Effect of preheating on liquid fuel evaporation on combustion in a model combustion chamber

A combustion model for a sprayed liquid fuel is developed, starting from the assumption that combustion of an individual drop is impossible, and the droplets are completely entrained in the moving medium. The model gives the a flame length close to that observed experimentally. It is established that the preheat time of the droplet is roughly the same as its evaporation time, and the temperature change in the air basically affects the droplet preheating and only weakly affects the droplet evaporation.Moscow. Translated from Fizika Goreniya i Vzryva, Vol. 27, No. 6, pp. 45–52, November–December, 1991.     

Effect of thrust on supersonic gas jet penetration in gas-solid fluidized beds

Most of the jet penetration studies in gas-solid fluidized beds are for subsonic gas jets, for which many correlations can be found in the literature. In this work, horizontal supersonic gas jets, produced by convergent-divergent nozzles, have been studied, and the intent was to investigate the relationship between the thrust produced by supersonic nozzles and the jet penetration. Different nozzle geometries were used, with three gases having different characteristics (air, helium and carbon dioxide) and at different pressures. All the experimental runs were performed with silica sand particles with the same particle size distribution, and the fluidization velocity was set at a constant value of 0.09 m/s.Jet penetration was measured with a set of triboelectric probes, and it was found that the correlation proposed by Merry, although originally developed for subsonic gas jets, fits really well the experimental results. It was also confirmed that jet penetration displays a strong correlation with the thrust produced by the convergent-divergent nozzles.A correlation originally proposed by Benjelloun's has been modified and the corrected correlation gives the best predictions for gas jet penetration     

煤粉燃烧室改烧混合煤的技术措施

我厂窑外分解窑和立波尔窑采用烟煤与无烟煤比例为３０％∶７０％的混合煤，这种煤的挥发分为８％～１２％、灰分为２０％～２４％、细度为２％～５％、水分＜３．５％、着火温度约６００℃。３台Φ３．５m×１０m中卸烘干生料磨配套的３个煤粉燃烧室仍然只能烧烟煤，每天２号煤磨（Φ２．２m×４．４m）要为此专门开机４h左右。如果燃烧室也烧混合煤，既可以节省每吨烟煤与无烟煤近９０元的差价，也可以停开２号煤磨。燃烧室所用煤计划与立波尔窑所用混合煤一样，由１号风扫煤磨（Φ２．８m×８m）磨制。本着尽可能节省投资的原则，我们采…     

Combustion of kerosene in a supersonic stream

Experiments on the organization of the combustion of kerosene in high-enthalpy supersonic air streams is analyzed. The use of promotor additives, as well as improvements in the atomization process, vaporization, and mixing, do not always facilitate efficient combustion development. The existence of a conversion process is found to have a significant effect on the ignition parameters. The burnup intensity can be ensured by adding hydrogen, and the relative position of the fuel injectors is important in that case. The fundamental role of wave structures in determining the length of the combustion zone in the channel is noted. The integral characteristics of combustion for hydrogen and kerosene are compared. Translated fromFizika Goreniya i Vzryva Vol. 35, No. 3, pp. 35–42, May–June 1999.     

Effect of fuel particle size on reaction rate in chemical looping combustion

Chemical looping combustion (CLC) uses an oxygen carrier circulating between an air and a fuel reactor to replace direct burning of fuels in air. The very low energy penalty for CO₂ separation in CLC gives it the potential to become an important technology on the way to a CO₂ neutral energy supply. In this work, the influence of the particle size of coal on the rate of reaction of the coal was investigated in a bed of oxygen carrier. In order to do this, a method to quench the reaction of coal with oxygen carriers at a specified time and measure the particle size distribution of the remaining coal was developed. Three size fractions of coal were used in the experiments: 90–125, 180–212 and 250–355 μm. Particle size distributions of the fuel show a decrease in particle size with time. The influence of devolatilisation of the coal on the coal particle size was measured, showing that coal particles do not break in the fluidized bed reactor used for the experiments. Reaction rates based on measurements of gas phase concentrations of CO₂, CO and CH₄ showed that the reaction rate is independent of the particle size. These results are in line with literature findings, as studies have shown that carbon gasification is size-independent at conditions similar to those in the performed CLC experiments.     

Effect of secondary mixing on fuel ignition and combustion in a diesel engine

The possibility of improving air-fuel mixture ignition by optimal contouring of the wall on which the jet is incident is confirmed. It is also shown that a decrease in the limiting temperature and in the ignition delay leads, in turn, to an increase in fuel-combustion efficiency, which ensures faster stabilization of engine operation after starting. Under diesel-engine nominal rating conditions, secondary mixing no longer has a profound effect on ignition and combustion processes. Institute of Theoretical and Applied Mechanics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 1, pp. 33–42, January–February, 1997     

Effect of the configuration of the rear wall of the cavity on combustion in a supersonic combustor

Results of an experimental study of a supersonic combustor with a solid (continuous) and discrete (discontinuous) rear wall of the cavity are reported. The tests are performed in a short-duration wind tunnel with an attached pipeline at the entrance Mach number of 3, total temperatures of 2550–3140 K, and static pressures of 178–195 kPa. Heated kerosene is used as a fuel. Data on ignition conditions and kerosene combustion efficiency are obtained for different cavity configurations. The drag of internal elements of the combustor, which form recess stabilizers, is estimated. An overall advantage of the combustor with a discrete rear wall of the cavity over a solid rear wall is demonstrated.     

Consideration of crystal structure defectiveness of a powder fuel carbon component in the combustion chamber of a plasma generator

A physicomathematical model and results are presented for numerical studies of gas temperature, plasma electrical conductivity, the Young's modulus of the microflame around aluminum particles, and also the completeness of carbon component combustion for a powder fuel in poly-and monodispersed approximations with movement of a two-phase mixture in a plasma generator combustion chamber. The level of the effect of considering crystal structure defectiveness for carbon particles on the change in these values is established, and it is also shown that under plasma generator conditions of the poly-dispersed model is less sensitive to the model selected for carbon particle combustion.NIIPMM, Tomsk State University, Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 1, pp. 31–36, January–February, 1994.