Radiative combustion of pyrolyzing fuel in a cylindrical combustor

Investigation on ignition and flame propagation of pyrolyzing fuel in a cylindrical combustor is accomplished. The pyrolyzing fuel of cylindrical shape is concentrically located in a combustor sustained at high temperature. Due to gravity, the buoyancy motion is inevitably incurred in the combustor and this affects the flame initiation and propagation behavior. The radiative heat transfer due to absorption gas plays an important role since it absorbs and emits radiative energy. Numerical studies have been performed over various parameters relevant to gas radiation as well as overheat ratios. The ignition criterion is decided on experimental basis. For the case of relatively small overheat ratio, the gas absorption reduces the flow intensity by the far-reaching effect of radiation. Visible blue flame hence does not evolve. For a high overheat ratio, the strong visible blue flame is generated and self-propagates. The gas radiation makes the considerable effect on ignition delay and flame thickness as well as thermal and reactive nature of visible blue flame.     

Modeling of unsteady filtration gas combustion

Unsteady filtration gas combustion with various gas flow parameters is studied by mathematical modeling. Transition processes due to a sudden change in the calorific value of the gas mixture, gas flow velocity, and flow direction are considered. Trends and mechanisms of change in the structure of the filtration gas combustion wave and its propagation velocity are analyzed for various types of transition processes. It is found that with a sudden change in gas flow parameters, the flame can abruptly move large distances in the porous medium. Subsequently, at the new flame localization, a wave of filtration gas combustion forms which corresponds to the changed parameters of the gas flow. If in the porous medium, the amount of heat is insufficient, the transition process ends with quenching. As the gas flow direction changes, the combustion wave continues to propagate in the former direction for some time, which can lead to the spread of the high-temperature zone in devices based on the reverse process with a homogeneous gas-phase reaction.     

Method of calculating the bed combustion of a solid fuel coke residue

An approximate method of solving the steady-state problem of the bed combustion of a solid fuel coke residue is proposed. The method is based on splitting the initial problem into thermal and chemical problems. The former represents the problem on the hydrodynamics and heat transfer in a blown heat-generating granular bed. The latter is the problem on the chemical conversion of a mixture of reactants in a specified temperature field. These auxiliary problems are combined into an iteration cycle to match their solutions. The model problem on the combustion of a milled peat coke residue was calculated for the cocurrent and countercurrent process schemes. The bed combustion of coke is calculated for the experimental conditions published in the literature. The calculated results are compared with the experimental data obtained under these conditions.     

Neutron-radioisotope monitoring of the heat of combustion of solid fuel

A radioisotope method is proposed for determining the heat of combustion of coal. This method is based on recording of the ?? radiation associated with the inelastic scattering of fast neutrons and the radiative capture of thermal neutrons by elements in the fuel.     

Change in the structure of the filtration combustion wave due to a fuel composition change

Transition processes due to a sharp change in the amount of fuel in carbon/inert material mixtures in a filtration combustion wave with superadiabatic heating were studied theoretically and experimentally. It was found that transition from a lean mixture to a rich mixture, in which the thermal wave changes structure from normal to inverse, was accompanied by significant local heating, whereas in the reverse change in the composition, a temperature increase was not observed.     

Modeling the structure of composite solid rocket fuel

Results are reported on the creation of a model for the structure of a composite solid rocket fuel in terms of such concepts as “pockets” and “interpocket bridges.” Appropriate model calculations and experimental data are presented, and the possibility of using the model for predicting the characteristics of the combustion process is pointed out. Translated fromFizika Goreniya i Vzryva Vol. 35, No. 2, pp. 35–40, Mach–April 1999.     

Steady combustion of solid fuel gas-suspensions. Laminar diffusion two-phase flame

Odessa. Translated from Fizika Goreniya Vzryva, Vol. 26, No. 6, 54–62, November–December, 1990.     

Theory of filtration combustion

Combustion, Explosion, and Shock Waves -     

The application of a multistage-bed model for residence-time analysis in chemical-looping combustion of solid fuel

The behavior of a 10 kW chemical-looping combustor for solid fuels, normally operated in continuous mode, has been studied by addition of fuel batches. From analysis of gas leaving the air reactor, it was possible to determine the residence time and residence-time distribution of particles in the fuel reactor. Knowing the solids inventory in the fuel reactor, the circulation mass flow could be directly correlated to measured operational data, i.e. pressure drop, temperature and gas flow in air reactor riser. Using results for carbon-capture efficiency and residence-time distribution, a model was developed which could determine a mass-based reaction-rate constant for char conversion. The reaction-rate constant of a Mexican petroleum coke at both 950 and 970 °C was calculated to 8.2 and 28.8 wt%/min, respectively. The reaction-rate constant of a South African coal at 950 °C was calculated to 26.1 wt%/min. This reaction-rate constant could also be determined independently from the conversion rates of char during the batch tests. The results showed a good agreement between the two approaches, indicating that the model well describes the behavior of the unit. From the determination of the circulation mass flow, and comparison with previous testing with different circulation, it was also possible to estimate the limit for which the ilmenite was unable to supply sufficient oxygen to achieve good conversion. This limit was compared to theoretical limits for ilmenite as well as the limit set by a heat balance. It was concluded that the latter will be the one setting the limit.     

双燃料燃烧炉在固碱生产中的应用

针对天然气与电石炉气成分及热值的差异,对固碱生产装置中燃烧炉炉头、工艺配管、控制系统、风机及安全装置等进行了技术改造,实现了天然气一电石炉气双燃料燃烧炉的正常运行。     

Modeling of multi-component fuel vaporization and combustion for gasoline and diesel spray

The present study applied a continuous thermodynamics approach to consider the multi-component nature of petroleum fuels during the vaporization process. A gamma distribution was used to describe the molecular weight of the fuel. The model was first used to study the vaporization of single diesel and gasoline drops. Results showed that the mean molecular weight of the fuel drop kept increasing, indicating that the lighter components vaporized earlier in the process. The present vaporization model was also integrated with an engine simulation code for diesel spray combustion study. Results of diesel spray modeling showed that heavy fuel components survived during the early vaporization process such that the drops in the outer regions of the spray were mostly composed of heavier components. In this study, detailed chemistry was used for diesel combustion modeling. Results showed that good levels of agreement between experiments and predictions were obtained in flame structures and soot distributions. Effects of ambient temperature in the sooting tendency of diesel spray were also predicted by the present model. Under the conditions studied , soot emissions were not seen for ambient temperature less than 850 K, which is consistent with the concept of low-temperature engine combustion for low emissions.