摘要:

A multidimensional model is used to study the penetration of the liquid fuel in a constant volume chamber under normal Diesel engine conditions. Comparisons of the liquid fuel penetration as predicted by the model with results from recent experiments show inadequate agreement but, more importantly, a sensitivity to the numerical resolution. A possible origin of this sensitivity is identified through a series of systematic studies of the different components of the spray model. These studies show that the sensitivity of the liquid penetration to the numerical resolution may be related to a dependence of the computed Sauter Mean Radius (SMR) of the drops on the grid resolution. A detailed study of this dependence relates it to the non-uniformity of the spatial distribution of drops in the chamber, in particular, within about 100 diameters of the injector orifice. This non-uniformity leads to the estimate of different number densities and, hence, different collision frequencies, on different grids. The non-uniformity of drop distribution is shown to be a function of time during the transient injection process and dependent on the vaporization rate. The work also leads to a conclusion about the possible size of injected drops in the Diesel spray.

ISSN:0010-2202    

DOI:10.1080/00102209808952070

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Experiments have been performed using a modern heavy-duty direct-injection diesel engine equipped with a common-rail, electronically-controlled high-pressure fuel injection system. The experimental results demonstrate the utility of using multiple or split fuel injections in combination with EGR for giving significant emissions reduction over the entire engine operating range. The mechanisms of emission reduction have been revealed by means of combustion visualization and CFD modeling. Soot is reduced due to the fact that the soot producing regions at the tip of the sprays are not replenished with fresh fuel when each injection is terminated and then restarted. The large reduction in soot possible with multiple injections allows the use of higher levels of EGR than is possible with single injections, so that NOxcan be reduced significantly while soot levels are simultaneously kept low.

ISSN:0010-2202    

DOI:10.1080/00102209808952071

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The cubic perovskile Lao0.2Sro0.8Cr0.2Fe0.8O3—x, a candidate material for oxygen separating membranes, was synthesized from a mixture of La2O3-SrO2-Cr-Fe-NaClCO4by Self-propagating High-temperature Synthesis (SHS). SrFeO3-xand LaCrO3were the main intermediates and the final composition and morphology was formed by interaction between them. The final structure was a solid solution of Fe and Sr rich oxides and La and Cr rich oxides. Decreasing the reactant particle size increased the homogeneity of the SHS product and increased the velocity of the propagating combustion front. Calcination of the SHS product at 1400°C for 5 hours produced very homogeneous Lao0.2Sro0.8Cr0.2Fe0.8O3—x,. The sinterability of powders made by SHS was better than those prepared by either GNP (glycine-nitrate process) or freeze-drying. A disc prepared from the SHS product by 10 hours calcination at 1400°C had a maximum electrical conductivity of 8.8 S.cm-1at 560°C in a pure oxygen environment, and its oxygen permeability was 3.35 × 10-9mols-1cm-2at 980°C in an oxygen partial pressure gradient from ˜4 × 10-5atm. to 0,2atm.

ISSN:0010-2202    

DOI:10.1080/00102209808952072

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Planar laser-induced fluorescence (PLIF) imaging and planar Mie scattering are used to examine the fuel distribution pattern (patternation) for advanced fuel injector concepts in kerosene burning, high pressure gas turbine combustors. Three fuel injector concepts for aerospace applications were investigated under a broad range of operating conditions. Planar fuel PLIF patternation results are contrasted with those obtained by planar Mie scattering. For one injector, further comparison is also made with data obtained through phase Doppler measurements. Differences in spray patterns for diverse conditions and fuel injector configurations are readily discernible. An examination of the data has shown that a direct determination of the fuel spray angle at realistic conditions is also possible. The results obtained in this study demonstrate the applicability and usefulness of these nonintrusive optical techniques for investigating fuel spray patternation under actual combustor conditions.

ISSN:0010-2202    

DOI:10.1080/00102209808952073

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The evaporation and mixing of kerosine emerging from a flat prefilming airblast atomizer was studied experimentally and numerically in an optical accessible, straight rectangular duct at conditions relevant for lean premixed and prevaponzed combustion. Liquid phase properties were measured by Phase-Doppler anemometry and fuel vapour concentrations were determined by an infrared light extinction technique. Computations were based on the Lagrangian particle tracking technique, and captured the spray features sufficiently well with and without taking into account the spray feedback on the gas field. A degree of evaporation of 95% was measured after l00mm for 9 bar air pressure, 750K air temperature and 120m/s air velocity. No autoignition of the fuel occurred. Parametric variations of pressure, temperature and velocity of the air flow, as well as of the initial temperature of the spray and of fuel loading were conducted. A strong influence of the initial fuel temperature on evaporation was found. The air pressure had mainly an indirect but strong effect through atomization quality.

ISSN:0010-2202    

DOI:10.1080/00102209808952074

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A novel pulverized coal fired burner, called “main burner with double primary air channels for pulverized coal”, is presented in this paper. Such a burner can burn various kinds of coals, including bituminous coal, low grade coal, lignite, semianthracite, anthracite, satisfying stability of combustion, controllability of the ignition location of pulverized coal, high efficiency, and low NOx, emission, thereby eliminating the unstable combustion caused by variation of coal quality and low load operation. It has not only solved the problem of low load operation and the combustion without oil assisting of Jiafu anthracite, which is the most difficult coal to burn in China, but also first successfully conducted the normal combustion in a tangentially pulverized anthracite fired furnace, as in a W-shaped flame furnace. According to the low load test on a tangentially pulverized coal fired furnace of 1025 t/h of anthracite combustion, its stability is superior to that of a W-shaped flame furnace with the same capacity, they will compete with each other in the future in China. This burner has been applied in the furnace of large scale, medium-and small-sized power stations in China, and even taken as finalized design for large tangentially low-volatile pulverized coal fired furnaces in Harbin Boiler Works, the biggest one in China. Also if used in W-shaped flame furnaces, it can further improve their combustion performance and reduce the steel consumption.

ISSN:0010-2202    

DOI:10.1080/00102209808952075

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The experiments simulating events taking place during multizone combustion of fibrous deinking byproduct generated in pulp and paper mill were conducted. The multizone heating consisted of the low-temperature region (< 1000°C), followed by the high-temperature zone (1500°C), and a second low-temperature region (« 1000°C) proceeded by sudden quenching. The simulation of such Low-High-Low temperature process (LHL) was conducted in a high-temperature Cahn TG-171 thermogravimetric furnace coupled with a Mattson Galaxy 5020 Fourier transform infrared spectrometer. Morphological changes of the fibrous byproduct, from a mixture of fibers through sintered particles formed between 1100 and 1400°C and molten ash particles observed above 1400°C, caused encapsulation and immobilization of heavy metals (Cd, Cu, Pb) within the ash. It was also found that the temperature-time history and CH:OH ratio are important physical/chemical parameters affecting the polycyclic aromatic compounds (PACs) formation. The PACs destruction occurred during the LHL process before PACs were emitted into the atmosphere. It seems that the multizone burning may be an attractive way for the clean and efficient disposal of contaminated industrial byproducts.

ISSN:0010-2202    

DOI:10.1080/00102209808952076

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Plastic waste is increasing every year. Gasification is one of many chemical recycling technologies. The authors carried out basic gasification tests on polyethylene. To produce a tar and soot free synthetic gas composed mainly of hydrogen and carbon monoxide which is a feed source for methanol fuel production, polyethylene pellets are gasified in the presence of oxygen and steam. The first step of the gasification process produces a soot-free gas with “tar”, the second step of the gasification process decomposes the "tar" produced in the first step. As a result, this closed, coupled two step gasification process has proven to be a tar and soot free gasification technology for plastic wastes.

ISSN:0010-2202    

DOI:10.1080/00102209808952077

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor