Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105889
Sandra Recio Balmaseda , T. Jeremy P. Karpowski , Arne Scholtissek, Christian Hasse
Rich-quench-lean (RQL) burners are a promising option for hydrogen applications due to their high flame stability and flashback safety. However, recent studies have identified significant modeling challenges related to differential diffusion (DD) and multi-regime (MR) combustion effects for these types of burners. While existing tabulated chemistry approaches for partially premixed flames improve predictions in MR conditions, they usually do not account for curvature effects, which are crucial in both premixed and non-premixed hydrogen flames. To address this gap, this study performs a fully resolved simulation of a turbulent 2D lifted hydrogen flame. The impact of curvature and partial premixing on the thermo-chemical state–space is systematically analyzed, revealing that partially premixed flame characteristics are strongly affected by curvature. A novel flamelet manifold is developed by extending prior partially premixed models to incorporate curvature effects using a non-premixed Composition Space Model (CSM). An a-priori analysis is conducted by comparing the new manifold against a standard non-premixed manifold and one accounting for partial premixing without curvature. The results demonstrate that solely the novel approach accurately reproduces the density and reaction rates across different combustion regimes, highlighting the critical role of curvature in MR hydrogen combustion. These findings pave the way for improved combustion modeling in hydrogen-fueled RQL burners, with potential extensions toward unified manifolds covering a broader range of operating conditions.
{"title":"Flamelet Generated Manifolds for Multi-Regime H2-Air Combustion: A-Priori Analysis with a Partially-Premixed Lifted Flame","authors":"Sandra Recio Balmaseda , T. Jeremy P. Karpowski , Arne Scholtissek, Christian Hasse","doi":"10.1016/j.proci.2025.105889","DOIUrl":"10.1016/j.proci.2025.105889","url":null,"abstract":"<div><div>Rich-quench-lean (RQL) burners are a promising option for hydrogen applications due to their high flame stability and flashback safety. However, recent studies have identified significant modeling challenges related to differential diffusion (DD) and multi-regime (MR) combustion effects for these types of burners. While existing tabulated chemistry approaches for partially premixed flames improve predictions in MR conditions, they usually do not account for curvature effects, which are crucial in both premixed and non-premixed hydrogen flames. To address this gap, this study performs a fully resolved simulation of a turbulent 2D lifted hydrogen flame. The impact of curvature and partial premixing on the thermo-chemical state–space is systematically analyzed, revealing that partially premixed flame characteristics are strongly affected by curvature. A novel flamelet manifold is developed by extending prior partially premixed models to incorporate curvature effects using a non-premixed Composition Space Model (CSM). An a-priori analysis is conducted by comparing the new manifold against a standard non-premixed manifold and one accounting for partial premixing without curvature. The results demonstrate that solely the novel approach accurately reproduces the density and reaction rates across different combustion regimes, highlighting the critical role of curvature in MR hydrogen combustion. These findings pave the way for improved combustion modeling in hydrogen-fueled RQL burners, with potential extensions toward unified manifolds covering a broader range of operating conditions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105889"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145319804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105826
Yue Sun , Siyang Jiao , Hongbo Guo , Qiang Li , Baolu Shi , Majie Zhao
In this paper, two-dimensional numerical simulations of oblique detonation waves at the altitude of 30 km are carried out using Navier-Stokes equations coupled detailed chemical reaction. We investigated the characteristic parameters and the morphology of oblique detonation induction region with different Mach number in ammonia/hydrogen/air mixtures and the effect of the hydrogen percentage on the initiation characteristics. The numerical simulation results show that, in pure ammonia, the transition from oblique shock wave to oblique detonation wave changes from abrupt to smooth type, and the length of induction region decreases by more than a factor of ten, as the Mach number increases from 10 to 12. While, the flow field structure of the oblique detonation wave induction region is more complex due to the presence of compression waves. When Ma = 10, a long induction region is detrimental to the initiation of oblique detonation. Hydrogen addition is a potential solution. As the hydrogen content increases from 0 % to 100 %, the characteristic length of the induction region is significantly reduced. In blended fuels with higher hydrogen content and lower ammonia content, the characteristic length becomes even shorter than that of pure hydrogen fuel. After adding hydrogen, the intensity of the compression waves decreases, and a smooth transition structure is formed. Additionally, the oblique detonation wave in ammonia can achieve higher pressure than that in hydrogen at the same equivalence ratio, and this effect is particularly significant under high Mach numbers. In summary, ammonia is more suitable as a fuel for oblique detonation engines at high Mach numbers, while adding hydrogen at low Mach numbers can improve detonation performance.
{"title":"Numerical investigation of the oblique detonation initiation in ammonia/hydrogen/air mixtures","authors":"Yue Sun , Siyang Jiao , Hongbo Guo , Qiang Li , Baolu Shi , Majie Zhao","doi":"10.1016/j.proci.2025.105826","DOIUrl":"10.1016/j.proci.2025.105826","url":null,"abstract":"<div><div>In this paper, two-dimensional numerical simulations of oblique detonation waves at the altitude of 30 km are carried out using Navier-Stokes equations coupled detailed chemical reaction. We investigated the characteristic parameters and the morphology of oblique detonation induction region with different Mach number in ammonia/hydrogen/air mixtures and the effect of the hydrogen percentage on the initiation characteristics. The numerical simulation results show that, in pure ammonia, the transition from oblique shock wave to oblique detonation wave changes from abrupt to smooth type, and the length of induction region decreases by more than a factor of ten, as the Mach number increases from 10 to 12. While, the flow field structure of the oblique detonation wave induction region is more complex due to the presence of compression waves. When <em>Ma</em> = 10, a long induction region is detrimental to the initiation of oblique detonation. Hydrogen addition is a potential solution. As the hydrogen content increases from 0 % to 100 %, the characteristic length of the induction region is significantly reduced. In blended fuels with higher hydrogen content and lower ammonia content, the characteristic length becomes even shorter than that of pure hydrogen fuel. After adding hydrogen, the intensity of the compression waves decreases, and a smooth transition structure is formed. Additionally, the oblique detonation wave in ammonia can achieve higher pressure than that in hydrogen at the same equivalence ratio, and this effect is particularly significant under high Mach numbers. In summary, ammonia is more suitable as a fuel for oblique detonation engines at high Mach numbers, while adding hydrogen at low Mach numbers can improve detonation performance.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105826"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145004324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105794
Daanish S. Tyrewala, Brian C. Kaul, Scott J. Curran, Derek A. Splitter
Ammonia (NH3) has garnered significant interest as an alternative fuel for meeting international emissions reduction mandates in sectors with high weight and distance requirements, such as shipping. Technical barriers and unanswered questions remain on the combustion strategies that can maximize ammonia utilization and minimize emissions. Prior research studies at the US Department of Energy’s Oak Ridge National Laboratory have shown strong performance with NH3 under dual-fuel mode using conventional diesel combustion (CDC) manifold air pressure settings. Diesel airflow was initially used to simplify retrofitting (no turbocharger modification), which resulted in air-fuel equivalence ratios (λ) greater than 1.5. To characterize potential improvements in dual-fuel NH3 combustion performance at richer in-cylinder conditions, a global λ sweep compared the use of early (E-pilot) and late (L-pilot) single diesel injections. The experiments were conducted at 1200 RPM and 12.8 ± 0.2 bar (75 % load), and λ was varied by decreasing the commanded air flow to the engine at greater than 90 % ammonia energy substitution level. A diesel injection timing sweep was conducted for both the injection strategies at fixed λ, and the timing with the lowest engine-out N2O emissions was identified. The results indicated an optimal balance between CO2,eq and thermal efficiency benefits both E-pilot and l-pilot injection strategy cases compared with CDC at a λ of 1.4. The indicated nitrogen-based emissions exhibited a strong correlation to the ratio of CA5–50 and ignition delay for l-pilot, but no apparent trend emerged for the E-pilot injection strategy at the tested boundary conditions.
{"title":"Experimental investigation of air-fuel equivalence ratio effects on advanced dual-fuel ammonia/diesel combustion on a single-cylinder medium-duty diesel engine at high load","authors":"Daanish S. Tyrewala, Brian C. Kaul, Scott J. Curran, Derek A. Splitter","doi":"10.1016/j.proci.2025.105794","DOIUrl":"10.1016/j.proci.2025.105794","url":null,"abstract":"<div><div>Ammonia (NH<sub>3</sub>) has garnered significant interest as an alternative fuel for meeting international emissions reduction mandates in sectors with high weight and distance requirements, such as shipping. Technical barriers and unanswered questions remain on the combustion strategies that can maximize ammonia utilization and minimize emissions. Prior research studies at the US Department of Energy’s Oak Ridge National Laboratory have shown strong performance with NH<sub>3</sub> under dual-fuel mode using conventional diesel combustion (CDC) manifold air pressure settings. Diesel airflow was initially used to simplify retrofitting (no turbocharger modification), which resulted in air-fuel equivalence ratios (<em>λ</em>) greater than 1.5. To characterize potential improvements in dual-fuel NH<sub>3</sub> combustion performance at richer in-cylinder conditions, a global <em>λ</em> sweep compared the use of early (E-pilot) and late (L-pilot) single diesel injections. The experiments were conducted at 1200 RPM and 12.8 ± 0.2 bar (75 % load), and <em>λ</em> was varied by decreasing the commanded air flow to the engine at greater than 90 % ammonia energy substitution level. A diesel injection timing sweep was conducted for both the injection strategies at fixed <em>λ</em>, and the timing with the lowest engine-out N<sub>2</sub>O emissions was identified. The results indicated an optimal balance between CO<sub>2,eq</sub> and thermal efficiency benefits both E-pilot and l-pilot injection strategy cases compared with CDC at a <em>λ</em> of 1.4. The indicated nitrogen-based emissions exhibited a strong correlation to the ratio of CA5–50 and ignition delay for l-pilot, but no apparent trend emerged for the E-pilot injection strategy at the tested boundary conditions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105794"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144841804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105804
Sydney L. Rzepka, Katie VanderKam, Michael E. Mueller
Partially cracked ammonia is a promising hydrogen-carrying fuel with logistical advantages compared to pure hydrogen. However, like hydrogen-air premixed flames, under fuel-lean conditions, ammonia/hydrogen/nitrogen-air premixed flames can be thermodiffusively unstable. These instabilities affect the flame propagation speeds as well as the local formation of nitrogen oxides and nitrous oxide (reactive nitrogen emissions). To assess the viability of partially cracked ammonia as a zero-carbon fuel, understanding and ultimately modeling these pollutants in thermodiffusively unstable flames is critical. In this work, detailed two-dimensional simulations of laminar premixed planar flames were conducted to understand the development of thermodiffusive instabilities in flames of ammonia/hydrogen/nitrogen mixtures and air. The degree of ammonia cracking was varied to understand the influence of fuel composition on the instability behavior and subsequent formation of nitrogen oxides and nitrous oxide. The detailed simulation results exhibit considerable differential diffusion effects and regions of increased and decreased reactive nitrogen emissions corresponding to local flame curvature. The databases from these detailed simulations were then used to evaluate a premixed manifold model. Manifold models significantly decrease computational cost by mapping the high-dimensional thermochemical state to a lower-dimensional manifold. A premixed manifold model is considered that includes differential diffusion and flame curvature. However, analysis of the databases from these detailed simulations revealed a very strong effect of transport orthogonal to the progress variable gradient, that is, tangential diffusion. Direct tangential diffusion effects are actually stronger for less cracked mixtures due to the larger flame thickness of flames with more ammonia content. For pollutants, direct tangential diffusion effects are important for all cracking ratios, and the existing formulation of the manifold model cannot accurately predict these species. Furthermore, indirect effects of tangential diffusion on pollutants through the local radical pool and equivalence ratio also influence pollutants and are apparently stronger for the higher cracking ratio. Implications for manifold modeling are discussed, and a generally applicable strategy for predicting pollutant mass fractions in partially cracked ammonia flames must directly model tangential diffusion effects rather than rely only a mixture fraction variable to account for only indirect tangential diffusion effects that are most important for fuels containing purely or mostly hydrogen.
{"title":"Tangential diffusion effects in thermodiffusively unstable ammonia/hydrogen/nitrogen-air laminar premixed flames","authors":"Sydney L. Rzepka, Katie VanderKam, Michael E. Mueller","doi":"10.1016/j.proci.2025.105804","DOIUrl":"10.1016/j.proci.2025.105804","url":null,"abstract":"<div><div>Partially cracked ammonia is a promising hydrogen-carrying fuel with logistical advantages compared to pure hydrogen. However, like hydrogen-air premixed flames, under fuel-lean conditions, ammonia/hydrogen/nitrogen-air premixed flames can be thermodiffusively unstable. These instabilities affect the flame propagation speeds as well as the local formation of nitrogen oxides and nitrous oxide (reactive nitrogen emissions). To assess the viability of partially cracked ammonia as a zero-carbon fuel, understanding and ultimately modeling these pollutants in thermodiffusively unstable flames is critical. In this work, detailed two-dimensional simulations of laminar premixed planar flames were conducted to understand the development of thermodiffusive instabilities in flames of ammonia/hydrogen/nitrogen mixtures and air. The degree of ammonia cracking was varied to understand the influence of fuel composition on the instability behavior and subsequent formation of nitrogen oxides and nitrous oxide. The detailed simulation results exhibit considerable differential diffusion effects and regions of increased and decreased reactive nitrogen emissions corresponding to local flame curvature. The databases from these detailed simulations were then used to evaluate a premixed manifold model. Manifold models significantly decrease computational cost by mapping the high-dimensional thermochemical state to a lower-dimensional manifold. A premixed manifold model is considered that includes differential diffusion and flame curvature. However, analysis of the databases from these detailed simulations revealed a very strong effect of transport orthogonal to the progress variable gradient, that is, tangential diffusion. Direct tangential diffusion effects are actually stronger for less cracked mixtures due to the larger flame thickness of flames with more ammonia content. For pollutants, direct tangential diffusion effects are important for all cracking ratios, and the existing formulation of the manifold model cannot accurately predict these species. Furthermore, indirect effects of tangential diffusion on pollutants through the local radical pool and equivalence ratio also influence pollutants and are apparently stronger for the higher cracking ratio. Implications for manifold modeling are discussed, and a generally applicable strategy for predicting pollutant mass fractions in partially cracked ammonia flames must directly model tangential diffusion effects rather than rely only a mixture fraction variable to account for only indirect tangential diffusion effects that are most important for fuels containing purely or mostly hydrogen.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105804"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145044043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105803
Alka Panda , Andrew Klingberg , Ronald K. Hanson
<div><div>Drop-in biofuels, such as Hydroprocessed Esters and Fatty Acids (HEFA), are designed to deliver performance comparable to petroleum-based jet fuels without requiring modifications to existing aircraft engines. These biofuels, which are primarily n- and isoalkanes, have been certified by ASTM for use in blends of up to 50% with conventional Jet A to take advantage of the physical properties of cycloalkanes and aromatics. Cycloalkanes and aromatics are integral components of conventional jet fuels, contributing to desirable physical and combustion properties. However, aromatics are both carcinogenic and major precursors to soot formation, prompting the need for safer and more sustainable alternatives. Bio-derived cycloalkanes have emerged as promising aromatic substitutes, offering comparable fuel properties while mitigating environmental and health risks. HEFA fuels provide an ideal platform for investigating how variations in cycloalkane structures (e.g., monosubstituted, polysubstituted, ring size) uniquely influence fuel reactivity at engine relevant conditions. While the physical properties of cycloalkanes blended with Jet A have been reported in the literature, this study examines the impact of cycloalkane additives on the formation of stable intermediates during HEFA pyrolysis. Combustion studies of jet fuels have shown that larger hydrocarbon molecules undergo pyrolysis to form stable intermediates, such as methane, ethylene, and <span><math><mo>></mo></math></span>C2 alkenes. As these intermediates govern the oxidation of the fuel, measuring their time histories and yields provides insight into the fuel reactivity at engine relevant conditions and supports the development of combustion models. Shock tube experiments were conducted to study the pyrolysis of HEFA blends with bio-derived cycloalkanes such as 1,4 dimethylcyclooctane, p-menthane, and n-butylcyclohexane. Multiwavelength laser absorption spectroscopy (LAS) was employed to measure the time-resolved evolution of the stable pyrolysis products. All three cycloalkanes have the same carbon number, allowing for a direct comparison of how structural differences influence the formation of pyrolysis products. Blends containing 30% cycloalkanes by volume in HEFA were analyzed in experiments utilizing 1% fuel/argon test mixtures at a nominal pressure of 2 atm over the temperature range of 1150–1450 K. Additionally, ignition delay times were measured for stoichiometric mixtures for HEFA and cycloalkane blends with oxygen at a nominal pressure of 2 atm over a temperature range of 1200–1400 K. These ignition delay times were used to compare the effect of blending on global combustion behavior. These results suggest that the addition of bio-derived cycloalkanes, which improve the energy density of jet fuels, do not negatively impact the combustion performance of HEFA. Hence, the comparative performance against aromatics should ultimately guide the selection of the most suitable cycl
{"title":"Understanding the impact of cycloalkane additives on the combustion of HEFA jet fuel","authors":"Alka Panda , Andrew Klingberg , Ronald K. Hanson","doi":"10.1016/j.proci.2025.105803","DOIUrl":"10.1016/j.proci.2025.105803","url":null,"abstract":"<div><div>Drop-in biofuels, such as Hydroprocessed Esters and Fatty Acids (HEFA), are designed to deliver performance comparable to petroleum-based jet fuels without requiring modifications to existing aircraft engines. These biofuels, which are primarily n- and isoalkanes, have been certified by ASTM for use in blends of up to 50% with conventional Jet A to take advantage of the physical properties of cycloalkanes and aromatics. Cycloalkanes and aromatics are integral components of conventional jet fuels, contributing to desirable physical and combustion properties. However, aromatics are both carcinogenic and major precursors to soot formation, prompting the need for safer and more sustainable alternatives. Bio-derived cycloalkanes have emerged as promising aromatic substitutes, offering comparable fuel properties while mitigating environmental and health risks. HEFA fuels provide an ideal platform for investigating how variations in cycloalkane structures (e.g., monosubstituted, polysubstituted, ring size) uniquely influence fuel reactivity at engine relevant conditions. While the physical properties of cycloalkanes blended with Jet A have been reported in the literature, this study examines the impact of cycloalkane additives on the formation of stable intermediates during HEFA pyrolysis. Combustion studies of jet fuels have shown that larger hydrocarbon molecules undergo pyrolysis to form stable intermediates, such as methane, ethylene, and <span><math><mo>></mo></math></span>C2 alkenes. As these intermediates govern the oxidation of the fuel, measuring their time histories and yields provides insight into the fuel reactivity at engine relevant conditions and supports the development of combustion models. Shock tube experiments were conducted to study the pyrolysis of HEFA blends with bio-derived cycloalkanes such as 1,4 dimethylcyclooctane, p-menthane, and n-butylcyclohexane. Multiwavelength laser absorption spectroscopy (LAS) was employed to measure the time-resolved evolution of the stable pyrolysis products. All three cycloalkanes have the same carbon number, allowing for a direct comparison of how structural differences influence the formation of pyrolysis products. Blends containing 30% cycloalkanes by volume in HEFA were analyzed in experiments utilizing 1% fuel/argon test mixtures at a nominal pressure of 2 atm over the temperature range of 1150–1450 K. Additionally, ignition delay times were measured for stoichiometric mixtures for HEFA and cycloalkane blends with oxygen at a nominal pressure of 2 atm over a temperature range of 1200–1400 K. These ignition delay times were used to compare the effect of blending on global combustion behavior. These results suggest that the addition of bio-derived cycloalkanes, which improve the energy density of jet fuels, do not negatively impact the combustion performance of HEFA. Hence, the comparative performance against aromatics should ultimately guide the selection of the most suitable cycl","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105803"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144810146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105863
Fabienne Werner, Trupti Kathrotia, Thomas Bierkandt, Joachim Schmid, Nina Gaiser, Jasmin Bachmann, Patrick Oßwald, Markus Köhler
Gas-phase oxidation of ethyl tert-butyl ether (ETBE) and methyl tert-butyl ether (MTBE) has been studied using molecular-beam mass spectrometry (MBMS) coupled with the DLR flow reactor for atmospheric and high-pressure measurements. Over a temperature range of 750-1200 K at 1 bar and 500-1200 K at 5 bar, MTBE and ETBE were measured at slightly fuel-rich conditions with an equivalence ratio of 1.2. These experiments have been modeled using chemical kinetic mechanisms. An updated version of our in-house mechanism DLR Concise and literature mechanisms were used to model measured flow reactor mole fraction species profiles. Good agreement between computed and experimental values is obtained for measurements at both pressure conditions.
{"title":"Oxidation of MTBE and ETBE at atmospheric and elevated pressure","authors":"Fabienne Werner, Trupti Kathrotia, Thomas Bierkandt, Joachim Schmid, Nina Gaiser, Jasmin Bachmann, Patrick Oßwald, Markus Köhler","doi":"10.1016/j.proci.2025.105863","DOIUrl":"10.1016/j.proci.2025.105863","url":null,"abstract":"<div><div>Gas-phase oxidation of ethyl <em>tert</em>-butyl ether (ETBE) and methyl <em>tert</em>-butyl ether (MTBE) has been studied using molecular-beam mass spectrometry (MBMS) coupled with the DLR flow reactor for atmospheric and high-pressure measurements. Over a temperature range of 750-1200 K at 1 bar and 500-1200 K at 5 bar, MTBE and ETBE were measured at slightly fuel-rich conditions with an equivalence ratio of 1.2. These experiments have been modeled using chemical kinetic mechanisms. An updated version of our in-house mechanism DLR Concise and literature mechanisms were used to model measured flow reactor mole fraction species profiles. Good agreement between computed and experimental values is obtained for measurements at both pressure conditions.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105863"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105880
Taha Poonawala, Álvaro Muelas, Javier Ballester
The combustion of the liquid heavy fraction obtained after distilling the raw tire pyrolysis oil poses some challenges analogous to those of heavy fuel oil (HFO). Namely, its evaporation process and the formation and subsequent slow oxidation of solid residues are the most relevant issues that need attention to achieve a clean conversion of this alternative fuel. However, despite its relevance, the combustion characteristics of this heavy fraction of tire pyrolysis oil (TPO) remains mostly unexplored. This work aims to fill this gap by characterizing in detail the liquid and solid burning stages, including the envelope flame, of single droplets of TPO, HFO and their blends. The morphology of the solid particles is also analyzed using SEM-EDX. TPO droplets are found to follow evolution stages similar to HFO, but with liquid consumption times ∼1.5 shorter and cenospheres significantly smaller (36–43 % the size of HFO cokes). TPO cenospheres are hollow and have thin (∼10 µm), sponge-like walls, showing large deposits of soot even on the inner surfaces. This results in a rapid oxidation of TPO cokes through a mixed burning regime, ∼4 times faster than HFO cenospheres (which rather burnt in a constant-diameter regime). All HFO-TPO blends exhibited perfect miscibility without requiring co-solvents, with TPO addition significantly reducing HFO viscosity. Interestingly, different TPO concentrations had a similar effect on the liquid droplet lifetime, with reductions ∼1 2%. Likewise, the initial cenosphere size was reduced to a similar degree (∼33 %) for different TPO addition levels, their consumption being also faster due to the increased porosity of the cenosphere walls. These favorable effects thus point to the potential of TPO/HFO blending as a promising method to utilize both fuels in a synergistical manner, as a means to valorize TPO and, at the same time, improve efficiency and reduce particulate emissions in HFO combustion.
{"title":"Comprehensive characterization of heavy fraction of tire pyrolysis oil and its blends with heavy oil: From liquid evaporation to coke combustion","authors":"Taha Poonawala, Álvaro Muelas, Javier Ballester","doi":"10.1016/j.proci.2025.105880","DOIUrl":"10.1016/j.proci.2025.105880","url":null,"abstract":"<div><div>The combustion of the liquid heavy fraction obtained after distilling the raw tire pyrolysis oil poses some challenges analogous to those of heavy fuel oil (HFO). Namely, its evaporation process and the formation and subsequent slow oxidation of solid residues are the most relevant issues that need attention to achieve a clean conversion of this alternative fuel. However, despite its relevance, the combustion characteristics of this heavy fraction of tire pyrolysis oil (TPO) remains mostly unexplored. This work aims to fill this gap by characterizing in detail the liquid and solid burning stages, including the envelope flame, of single droplets of TPO, HFO and their blends. The morphology of the solid particles is also analyzed using SEM-EDX. TPO droplets are found to follow evolution stages similar to HFO, but with liquid consumption times ∼1.5 shorter and cenospheres significantly smaller (36–43 % the size of HFO cokes). TPO cenospheres are hollow and have thin (∼10 µm), sponge-like walls, showing large deposits of soot even on the inner surfaces. This results in a rapid oxidation of TPO cokes through a mixed burning regime, ∼4 times faster than HFO cenospheres (which rather burnt in a constant-diameter regime). All HFO-TPO blends exhibited perfect miscibility without requiring co-solvents, with TPO addition significantly reducing HFO viscosity. Interestingly, different TPO concentrations had a similar effect on the liquid droplet lifetime, with reductions ∼1 2%. Likewise, the initial cenosphere size was reduced to a similar degree (∼33 %) for different TPO addition levels, their consumption being also faster due to the increased porosity of the cenosphere walls. These favorable effects thus point to the potential of TPO/HFO blending as a promising method to utilize both fuels in a synergistical manner, as a means to valorize TPO and, at the same time, improve efficiency and reduce particulate emissions in HFO combustion.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105880"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105912
Andrea Locaspi , Alessandro Pegurri , Marco Mehl , Matteo Pelucchi , Sittichai Natesakhawat , Hang Zhou , Yupeng Xu , Ping Wang , Mehrdad Shahnam , Tiziano Faravelli
In a circular economy approach, plastic waste is a source of valuable chemicals and energy vectors. Thermochemical technologies such as pyrolysis, gasification, and combustion enable the valorization of even complex and contaminated waste streams. While condensed-phase degradation governs overall reactivity, accurately modeling the gas-phase reactivity of pyrolysis products is essential for scaling up valorization processes in industrial reactors. Isolating the pyrolysis behavior of volatiles first allows the decoupling of complexities associated with the low-temperature oxygen reactivity. This work presents a semi-detailed kinetic model to address the pyrolytic gas-phase reactivity of volatiles formed during the thermal degradation of polyethylene (PE). The model builds on a validated multi-step condensed-phase kinetic model and employs established lumping approaches. Short-chain compounds are modeled with high detail, while long-chain ones are described by surrogate species representative of diesel-cuts (NC16H32) and waxes (NC30H60). The reactivity of short chains is described through the comprehensive CRECK kinetic model by incorporating recent experimental data to refine reaction pathways of C5C7 olefins. Due to the lack of experimental data for longer olefins, their reactivity is modeled by analogy to the shorter ones, ensuring an asymptotic behavior with increasing carbon numbers. The semi-detailed model is validated against experimental data on PE pyrolysis, assuming instantaneous mixing of the inert inlet flow with released volatiles, followed by a segregated plug-flow behavior. Validation across different reactor setups confirms the model’s capability to predict detailed product distributions. Despite minor discrepancies, the proposed model effectively captures experimental trends. Future work will address modeling the reactivity in oxygen-containing environments.
{"title":"A semi-detailed pyrolytic gas-phase kinetic model for the volatiles of polyethylene thermal degradation","authors":"Andrea Locaspi , Alessandro Pegurri , Marco Mehl , Matteo Pelucchi , Sittichai Natesakhawat , Hang Zhou , Yupeng Xu , Ping Wang , Mehrdad Shahnam , Tiziano Faravelli","doi":"10.1016/j.proci.2025.105912","DOIUrl":"10.1016/j.proci.2025.105912","url":null,"abstract":"<div><div>In a circular economy approach, plastic waste is a source of valuable chemicals and energy vectors. Thermochemical technologies such as pyrolysis, gasification, and combustion enable the valorization of even complex and contaminated waste streams. While condensed-phase degradation governs overall reactivity, accurately modeling the gas-phase reactivity of pyrolysis products is essential for scaling up valorization processes in industrial reactors. Isolating the pyrolysis behavior of volatiles first allows the decoupling of complexities associated with the low-temperature oxygen reactivity. This work presents a semi-detailed kinetic model to address the pyrolytic gas-phase reactivity of volatiles formed during the thermal degradation of polyethylene (PE). The model builds on a validated multi-step condensed-phase kinetic model and employs established lumping approaches. Short-chain compounds are modeled with high detail, while long-chain ones are described by surrogate species representative of diesel-cuts (NC<sub>16</sub>H<sub>32</sub>) and waxes (NC<sub>30</sub>H<sub>60</sub>). The reactivity of short chains is described through the comprehensive CRECK kinetic model by incorporating recent experimental data to refine reaction pathways of C<sub>5</sub><sub><img></sub>C<sub>7</sub> olefins. Due to the lack of experimental data for longer olefins, their reactivity is modeled by analogy to the shorter ones, ensuring an asymptotic behavior with increasing carbon numbers. The semi-detailed model is validated against experimental data on PE pyrolysis, assuming instantaneous mixing of the inert inlet flow with released volatiles, followed by a segregated plug-flow behavior. Validation across different reactor setups confirms the model’s capability to predict detailed product distributions. Despite minor discrepancies, the proposed model effectively captures experimental trends. Future work will address modeling the reactivity in oxygen-containing environments.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105912"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145262552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105938
M. Kovács , M. Papp , I. Gy. Zsély , T. Nagy , T. Turányi
A comprehensive uncertainty analysis was conducted on a recently proposed optimized detailed methanol/NOx combustion mechanism, focusing on its predictions for the experimental data used as targets in the optimization. The primary sources of model uncertainty in both the initial and the optimized mechanisms were compared. The propagation of uncertainties in kinetic and thermodynamic model parameters to the simulation results was investigated using approaches of varying complexity. Both absolute model uncertainties and, as a novelty, those normalized by experimental uncertainties were considered. The effect of correlation among the Arrhenius parameters in optimized reactions was examined through local uncertainty analysis. Accounting for parameter correlations yielded a more accurate representation of model uncertainty, although using the temperature-average of the uncertainty parameters also provided a reasonable approximation. The impact of correlations among all kinetic parameters was assessed using global uncertainty analysis with Monte Carlo sampling, which supported these conclusions. The analyses demonstrated that parameter optimization can significantly reduce model uncertainty. On average, the root-mean-square model uncertainty, normalized by the experimental uncertainty, decreased from a factor of 5.5 to 2.4 upon optimization. The dominant uncertainty contributions from the CH2O + NO2 = HONO +HCO and CH3OH + NO2 = HONO + CH2OH reactions were effectively eliminated in the process. However, reactions involving the CH2OH radical with NO2, NO, HNO, and O2 remained significant sources of uncertainty. To further reduce the model uncertainty, future research should focus on these reactions. This includes indirect experimental measurements sensitive to these pathways, as well as direct measurements or theoretical calculations of their rate coefficients.
{"title":"Uncertainty quantification of a newly optimized methanol/NOx combustion mechanism","authors":"M. Kovács , M. Papp , I. Gy. Zsély , T. Nagy , T. Turányi","doi":"10.1016/j.proci.2025.105938","DOIUrl":"10.1016/j.proci.2025.105938","url":null,"abstract":"<div><div>A comprehensive uncertainty analysis was conducted on a recently proposed optimized detailed methanol/NOx combustion mechanism, focusing on its predictions for the experimental data used as targets in the optimization. The primary sources of model uncertainty in both the initial and the optimized mechanisms were compared. The propagation of uncertainties in kinetic and thermodynamic model parameters to the simulation results was investigated using approaches of varying complexity. Both absolute model uncertainties and, as a novelty, those normalized by experimental uncertainties were considered. The effect of correlation among the Arrhenius parameters in optimized reactions was examined through local uncertainty analysis. Accounting for parameter correlations yielded a more accurate representation of model uncertainty, although using the temperature-average of the <span><math><mrow><mi>f</mi><mo>(</mo><mi>T</mi><mo>)</mo></mrow></math></span> uncertainty parameters also provided a reasonable approximation. The impact of correlations among all kinetic parameters was assessed using global uncertainty analysis with Monte Carlo sampling, which supported these conclusions. The analyses demonstrated that parameter optimization can significantly reduce model uncertainty. On average, the root-mean-square model uncertainty, normalized by the experimental uncertainty, decreased from a factor of 5.5 to 2.4 upon optimization. The dominant uncertainty contributions from the CH<sub>2</sub>O + NO<sub>2</sub> = HONO +HCO and CH<sub>3</sub>OH + NO<sub>2</sub> = HONO + CH<sub>2</sub>OH reactions were effectively eliminated in the process. However, reactions involving the CH<sub>2</sub>OH radical with NO<sub>2</sub>, NO, HNO, and O<sub>2</sub> remained significant sources of uncertainty. To further reduce the model uncertainty, future research should focus on these reactions. This includes indirect experimental measurements sensitive to these pathways, as well as direct measurements or theoretical calculations of their rate coefficients.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105938"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145319805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.proci.2025.105853
Xianqing Zhu , Liping Wu , Mian Xu , Zhipeng Shi , Xuhui Jiang , Yun Huang , Ao Xia , Jun Li , Xun Zhu , Qiang Liao
Spent ternary lithium-ion batteries (NCM) are rich in catalytically active transition metals (such as Ni and Co) and have high potential for constructing a catalyst used for the catalytic reforming of biomass pyrolysis volatiles. Therefore, in this study, a novel Ni-Co bimetallic catalyst (MPyNCM/HZSM-5) was fabricated by simultaneously recovering the Ni and Co components from the magnetic components of pyrolysis products of spent NCM (MPyNCM) and loading them on HZSM-5 support. The catalytic reforming performance and mechanism of MPyNCM/HZSM-5 for wheat straw (WS) pyrolysis volatiles were explored for the first time. The results showed that the MPyNCM/HZSM-5 catalyst had a mesoporous structure (average pore size around 5 nm), with the uniform distribution of the active metals Ni and Co on its surface. The MPyNCM/HZSM-5 catalytic reforming had the highest syngas yield, H2 yield and H2 concentration, with the H2 yield reaching 1.19 mmol/g WS and 1.38 times higher than that of the HZSM-5 support. In addition, the MPyNCM/HZSM-5 significantly boosted the generation of aromatic hydrocarbons compounds and reduced the oxygen content of the obtained bio-oils, with the content of aromatic hydrocarbons reaching 29.36 %, which was 48.6 % higher than that of the HZSM-5 support. The synergistic effect between the Ni and Co metals made MPyNCM/HZSM-5 have comparable acid sites amount, high-temperature oxygen defects and reducibility to those of the Ni-Co/HZSM-5 catalysts. These chemical properties jointly promoted the deoxygenation and aromatization reactions of volatile macromolecules under MPyNCM/HZSM-5 catalysis. This study provides a novel approach to constructing a highly efficient catalyst from spent lithium-ion batteries for catalytic pyrolysis of biomass.
{"title":"Enhanced catalytic upgrading of biomass wastes pyrolysis vapors over Ni-Co modified HZSM-5 catalyst derived from spent ternary lithium-ion batteries","authors":"Xianqing Zhu , Liping Wu , Mian Xu , Zhipeng Shi , Xuhui Jiang , Yun Huang , Ao Xia , Jun Li , Xun Zhu , Qiang Liao","doi":"10.1016/j.proci.2025.105853","DOIUrl":"10.1016/j.proci.2025.105853","url":null,"abstract":"<div><div>Spent ternary lithium-ion batteries (NCM) are rich in catalytically active transition metals (such as Ni and Co) and have high potential for constructing a catalyst used for the catalytic reforming of biomass pyrolysis volatiles. Therefore, in this study, a novel Ni-Co bimetallic catalyst (MPyNCM/HZSM-5) was fabricated by simultaneously recovering the Ni and Co components from the magnetic components of pyrolysis products of spent NCM (MPyNCM) and loading them on HZSM-5 support. The catalytic reforming performance and mechanism of MPyNCM/HZSM-5 for wheat straw (WS) pyrolysis volatiles were explored for the first time. The results showed that the MPyNCM/HZSM-5 catalyst had a mesoporous structure (average pore size around 5 nm), with the uniform distribution of the active metals Ni and Co on its surface. The MPyNCM/HZSM-5 catalytic reforming had the highest syngas yield, H<sub>2</sub> yield and H<sub>2</sub> concentration, with the H<sub>2</sub> yield reaching 1.19 mmol/g WS and 1.38 times higher than that of the HZSM-5 support. In addition, the MPyNCM/HZSM-5 significantly boosted the generation of aromatic hydrocarbons compounds and reduced the oxygen content of the obtained bio-oils, with the content of aromatic hydrocarbons reaching 29.36 %, which was 48.6 % higher than that of the HZSM-5 support. The synergistic effect between the Ni and Co metals made MPyNCM/HZSM-5 have comparable acid sites amount, high-temperature oxygen defects and reducibility to those of the Ni-Co/HZSM-5 catalysts. These chemical properties jointly promoted the deoxygenation and aromatization reactions of volatile macromolecules under MPyNCM/HZSM-5 catalysis. This study provides a novel approach to constructing a highly efficient catalyst from spent lithium-ion batteries for catalytic pyrolysis of biomass.</div></div>","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"41 ","pages":"Article 105853"},"PeriodicalIF":5.2,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145104310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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