channel experiments produced results similar to those from tubes. Introduction of venting (decrease of the degree of confinement) greatly reduces effectiveness of the positive-feedback mechanism. Obstacles appear to enhance the combustion rate considerably. 

J. Kim and J. S. Kim, Modelling of lifted turbulent diffusion flames in a channel mixing layer by the flame hole dynamics. Combust. Theory Model. 10 21-37, 2006. 

The propagation of premixed flames in closed vessels has been a subject of combustion research since its inception as a defined field of study in the late 1800s, when Mallard and LeChatelier [1] explored the behavior of explosions in the tunnels of coal mines. In the early decades of the twentieth century, experimenters used streak cameras to monitor the progress of premixed flame fronts propagating in tubes and channels without... 

Teodorezyk, A., Lee, J.H.S., and Knystautas, R., The structure of fast turbulent flames in very rough, obstacle-filled channels. Proc. Combust. Inst., 23, 735,1990. 

Gamezo, V.N., Ogawa, T. and Oran, E.S., Numerical simulations of flame propagation and DDT in obstructed channels filled with hydrogen-air mixture, Proc. Combust. Inst., 31, 2463,2007. 

V.N. Gamezo, T. Ogawa, and E.S. Oran, Flame acceleration and ddt in channels with obstacles Effect of obstacle spacing. Combust. Flame, published online July 2008. 

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