Numerical Analysis of Coal Combustion in Circulating Fluidized Bed
combustion of coal is used in circulating fluidized bed combustion system. This work is concerned about gas–solid two-phase mixtures flowing upwards through the fast beds. The type of information resulting from various ways of analyzing the pressure variations and the effect of superficial velocity on pressure in fluidized beds are discussed. This paper presents the standard k–є and two-phase turbulence model used to describe the gas–solids flow in a CFB.The analysis of temperature and density in coal combustion is done by discrete phase model (DPM) and non pre mixed combustion in species model through the PDF file creation in DPM model. The flow temperature and density in the system were modeled by solving the continuity and momentum equations of the gas flow by using the CFD analysis. The fluidizing velocity has been taken as 4 m/s and the effects of operating parameters on mole fraction, mean density and mean temperature are discussed in this paper. It is observed that the mean density of minimum and maximum mean mixture fraction along the scaled variance is significant.
Numerical Analysis of Combustor Flow Fields in Supersonic Flow Regime with Spalart-Allmaras and k-ε Turbulence Models
In this numerical study, supersonic combustion of hydrogen has been presented for Mach 2. The combustor has a single fuel injection parallel to the main flow from the base. Finite rate chemistry model with k-e model and Spalart-Allmaras (S-A) Model have been used for modeling of supersonic combustion. The coupled phenomena of mixing and burning cm only be numerically modeled with the inclusion of a finite-rate chemical kinetic mechanism. The main issue in supersonic combustion is proper mixing within short burst of time. Attention is paid to the local intensity of heat release, which determines, together with the duct geometry, techniques for flame initiation and stabilization, injection techniques and quality of mixing the fuel with oxidizer, the gas-dynamic flow regime. The two-dimensional mathematical model involves the k-e and Spalarts-Allmaras turbulence model, modified for supersonic compressibility, and a detailed kinetic mechanism of mixture combustion. The five main parameters were considered like Mach number stagnation temperature, mass fraction, stagnation pressure and velocity. The result shows the better mixing of fuel and the flame speed increases almost linearly. The stagnation temperature in the combustion reaches up to 2820K. Fluctuation in pressure and Mach number was due to shock train. Supersonic combustion is the key enabling technology for sustained hypersonic flights. In scramjet engines of current interest, the combustor length is typically of the order of 1 m, and the residence time of the mixture is of the order of Milliseconds. Due to the high supersonic flow speed in the combustion chamber, problems arise in the mixing of the reactants, flame anchoring and stability and completion of combustion within the limited combustor length. The flow field in the scramjet combustor is highly complex. It is shown that when the flight speed is low, the kinetic energy of the air is not enough to be used for the optimal compression. Further compression by machines is needed in order to obtain a higher efficiency. For example, a turbojet employs a turbine machine for further compression. When the flight speed is higher than a certain value, the air flow entering a combustor will remain to be supersonic after the optimal compression. With a further compression (i. e. deceleration), the efficiency
Byron: Augustan and Romantic
The impact of Byron's writings - an evaluative approach, William St Clair "My brain is feminine" - Byron and the poetry of deception, Jerome J. McGann Byron and the romantic heroine, Malcolm Kelsall Byron and the Empire in the East, Marilyn Butler Byron Augustan - mutations of mock-heroic in "Don Juan" and Shelley's "Peter Bell the Third", Claude Rawson continuities and discontinuities of language and voice in Dryden, Pope, and Byron, Bernard Beatty Augustan satires and Panegyrics on London and Byron's image of the city, Michael Gassermeier Byron, Pope, and the Grand Tour, Michael G. Cooke Byron in Italy - the return of Augustus, Donald H. Reiman "Don Juan" transformed, Anne Barton Byron's "Wrong Revolutionary System" and romanticism, Hermann Fischer the quintessential Byron, Leslie A. Marchand.