Analysis of the Flow in the Combustor—Transition Piece Considering the Variation in the Fuel Composition

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
J. Arturo Alfaro-Ayala ◽  
A. Gallegos-Muñoz ◽  
J. Manuel Riesco-Ávila ◽  
M. Flores-López ◽  
A. Campos-Amezcua ◽  
...  
Keyword(s):  
Radial Direction ◽  
Combustion Process ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
Maximum Temperature ◽  
Fuel Composition ◽  
Temperature Profiles ◽  
Three Dimensional Model ◽  
Order Polynomial ◽  
Transition Piece

An analysis of the flow that depends on the fuel composition (natural gas) in the combustor–transition piece system, applying computational fluid dynamics, is presented. The study defines the velocity and temperature profiles at the exit of the transition piece and the hot streak along the system. The variation of the composition in the fuel depends of the amount of N2 contained in the fuel, and the hot track influences on the temperature distribution at the input of the first stage of vanes and blades of the gas turbine. The study takes place in a three-dimensional model in steady state using FLUENT® 6.3.26, applying the k-ε turbulence model and chemical equilibrium to the combustion process. The results show the influence of the transition piece geometry over the velocity and temperature profiles, principally, in the radial direction. The velocity profiles on the radial direction can be represented by six order polynomial and the temperature profile by third order polynomial. The temperature and velocity profiles keep a symmetry profile and they can be represented by six order polynomial at the circumferential direction. Knowing these profiles, it is possible to compute a more exact study of the heat transfer at vanes and blades of the first stage of the turbine to evaluate the performance and life of them. On the other hand, considering from 2% to 10% of N2 in the fuel composition, the maximum temperature is reduced in the combustion process and consequently the NOx emissions too.

Analysis of the Flow in the Combustor-Transition Piece Considering the Variation in the Fuel Composition

2010 ◽  
Author(s):  
J. Arturo Alfaro Ayala ◽  
Armando Gallegos Mun˜oz ◽  
J. Manuel Riesco A´vila ◽  
Marco Polo Flores Lo´pez ◽  
Alfonso Campos Amezcua ◽  
...  
Keyword(s):  
Radial Direction ◽  
Combustion Process ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
Maximum Temperature ◽  
Fuel Composition ◽  
Temperature Profiles ◽  
Three Dimensional Model ◽  
Order Polynomial ◽  
Transition Piece

An analysis of the flow that depends of the fuel composition (natural gas) in the combustor-transition piece system, applying Computational Fluid Dynamics, is presented. The study defines the velocity and temperature profiles at the exit of the transition piece and the hot streak along the system. The variation of the composition in the fuel depends of the amount of N2 contained in the fuel, and the hot track influences on the temperature distribution at the input of the first stage of vanes and blades of the gas turbine. The study takes place in a three-dimensional model in steady state using FLUENT ® 6.3.26, applying the k-ε turbulence model and chemical equilibrium to the combustion process. The results show the influence of the transition piece geometry over the velocity and temperature profiles, principally, in the radial direction. The velocity profiles on the radial direction can be represented by six order polynomial and the temperature profile by third order polynomial. The temperature and velocity profiles keep a symmetry profile and they can be represented by six order polynomial at the circumferential direction. Knowing these profiles, it is possible to compute a more exact study of the heat transfer at vanes and blades of the first stage of the turbine to evaluate the performance and life of them. On the other hand, considering from 5% to 10% of N2 in the fuel composition, the maximum temperature is reduced in the combustion process and consequently the NOx emissions too.

An Insight into Combustion Process in a Spark Ignition Engine Using Three Dimensional Modeling

2011 ◽  
Vol 110-116 ◽  
pp. 3016-3024
Author(s):  
Moslem Yousefi ◽  
F. Ommi ◽  
Mehdi Farajpour
Keyword(s):  
Combustion Process ◽  
Three Dimensional ◽  
Engine Performance ◽  
Spark Ignition ◽  
Spark Ignition Engine ◽  
Experimental Result ◽  
Maximum Temperature ◽  
Three Dimensional Model ◽  
Three Dimensional Modeling ◽  
Spark Plug

In this paper a three dimensional model of a spark ignition engine is presented using KIVA-3V code to investigate the combustion process of engine and gain a better understanding of what happens during this stage. The Whole engine cycle is simulated and the validity of the model is examined by experimental result of in-cylinder bulk pressure. the effect of ignition timing, spark plug location on the engine performance and pollutants of this engine has been investigated .The numerical results show that Relocating the spark plug near to the exhaust valves in order of taking advantage of higher temperature does not have the desired results. Using lean excessive air results in decreasing advancing the ignition results in an increase in the maximum bulk pressure and power of engine. Due to increase in maximum temperature of the combustion chamber the amount of NOx rises, too.

Modeling of Solids and Gas Mixing Effects in Large-Scale CFB Combustors

2003 ◽  
Author(s):  
Karsten Luecke ◽  
Ernst-Ulrich Hartge ◽  
Joachim Werther
Keyword(s):  
Combustion Chamber ◽  
Residence Time ◽  
Large Scale ◽  
Control Volume ◽  
Combustion Process ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Cross Sectional ◽  
Fuel Feed ◽  
Cross Section Area

In a CFB combustor the reacting solids are locally fed into the combustion chamber. These reactants have to be dispersed across the reactor’s cross-sectional area. Since the rate of mixing is limited this leads to a mal-distribution of the reactants and to locally varying reaction conditions. In order to describe the influence of mixing a three-dimensional model of the combustion chamber is suggested here. The model is divided into three sub-topics. First, the flow structure in terms of local gas and solids velocities and solids volume concentrations is described. Second, mixing of the solids and the gas phase has to be quantified by defining dispersion coefficients, and finally the combustion process itself, i.e. the reaction kinetics, has to be modeled. Employing the information of the three sub-models mass balances for the reactants at each finite control volume inside the CFB combustion chamber can be formulated. The model was validated against data from measurements in the large-scale combustor of Chalmers University of Technology in Go¨teborg/Sweden. Concentration gradients concerning the char phase are only moderate. However, the spatial distribution of the oxygen shows strong non-uniformities, especially under conditions of staged combustion. In further predictive calculations, the influence of the fuel supply arrangement on the emissions of industrial sized CFB boilers was studied. Furthermore, the influence of the fuel composition on the feeding technique has been examined. High volatile fuels tend to form plumes of unburned hydrocarbons near the fuel feed point, and might therefore need more feed points per square meter cross-section area. Since the average gas residence time in the primary cyclone of a CFB plant is about 30–40% of the total gas residence time, a considerable burn-off of not completely oxidized gas species may occur here. An effectively used cyclone may remedy to a certain extent the negative impacts of incomplete mixing in the combustion chamber.

CFD Assisted Design of Micro GT Combustor

2009 ◽  
Author(s):  
Yeshayahou Levy ◽  
Vladimir Erenburg ◽  
Yakov Goldman ◽  
Valery Sherbaum ◽  
Vitaly Ovcharenko
Keyword(s):  
Heat Transfer ◽  
Cfd Simulation ◽  
Combustion Process ◽  
Three Dimensional ◽  
Heat Radiation ◽  
Working Fluid ◽  
Stoichiometric Ratio ◽  
Three Dimensional Model ◽  
Successful Operation ◽  
Predicted Values

The work presents the development of a micro-combustor design, where the combustion process was simulated by CFD and tested experimentally. The inner diameter of the first model was 5.5 mm, the exit diameter 2.5 mm, and the length 24.5 mm. The designed heat release was 200W. Some modifications of the microcombustor were studied. Three-dimensional model for combustion simulations was used. The ‘conjugate heat transfer’ methodology, based on a simultaneous solution of the heat transfer equations for gas and combustor walls, coupled with equations for the working fluid, enabled the prediction of the combustor wall temperatures. To check model convergence 2 simulations with different number of cells were carried out. Effect of heat radiation was also studied by the CFD simulation. The fuel is methane and stoichiometric ratio was simulated. Reactive flow calculations were carried out with a two-step reaction. The analysis of the simulated results was based on the obtained velocity profiles, concentration and temperature distributions within the liner. Preliminary simulations showed that the first combustor design had inefficient combustion. The reason was poor mixing of methane and air inside the mixing chamber and deterioration of the combustion by dilution holes. Consequently, the combustor design was modified and simulated. The simulation showed that the modification significantly improved mixing and combustion process and better combustion was provided. Due to complexity associated with performing combustion experiments in such small dimensions, only limited data could be recorded. A small combustor was manufactured and tests and demonstrated its successful operation. Measurements of temperature and optical UV-VIS-IR - emissions at the combustor exit were obtained. The experimental and simulation results are compared and a good qualitative agreement was found between the experiments and the predicted values.

Numerical Simulation on Effect of Nozzle-Hole Layout on Spray Characteristics and Combustion in a DI Diesel Engine

2012 ◽  
Vol 476-478 ◽  
pp. 448-452
Author(s):  
Jun Zhang ◽  
Chang Pu Zhao ◽  
Nai Zhuan Chen ◽  
Da Lu Dong ◽  
Bo Zhong
Keyword(s):  
Numerical Simulation ◽  
Diesel Engine ◽  
Direct Injection ◽  
Combustion Process ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Spray Characteristics ◽  
Fuel Atomization ◽  
Di Diesel Engine ◽  
Nozzle Hole

Diesel spray characteristics are closely related to the combustion of the engine where the spray tip penetration and the fuel atomization play a key role especially for direct injection (DI) diesel engine. With different nozzles, the fuel atomization and evaporation will be different thereby affecting the combustion and emission characteristics. A three-dimensional model is built based on the parameters of a DI diesel engine, and its validation is also validated. Three nozzle-hole layouts are designed in this research, including the conventional hole, multi-hole, and group-hole. The spray characteristics and combustion process are studied with three different nozzle-hole layouts by the way of numerical simulation. Further more, the effect of inter-hole spacing of group-hole nozzle on the evaporation rate and combustion process is researched here.

Three-Dimensional Flow Patterns in the Upper Human Airways

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Katrin Bauer ◽  
Alexander Rudert ◽  
Christoph Brücker
Keyword(s):  
Secondary Flow ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Velocity Profiles ◽  
Conventional Mechanical Ventilation ◽  
Flow Structures ◽  
Three Dimensional Model ◽  
Short Branch ◽  
Sixth Generation ◽  
Human Airways

Flow dynamics are studied for different ventilation conditions at a three-dimensional model of the human lung airways. The model is based on Horsfield and Weibel data and bifurcates down to the sixth generation. The flow is analyzed numerically and compared to experimental data received from exactly the same model. Numerical and experimental results agree well. Based on this agreement, flow behavior for conventional mechanical ventilation (CMV) as well as for high frequency oscillatory ventilation (HFOV) conditions can be analyzed. Velocity profiles as well as secondary flow structures are investigated during different phases of the unsteady flow. It is shown that the velocity profiles at peak inspiration and expiration are very similar for CMV and HFOV, probably due to too short branch lengths for the development of a frequency-dependent velocity profile. At the flow reversal times, characteristic zones of bidirectional mass flow emerge with increasing amplitude at higher frequencies. Furthermore, secondary flow structures are analyzed. This investigation reveals that the structures only depend on the local curvature and branch orientation, but are not influenced much by the nearby upper or lower branching generations.

Thermal Analysis of a NAC-LWT Cask Under Normal and Fire Accident Conditions

2012 ◽  
Author(s):  
Ketan Mittal ◽  
Miles Greiner
Keyword(s):  
Initial Conditions ◽  
Three Dimensional ◽  
Maximum Temperature ◽  
Three Dimension ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Neutron Shield ◽  
Fire Environment ◽  
Finite Element Package ◽  
Accident Conditions

Two and three dimensional thermal models of a Nuclear Assurance Corporation Legal Weight Truck (NAC-LWT) cask were constructed using the PATRAN commercial finite element package. The two-dimensional model included the effect of radial stiffeners in the package’s external neutron shield but three-dimensional model did not. A normal conditions of transport (NCT) simulation using both models predicted the peak cladding temperature was roughly 210°C. The NCT package temperatures were used as initial conditions for transient fire/post-fire simulations. Different assumptions were used to determine when the neutron shield liquid drained from the tank and was replaced by air. When the liquid was assumed to remain within the tank during and after the fire, the peak cladding temperature was predicted to exhibit a temporal maximum of roughly 300°C, approximately 6 hours after the end of the fire. If the liquid drained from the tank during the fire, the cladding temperature did not exhibit a temporal peak. Rather, it eventually reached a maximum temperature of roughly 280°C, which is the steady state NCT peak temperature when air is in the neutron shield tank. This undergraduate project will be used to lay down a foundation for further research on NAC-LWT casks. Two and three dimension package of the cask will be constructed using ANSYS, and simulations will be run for NCT and fire/post-fire conditions. The models will also be linked to Container Analysis Fire Environment (CAFE) to predict response of the package in fire.

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