Modeling Static Instabilities of Biogas Flames in a Stirred-Reactor Using Detailed Chemical Kinetics Simulations

2013 ◽  
Author(s):  
Christopher D. Bolin ◽  
Abraham Engeda
Keyword(s):  
Gas Turbines ◽  
Static Stability ◽  
Gas Turbine Combustor ◽  
Detailed Chemical Kinetics ◽  
Reduced Mechanism ◽  
Stirred Reactor ◽  
Primary Zone ◽  
Stability Limits ◽  
Different Sources ◽  
Detailed Chemical

Kinetic modeling of lean static stability limits of the combustion of biogas type fuels in a model of an ideal primary zone of a gas turbine combustor is presented here. In this study, CH4 is diluted with CO2 to simulate a range of gases representative of the products of anaerobic digestion of organic materials from different sources (e.g., landfill and animal waste digester). Fuels of this type are of interest for use in small gas turbines used in distributed generation applications. Predictions made by two detailed mechanisms (GRI-Mech 3.0 and San Diego) and one reduced mechanism (GRI-Mech 1.2, reduced) are employed to investigate the underlying kinetics near lean extinction. Approximate correlations to lean extinction are extracted from these results and compared to those of other fuels.

Numerical Simulation for the Preliminary Design of Fuel Flexible Stationary Gas Turbine Combustors Using Conventional and Alternative Fuels

2012 ◽  
Author(s):  
Washington Orlando Irrazabal Bohorquez ◽  
João Roberto Barbosa ◽  
Rob Johan Maria Bastiaans ◽  
Philip de Goey
Keyword(s):  
Numerical Simulation ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Alternative Fuels ◽  
High Efficiency ◽  
Numerical Study ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Gas Turbine Combustor ◽  
Primary Zone

Currently, high efficiency and low emissions are most important requisites for the design of modern gas turbines due to the strong environmental restrictions around the world. In the past years, alternative fuels have been considered for application in industrial gas turbines. Therefore, combustor performance, pollutant emissions and the ability to burn several fuels became of much concern and high priority has been given to the combustor design. This paper describes a methodology focused on the design of stationary gas turbines combustion chambers with the ability to efficiently burn conventional and alternative fuels. A simplified methodology is used for the calculations of the equilibrium temperature and chemical species in the primary zone of a gas turbine combustor. Direct fuel injection and diffusion flames, together with numerical methods like Newton-Raphson, LU Factorization and Lagrange Polynomials, are used for the calculations. Diesel, ethanol and methanol fuels were chosen for the numerical study. A computer code sequentially calculates the main geometry of the combustor. From the numerical simulation it is concluded that the basic gas turbine combustor geometry, for some operating conditions and burning diesel, ethanol or methanol, are of similar sizes, because the development of aerodynamic characteristics predominate over the thermochemical properties. It is worth to note that the type of fuel has a marked effect on the stability and combustion advancement in the combustor. This can be seen when the primary zone is analyzed under a steady-state operating condition. At full power, the pressure is 1.8 MPa and the temperature 1,000 K at the combustor inlet. Then, the equivalence ratios in the primary zone are 1.3933 (diesel), 1.4352 (ethanol) and 1.3977 (methanol) and the equilibrium temperatures for the same operating conditions are 2,809 K (diesel), 2,754 K (ethanol) and 2,702 K (methanol). This means that the combustor can reach similar flame stability conditions, whereas the combustion efficiency will require richer fuel/air mixtures of ethanol or methanol are burnt instead of diesel. Another important result from the numerical study is that the concentration of the main pollutants (CO, CO2, NO, NO2) is reduced when ethanol or methanol are burnt, in place of diesel.

Flammability Limits of Low BTU Gases: Computations in a Perfectly Stirred Reactor and Experiments

2001 ◽  
Author(s):  
Fredrik Hermann ◽  
Thomas Ruck ◽  
Jens Klingmann ◽  
Fabian Mauss
Keyword(s):  
Residence Time ◽  
Gas Turbines ◽  
Thermodynamic Quantities ◽  
Flammability Limits ◽  
Gaseous Fuels ◽  
Stirred Reactor ◽  
Stability Limits ◽  
Extinction Point ◽  
Lower Heating ◽  
Made In

The demand for gas turbines suitable for Low Btu gases is increasing worldwide. This paper presents a theoretical and experimental investigation of the flammability limits of Low Btu gases for gas turbine applications. Most modern gas turbines utilize premixed combustion, making it important to know at which fuel-air ratio the flame extinguishes. The flammability limit for a gaseous fuel is a property, which is coupled to both thermodynamic quantities and the shape of the combustion chamber. Consequently, this property is characteristic for each combustor and for each fuel. The experiments were made in an atmospheric pressure premixed combustor at Alstom Power Technology Ltd. Switzerland, adapted for Low Btu gaseous fuels. Five different residual gases from chemical factories were investigated. The gases consisted of methane, carbon monoxide, hydrogen and nitrogen, with lower heating values about 2-3.5 MJ/kg for all examined gases (Table 1). A steady state Perfectly Stirred Reactor (PSR) was used as a model for the primary combustion zone. The reactions were modeled by a detailed mechanism for methane with 61 species and 667 reactions, developed by Warnatz [1]. The PSR calculations were done by decreasing the residence time until the combustion in the PSR extinguished. These calculations were repeated for different equivalence ratios to obtain the relation between the residence time and the limit of flammability. The calculations showed a relationship between the residence time in the PSR and the extinction point. It was found that the computed values of the flammability limits, or more correctly called stability limits, qualitatively follow the experimental results. However, since the computational results are strongly dependent on the residence time, a comparison with the experiments must include the residence time of the real burner, which is difficult to define.

Biogas Combustion and Chemical Kinetics for Gas Turbine Applications

2008 ◽  
Author(s):  
Saeed Jahangirian ◽  
Abraham Engeda
Keyword(s):  
Gas Turbine ◽  
Chemical Kinetics ◽  
Laminar Flame ◽  
Biogas Production ◽  
Agricultural Waste ◽  
Detailed Chemical Kinetics ◽  
Fuel Blends ◽  
Reduced Mechanism ◽  
Turbine Design ◽  
Detailed Chemical

Biogas is produced from anaerobic digestion of biodegradable materials such as agricultural waste, animal waste, and municipal solid waste and its main constituents are CH4 and CO2. A review of biogas production and benefits as well as its combustion as an alternative gas turbine fuel is presented. To further understand the characteristics of biogas combustion, a detailed chemical kinetics study of biogas is conducted using the GRI-Mech 3.0 and the San Diego detailed mechanisms and a reduced mechanism in a counterflow configuration. Ignition delays and laminar flame speeds of some gaseous fuel blends which simulate biogas are calculated. Effects of the concentration of each species in the blend are discussed as well as its chemical contribution in the biogas combustion. Approximate analytical correlations are extracted from these results for quantitative predictions. Results of this study will provide valuable data both for gas turbine manufacturers and for biogas producers to modify the gas turbine design for biogas and to figure out how much cleaning and upgrading is required for biogas turbines.

scholarly journals Application of a Micro-/Macro-Mixing Two Reactor Model to a Single-Cup Low-Emissions Combustor

1998 ◽  
Author(s):  
T. J. Held ◽  
H. C. Mongia ◽  
J. H. Tonouchi
Keyword(s):  
Gas Turbine ◽  
Preliminary Design ◽  
Gas Turbine Combustor ◽  
Detailed Chemical Kinetics ◽  
Reactor Model ◽  
Combustion Dynamics ◽  
Design Variables ◽  
Successful Design ◽  
Dynamics Simulations ◽  
Detailed Chemical

During the preliminary design and analysis phase of a gas turbine combustor, trade studies of the effects of design variables on emissions and operability are necessary to ensure a successful design. Due to the considerable resources required for full computational combustion dynamics simulations, simplified design tools are required for rapid analysis of a large number of design variable combinations. In a previous paper, a semi-analytical model of a gas turbine combustor was described (Tonouchi, et al., 1997). The model employs a gas particle Monte Carlo technique to simulate the effects of finite-rate micro- and macro-mixing, including full detailed chemical kinetics (Bowman, et al., 1997). Initial model validation work focused on emissions calculations for conventional rich dome combustors. This work presents NOx and CO emissions calculations for a single-cup natural gas-fired dry low emissions (DUE) combustor, and comparison to experimental data. The effect of parametric variation of the micro- and macro-mixing model constants, assigned volumes of the primary and secondary zones, and inlet unmixedness on the results are also presented.

Establishing Operating Limits in a Commercial Lean Premixed Combustor Operating on Synthesis Gas Pertaining to Flashback and Blowout

2012 ◽  
Author(s):  
David Page ◽  
Brendan Shaffer ◽  
Vincent McDonell
Keyword(s):  
Natural Gas ◽  
Synthesis Gas ◽  
Gas Turbines ◽  
Key Factors ◽  
High Hydrogen ◽  
Lean Blowout ◽  
Stirred Reactor ◽  
Operating Limits ◽  
The Stability ◽  
Stability Limits

Operability issues such as flashback and lean blow out are phenomena that must be addressed for successful commercial operation of stationary gas turbines. The present work focuses on flashback and lean blow out of premixed jet flames in a combustor from a commercially available gas turbine operating on synthesis gas compositions. The issue of flashback is exacerbated when operating on fuels with high hydrogen content due to the increased reactivity of hydrogen, thus increasing the propensity for flashback. Operating margins for mixtures of natural gas and carbon monoxide in hydrogen are reported. The results interestingly demonstrate reduced stability for mixtures of H2/NG than for H2/CO. Increasing H2 percentage from 0% to 100% reduced blowout equivalence ratios from Φ = 0.63 to Φ = 0.29 for H2/NG and Φ = 0.42 to Φ = 0.29 for H2/CO. In addition, results obtained for inlet temperatures of 300K and 623K are compared and show an upward shift of the stability limits for higher preheats. Modeling of the experimental data using a perfectly stirred reactor predicts the effect of the addition of H2 to natural gas on the blowout limits. With regards to flashback some key factors that dominate the characteristics are identified and attempts to correlate data are carried out. The results show that lean blowout and flashback occur at the same AFT, regardless of preheat temperatures. AFT at flashback and lean blowout are compared to a more fundamental burner [1] with results indicating reasonable scalability.

A Comparison of Constraint and Constraint Potential Forms of the Rate-Controlled Constraint-Equilibrium Method

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Fatemeh Hadi ◽  
M. Reza H. Sheikhi
Keyword(s):  
Performance Studies ◽  
Computation Time ◽  
Rate Equations ◽  
Detailed Chemical Kinetics ◽  
Effective Implementation ◽  
Computational Performance ◽  
Stirred Reactor ◽  
Wide Range ◽  
Rate Controlled ◽  
Detailed Chemical

A comparative assessment is made of two implementations of the rate-controlled constrained-equilibrium (RCCE) method. These are the constraint and constraint potential formulations in which rate equations are solved for the RCCE constraints and constraint potentials, respectively. The two forms are equivalent mathematically; however, they involve different numerical procedures and thus show different computational performance. The main objective of this study is to compare the accuracy and numerical efficiency of the two formulations to attain the most effective implementation of the RCCE in turbulent combustion simulations. The RCCE method is applied to study methane oxygen combustion in an adiabatic, isobaric well stirred reactor. Simulations are carried out over a wide range of initial temperatures and equivalence ratios. Performance studies are conducted and RCCE results are compared with those obtained by direct integration of detailed chemical kinetics. The results show that both methods provide very accurate representation of the kinetics. It is also demonstrated that while the constraint form involves less numerical stiffness, the constraint potential implementation results in more saving in computation time.

Numerical CFD evaluation of a flameless burner using detailed chemical kinetics

2017 ◽  
Author(s):  
Marco Antonio Nascimento ◽  
Lucilene Oliveria Rodrigues ◽  
Fagner Luis Goulart Dias
Keyword(s):  
Chemical Kinetics ◽  
Detailed Chemical Kinetics ◽  
Flameless Burner ◽  
Detailed Chemical

PARALLEL SOLVER FOR THE SIMULATIONS OF DETONATION WAVES ON UNSTRUCTURED GRIDS

2020 ◽  
Author(s):  
A. I. Lopato ◽  
◽  
A. G. Eremenko ◽  
Keyword(s):  
Chemical Kinetics ◽  
Numerical Scheme ◽  
Unstructured Grids ◽  
Numerical Study ◽  
Numerical Approach ◽  
Detonation Waves ◽  
Detailed Chemical Kinetics ◽  
Parallel Solver ◽  
Further Development ◽  
Detailed Chemical

Recently, we developed a numerical approach for the simulation of detonation waves on fully unstructured grids and applied it to the numerical study of the mechanisms of detonation initiation in multifocusing systems. Current work is devoted to further development of our numerical approach, namely, parallelization of the numerical scheme and introduction of more comprehensive detailed chemical kinetics scheme.

scholarly journals Numerical Investigation of Pressure Influence on the Confined Turbulent Boundary Layer Flashback Process

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 146 ◽  
Author(s):  
Aaron Endres ◽  
Thomas Sattelmayer
Keyword(s):  
Boundary Layer ◽  
Gas Turbines ◽  
Separation Zone ◽  
Turbulent Flame ◽  
Pressure Rise ◽  
Flame Speed ◽  
Zone Size ◽  
Detailed Chemical Kinetics ◽  
Turbulent Flame Speed ◽  
Quenching Distance

Boundary layer flashback from the combustion chamber into the premixing section is a threat associated with the premixed combustion of hydrogen-containing fuels in gas turbines. In this study, the effect of pressure on the confined flashback behaviour of hydrogen-air flames was investigated numerically. This was done by means of large eddy simulations with finite rate chemistry as well as detailed chemical kinetics and diffusion models at pressures between 0 . 5 and 3 . It was found that the flashback propensity increases with increasing pressure. The separation zone size and the turbulent flame speed at flashback conditions decrease with increasing pressure, which decreases flashback propensity. At the same time the quenching distance decreases with increasing pressure, which increases flashback propensity. It is not possible to predict the occurrence of boundary layer flashback based on the turbulent flame speed or the ratio of separation zone size to quenching distance alone. Instead the interaction of all effects has to be accounted for when modelling boundary layer flashback. It was further found that the pressure rise ahead of the flame cannot be approximated by one-dimensional analyses and that the assumptions of the boundary layer theory are not satisfied during confined boundary layer flashback.

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