Simulation of Turbulent Lifted Flames Using a Partially Premixed Coherent Flame Model

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Yongzhe Zhang ◽  
Rajesh Rawat
Keyword(s):  
Turbulent Combustion ◽  
Practical Interest ◽  
Flame Stabilization ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Jet Flame ◽  
Premixed Turbulent Combustion ◽  
Partially Premixed Combustion ◽  
Lifted Flames ◽  
Partially Premixed

Partially premixed combustion occurs in many combustion devices of practical interest, such as gas-turbine combustors. Development of corresponding turbulent combustion models is important to improve the design of these systems in efforts to reduce fuel consumption and pollutant emissions. Turbulent lifted flames have been a canonical problem for testing models designed for partially premixed turbulent combustion. In this paper we propose modifications to the coherent flame model so that it can be brought to the simulation of partially premixed combustion. For the primary premixed flame, a transport equation for flame area density is solved in which the wrinkling effects of the flame stretch and flame annihilation are considered. For the subsequent nonpremixed zone, a laminar flamelet presumed probability density function (PPDF) methodology, which accounts for the nonequilibrium and finite-rate chemistry effects, is adopted. The model is validated against the experimental data on a lifted H2∕N2 jet flame issuing into a vitiated coflow. In general there is fairly good agreement between the calculations and measurements both in profile shapes and peak values. Based on the simulation results, the flame stabilization mechanism for lifted flames is investigated.

Simulation of Turbulent Lifted Flames Using a Partially-Premixed Coherent Flame Model (PCFM)

2008 ◽  
Author(s):  
Yongzhe Zhang ◽  
Rajesh Rawat
Keyword(s):  
Turbulent Combustion ◽  
Practical Interest ◽  
Flame Stabilization ◽  
Premixed Combustion ◽  
Pollutant Emissions ◽  
Jet Flame ◽  
Premixed Turbulent Combustion ◽  
Partially Premixed Combustion ◽  
Lifted Flames ◽  
Partially Premixed

Partially-premixed combustion occurs in many combustion devices of practical interest, such as gas-turbine combustors. Development of corresponding turbulent combustion models is important to improve the design of these systems in efforts to reduce fuel consumption and pollutant emissions. Turbulent lifted flames have been a canonical problem for testing models designed for partially-premixed turbulent combustion. In this paper we propose modifications to the coherent flame model (CFM) so that it can be brought to the simulation of partially-premixed combustion. For the primary premixed flame, a transport equation for flame area density is solved in which the wrinkling effects of the flame stretch and flame annihilation are considered. For the subsequent non-premixed zone, a laminar flamelet PPDF methodology, which accounts for the non-equilibrium and finiterate chemistry effects, is adopted. The model is validated against the experimental data on a lifted H2/N2 jet flame issuing into a vitiated coflow. In general there is fairly good agreement between the calculations and measurements both in profile shapes and peak values. Based on the simulation results the flame stabilization mechanism for lifted flames is investigated.

Dynamics of Flame Stabilized by Triangular Bluff Body in Partially Premixed Methane-Air Combustion

2011 ◽  
Author(s):  
T. V. Santosh Kumar ◽  
P. R. Alemela ◽  
J. B. W. Kok
Keyword(s):  
Heat Release ◽  
Vortex Shedding ◽  
Bluff Body ◽  
Reaction Rates ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Premixed Combustion ◽  
Partially Premixed Combustion ◽  
Computational Fluid Dynamics Analysis ◽  
Partially Premixed

In the design and operational tuning of gas turbine combustors it is important to be able to predict the interaction of the flame stabilization recirculation area with the burner aerodynamics. In the present paper transient computational fluid dynamics analysis is used to study these effects. Vortex interactions with the flame play a key role in many practical combustion systems. The interactions drive a large class of combustion instabilities and are responsible for changing the reaction rates, shape of the flame and the global heat release rate. The evolution of vortex shedding in reactive flows and its effects on the dynamics of the flame are important to be predicted. The present study describes dynamics of bluff body stabilized flames in a partially premixed combustion system. The bluff body is an equilateral wedge that induces the flame recirculation zone. The wedge is positioned at one-third length of the duct, which, is acoustically closed at the bottom end and open at the top. Transient computational modeling of partially premixed combustion is carried out using the commercial ANSYS CFX code and the results show that the vortex shedding has a destabilizing effect on the combustion process. Scale Adaptive Simulation turbulence model is used to compare between non-reacting cases and combustion flows to show the effects of aerodynamics-combustion coupling. The transient data reveals that frequency peaks of pressure and temperature spectra and is consistent with the longitudinal natural frequencies and Kelvin-Helmholtz instability frequency for reactive flow simulations. The same phenomenon is observed at different operating conditions of varying power. It has also been shown that the pressure and heat release are in phase, satisfying the Rayleigh criterion and therefore indicating the presence of aerodynamic-combustion instability. The data are compared to the scarce data on experiments and simulations available in literature.

Combustion Modeling of Partially Premixed Flames

2010 ◽  
Author(s):  
Ilona Zimmermann ◽  
Michael Pfitzner
Keyword(s):  
Turbulent Combustion ◽  
Laminar Flame ◽  
Mixture Fraction ◽  
Combustion Modeling ◽  
Premixed Turbulent Combustion ◽  
Combustion Models ◽  
Partially Premixed Combustion ◽  
Partially Premixed Flames ◽  
Standard Models ◽  
Partially Premixed

Accurate and properly validated turbulence-chemistry interaction models for RANS combustion computational fluid dynamics (CCFD) simulations are required in support of the development process of modern gas turbine combustors. Although standard models are available for fully premixed and purely non premixed turbulent combustion, models describing partially pre-mixed combustion are still under development. A new model for the simulation of turbulent partially premixed combustion is presented, which combines features of non premixed and fully pre-mixed combustion models and reduces to these respective standard models in the limiting cases. Transport equations for mixture fraction and its variance as well as one progress variable are solved. Fluctuations of mixture fraction are taken into account through a presumed beta PDF assumption. The laminar flame speed for the whole range of mixture fractions is evaluated using correlations for lean and rich extinction limits based on experimental results from the literature. The model is validated using hydrogen and methane jet flames.

Effects of porous media on partially premixed combustion and heat transfer in meso-scale burners fuelled with ethanol

Energy ◽  
2021 ◽  
pp. 120191
Author(s):  
Xinjian Chen ◽  
Junwei Li ◽  
Dan Zhao ◽  
Muhammad Tahir Rashid ◽  
Xinyuan Zhou ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Premixed Combustion ◽  
Partially Premixed Combustion ◽  
Partially Premixed ◽  
Meso Scale

Effects of Different Type of Gasoline Fuels on Heavy Duty Partially Premixed Combustion

2009 ◽  
Vol 2 (2) ◽  
pp. 71-88 ◽  
Author(s):  
Vittorio Manente ◽  
Bengt Johansson ◽  
Per Tunestal ◽  
William Cannella
Keyword(s):  
Premixed Combustion ◽  
Heavy Duty ◽  
Partially Premixed Combustion ◽  
Partially Premixed

Characterization of Partially Premixed Combustion With Ethanol: EGR Sweeps, Low and Maximum Loads

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Vittorio Manente ◽  
Bengt Johansson ◽  
Pert Tunestal
Keyword(s):  
High Efficiency ◽  
Pressure Rise ◽  
Premixed Combustion ◽  
Maximum Pressure ◽  
Pressure Rise Rate ◽  
Start Of Injection ◽  
Partially Premixed Combustion ◽  
Rise Rate ◽  
Partially Premixed ◽  
Gas Recirculation

Exhaust gas recirculation (EGR) sweeps were performed on ethanol partially premixed combustion (PPC) to show different emission and efficiency trends as compared with diesel PPC. The sweeps showed that when the EGR rate is increased, the efficiency does not diminish, HC trace is flat, and CO is low even with 45% of EGR. NOx exponentially decreases by increasing EGR while soot levels are nearly zero throughout the sweep. The EGR sweeps underlined that at high EGR levels, the pressure rise rate is a concern. To overcome this problem and keep high efficiency and low emissions, a sweep in the timing of the pilot injection and pilot-main ratio was done at ∼16.5 bars gross IMEP. It was found that with a pilot-main ratio of 50:50, and by placing the pilot at −60 with 42% of EGR, NOx and soot are below EURO VI levels; the indicated efficiency is 47% and the maximum pressure rise rate is below 10 bar/CAD. Low load conditions were examined as well. It was found that by placing the start of injection at −35 top dead center, the efficiency is maximized, on the other hand, when the injection is at −25, the emissions are minimized, and the efficiency is only 1.64% lower than its optimum value. The idle test also showed that a certain amount of EGR is needed in order to minimize the pressure rise rate.

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