Turbulent flame speed for hydrogen-rich fuel gases at gas turbine relevant conditions

Abstract Three Flamelet Generated Manifold reaction source term closure options and two different reactor types are examined with Large Eddy Simulation of an industrial gas turbine combustor operating at 3 bar. This work presents the results for the SGT-100 Dry Low Emission (DLE) gas turbine provided by Siemens Industrial Turbomachinery Ltd. The related experimental study was performed at the German Aerospace Centre, DLR, Stuttgart, Germany. The FGM model approximates the thermo-chemistry in a turbulent flame as that in a simple 0D constant pressure ignition reactors and 1D strained opposed-flow premixed reactors, parametrized by mixture fraction, progress variable, enthalpy and pressure. The first objective of this work is to compare the flame shape and position predicted by these two FGM reactor types. The Kinetic Rate (KR) model, studied in this work, uses the chemical rate from the FGM with assumed shapes, which are a Beta function for mixture fraction and delta functions for reaction progress variable and enthalpy. Another model investigated is the Turbulent Flame-Speed Closure (TFC) model with Zimont turbulent flame speed, which propagates premixed flame fronts at specified turbulent flame speeds. The Thickened Flame Model (TFM), which artificially thickens the flame to sufficiently resolve the internal flame structure on the computational grid, is also explored. Therefore, a second objective of this paper is to compare KR, TFC and TFM with the available experimental data.

Download Full-text

Boundary Layer Flashback Prediction for Turbulent Premixed Jet Flames: Comparison of Two Models

Volume 4A: Combustion, Fuels, and Emissions ◽

10.1115/gt2019-90507 ◽

2019 ◽

Author(s):

Alireza Kalantari ◽

Nicolas Auwaijan ◽

Vincent McDonell

Keyword(s):

Boundary Layer ◽

Gas Turbine ◽

Gas Turbines ◽

Turbulent Flame ◽

Flame Speed ◽

Operating Conditions ◽

Pollutant Emissions ◽

Jet Flames ◽

Turbulent Flame Speed ◽

Turbulent Premixed

Abstract Lean-premixed combustion is commonly used in gas turbines to achieve low pollutant emissions, in particular nitrogen oxides. But use of hydrogen-rich fuels in premixed systems can potentially lead to flashback. Adding significant amounts of hydrogen to fuel mixtures substantially impacts the operating range of the combustor. Hence, to incorporate high hydrogen content fuels into gas turbine power generation systems, flashback limits need to be determined at relevant conditions. The present work compares two boundary layer flashback prediction methods developed for turbulent premixed jet flames. The Damköhler model was developed at University of California Irvine (UCI) and evaluated against flashback data from literature including actual engines. The second model was developed at Paul Scherrer Institut (PSI) using data obtained at gas turbine premixer conditions and is based on turbulent flame speed. Despite different overall approaches used, both models characterize flashback in terms of similar parameters. The Damköhler model takes into account the effect of thermal coupling and predicts flashback limits within a reasonable range. But the turbulent flame speed model provides a good agreement for a cooled burner, but shows less agreement for uncooled burner conditions. The impact of hydrogen addition (0 to 100% by volume) to methane or carbon monoxide is also investigated at different operating conditions and flashback prediction trends are consistent with the existing data at atmospheric pressure.

Download Full-text

Evaluation of Reduced Kinetics in Simulation of Gasified Biomass Gas Combustion

Volume 1B: Combustion, Fuels and Emissions ◽

10.1115/gt2013-95565 ◽

2013 ◽

Author(s):

Xiaoxiang Zhang ◽

Nur Farizan Munjat ◽

Jeevan Jayasuriya ◽

Reza Fakhrai ◽

Torsten Fransson

Keyword(s):

Gas Turbine ◽

Chemical Kinetics ◽

Cfd Simulation ◽

Laminar Flame ◽

Turbulent Flame ◽

Flame Speed ◽

Turbulent Flame Speed ◽

Operation Conditions ◽

Simulation Results ◽

Gas Turbine Combustion

It is essentially important to use appropriate chemical kinetic models in the simulation process of gas turbine combustion. To integrate the detailed kinetics into complex combustion simulations has proven to be a computationally expensive task with tens to thousands of elementary reaction steps. It has been suggested that an appropriate simplified kinetics which are computationally efficient could be used instead. Therefore reduced kinetics are often used in CFD simulation of gas turbine combustion. At the same time, simplified kinetics for specific fuels and operation conditions need to be carefully selected to fulfill the accuracy requirements. The applicability of several simplified kinetics for premixed Gasified Biomass Gas (GBG) and air combustion are evaluated in this paper. The current work is motivated by the growing demand of gasified biomass gas (GBG) fueled combustion. Even though simplified kinetic schemes developed for hydrocarbon combustions are published by various researchers, there is little research has been found in literature to evaluate the ability of the simplified chemical kinetics for the GBG combustion. The numerical Simulation tool “CANTERA” is used in the current study for the comparison of both detailed and simplified chemical kinetics. A simulated gas mixture of CO/H2/CH4/CO2/N2 is used for the current evaluation, since the fluctuation of GBG components may have an unpredictable influence on the simulation results. The laminar flame speed has an important influence with flame stability, extinction limits and turbulent flame speed, here it is chosen as an indicator for validation. The simulation results are compared with the experimental data from the previous study [1] which is done by our colleagues. Water vapour which has shown a dilution effect in the experimental study are also put into concern for further validation. As the results indicate, the reduced kinetics which are developed for hydrocarbon or hydrogen combustion need to be highly optimized before using them for GBG combustion. Further optimization of the reduced kinetics is done for GBG and moderate results are achieved using the optimized kinetics compared with the detailed combustion kinetics.

Download Full-text

Turbulent Flame Speed as an Indicator for Flashback Propensity of Hydrogen-Rich Fuel Gases

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4025068 ◽

2013 ◽

Vol 135 (11) ◽

Cited By ~ 14

Author(s):

Yu-Chun Lin ◽

Salvatore Daniele ◽

Peter Jansohn ◽

Konstantinos Boulouchos

Keyword(s):

Gas Turbine ◽

Flame Propagation ◽

Carbon Capture ◽

Turbulent Flame ◽

Flame Speed ◽

Turbulent Flame Speed ◽

Velocity Gradients ◽

Fuel Mixtures ◽

Operational Range ◽

Rich Mixtures

The turbulent flame speed (ST) is proposed to be an indicator of the flashback propensity for hydrogen-rich fuel gases at gas turbine relevant conditions. Flashback is an inevitable issue to be concerned about when introducing fuel gases containing high hydrogen content to gas turbine engines, which are conventionally fueled with natural gas. These hydrogen-containing fuel gases are present in the process of the integrated gasification combined cycle (IGCC), with and without precombustion carbon capture, and both syngas (H2 + CO) and hydrogen with various degrees of inert dilution fall in this category. Thus, a greater understanding of the flashback phenomenon for these mixtures is necessary in order to evolve the IGCC concept (either with or without carbon capture) into a promising candidate for clean power generation. Compared to syngas, the hydrogen-rich fuel mixtures exhibit an even narrower operational envelope between the occurrence of lean blow out and flashback. When flashback occurs, the flame propagation is found to occur exclusively in the boundary layer of the pipe supplying the premixed fuel/air mixture to the combustor. This finding is based on the experimental investigation of turbulent lean-premixed nonswirled confined jet flames for three fuel mixtures with H2 > 70 vol. %. Measurements were performed up to 10 bar at a fixed bulk velocity at the combustor inlet (u0 = 40 m/s) and preheat temperature (T0 = 623 K). Flame front characteristics were retrieved via planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) diagnostics and the turbulent flame speed (ST) was derived, accordingly, from the perspective of a global consumption rate. Concerning the flashback limit, the operational range of the hydrogen-rich mixtures is found to be well represented by the velocity gradients prescribed by the flame (gc) and the flow (gf), respectively. The former (gc) is determined as ST/(Le × δL0), where Le is the Lewis number and δL0 is the calculated thermal thickness of the one-dimensional laminar flame. The latter (gf) is predicted by the Blasius correlation for fully developed turbulent pipe flow and it indicates the capability with which the flow can counteract the opposed flame propagation. Our results show that the equivalence ratios at which the two velocity gradients reach similar levels correspond well to the flashback limits observed at various pressures. The methodology is also found to be capable of predicting the aforementioned difference in the operational range between syngas and hydrogen-rich mixtures.

Download Full-text

Measurements of the reactivity of premixed, stagnation, methane-air flames at gas turbine relevant pressures

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4041125 ◽

2018 ◽

Vol 141 (1) ◽

Cited By ~ 2

Author(s):

Philippe Versailles ◽

Antoine Durocher ◽

Gilles Bourque ◽

Jeffrey M. Bergthorson

Keyword(s):

Gas Turbine ◽

Laminar Flame ◽

Turbulent Flame ◽

Flame Speed ◽

Turbine Engines ◽

Gas Turbine Engines ◽

Chemical Modeling ◽

Transient Phenomena ◽

Turbulent Flame Speed ◽

Development And Validation

The adiabatic, unstrained, laminar flame speed, SL, is a fundamental combustion property, and a premier target for the development and validation of thermochemical mechanisms. It is one of the leading parameters determining the turbulent flame speed, the flame position in burners and combustors, and the occurrence of transient phenomena, such as flashback and blowout. At pressures relevant to gas turbine engines, SL is generally extracted from the continuous expansion of a spherical reaction front in a combustion bomb. However, independent measurements obtained in different types of apparatuses are required to fully constrain thermochemical mechanisms. Here, a jet-wall, stagnation burner designed for operation at gas turbine relevant conditions is presented, and used to assess the reactivity of premixed, lean-to-rich, methane–air flames at pressures up to 16 atm. One-dimensional (1D) profiles of axial velocity are obtained on the centerline axis of the burner using particle tracking velocimetry, and compared to quasi-1D flame simulations performed with a selection of thermochemical mechanisms available in the literature. Significant discrepancies are observed between the numerical and experimental data, and among the predictions of the mechanisms. This motivates further chemical modeling efforts, and implies that designers in industry must carefully select the mechanisms employed for the development of gas turbine combustors.

Download Full-text

Turbulent Flame Speed as an Indicator for Flashback Propensity of Hydrogen-Rich Fuel Gases

Volume 1B: Combustion, Fuels and Emissions ◽

10.1115/gt2013-95518 ◽

2013 ◽

Cited By ~ 1

Author(s):

Y.-C. Lin ◽

S. Daniele ◽

P. Jansohn ◽

K. Boulouchos

Keyword(s):

Gas Turbine ◽

Flame Propagation ◽

Carbon Capture ◽

Turbulent Flame ◽

Flame Speed ◽

Turbulent Flame Speed ◽

Velocity Gradients ◽

Fuel Mixtures ◽

Operational Range ◽

Rich Mixtures

The turbulent flame speed (ST) is proposed to be an indicator of flashback propensity for hydrogen-rich fuel gases at gas turbine relevant conditions. Flashback is an inevitable issue to be concerned about when introducing fuel gases containing high hydrogen content to gas turbine engines, which are conventionally fueled with natural gas. These hydrogen-containing fuel gases are present in the process of the integrated gasification combined cycle (IGCC) with and without pre-combustion carbon capture, and both syngas (H2 + CO) and hydrogen with various degree of inert dilution fall in this category. More understanding on the flashback phenomenon for these mixtures is thus necessary in order to evolve the IGCC concept (either with or without carbon capture) into a promising candidate for clean power generation. Compared to syngas, the hydrogen-rich fuel mixtures exhibit an even narrower operational envelope between the occurrence of lean blow out and flashback. When flashback occurs, the flame propagation is found to happen exclusively in the boundary layer of the pipe supplying the premixed fuel/air mixture to the combustor. This finding is based on the experimental investigation of turbulent, lean-premixed, non-swirled, confined jet flames for three fuel mixtures with H2 > 70 Vol. %. Measurements were performed up to 10 bar at fixed bulk velocity at the combustor inlet (u0 = 40 m/s) and preheat temperature (T0 = 623 K). Flame front characteristics were retrieved via OH-PLIF diagnostics, and turbulent flame speed (ST) was derived accordingly from the perspective of a global consumption rate. Concerning the flashback limit, the operational range of the hydrogen-rich mixtures is found to be well represented by the velocity gradients prescribed respectively by the flame (gc) and the flow (gf). The former (gc) is determined as ST/(Le × δL0), where Le is the Lewis number and δL0 is the calculated thermal thickness of the one-dimensional laminar flame. The latter (gf) is predicted by the Blasius correlation for fully developed turbulent pipe flow, and it indicates the capability with which the flow can counteract the opposed flame propagation. Our results show that the equivalence ratios at which the two velocity gradients reach similar levels correspond well to the flashback limits observed at various pressures. The methodology is also found to be capable of predicting the aforementioned difference in the operational range between syngas and hydrogen-rich mixtures.

Download Full-text

Measurements of the Reactivity of Premixed, Stagnation, Methane-Air Flames at Gas Turbine Relevant Pressures

Volume 4B: Combustion, Fuels, and Emissions ◽

10.1115/gt2018-77018 ◽

2018 ◽

Author(s):

Philippe Versailles ◽

Antoine Durocher ◽

Gilles Bourque ◽

Jeffrey M. Bergthorson

Keyword(s):

Gas Turbine ◽

Laminar Flame ◽

Turbulent Flame ◽

Flame Speed ◽

Turbine Engines ◽

Gas Turbine Engines ◽

Chemical Modeling ◽

Turbulent Flame Speed ◽

Development And Validation ◽

Selection Of

The adiabatic, unstrained, laminar flame speed, SL, is a fundamental combustion property, and a premier target for the development and validation of thermochemical mechanisms. It is one of the leading parameters determining the turbulent flame speed, the flame position in burners and combustors, and the occurrence of transient processes, such as flashback and blowout. At pressures relevant to gas turbine engines, SL is generally extracted from the continuous expansion of a spherical reaction front in a combustion bomb. However, independent measurements obtained in different types of apparatuses are required to fully constrain thermochemical mechanisms. Here, a jet-wall, stagnation burner designed for operation at gas turbine relevant conditions is presented, and used to assess the reactivity of premixed, lean-to-rich, methane-air flames at pressures up to 16 atm. One-dimensional (1D) profiles of axial velocity are obtained on the centreline axis of the jet-wall burner using Particle Tracking Velocimetry, and compared to quasi-1D flame simulations performed with a selection of thermochemical mechanisms available in the literature. Significant discrepancies are observed between the numerical and experimental data, and among the predictions of the mechanisms. This motivates further chemical modeling efforts, and implies that designers in industry must carefully select the mechanisms employed for the development of gas turbine combustors.

Download Full-text

Flame Front Characteristic and Turbulent Flame Speed of Lean Premixed Syngas Combustion at Gas Turbine Relevant Conditions

Volume 2: Combustion, Fuels and Emissions ◽

10.1115/gt2009-59477 ◽

2009 ◽

Cited By ~ 7

Author(s):

S. Daniele ◽

P. Jansohn ◽

K. Boulouchos

Keyword(s):

Flame Front ◽

Gas Turbine ◽

Turbulent Flame ◽

Front Surface ◽

Flame Speed ◽

Inlet Temperature ◽

Oh Radicals ◽

High Hydrogen ◽

Turbulent Flame Speed ◽

Front Detection

This paper focuses on the description of the turbulent flame speed, at gas turbine like conditions, for different syngas mixtures, selected in order to simulate syngas compositions typically derived from gasification of coal, oil, biomass, and used for power generation in integrated gasification combined cycle (IGCC) processes. In this paper the turbulent flame speed is reported as global consumption rate and calculated based on a mass continuity approach applied to the combustor inlet area and the flame front surface, which was detected experimentally. Flame front detection was done by means of planar laser induced fluorescence technique taking OH radicals as seeding dyes. An in-house developed flame front detection software tool has been further improved and utilized in this work in order to better fit ultra-lean H2-rich flames. Experiments were carried out in a High Pressure Test Rig for operating pressures up to 15 bar. Data provided in this paper will focus on a pressure level of 5 bar, adiabatic flame temperatures up to 1900 K, inlet velocities from 40 to 80 m/s, and inlet temperature of 672 and 772 K. As expected, the results highlight the strongly elevated values of turbulent flame speed for high hydrogen containing fuel gas mixtures. Compared with flame speed data for pure CH4 the ratio (STSyn/STCH4) takes up values of 7 to 8. In absolute terms values go up even beyond 10 m/s. With increased H2 content in the mixture the burning velocity raises, due to the faster chemical kinetics characteristic of this compound and due to physical properties of H2 (Le<1) which enhance flame front corrugation (i.e. flame front surface). Inlet velocity and pressure variations showed to have weak effect on the average flame front position whereas this last parameter is strongly affected by the mixture composition, the equivalence ratio and inlet temperature.

Download Full-text

Turbulent flame speed for syngas at gas turbine relevant conditions

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2010.05.057 ◽

2011 ◽

Vol 33 (2) ◽

pp. 2937-2944 ◽

Cited By ~ 81

Author(s):

S. Daniele ◽

P. Jansohn ◽

J. Mantzaras ◽

K. Boulouchos

Keyword(s):

Gas Turbine ◽

Turbulent Flame ◽

Flame Speed ◽

Turbulent Flame Speed

Download Full-text

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

Fluids ◽

10.3390/fluids4030146 ◽

2019 ◽

Vol 4 (3) ◽

pp. 146 ◽

Cited By ~ 2

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.

Download Full-text