H. Kutkan, A. Amato, G. Campa, L. Tay-Wo-Chong, E. Æsøy
This paper presents large eddy simulation (LES) turbulent combustion models for premixed methane/hydrogen/air mixtures which account for stretch, heat loss and Lewis number effects by means of a previously proposed turbulent flame speed expression [1]. In this expression stretch and heat loss effects are introduced by means of strained non-adiabatic laminar consumption speed calculations in fresh-to-burnt counter flow configurations with detailed chemistry, and preferential diffusion of hydrogen is accounted for by calculating an effective Lewis number of the reactants. To validate and analyze the performance of the models, large eddy simulations of fully premixed atmospheric bluff body stabilized methane/hydrogen/air flames are compared against experimental measurements [2, 3]. Heat release distributions and mean flame shapes are compared against OH* chemiluminescence data. Flame dynamics are investigated by extracting flame transfer functions (FTFs) with system identification (SI) methods and comparing them with measured FTFs from experiments.
{"title":"LES of Turbulent Premixed CH4/H2/Air Flames With Stretch and Heat Loss for Flame Characteristics and Dynamics","authors":"H. Kutkan, A. Amato, G. Campa, L. Tay-Wo-Chong, E. Æsøy","doi":"10.1115/gt2022-82397","DOIUrl":"https://doi.org/10.1115/gt2022-82397","url":null,"abstract":"\u0000 This paper presents large eddy simulation (LES) turbulent combustion models for premixed methane/hydrogen/air mixtures which account for stretch, heat loss and Lewis number effects by means of a previously proposed turbulent flame speed expression [1]. In this expression stretch and heat loss effects are introduced by means of strained non-adiabatic laminar consumption speed calculations in fresh-to-burnt counter flow configurations with detailed chemistry, and preferential diffusion of hydrogen is accounted for by calculating an effective Lewis number of the reactants.\u0000 To validate and analyze the performance of the models, large eddy simulations of fully premixed atmospheric bluff body stabilized methane/hydrogen/air flames are compared against experimental measurements [2, 3]. Heat release distributions and mean flame shapes are compared against OH* chemiluminescence data. Flame dynamics are investigated by extracting flame transfer functions (FTFs) with system identification (SI) methods and comparing them with measured FTFs from experiments.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"31 10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124477402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. V. Cojocea, Tudor Cuciuc, I. Porumbel, Mihnea Gall, B. Gherman, D. Crunteanu
Detonation combustion unveils avenues towards increased performances and efficiencies of classic deflagration architectures and enables opportunities for supersonic flight platforms. Furthermore, their primarily fuel candidate, Hydrogen, which is prone to detonation, has enormous potential in both industrial and mobility decarbonization. Nonetheless supersonic flame propagation is associated with disadvantages in terms of aerodynamic and thermal losses, which raises difficulties in achieving practical applications. Moreover, to achieve a safe and reliable energy conversion, Hydrogen combustion needs special attention. This paper addresses the analysis of a Hydrogen fuelled pulsed detonation combustor, to contribute to the understanding of the high-speed mixing performance and to improve the specific know-how regarding pressure gain combustors. By means of Z-type Schlieren visualization technique, the structure of the engine’s exhaust plume is determined to capture the intrinsic unsteady phenomena of the detonation process. Qualitative instantaneous static pressure results are presented and correlated to the Schlieren images to evaluate the cycle stages and its operating frequency.
{"title":"Experimental Investigations of Hydrogen Fuelled Pulsed Detonation Combustor","authors":"A. V. Cojocea, Tudor Cuciuc, I. Porumbel, Mihnea Gall, B. Gherman, D. Crunteanu","doi":"10.1115/gt2022-82393","DOIUrl":"https://doi.org/10.1115/gt2022-82393","url":null,"abstract":"\u0000 Detonation combustion unveils avenues towards increased performances and efficiencies of classic deflagration architectures and enables opportunities for supersonic flight platforms. Furthermore, their primarily fuel candidate, Hydrogen, which is prone to detonation, has enormous potential in both industrial and mobility decarbonization. Nonetheless supersonic flame propagation is associated with disadvantages in terms of aerodynamic and thermal losses, which raises difficulties in achieving practical applications. Moreover, to achieve a safe and reliable energy conversion, Hydrogen combustion needs special attention. This paper addresses the analysis of a Hydrogen fuelled pulsed detonation combustor, to contribute to the understanding of the high-speed mixing performance and to improve the specific know-how regarding pressure gain combustors. By means of Z-type Schlieren visualization technique, the structure of the engine’s exhaust plume is determined to capture the intrinsic unsteady phenomena of the detonation process. Qualitative instantaneous static pressure results are presented and correlated to the Schlieren images to evaluate the cycle stages and its operating frequency.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132309093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Mohammad, Nicholas Magina, Brian R. Volk, K. Mcmanus
As the interest in high hydrogen operation is gaining momentum, this paper quantifies the impacts associated with switching from natural gas to 100% hydrogen, leveraging both modelling techniques and experimental data. From the modeling standpoint, a perfectly stirred reactor network model was setup in Cantera. Flame speed increases of up to 50 times that of natural gas were observed with increasing hydrogen content, indicating a significant increase in flashback propensity. This suggests that DLE combustion systems might offer an advantage over RQL systems, operating at low equivalence ratios where the flame speed impact is milder. Additionally, the model shows that the blow off time can be used to classify hydrogen operation into three regimes. With increasing hydrogen content, the BOT begins similar to that of propane and declines at different rates in each regime, establishing the added operational challenges associated with high hydrogen content operation. Equivalence ratio dependencies were investigated along with NOx penalties, where a predicted penalty of ∼40–65% was observed within the flame temperature range of 1750–1950K. Experimentally, a new advanced mixer was used, enabling operation of the full spectrum of natural gas and hydrogen blends up to 100% hydrogen. The impact of hydrogen content on NOx emissions for a representative operating condition was investigated. Comparisons with the model predictions were made, revealing discrepancies, which were investigated and justified thru a mixedness and residence time framework. Finally, the authors show that the proper way to regulate future combustors running with 100% hydrogen should be based on NOx and not NOx15. The findings reported here help clarify and shape the future hydrogen enabling technologies, reaffirming the need for compact and shorter combustors than are used in current technologies.
{"title":"Impact of High Hydrogen Operation on Combustor Performance","authors":"B. Mohammad, Nicholas Magina, Brian R. Volk, K. Mcmanus","doi":"10.1115/gt2022-83630","DOIUrl":"https://doi.org/10.1115/gt2022-83630","url":null,"abstract":"\u0000 As the interest in high hydrogen operation is gaining momentum, this paper quantifies the impacts associated with switching from natural gas to 100% hydrogen, leveraging both modelling techniques and experimental data. From the modeling standpoint, a perfectly stirred reactor network model was setup in Cantera. Flame speed increases of up to 50 times that of natural gas were observed with increasing hydrogen content, indicating a significant increase in flashback propensity. This suggests that DLE combustion systems might offer an advantage over RQL systems, operating at low equivalence ratios where the flame speed impact is milder. Additionally, the model shows that the blow off time can be used to classify hydrogen operation into three regimes. With increasing hydrogen content, the BOT begins similar to that of propane and declines at different rates in each regime, establishing the added operational challenges associated with high hydrogen content operation. Equivalence ratio dependencies were investigated along with NOx penalties, where a predicted penalty of ∼40–65% was observed within the flame temperature range of 1750–1950K. Experimentally, a new advanced mixer was used, enabling operation of the full spectrum of natural gas and hydrogen blends up to 100% hydrogen. The impact of hydrogen content on NOx emissions for a representative operating condition was investigated. Comparisons with the model predictions were made, revealing discrepancies, which were investigated and justified thru a mixedness and residence time framework. Finally, the authors show that the proper way to regulate future combustors running with 100% hydrogen should be based on NOx and not NOx15. The findings reported here help clarify and shape the future hydrogen enabling technologies, reaffirming the need for compact and shorter combustors than are used in current technologies.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125841728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Feiz, Wei Zhao, D. Kubicki, M. Frackowiak, Vivek Kumar, H. Jadeja, Pravin M. Nakod, S. Shrivastava, Sravankumar Nallamothu, M. Lambert, J. Lee, Jinkwan Song
One of the most used spray configurations for gas turbines and power combustors is liquid jet in crossflow. The process of breakup of liquid jet is very complex and understanding this mechanism is of paramount importance in engine design. This has led to the commencement of several studies from leading research groups [1–6]. Several new modeling methods such as the Madabhushi breakup model or more detailed VOF and Level set methods have been used successfully to understand and describe these complex breakup processes. However, most of these studies have been restricted to liquid jet in uniform single stream crossflow. In reality, these jets could be subjected to several gaseous streams and the breakup mechanism may vary significantly. Recently there have been some studies to understand the effect of non-uniformities on the crossflow velocity distribution and the droplet diameter. In the current work, we attempt to extend the scope of the Madabhushi breakup model to jets subjected to non-uniform crossflow. Non-uniform crossflow is created by co-directional and parallel gas flow using several hollow tubes. Locally, the momentum flux ratio changes by a factor of 4 and uniformity ratio (the ratio of the velocities of the two gas streams) of 2. A modified version of the Madabhushi model as proposed by Lambert et. al is used here to simulate the jet breakup. Model tuning has been conducted using University of Cincinnati Research data specifically designed for this configuration in partnership with General Electric Company. For turbulence, realizable k-ε with scalable wall function is used. The droplets are tracked using Ansys Fluent Discrete Particle Model (DPM). A second modeling approach VOF-to-DPM is also used which uses VOF equation along with LES with Dynamic Kinetic Energy Subgrid-Scale Model. This model requires no fine tuning of parameters and is more accurate but comes with more computational expense. Various simulations are performed with pure water, pure diesel and emulsified diesel and water with uniform and non-uniform cross flows inside a chamber at a pressure of 50psi. Overall, the trends due to difference in material properties of the two liquids especially on penetration and Sauter mean diameter are well captured. The droplet characteristics such as axial velocity, Sauter mean diameter and volumetric flux are compared with experimental measurements and shows reasonable agreement. Overall, the liquid penetration is within reasonable accuracy. Discrepancies were seen in the spatial variation of the spray quantities such as Sauter mean diameter, droplet axial velocity etc. The simulation revealed a more averaged field whereas in experiments some layering was observed with bigger droplets at the edge of the spray, away from the wall.
{"title":"Numerical Modeling of Liquid Jet in Non-Uniform Crossflow Using Enhanced Madabhushi Model","authors":"H. Feiz, Wei Zhao, D. Kubicki, M. Frackowiak, Vivek Kumar, H. Jadeja, Pravin M. Nakod, S. Shrivastava, Sravankumar Nallamothu, M. Lambert, J. Lee, Jinkwan Song","doi":"10.1115/gt2022-82766","DOIUrl":"https://doi.org/10.1115/gt2022-82766","url":null,"abstract":"\u0000 One of the most used spray configurations for gas turbines and power combustors is liquid jet in crossflow. The process of breakup of liquid jet is very complex and understanding this mechanism is of paramount importance in engine design. This has led to the commencement of several studies from leading research groups [1–6]. Several new modeling methods such as the Madabhushi breakup model or more detailed VOF and Level set methods have been used successfully to understand and describe these complex breakup processes. However, most of these studies have been restricted to liquid jet in uniform single stream crossflow. In reality, these jets could be subjected to several gaseous streams and the breakup mechanism may vary significantly. Recently there have been some studies to understand the effect of non-uniformities on the crossflow velocity distribution and the droplet diameter. In the current work, we attempt to extend the scope of the Madabhushi breakup model to jets subjected to non-uniform crossflow. Non-uniform crossflow is created by co-directional and parallel gas flow using several hollow tubes. Locally, the momentum flux ratio changes by a factor of 4 and uniformity ratio (the ratio of the velocities of the two gas streams) of 2. A modified version of the Madabhushi model as proposed by Lambert et. al is used here to simulate the jet breakup. Model tuning has been conducted using University of Cincinnati Research data specifically designed for this configuration in partnership with General Electric Company. For turbulence, realizable k-ε with scalable wall function is used. The droplets are tracked using Ansys Fluent Discrete Particle Model (DPM). A second modeling approach VOF-to-DPM is also used which uses VOF equation along with LES with Dynamic Kinetic Energy Subgrid-Scale Model. This model requires no fine tuning of parameters and is more accurate but comes with more computational expense.\u0000 Various simulations are performed with pure water, pure diesel and emulsified diesel and water with uniform and non-uniform cross flows inside a chamber at a pressure of 50psi. Overall, the trends due to difference in material properties of the two liquids especially on penetration and Sauter mean diameter are well captured. The droplet characteristics such as axial velocity, Sauter mean diameter and volumetric flux are compared with experimental measurements and shows reasonable agreement. Overall, the liquid penetration is within reasonable accuracy. Discrepancies were seen in the spatial variation of the spray quantities such as Sauter mean diameter, droplet axial velocity etc. The simulation revealed a more averaged field whereas in experiments some layering was observed with bigger droplets at the edge of the spray, away from the wall.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125964405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As rotating detonation engine (RDE) technologies progress in maturity, the importance of monitoring methods progressing towards development of active control becomes more critical. High-speed processing of experimental RDE data on a time scale approaching real-time diagnostics will likely only be accomplished through the use of machine learning. This study aims to develop and deploy a real-time monitoring technique which integrates flame image classification by a convolutional neural network (CNN) and ionization current signal analysis with the goal of determining detonation wave number, direction, frequency, and individual wave speeds throughout experimental RDE operational windows. Wave mode identification through single image CNN classification bypasses the need to evaluate sequential images and offers instantaneous identification of the wave mode present in the RDE annulus. The output of the existing CNN is utilized alongside a correlation of ion probe data to generate diagnostic outputs. The diagnostic acquires live data using a modified experimental setup as well as Pylon and PyDAQmx libraries within a Python data acquisition environment. Lab-deployed diagnostic results are presented across a variety of wave modes, operating conditions, and data quality, currently executed at 3–4 Hz with a variety of iteration speed optimization options to be considered as future work. These speeds exceed that of conventional techniques and offer a proven structure for real-time RDE monitoring, which will play a vital role in the development of active control, necessary for the extension of operational capabilities and RDE technology maturation toward industrial integration.
{"title":"Use of Convolutional Neural Network Image Classification and High-Speed Ion Probe Data Towards Real-Time Detonation Characterization in a Water-Cooled Rotating Detonation Engine","authors":"Kristyn B. Johnson, D. Ferguson, A. Nix","doi":"10.1115/gt2022-83401","DOIUrl":"https://doi.org/10.1115/gt2022-83401","url":null,"abstract":"\u0000 As rotating detonation engine (RDE) technologies progress in maturity, the importance of monitoring methods progressing towards development of active control becomes more critical. High-speed processing of experimental RDE data on a time scale approaching real-time diagnostics will likely only be accomplished through the use of machine learning. This study aims to develop and deploy a real-time monitoring technique which integrates flame image classification by a convolutional neural network (CNN) and ionization current signal analysis with the goal of determining detonation wave number, direction, frequency, and individual wave speeds throughout experimental RDE operational windows. Wave mode identification through single image CNN classification bypasses the need to evaluate sequential images and offers instantaneous identification of the wave mode present in the RDE annulus. The output of the existing CNN is utilized alongside a correlation of ion probe data to generate diagnostic outputs. The diagnostic acquires live data using a modified experimental setup as well as Pylon and PyDAQmx libraries within a Python data acquisition environment. Lab-deployed diagnostic results are presented across a variety of wave modes, operating conditions, and data quality, currently executed at 3–4 Hz with a variety of iteration speed optimization options to be considered as future work. These speeds exceed that of conventional techniques and offer a proven structure for real-time RDE monitoring, which will play a vital role in the development of active control, necessary for the extension of operational capabilities and RDE technology maturation toward industrial integration.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127480903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, an experimental investigation is conducted to assess the impact of the flare geometry on the mean flow field generated by radial-radial swirlers. Two-dimensional two-component PIV measurements are performed on the mid-plane of a non-reacting planar combustor test section. Three-dimensional numerical simulations are conducted for selected cases to support experimental observations. In a previous study conducted in the same setup, counter-rotating radial-radial swirlers without flare extension were investigated. In this study, in addition to the previously studied baseline swirler geometry, four different swirlers are investigated with three different flare geometries (a rounded flare geometry with a radius of 4 mm and two chamfered flares at angles of 27.5° and 45°) with the rounded one having both co- and counter-rotating configurations. Analysis of the time-averaged flow fields reveals that there is an increase in radial velocity values and a decrease in axial velocity values as a result of the introduction of the flare geometry, which results in a sudden expansion of the swirling jet. When different flare geometries are compared, almost identical flow fields are observed and the formation of a CRZ is not observed for any geometry that employs a flare geometry. Although the maximum negative axial velocity values decrease for geometries with flare, due to the increase of the recirculation radius, the recirculating mass flow rate is higher than the baseline swirler. On the other hand, the recirculating mass flow rate is higher in the co-rotating swirler configuration due to stronger adverse pressure gradient along the central axis of the jet when compared to counter-rotating configuration. Coherent flow structures are identified by using the snapshot POD method and different mode shapes obtained for swirlers with and without flare geometry are reported. It is shown that the change of the sense of rotation and flare geometry does not bring about any differences in the POD modes and their energy contents for the given swirl number and confinement conditions.
{"title":"Effect of Flare Geometry on the Flow Field of Radial-Radial Swirlers","authors":"Ayşe Bay, Firat Kiyici, M. Perçin","doi":"10.1115/gt2022-83234","DOIUrl":"https://doi.org/10.1115/gt2022-83234","url":null,"abstract":"\u0000 In this study, an experimental investigation is conducted to assess the impact of the flare geometry on the mean flow field generated by radial-radial swirlers. Two-dimensional two-component PIV measurements are performed on the mid-plane of a non-reacting planar combustor test section. Three-dimensional numerical simulations are conducted for selected cases to support experimental observations. In a previous study conducted in the same setup, counter-rotating radial-radial swirlers without flare extension were investigated. In this study, in addition to the previously studied baseline swirler geometry, four different swirlers are investigated with three different flare geometries (a rounded flare geometry with a radius of 4 mm and two chamfered flares at angles of 27.5° and 45°) with the rounded one having both co- and counter-rotating configurations. Analysis of the time-averaged flow fields reveals that there is an increase in radial velocity values and a decrease in axial velocity values as a result of the introduction of the flare geometry, which results in a sudden expansion of the swirling jet. When different flare geometries are compared, almost identical flow fields are observed and the formation of a CRZ is not observed for any geometry that employs a flare geometry. Although the maximum negative axial velocity values decrease for geometries with flare, due to the increase of the recirculation radius, the recirculating mass flow rate is higher than the baseline swirler. On the other hand, the recirculating mass flow rate is higher in the co-rotating swirler configuration due to stronger adverse pressure gradient along the central axis of the jet when compared to counter-rotating configuration. Coherent flow structures are identified by using the snapshot POD method and different mode shapes obtained for swirlers with and without flare geometry are reported. It is shown that the change of the sense of rotation and flare geometry does not bring about any differences in the POD modes and their energy contents for the given swirl number and confinement conditions.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126264251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Swirl-assisted distributed combustion was investigated with hydrogen-enriched methane. Distributed reaction zones were fostered from a conventional swirl-flame at a heat release intensity of 5.72 MW/m3-atm by diluting the main airstream with either carbon dioxide or nitrogen. The effect of hydrogen addition to the fuel mixture on the performance of distributed combustion was studied for reaction zone stability, variation of blowoff equivalence ratio, and emissions of nitrogen oxide, carbon monoxide, and carbon dioxide. High-speed imaging of reaction zone chemiluminescence was performed for different cases without any spectral filtering. Gradual increase of %H2 in the fuel mixture increased the chemiluminescence intensity in both the swirl and distributed combustion cases. The standoff distance was gradually reduced with hydrogen enrichment along with the appearance of a narrow flame shape from increased reactivity in the flame brush. Fluctuation of pressure (p′) and heat release (q′) was qualitatively measured from the microphone and photomultiplier (fitted with CH* filter) signals at different %H2 enrichments. The amplitude of fluctuation of p′ and q′ showed the existence of a common peak in swirl combustion indicating the possibility of thermo-acoustic coupling. This peak diminished in distributed combustion for H2 enrichment between 0–20% providing enhanced stability compared to swirl combustion. However, a small peak common to p′ and q′ appeared at 40% H2-enrichment indicating the departure of this reaction zone from its distributed nature. Such fluctuations of reaction zones were further investigated with the proper orthogonal decomposition to verify if the vortex shedding influenced these fluctuations. The appearance of vortex shedding characteristics for the distributed combustion with 40% H2-enrichment was found to be responsible for the fluctuations of reaction zones resulting in a departure from the purely distributed behavior. Measurement of lean blowoff equivalence ratios (ϕLBO) at different combustion conditions showed extension of ϕLBO in distributed combustion indicating wider operational limits in distributed combustion. The performance of distributed reaction zones was analyzed from the exhaust emission characteristics of NO, CO, and CO2. The NO levels (ppm) gradually increased in conventional swirl combustion while it consistently decreased in distributed combustion with the increase of %H2. The increase in NO in normal swirl combustion was attributed to the increase in flame temperature. The overall exhaust CO (ppm) decreased with hydrogen enrichment. The exhaust CO2 gradually decreased with %H2-enrichment for both swirl and distributed reaction zones. The higher CO2 observed with CO2 dilution (compared to N2 dilution) is attributed to the usage of CO2 as the diluent. Emission characteristics were also investigated with preheating of inlet airstream (in the range 373–573 K) to study the performance of distributed combustion r
{"title":"Performance of Swirl-Stabilized Distributed Combustion With Hydrogen-Enriched Methane: Stability, Blowoff and Emissions","authors":"Rishi Roy, Khuong Nguyen, Trevor Stuart, A. Gupta","doi":"10.1115/gt2022-82062","DOIUrl":"https://doi.org/10.1115/gt2022-82062","url":null,"abstract":"\u0000 Swirl-assisted distributed combustion was investigated with hydrogen-enriched methane. Distributed reaction zones were fostered from a conventional swirl-flame at a heat release intensity of 5.72 MW/m3-atm by diluting the main airstream with either carbon dioxide or nitrogen. The effect of hydrogen addition to the fuel mixture on the performance of distributed combustion was studied for reaction zone stability, variation of blowoff equivalence ratio, and emissions of nitrogen oxide, carbon monoxide, and carbon dioxide. High-speed imaging of reaction zone chemiluminescence was performed for different cases without any spectral filtering. Gradual increase of %H2 in the fuel mixture increased the chemiluminescence intensity in both the swirl and distributed combustion cases. The standoff distance was gradually reduced with hydrogen enrichment along with the appearance of a narrow flame shape from increased reactivity in the flame brush. Fluctuation of pressure (p′) and heat release (q′) was qualitatively measured from the microphone and photomultiplier (fitted with CH* filter) signals at different %H2 enrichments. The amplitude of fluctuation of p′ and q′ showed the existence of a common peak in swirl combustion indicating the possibility of thermo-acoustic coupling. This peak diminished in distributed combustion for H2 enrichment between 0–20% providing enhanced stability compared to swirl combustion. However, a small peak common to p′ and q′ appeared at 40% H2-enrichment indicating the departure of this reaction zone from its distributed nature. Such fluctuations of reaction zones were further investigated with the proper orthogonal decomposition to verify if the vortex shedding influenced these fluctuations. The appearance of vortex shedding characteristics for the distributed combustion with 40% H2-enrichment was found to be responsible for the fluctuations of reaction zones resulting in a departure from the purely distributed behavior. Measurement of lean blowoff equivalence ratios (ϕLBO) at different combustion conditions showed extension of ϕLBO in distributed combustion indicating wider operational limits in distributed combustion. The performance of distributed reaction zones was analyzed from the exhaust emission characteristics of NO, CO, and CO2. The NO levels (ppm) gradually increased in conventional swirl combustion while it consistently decreased in distributed combustion with the increase of %H2. The increase in NO in normal swirl combustion was attributed to the increase in flame temperature. The overall exhaust CO (ppm) decreased with hydrogen enrichment. The exhaust CO2 gradually decreased with %H2-enrichment for both swirl and distributed reaction zones. The higher CO2 observed with CO2 dilution (compared to N2 dilution) is attributed to the usage of CO2 as the diluent. Emission characteristics were also investigated with preheating of inlet airstream (in the range 373–573 K) to study the performance of distributed combustion r","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132058123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bernhard Stiehl, M. Otto, Malcolm K. Newmyer, Max K. Fortin, Tommy Genova, K. Ahmed, J. Kapat, Stefano Orsino, C. Arguinzoni
The present paper numerically studies the impact of three gaseous fuels on the reaction characteristics and pollutant formation in a lean combustion system. The models include an equilibrium calculation with Ansys-Chemkin-Pro, as well as a 3D half-width CFD model using Large Eddy Simulation (LES) and Adaptive Mesh Refinement (AMR) models. The outcomes are targeted to benefit the transition to carbon-free operation of aviation turbines. Three fuels, methane (CH4), hydrogen (H2), and ammonia (NH3) as well as blends thereof were compared at constant equivalence ratios to obtain a firing temperature level of T = 1800°C. The kinetic mechanism in use was suggested and validated by Okafor et al., including 42 species to describe CH4/H2/NH3-air combustion and NOx chemistry. The formation of nitrogen oxide pollutants (NO, NO2 and N2O) were analyzed to determine the sensitivity to the three fuels and their blends. Secondly, a fuel injector scaling study was performed, and a significantly larger jet diameter was selected to compensate for the increased stoichiometric mixture fraction and reduced blend density relative to CH4-fueled architecture. Lastly, the three-dimensional AMR-LES model provided validation of the injector re-sizing, as well as further insight into the expected fuel-air distribution by convective mixing. While the substitution of methane-fueled gas turbines with carbon-free alternatives is generally feasible, blending of H2 and NH3 fuels could be a promising strategy to utilize existing turbine combustors, while retaining reaction timescales close to those of CH4-powered systems.
{"title":"Numerical Study of Three Gaseous Fuels on the Reactor Length and Pollutant Formation Under Lean Gas Turbine Conditions","authors":"Bernhard Stiehl, M. Otto, Malcolm K. Newmyer, Max K. Fortin, Tommy Genova, K. Ahmed, J. Kapat, Stefano Orsino, C. Arguinzoni","doi":"10.1115/gt2022-83343","DOIUrl":"https://doi.org/10.1115/gt2022-83343","url":null,"abstract":"The present paper numerically studies the impact of three gaseous fuels on the reaction characteristics and pollutant formation in a lean combustion system. The models include an equilibrium calculation with Ansys-Chemkin-Pro, as well as a 3D half-width CFD model using Large Eddy Simulation (LES) and Adaptive Mesh Refinement (AMR) models. The outcomes are targeted to benefit the transition to carbon-free operation of aviation turbines. Three fuels, methane (CH4), hydrogen (H2), and ammonia (NH3) as well as blends thereof were compared at constant equivalence ratios to obtain a firing temperature level of T = 1800°C. The kinetic mechanism in use was suggested and validated by Okafor et al., including 42 species to describe CH4/H2/NH3-air combustion and NOx chemistry. The formation of nitrogen oxide pollutants (NO, NO2 and N2O) were analyzed to determine the sensitivity to the three fuels and their blends. Secondly, a fuel injector scaling study was performed, and a significantly larger jet diameter was selected to compensate for the increased stoichiometric mixture fraction and reduced blend density relative to CH4-fueled architecture. Lastly, the three-dimensional AMR-LES model provided validation of the injector re-sizing, as well as further insight into the expected fuel-air distribution by convective mixing. While the substitution of methane-fueled gas turbines with carbon-free alternatives is generally feasible, blending of H2 and NH3 fuels could be a promising strategy to utilize existing turbine combustors, while retaining reaction timescales close to those of CH4-powered systems.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"12 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133205156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Undavalli, J. Hamilton, E. Ubogu, I. Ahmed, B. Khandelwal
The study aims to establish the behavior of hydro processed esters and fatty acids (HEFA), as a type of alternative fuel with a conventional Jet A-1 as a reference fuel using a GTCP85 aircraft auxiliary power unit (APU). The research evaluates the impact of fuel properties on emissions using HEFA (blends in 18 proportions) and Jet A-1. With increasing HEFA proportions in the fuel, it is observed that reduction of gaseous emissions is not absolute. No specific trend of gaseous emissions reduction, in terms of aromatic and hydrogen content, were observed for the 18 blend ratios tested. For 50:50 blend of HEFA and Jet A-1, which meets current American Society for Testing and Materials (ASTM) specifications D7566 as drop-in fuel to D1655, the average reduction of NOX, CO, UHC emissions in PPM are ∼ 40%, 18%, and 28%, respectively. In contrast, no significant difference observed in CO2 emissions as compared with Jet A-1. Furthermore, the smoke number is proportional to the aromatic fuel content, fuel density (at 15°C), and carbon content irrespective of load condition. Conversely, the smoke number tends to be inversely proportional to the hydrogen, Sulphur, iso-paraffinic, and heat content of the fuel. Finally, these findings will contribute to the knowledge of fuel properties on impact engine performance and emissions as the aviation industry moves towards 100% SAFs.
该研究的目的是建立氢加工酯和脂肪酸(HEFA)作为一种替代燃料的行为，使用GTCP85飞机辅助动力装置(APU)，以传统的Jet a -1作为参考燃料。该研究使用HEFA(按18种比例混合)和Jet A-1来评估燃料特性对排放的影响。随着燃料中HEFA比例的增加，气体排放的减少不是绝对的。在测试的18种混合比例中，没有观察到气体排放减少的具体趋势，就芳香和氢含量而言。HEFA和Jet A-1以50:50的比例混合，符合当前美国材料测试协会(ASTM)规范D7566作为直接燃料到D1655，氮氧化物，一氧化碳，UHC排放量在PPM中平均减少约40%，18%和28%。相比之下，与喷气机A-1相比，CO2排放量没有显著差异。此外，烟数与芳香燃料含量、燃料密度(在15°C时)和碳含量成正比，而与负载条件无关。相反，烟数往往与燃料的氢、硫、异石蜡和热含量成反比。最后，随着航空业向100% SAFs迈进，这些发现将有助于了解燃料特性对发动机性能和排放的影响。
{"title":"Impact of HEFA Fuel Properties on Gaseous Emissions and Smoke Number in a Gas Turbine Engine","authors":"V. Undavalli, J. Hamilton, E. Ubogu, I. Ahmed, B. Khandelwal","doi":"10.1115/gt2022-82201","DOIUrl":"https://doi.org/10.1115/gt2022-82201","url":null,"abstract":"\u0000 The study aims to establish the behavior of hydro processed esters and fatty acids (HEFA), as a type of alternative fuel with a conventional Jet A-1 as a reference fuel using a GTCP85 aircraft auxiliary power unit (APU). The research evaluates the impact of fuel properties on emissions using HEFA (blends in 18 proportions) and Jet A-1. With increasing HEFA proportions in the fuel, it is observed that reduction of gaseous emissions is not absolute. No specific trend of gaseous emissions reduction, in terms of aromatic and hydrogen content, were observed for the 18 blend ratios tested. For 50:50 blend of HEFA and Jet A-1, which meets current American Society for Testing and Materials (ASTM) specifications D7566 as drop-in fuel to D1655, the average reduction of NOX, CO, UHC emissions in PPM are ∼ 40%, 18%, and 28%, respectively. In contrast, no significant difference observed in CO2 emissions as compared with Jet A-1. Furthermore, the smoke number is proportional to the aromatic fuel content, fuel density (at 15°C), and carbon content irrespective of load condition. Conversely, the smoke number tends to be inversely proportional to the hydrogen, Sulphur, iso-paraffinic, and heat content of the fuel. Finally, these findings will contribute to the knowledge of fuel properties on impact engine performance and emissions as the aviation industry moves towards 100% SAFs.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116526595","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents numerical investigations of turbulent premixed bluff-body stabilized flame by emphasizing the influence of pressure gradient on flame-vortex interaction and flame stability for lean combustion applications. Large eddy simulations of four different geometrical configurations, diffuser 3°, diffuser 1.5°, nominal, and nozzle that resulted in mild to strong pressure gradients are presented. Numerical investigations allowed determining the effects of geometry-induced pressure gradient on the flame structure, development of the flame-front vorticity and turbulent structures and flame stabilization. It is shown that the pressure gradient plays a key role for the spatial and temporal development of the flame front vorticity and baroclinic torque. The flow deceleration in diffuser geometries suppresses the flame-induced vorticity mechanisms, which in turn lead to large wrinkle forms of the flame and may lead to local extinctions along the flame front. The favorable pressure gradient in the nozzle geometry, on the contrary, increases the baroclinic torque that restrains the development of the shear layer vorticity and hence prevents local extinctions.
{"title":"Influence of Pressure Gradient on Flame-Vortex Interaction and Flame Stability","authors":"Yagiz Yalcinkaya, O. E. Bozkurt, A. G. Gungor","doi":"10.1115/gt2022-82517","DOIUrl":"https://doi.org/10.1115/gt2022-82517","url":null,"abstract":"\u0000 This study presents numerical investigations of turbulent premixed bluff-body stabilized flame by emphasizing the influence of pressure gradient on flame-vortex interaction and flame stability for lean combustion applications. Large eddy simulations of four different geometrical configurations, diffuser 3°, diffuser 1.5°, nominal, and nozzle that resulted in mild to strong pressure gradients are presented. Numerical investigations allowed determining the effects of geometry-induced pressure gradient on the flame structure, development of the flame-front vorticity and turbulent structures and flame stabilization. It is shown that the pressure gradient plays a key role for the spatial and temporal development of the flame front vorticity and baroclinic torque. The flow deceleration in diffuser geometries suppresses the flame-induced vorticity mechanisms, which in turn lead to large wrinkle forms of the flame and may lead to local extinctions along the flame front. The favorable pressure gradient in the nozzle geometry, on the contrary, increases the baroclinic torque that restrains the development of the shear layer vorticity and hence prevents local extinctions.","PeriodicalId":395231,"journal":{"name":"Volume 3B: Combustion, Fuels, and Emissions","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124546705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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