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A numerical simulation study was conducted for a jetting fluidized bed coal gasifier with a conical distributor. It was based on a steady-state model which took account of hydrodynamics, mass heat transfer and reactions in the grid zone, bubble zone and freeboard zone of the gasifier. Temperature of the particles and gas in the jet, compositions in the dilute phase and the dense phase, and some...
The investigation of particle-laden turbulent flow in a newly developed rich/lean pulverized coal nozzle interior is presented in this paper. A stochastic particle dispersion model and a model of particle–wall collision are employed for numerical simulation. Various cases of different particle diameters, positions of the baffle-board and the diaphragm are numerically investigated. The flow characteristics...
A numerical simulation approach is given to investigate the characteristics of coal particle flow, heat transfer and combustion processes in a W-shaped furnace. In order to obtain, in detail, behaviors of coal combustion, many different coal particle sizes of two different load cases are used to predict the characteristics of combustion. The conclusions of the characteristics of coal particle trajectories,...
Effects of moisture in coal on pulverized coal combustion characteristics are investigated by means of a three-dimensional numerical simulation. The results show that as the moisture increases, flame temperature and NO x mole fraction decrease, while O 2 mole fraction increases in the region near the burner, and the peaks of the flame temperature and NO x mole fraction shift...
The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the...
A three-dimensional numerical simulation is applied to a pulverized coal combustion field in a test furnace equipped with an advanced low-NO x burner called CI-α burner, and the detailed combustion characteristics are investigated. In addition, the validities of the existing NO x formation and reduction models are examined. The results show that a recirculation flow is formed in the...
An open swirl-stabilized turbulent premixed flame is studied numerically. This study provides a better understanding of the flame properties by simulating the flow field, combustion and heat transfer. Spalding's stretch-cut-slide model is extended to determine the mixing controlled fuel burning rate. Although the flame is stabilized by swirl, the flame zone is found to be free of swirl. Simulations...
This paper presents modeling of a coal gasification reaction, and prediction of gasification performance for an entrained flow coal gasifier. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. The coal gasification model suggested in this paper...
This paper deals with numerical analysis of injection process using biodiesel/mineral diesel fuel blends with the aim to search for the potentials to reduce engine harmful emissions. The considered fuels are neat biodiesel from rapeseed oil and its blends with mineral diesel D2. For the numerical analysis a one-dimensional mathematical model is employed. In order to model accurately the investigated...
A novel Null-type sampling nozzle with six sampling holes was developed to measure the particle concentrations and size distributions in high-pressure natural gas flows under isokinetic sampling conditions. The isokinetic sampling performances of sampling nozzles were investigated by experiments and numerical simulations with standard κ–ε turbulent model. The maximum deviation between the experimental...
The objective of this study is to investigate the mixture formation process of sprays injected from two-hole nozzles for direct-injection spark-ignition (DISI) engines. Spray characteristics were examined for vapor and liquid mass distributions, spray tip penetration and spray angle using the laser absorption–scattering (LAS) technique and the computational fluid dynamics (CFD) simulation. Other characteristics...
The working process of a porous medium (PM) engine, characterized as periodic contact type and fueled with liquid fuel as Isooctane, is simulated by using an improved version of KIVA-3V. A modified volume-averaged method is proposed for describing the interaction between fuel droplets and the solid phase of the PM. The improved version of KIVA-3V was validated by simulating the experiment of Zhdanok...
Motivated by detailed designs of industrial porous burners published in patents, the combustion of methane–air mixtures in a two-section porous burner has been studied numerically. The software FLUENT is used to solve a two-dimensional transient mathematical model of the combustion. In order to reveal the reality of the combustion in porous media, the user defined function (UDF) is used to extend...
The numerical simulation of Solid Recovered Fuels (SRF) co-combustion in pulverised coal power plants requires a flexible particle model, which among other properties should be able to predict the aerodynamic behaviour of the irregular-shaped particles, especially their trajectories along the boiler axis. This will help to provide vital information on whether the SRF particles are entrained in the...
In this paper we study the transient heat conduction in a piston of a diesel engine, subjected to a periodic boundary condition on the surface in contact with the combustion gases. The heat transfer coefficient at the top surface was modeled taking into account the temperature and pressure inside the combustion chamber. Such instantaneous pressure was measured using a special probe for an engine operating...
In top-blown oxygen converter steelmaking process, a large amount of high-temperature off-gas is produced, and the off-gas is a precious valuable fuel containing high concentration of carbon monoxide (CO). Numerical model is developed for top-blown oxygen converter off-gas formation, the off-gas formation is simulated using the developed model, and the influences of the operating model of converter...
The conical-spray injector is capable of achieving lean mixture with high homogeneity in the cylinder for diesel Premixed charge compression ignition (PCCI) engine with advanced injection timing. To better understand the cavitating flow inside the conical-spray injector, numerical simulations have been conducted by using a mixture multiphase model and a full cavitation model in this study. The results...
In this paper, the performance and efficiency of improved oil recovery in fractured porous media utilizing the cyclic CO 2 injection process (otherwise known as CO 2 huff-n-puff) are examined for immiscible, near-miscible and miscible pressure conditions. The main approach involved the comparison of simulation results to experimental data obtained from a laboratory CO 2 huff-n-puff...
The effect of the devolatilization model on the coal particle behavior is investigated in detail by performing numerical simulations of a simple pulverized coal jet flame formed by a small jet burner (0.5kg-coal/h) [S. Hwang et al., Energy & Fuels 2005;19:382–92]. As the devolatilization model, widely-used conventional devolatilization model, two competing reaction rate model and newly-proposed...
The effects of equivalence ratio, fuel droplet size, and radiation on jet spray flame are investigated by means of two-dimensional direct numerical simulation (DNS). In addition, the validity of an extended flamelet/progress-variable approach (EFPV), in which heat transfer between droplets and ambient fluid including radiation is exactly taken into account, is examined. n-decane (C 10 H ...
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