felix guethe - Academia.edu (original) (raw)

Papers by felix guethe

Journal of Engineering for Gas Turbines and Power, 2020

The aim of this work is to examine the state-of-the-art turbulent flame speed (ST) correlations a... more The aim of this work is to examine the state-of-the-art turbulent flame speed (ST) correlations and optimize their adjustable parameters to best match a wide range experimental turbulent premixed combustion results. Based on previous work, four correlations have been selected for this study. Using a matlab-based Nelder–Mead simplex direct search method, each correlation's adjustable parameters are optimized such that their mean absolute percentage error (MAPE) is minimized. In addition to the literature correlations, a new empirical correlation is developed using the same search method to define constants and powers in the expression. Two sets of optimized parameters are proposed to account for atmospheric and elevated (0.2–3.0 MPa) pressure flames. Each correlation is tested further, examining their ability to match ST trends for varying equivalence ratio (φ) and turbulent velocity ratio (u′/SL). It was found that a minimum of two correlations and two sets of adjustable paramet...

As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions... more As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions, renewable energy sources are needed to meet the increasing energy demand in the near future. Biomass, consisting mostly of plant based organic materials, is a promising alternative to fossil fuels for carbon-neutral energy production. Unfortunately, during the gasification process, the nitrogen content in biomass is converted to NH3, which is then oxidized in the combustion process, leading to high NOx emissions through the fuel-NO pathway. The high NOx emissions from NH3 and NH3-containing fuels have prevented their implementation at scale. Depending on the gasification process, source of biomass, and combustion technology, the NH3 and water content can vary greatly. This works focuses on blends of 2% (mol) NH3 in CH4 diluted by up to 55% (mass) water. The combustion process is modelled by freeflame connected to a plug flow reactor (PFR), achieving a total residence time of 100 ms. NOx emissions were investigated under different equivalence ratios (ϕ = 0.45-2.2) at elevated pressure (40 atm). NO emission index is introduced to quantify and identify the the optimal conditions that minimize the total NOx and NH3 emissions, which were found to be slightly fuel rich and long residence time. Under the optimal condition, NO concentration increases rapidly as NH3 is added to the fuel mixture, reaching superequilibrium concentrations before decreasing. Main pathways involved in the N chemistry were identified from reaction pathway analysis. Even for only 2% NH3, NO production and reburn from NH3 (fuel-NO pathway) are the most dominant routes contributing to NO emission. In the flame front region, the abundance of OH radicals promotes NH3 − → NO via HNO. The NO produced in the flame front then reacts with NHi radicals, forming NNH and N2O which promotes the conversion of NH3 to N2. Mechanisms vary greatly in terms of NO predictions, the numerical results presented from the present study can be used to compare against fundamental NO measurements in NH3 doped flames to assess and improve the fuel-NO chemistry of different mechanisms. Current findings regarding the chemical interactions of NH3 − → NO/N2 suggest that the conventional operating strategies for minimizing NOx emission in CH4 flames (lean burn, short residence time) are applicable to NH3/CH4 flames, and could provide insights into the design shift that is necessary for 100% NH3 combustion systems where fuel-NO chemistry is dominant.

A model for NOx emissions from turbulent premixed and partially premixed flames in gas turbines c... more A model for NOx emissions from turbulent premixed and partially premixed flames in gas turbines combustors is developed. The model is based on splitting NOx formation into a fast (\u201dprompt\u201d) high Damk\ua8ohler number and a slow (\u201dpostflame\u201d) low Damk\ua8ohler number contributions. A novel idea is presented for modelling prompt NOx. Given their development within the narrow heat release region (flamelet), prompt NOx are modelled coupled to heat release, i.e. according to a flamelet type combustion model. Postflame NOx are accounted for via direct incorporation of a formation rate obtained from the Zeldovich mechanism, integrated with a presumed shape probability density function (pdf) of the fuel mixture fraction f. The model is incorporated into a commercial 3D-CFD solver and shown to give reasonable agreement with NOx experimental data measured from flames stabilized in the ALSTOM EV double cone burner. The model is also incorporated into a less computationally expensive reactor network using detailed chemistry where unmixedness levels at the flame are obtained from CFD results or experiments. The proposed split of NOx into the prompt and postflame contributions gives finally the opportunity to explain observed experimental dependency of total NOx from pressure and unmixedness

The clusters were prepared either in a pure molecular beam (pmB) of DFE or in a molecular beam se... more The clusters were prepared either in a pure molecular beam (pmB) of DFE or in a molecular beam seeded in Argon. Typically 3 to 5 bar of pure DFE or its mixture with Argon were expanded through a cylindrical nozzle of 70μm diameter. The nozzle was operated at a temperature of 255K. Depending on the mixing ratio different fragmentation patterns were observed in the mass spectra indicating different compositions of the neutral cluster beam. Larger clusters (trimer and higher) seem to be favored by mixing ratios between 30:1 and 60:1 (Ar to DFE). At a mixing ratio of 50:1 (Ar to DFE) the DFE dimer is the most abundant ion in the mass spectrum apart from the Ar monomer.

To limit global warming, meet growing global energy demand and to increase security of supply, en... more To limit global warming, meet growing global energy demand and to increase security of supply, enormous investments are now being made in renewable electricity generation. A high-efficiency process, called the Biomassfired TopCycle (BTC), is being developed by Phoenix BioPower to address this market. By increasing the electrical efficiency, a cost-efficient and scalable solution is provided. As the primary fuel is biomass, carbon dioxide removals (negative emissions) can be achieved when combined with CO2 capture and sequestration. Further attributes are a high fuel flexibility including 100 % hydrogen utilization and good off-design performance, therefore allowing a dispatchable and flexible solution for renewable energy. This paper presents the BTC process, and associated components, and evaluates among others a new patented gasifier design for efficient and cost-effective operations at pressure. The BTC cycle is compared to conventional cycles and the improved performance of BTC is explained. Further, the BTC development program is described including the commissioning of a so-called fuel-to-flame test rig. From a commercial outlook the potential for the BTC concept to decarbonize our energy systems in different applications is promising, including cost-effective negative emissions in BECCS applications. The product range is presented, from 10 to 100 MWe to address the market for renewable power, heat, and negative CO2 emission.

As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions... more As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions, renewable energy sources are needed to meet the increasing energy demand in the near future. Biomass, consisting mostly of plant based organic materials, is a promising alternative to fossil fuels for carbon-neutral energy production. Unfortunately, during the gasification process, the nitrogen content in biomass is converted to NH3, which is then oxidized in the combustion process, leading to high NOx emissions through the fuel-NO pathway. The high NOx emissions from NH3 and NH3-containing fuels have prevented their implementation at scale. Depending on the gasification process, source of biomass, and combustion technology, the NH3 and water content can vary greatly. This works focuses on blends of 2% (mol) NH3 in CH4 diluted by up to 55% (mass) water. The combustion process is modelled by freeflame connected to a plug flow reactor (PFR), achieving a total residence time of 100 ms. NOx emissions were investigated under different equivalence ratios (ϕ = 0.45-2.2) at elevated pressure (40 atm). NO emission index is introduced to quantify and identify the the optimal conditions that minimize the total NOx and NH3 emissions, which were found to be slightly fuel rich and long residence time. Under the optimal condition, NO concentration increases rapidly as NH3 is added to the fuel mixture, reaching superequilibrium concentrations before decreasing. Main pathways involved in the N chemistry were identified from reaction pathway analysis. Even for only 2% NH3, NO production and reburn from NH3 (fuel-NO pathway) are the most dominant routes contributing to NO emission. In the flame front region, the abundance of OH radicals promotes NH3 − → NO via HNO. The NO produced in the flame front then reacts with NHi radicals, forming NNH and N2O which promotes the conversion of NH3 to N2. Mechanisms vary greatly in terms of NO predictions, the numerical results presented from the present study can be used to compare against fundamental NO measurements in NH3 doped flames to assess and improve the fuel-NO chemistry of different mechanisms. Current findings regarding the chemical interactions of NH3 − → NO/N2 suggest that the conventional operating strategies for minimizing NOx emission in CH4 flames (lean burn, short residence time) are applicable to NH3/CH4 flames, and could provide insights into the design shift that is necessary for 100% NH3 combustion systems where fuel-NO chemistry is dominant.

The aim of this work is to provide insight into the state-of-the-art turbulent flame speed (ST) c... more The aim of this work is to provide insight into the state-of-the-art turbulent flame speed (ST) correlations and to determine the most appropriate correlations to use under different turbulent premixed combustion conditions. The accuracies of 16 correlations for ST are determined using a large volume of data over a range of conditions. Accuracy is based on a mean absolute percentage error (MAPE). The comparison is completed once using the original authors' adjustable parameters and a second time using parameters proposed by the current work that minimize MAPE for four different groups of data. Based on the results of the analysis using the newly-suggested parameters, the five most accurate correlations are then further examined to evaluate their respective abilities to predict trends under various turbulent conditions. While many correlations perform well over the range of data (MAPE < 33%), no single correlation can predict all experimentally-observed trends for methane flames under these conditions. Further issues are found when predicting trends for larger hydrocarbons; ethane and propane. Although low errors are again found (MAPE < 25%), correlations are not generally able to replicate the observed trends of experimental data for C2H6 and C3H8. While it is commonly accepted that no single correlation can accurately predict ST, this work has shown that the correlation derived by Muppala provides the closest overall agreement to the data examined. However it cannot be defined as a general correlation. For this reason the authors have proposed to continue development of an ST modeling tool based on a modified version of the Cantera 1D freely propagating laminar flame speed (SL) code. Greater cooperation in the ST research community to expand the range of available experimental data and better enable direct comparison of data and correlations from different experiments is also recommended.

International Journal of Mass Spectrometry and Ion Processes, 1998

The journal of physical chemistry. A, Jan 15, 2016

To simulate emissions of nitrogen-containing compounds in practical combustion environments, it i... more To simulate emissions of nitrogen-containing compounds in practical combustion environments, it is necessary to have accurate values for their thermochemical parameters, as well as accurate kinetic values to describe the rates of their formation and decomposition. Significant disparity is observed in the literature for the former, and we therefore present herein high-accuracy ab initio gas-phase thermochemistry for 60 nitrogenous compounds, many of which are important in the formation and consumption chemistry of NOx species. Several quantum-chemical composite methods (CBS-APNO, G3, and G4) were utilized to derive enthalpies of formation via the atomization method. Entropies and heat capacities were calculated from traditional statistical thermodynamics, with oscillators treated as anharmonic based on ro-vibrational property analyses carried out at the B3LYP/cc-pVTZ level of theory. The use of quantum chemical methods, along with the treatments of anharmonicities and hindered rotors...

Volume 4B: Combustion, Fuels and Emissions, 2016

In recent years, market trends towards higher power generation flexibility are driving gas turbin... more In recent years, market trends towards higher power generation flexibility are driving gas turbine requirements of operation at stable conditions and below environmental emission guarantees over a wide range of operating conditions, such as load, and for changing fuels. In order to achieve these targets, engine components and operation concept need to be optimized to minimise emissions (e.g. CO, NOx) and combustion instabilities, as well as to maximize component lifetime. Therefore the combination of field experience, experimental studies and theoretical modelling of flames with state of the art tools play a key role in enabling the development of such solutions. For many applications the relative changes of reactivity due to changes in operation conditions are important thus in this report a few examples are shown, where chemical kinetics simulations are used to determine the reactivity and to predict engine behaviour. The predicted trends are validated by correlating them to valid...

The invention relates to a method for operating a power plant (22) with a connected air separatio... more The invention relates to a method for operating a power plant (22) with a connected air separation plant (10) in which fed a first partial power of the power plant (22) to an electrical supply network (28) and a second partial power of the power plant (22) for operating at least a compressor (12) of the air separation plant (10) is provided. According to the invention it is provided that the sum of the partial performance is constant and if the second partial power required to power demand of the at least one compressor (12) for delivering from the air separation plant (10) the amount of compressed air exceeds, excess compressed air (a compressed air reservoir 36) is supplied.

44th AIAA Aerospace Sciences Meeting and Exhibit, 2006

Journal of Engineering for Gas Turbines and Power, 2020

The aim of this work is to examine the state-of-the-art turbulent flame speed (ST) correlations a... more The aim of this work is to examine the state-of-the-art turbulent flame speed (ST) correlations and optimize their adjustable parameters to best match a wide range experimental turbulent premixed combustion results. Based on previous work, four correlations have been selected for this study. Using a matlab-based Nelder–Mead simplex direct search method, each correlation's adjustable parameters are optimized such that their mean absolute percentage error (MAPE) is minimized. In addition to the literature correlations, a new empirical correlation is developed using the same search method to define constants and powers in the expression. Two sets of optimized parameters are proposed to account for atmospheric and elevated (0.2–3.0 MPa) pressure flames. Each correlation is tested further, examining their ability to match ST trends for varying equivalence ratio (φ) and turbulent velocity ratio (u′/SL). It was found that a minimum of two correlations and two sets of adjustable paramet...

As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions... more As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions, renewable energy sources are needed to meet the increasing energy demand in the near future. Biomass, consisting mostly of plant based organic materials, is a promising alternative to fossil fuels for carbon-neutral energy production. Unfortunately, during the gasification process, the nitrogen content in biomass is converted to NH3, which is then oxidized in the combustion process, leading to high NOx emissions through the fuel-NO pathway. The high NOx emissions from NH3 and NH3-containing fuels have prevented their implementation at scale. Depending on the gasification process, source of biomass, and combustion technology, the NH3 and water content can vary greatly. This works focuses on blends of 2% (mol) NH3 in CH4 diluted by up to 55% (mass) water. The combustion process is modelled by freeflame connected to a plug flow reactor (PFR), achieving a total residence time of 100 ms. NOx emissions were investigated under different equivalence ratios (ϕ = 0.45-2.2) at elevated pressure (40 atm). NO emission index is introduced to quantify and identify the the optimal conditions that minimize the total NOx and NH3 emissions, which were found to be slightly fuel rich and long residence time. Under the optimal condition, NO concentration increases rapidly as NH3 is added to the fuel mixture, reaching superequilibrium concentrations before decreasing. Main pathways involved in the N chemistry were identified from reaction pathway analysis. Even for only 2% NH3, NO production and reburn from NH3 (fuel-NO pathway) are the most dominant routes contributing to NO emission. In the flame front region, the abundance of OH radicals promotes NH3 − → NO via HNO. The NO produced in the flame front then reacts with NHi radicals, forming NNH and N2O which promotes the conversion of NH3 to N2. Mechanisms vary greatly in terms of NO predictions, the numerical results presented from the present study can be used to compare against fundamental NO measurements in NH3 doped flames to assess and improve the fuel-NO chemistry of different mechanisms. Current findings regarding the chemical interactions of NH3 − → NO/N2 suggest that the conventional operating strategies for minimizing NOx emission in CH4 flames (lean burn, short residence time) are applicable to NH3/CH4 flames, and could provide insights into the design shift that is necessary for 100% NH3 combustion systems where fuel-NO chemistry is dominant.

A model for NOx emissions from turbulent premixed and partially premixed flames in gas turbines c... more A model for NOx emissions from turbulent premixed and partially premixed flames in gas turbines combustors is developed. The model is based on splitting NOx formation into a fast (\u201dprompt\u201d) high Damk\ua8ohler number and a slow (\u201dpostflame\u201d) low Damk\ua8ohler number contributions. A novel idea is presented for modelling prompt NOx. Given their development within the narrow heat release region (flamelet), prompt NOx are modelled coupled to heat release, i.e. according to a flamelet type combustion model. Postflame NOx are accounted for via direct incorporation of a formation rate obtained from the Zeldovich mechanism, integrated with a presumed shape probability density function (pdf) of the fuel mixture fraction f. The model is incorporated into a commercial 3D-CFD solver and shown to give reasonable agreement with NOx experimental data measured from flames stabilized in the ALSTOM EV double cone burner. The model is also incorporated into a less computationally expensive reactor network using detailed chemistry where unmixedness levels at the flame are obtained from CFD results or experiments. The proposed split of NOx into the prompt and postflame contributions gives finally the opportunity to explain observed experimental dependency of total NOx from pressure and unmixedness

The clusters were prepared either in a pure molecular beam (pmB) of DFE or in a molecular beam se... more The clusters were prepared either in a pure molecular beam (pmB) of DFE or in a molecular beam seeded in Argon. Typically 3 to 5 bar of pure DFE or its mixture with Argon were expanded through a cylindrical nozzle of 70μm diameter. The nozzle was operated at a temperature of 255K. Depending on the mixing ratio different fragmentation patterns were observed in the mass spectra indicating different compositions of the neutral cluster beam. Larger clusters (trimer and higher) seem to be favored by mixing ratios between 30:1 and 60:1 (Ar to DFE). At a mixing ratio of 50:1 (Ar to DFE) the DFE dimer is the most abundant ion in the mass spectrum apart from the Ar monomer.

To limit global warming, meet growing global energy demand and to increase security of supply, en... more To limit global warming, meet growing global energy demand and to increase security of supply, enormous investments are now being made in renewable electricity generation. A high-efficiency process, called the Biomassfired TopCycle (BTC), is being developed by Phoenix BioPower to address this market. By increasing the electrical efficiency, a cost-efficient and scalable solution is provided. As the primary fuel is biomass, carbon dioxide removals (negative emissions) can be achieved when combined with CO2 capture and sequestration. Further attributes are a high fuel flexibility including 100 % hydrogen utilization and good off-design performance, therefore allowing a dispatchable and flexible solution for renewable energy. This paper presents the BTC process, and associated components, and evaluates among others a new patented gasifier design for efficient and cost-effective operations at pressure. The BTC cycle is compared to conventional cycles and the improved performance of BTC is explained. Further, the BTC development program is described including the commissioning of a so-called fuel-to-flame test rig. From a commercial outlook the potential for the BTC concept to decarbonize our energy systems in different applications is promising, including cost-effective negative emissions in BECCS applications. The product range is presented, from 10 to 100 MWe to address the market for renewable power, heat, and negative CO2 emission.

As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions... more As our society transitioning away from fossil fuel-based energy system to reduce carbon emissions, renewable energy sources are needed to meet the increasing energy demand in the near future. Biomass, consisting mostly of plant based organic materials, is a promising alternative to fossil fuels for carbon-neutral energy production. Unfortunately, during the gasification process, the nitrogen content in biomass is converted to NH3, which is then oxidized in the combustion process, leading to high NOx emissions through the fuel-NO pathway. The high NOx emissions from NH3 and NH3-containing fuels have prevented their implementation at scale. Depending on the gasification process, source of biomass, and combustion technology, the NH3 and water content can vary greatly. This works focuses on blends of 2% (mol) NH3 in CH4 diluted by up to 55% (mass) water. The combustion process is modelled by freeflame connected to a plug flow reactor (PFR), achieving a total residence time of 100 ms. NOx emissions were investigated under different equivalence ratios (ϕ = 0.45-2.2) at elevated pressure (40 atm). NO emission index is introduced to quantify and identify the the optimal conditions that minimize the total NOx and NH3 emissions, which were found to be slightly fuel rich and long residence time. Under the optimal condition, NO concentration increases rapidly as NH3 is added to the fuel mixture, reaching superequilibrium concentrations before decreasing. Main pathways involved in the N chemistry were identified from reaction pathway analysis. Even for only 2% NH3, NO production and reburn from NH3 (fuel-NO pathway) are the most dominant routes contributing to NO emission. In the flame front region, the abundance of OH radicals promotes NH3 − → NO via HNO. The NO produced in the flame front then reacts with NHi radicals, forming NNH and N2O which promotes the conversion of NH3 to N2. Mechanisms vary greatly in terms of NO predictions, the numerical results presented from the present study can be used to compare against fundamental NO measurements in NH3 doped flames to assess and improve the fuel-NO chemistry of different mechanisms. Current findings regarding the chemical interactions of NH3 − → NO/N2 suggest that the conventional operating strategies for minimizing NOx emission in CH4 flames (lean burn, short residence time) are applicable to NH3/CH4 flames, and could provide insights into the design shift that is necessary for 100% NH3 combustion systems where fuel-NO chemistry is dominant.

The aim of this work is to provide insight into the state-of-the-art turbulent flame speed (ST) c... more The aim of this work is to provide insight into the state-of-the-art turbulent flame speed (ST) correlations and to determine the most appropriate correlations to use under different turbulent premixed combustion conditions. The accuracies of 16 correlations for ST are determined using a large volume of data over a range of conditions. Accuracy is based on a mean absolute percentage error (MAPE). The comparison is completed once using the original authors' adjustable parameters and a second time using parameters proposed by the current work that minimize MAPE for four different groups of data. Based on the results of the analysis using the newly-suggested parameters, the five most accurate correlations are then further examined to evaluate their respective abilities to predict trends under various turbulent conditions. While many correlations perform well over the range of data (MAPE < 33%), no single correlation can predict all experimentally-observed trends for methane flames under these conditions. Further issues are found when predicting trends for larger hydrocarbons; ethane and propane. Although low errors are again found (MAPE < 25%), correlations are not generally able to replicate the observed trends of experimental data for C2H6 and C3H8. While it is commonly accepted that no single correlation can accurately predict ST, this work has shown that the correlation derived by Muppala provides the closest overall agreement to the data examined. However it cannot be defined as a general correlation. For this reason the authors have proposed to continue development of an ST modeling tool based on a modified version of the Cantera 1D freely propagating laminar flame speed (SL) code. Greater cooperation in the ST research community to expand the range of available experimental data and better enable direct comparison of data and correlations from different experiments is also recommended.

International Journal of Mass Spectrometry and Ion Processes, 1998

The journal of physical chemistry. A, Jan 15, 2016

To simulate emissions of nitrogen-containing compounds in practical combustion environments, it i... more To simulate emissions of nitrogen-containing compounds in practical combustion environments, it is necessary to have accurate values for their thermochemical parameters, as well as accurate kinetic values to describe the rates of their formation and decomposition. Significant disparity is observed in the literature for the former, and we therefore present herein high-accuracy ab initio gas-phase thermochemistry for 60 nitrogenous compounds, many of which are important in the formation and consumption chemistry of NOx species. Several quantum-chemical composite methods (CBS-APNO, G3, and G4) were utilized to derive enthalpies of formation via the atomization method. Entropies and heat capacities were calculated from traditional statistical thermodynamics, with oscillators treated as anharmonic based on ro-vibrational property analyses carried out at the B3LYP/cc-pVTZ level of theory. The use of quantum chemical methods, along with the treatments of anharmonicities and hindered rotors...

Volume 4B: Combustion, Fuels and Emissions, 2016

In recent years, market trends towards higher power generation flexibility are driving gas turbin... more In recent years, market trends towards higher power generation flexibility are driving gas turbine requirements of operation at stable conditions and below environmental emission guarantees over a wide range of operating conditions, such as load, and for changing fuels. In order to achieve these targets, engine components and operation concept need to be optimized to minimise emissions (e.g. CO, NOx) and combustion instabilities, as well as to maximize component lifetime. Therefore the combination of field experience, experimental studies and theoretical modelling of flames with state of the art tools play a key role in enabling the development of such solutions. For many applications the relative changes of reactivity due to changes in operation conditions are important thus in this report a few examples are shown, where chemical kinetics simulations are used to determine the reactivity and to predict engine behaviour. The predicted trends are validated by correlating them to valid...

The invention relates to a method for operating a power plant (22) with a connected air separatio... more The invention relates to a method for operating a power plant (22) with a connected air separation plant (10) in which fed a first partial power of the power plant (22) to an electrical supply network (28) and a second partial power of the power plant (22) for operating at least a compressor (12) of the air separation plant (10) is provided. According to the invention it is provided that the sum of the partial performance is constant and if the second partial power required to power demand of the at least one compressor (12) for delivering from the air separation plant (10) the amount of compressed air exceeds, excess compressed air (a compressed air reservoir 36) is supplied.

44th AIAA Aerospace Sciences Meeting and Exhibit, 2006