Fundamental equations are given for gas-solid flows when the effect of compression of the gas is significant. Problems of unsteady propagation of shock waves in the two-phase system are solved numerically. The relaxation nature of the flow induced by the shock wave is investigated. The influence of nonuniformity of particle size on the shock propagation is also discussed.
Many aerosol phenomena such as deposition of aerosol particles on a wall surface and their collection by an obstracle in a stream are related to the instability of aero-colloidal system comparing to hydro-colloidal system. In this article, general features of aerosol phenomena are overviewed for several typical cases and then their theoretical simulation methods are explained.
A forced vortex-type centrifugal air classifier has the advantages of fine cut-size and high classification accuracy. It's capacity for classifying submicron particles attracts attention. Various types of classifiers are on the market. However, the classification mechanism has not been clarified. We describe simulation of particle motion in a classifier. Effects of the initial angular position and circumferential velocity of a particle at injection into the classifier and of capturing accuracy are also discussed, based on results of particle trajectories.
Presently there are many projects in progress to construct large-scale coal-fired power plants and coal centers. Coal consumed at these plants amounts to several million tons per year. Prediction of coal particle dispersion caused by handling large amounts of coal is required to assess environmental impact. This report describes the emission rates from coal storage piles and coal dropping processes, and presents simulation method to predict the dust deposition due to coal handling facilities.
It is important to determine unburnt carbon content and temperature distribution for design and operation of coal fired boiler. A numerical simulation of combustion flows in a coal-fired boiler furnace has been done using Reynolds equations, including solid gas two-phase flow. Gas flow patterns, coal behavior and diameter variation, and distributions of the heat release rate, temperature, and oxygen concentration have been obtained as numerical simulation results. Moreover, it has been made clear that coal trajectory and its diameter effect the heat release rate and unburnt carbon content.
A bubbling-type fluidized bed boiler uses the bed slumping and activation technique for controlling steam output. Because of this unique technique incorporated into the boiler design, the prediction and assessment of boiler performance are required during the initial boiler design stage for achieving a specified boiler operation mode. The intention of this paper is to provide subscribers with current knowledge regarding a computer simulation of boiler load control based on the present author's own experience in developing commercial size bubbling-type fluidized bed boilers. Brief review of the fundamental aspect of fluidized bed boilers is followed by the description of bed slumping and activation operation using a particle mixing model. A representative result of the computed fluidized bed temperature transient during load increase is presented for a large size bubbling fluidized bed boiler. Areas for further research are presented for both bubbling-type and circulating-type fluidized bed boilers.
A numerical three-dimensional simulation model of a fluidized bed refuse incinerator, which is based upon the lateral dispersion model and two-phase model, was developed. Separating refuse into three components, moistrure, ash and combustibles, combus tion characteristic was formulated by estimating the diameter of combustibles, ignition temperature and transition temperature from reaction to diffusion in the controlling region. Temperature distribution of the emulsion phase and oxygen concentration distribution in the fluidized bed from the calculation were compared with data obtained from the experiment. The calculated results coincided well with the experimental results. The method of modeling and basic and experimental equations in this model were confirmed to be accurately applicable to the numerical calculation. Moreover, the relation between the scale of the fluidized bed and the performance of the incinerator was discussed on the basis of simulation by the mathematical model.
Air flow in a pnematic capsule pipeline is numerically simulated by the method of characteristics in each region bounded by capsules and or fixed boundaries such as a pipe inlet or exit. Capsules are considered a point mass and as a moving discontinuity travelling using capsule velocity for calculation of air flow. Capsules are assumed to be driven by the pressure difference across the capsule. The influence of capsule trajectories on the characteristic curves is treated by _??_ method. By this calculation the pressure and velocity of air in a pipeline and each capsule trajectory are obtained as a function of time for several transport conditions, and comparison with measurements is discussed for some cases.