Pub Date : 2024-09-14DOI: 10.1016/j.proci.2024.105706
Anjul Pandey, Maximilian Karsch, Andreas Kronenburg
Agglomerate growth and the evolution of the agglomerate size distribution is determined by the collision frequencies between the agglomerates of the different size classes. For size distributions that can be parameterized by the agglomerates size only, expressions for the collision kernels exist and agglomerate growth can be predicted with sufficient accuracy. In the case of systems with polydisperse primary particles such as the agglomeration of soot or of systems with several components such as the flame synthesis of nanoparticles with taylor-made catalytic properties, a bi- or polydisperse size distribution is needed to account for the effects of the different primary particle sizes. In the present paper, collision frequency are obtained from a large series of Langevin dynamics (LD) simulations that are largely “model-free”. Bi-disperse primary particle systems are investigated where the size ratios of the primary particles are varied from unity to a factor of up to six. An analytic expression for an effective collision radius is suggested and accounts for functional dependencies on agglomerate size, composition and fractal dimension. Independent simulations for the evolution of the population balance equation (PBE) for the bi-variate agglomerate size distribution are conducted and assessed by comparison with corresponding Langevin dynamics simulations. The agreement between PBE solution and LD simulation results is generally very good indicating sufficient accuracy in modelling the collision kernel. Additional PBE simulation for mono-variate size distributions notably underpredict collision rates and errors of up to 140% in the total number of agglomerates can be expected by the end of a simulation for the larger size ratios. Errors are small for size ratios of two, but overall, a bi-variate parameterization of the population size distribution is needed to accurately predict agglomerate growth if the size ratio between the primary particles is notably larger than two.
{"title":"Modelling collision frequencies and predicting bi-variate agglomerate size distributions for bi-disperse primary particle systems","authors":"Anjul Pandey, Maximilian Karsch, Andreas Kronenburg","doi":"10.1016/j.proci.2024.105706","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105706","url":null,"abstract":"Agglomerate growth and the evolution of the agglomerate size distribution is determined by the collision frequencies between the agglomerates of the different size classes. For size distributions that can be parameterized by the agglomerates size only, expressions for the collision kernels exist and agglomerate growth can be predicted with sufficient accuracy. In the case of systems with polydisperse primary particles such as the agglomeration of soot or of systems with several components such as the flame synthesis of nanoparticles with taylor-made catalytic properties, a bi- or polydisperse size distribution is needed to account for the effects of the different primary particle sizes. In the present paper, collision frequency are obtained from a large series of Langevin dynamics (LD) simulations that are largely “model-free”. Bi-disperse primary particle systems are investigated where the size ratios of the primary particles are varied from unity to a factor of up to six. An analytic expression for an effective collision radius is suggested and accounts for functional dependencies on agglomerate size, composition and fractal dimension. Independent simulations for the evolution of the population balance equation (PBE) for the bi-variate agglomerate size distribution are conducted and assessed by comparison with corresponding Langevin dynamics simulations. The agreement between PBE solution and LD simulation results is generally very good indicating sufficient accuracy in modelling the collision kernel. Additional PBE simulation for mono-variate size distributions notably underpredict collision rates and errors of up to 140% in the total number of agglomerates can be expected by the end of a simulation for the larger size ratios. Errors are small for size ratios of two, but overall, a bi-variate parameterization of the population size distribution is needed to accurately predict agglomerate growth if the size ratio between the primary particles is notably larger than two.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"21 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258761","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 : 2024-09-14DOI: 10.1016/j.proci.2024.105764
Fanliang Ge, Anthony Hamins, Tinting Qiu, Jie Ji
Pool fires are the most prevalent accidents in the process industry. Revealing the physical mechanism of pool fire has both fundamental and practical applications in process safety and risk analysis. This paper intends to study the radiation blockage phenomenon caused by fuel vapor and flame in pool fires. Combustion and evaporation (non-combustion) experiments under different external radiative heat fluxes have been conducted to differentiate the radiation blockage of the fuel vapor and the flame. Four different sooting fuels including methanol, ethanol, n-heptane and toluene were used in the experiments. The radiation blockage of fuel vapor was determined through evaporation experiments. The radiation blockage of flame and the total radiation blockage of pool fires were investigated by burning experiments. Based on the assumptions of radiation gray for flame radiation and external radiation, the effective radiation blockage was determined. It is found that the effective radiation blockage coefficient of the fuel vapor increases with fuel mass flux first, and then gradually approaches a constant value because the radiation absorption capacity of the fuel vapor tends to saturate with the increase of fuel mass flux. The correlations between the fuel vapor radiation blockage coefficient and fuel mass flux are established based on theoretical analysis and experimental data. Moreover, the flame blockage coefficient decreases with external radiation for methanol, ethanol and n-heptane because the fire expands, causing enhanced radiative heat feedback from the flame. For the heavily sooting fuel, toluene, the flame radiation blockage almost remains constant with external radiation due to high soot concentrations.
{"title":"Experimental research on radiation blockage of the fuel vapor and flame in pool fires","authors":"Fanliang Ge, Anthony Hamins, Tinting Qiu, Jie Ji","doi":"10.1016/j.proci.2024.105764","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105764","url":null,"abstract":"Pool fires are the most prevalent accidents in the process industry. Revealing the physical mechanism of pool fire has both fundamental and practical applications in process safety and risk analysis. This paper intends to study the radiation blockage phenomenon caused by fuel vapor and flame in pool fires. Combustion and evaporation (non-combustion) experiments under different external radiative heat fluxes have been conducted to differentiate the radiation blockage of the fuel vapor and the flame. Four different sooting fuels including methanol, ethanol, n-heptane and toluene were used in the experiments. The radiation blockage of fuel vapor was determined through evaporation experiments. The radiation blockage of flame and the total radiation blockage of pool fires were investigated by burning experiments. Based on the assumptions of radiation gray for flame radiation and external radiation, the effective radiation blockage was determined. It is found that the effective radiation blockage coefficient of the fuel vapor increases with fuel mass flux first, and then gradually approaches a constant value because the radiation absorption capacity of the fuel vapor tends to saturate with the increase of fuel mass flux. The correlations between the fuel vapor radiation blockage coefficient and fuel mass flux are established based on theoretical analysis and experimental data. Moreover, the flame blockage coefficient decreases with external radiation for methanol, ethanol and n-heptane because the fire expands, causing enhanced radiative heat feedback from the flame. For the heavily sooting fuel, toluene, the flame radiation blockage almost remains constant with external radiation due to high soot concentrations.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258820","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 : 2024-09-12DOI: 10.1016/j.proci.2024.105207
Carola Kuhn, Marco Kirn, Steffen Tischer, Olaf Deutschmann
Iron is a promising energy carrier with the potential to store substantial amounts of energy over extended time periods with minimal losses. For instance, the energy from green hydrogen sources can be used to reduce iron oxides, be stored or transported, and thus be regained by exothermic oxidation of the iron. This work explores the influence of oxygen partial pressure and temperature on the oxidation process in a fixed-bed reactor. Furthermore, the analysis extends to the reduction of oxidized iron particles at varying temperatures. The experimental findings highlight that both oxidation and reduction progress through the fixed-bed reactor as distinct reaction fronts. In the oxidation process, the speed of the reaction front increases with rising oxygen content and temperature, resulting in a higher reaction rate and a correspondingly increased heat release. Conversely, the reaction rate for reduction experiences a notable decrease for 600°C and 700°C. The reprocessability of the iron powder was validated for up to 16 cycles under the optimal reaction conditions established. Furthermore, it was demonstrated that the performance improves with an increasing number of cycles. This improvement is attributed to the formation of pores due to density changes and the subsequent creation of a larger surface area, mitigating the negative effects of sintering and agglomeration.
{"title":"Micron-sized iron particles as energy carrier: Cycling experiments in a fixed-bed reactor","authors":"Carola Kuhn, Marco Kirn, Steffen Tischer, Olaf Deutschmann","doi":"10.1016/j.proci.2024.105207","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105207","url":null,"abstract":"Iron is a promising energy carrier with the potential to store substantial amounts of energy over extended time periods with minimal losses. For instance, the energy from green hydrogen sources can be used to reduce iron oxides, be stored or transported, and thus be regained by exothermic oxidation of the iron. This work explores the influence of oxygen partial pressure and temperature on the oxidation process in a fixed-bed reactor. Furthermore, the analysis extends to the reduction of oxidized iron particles at varying temperatures. The experimental findings highlight that both oxidation and reduction progress through the fixed-bed reactor as distinct reaction fronts. In the oxidation process, the speed of the reaction front increases with rising oxygen content and temperature, resulting in a higher reaction rate and a correspondingly increased heat release. Conversely, the reaction rate for reduction experiences a notable decrease for 600°C and 700°C. The reprocessability of the iron powder was validated for up to 16 cycles under the optimal reaction conditions established. Furthermore, it was demonstrated that the performance improves with an increasing number of cycles. This improvement is attributed to the formation of pores due to density changes and the subsequent creation of a larger surface area, mitigating the negative effects of sintering and agglomeration.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"43 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258821","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}
Soot is an unwelcome by-product of combustion that not only raises public health issues but also plays a role in climate change and, more practically, deteriorates engine performances. Although critical for the design of low-soot burners, the numerical prediction of soot phenomena remains a challenge. Among other, one major difficulty is linked to the numerous chemical species involved in the chemistry of gaseous soot precursors (PAHs). In this paper, an improved modeling methodology is proposed to describe PAHs, which relaxes standard assumptions on transport properties and number of PAHs, two aspects which play a major role on the PAH evolution. To do so, a hybrid method has been developed, coupling semi-detailed chemistry integration for the accurate flame structure description, with pre-tabulated quantities issued from prior simple calculations for gaseous soot precursors modeling. In addition the classical flamelet approach has been extended to account for non-unity Lewis numbers. The proposed modeling approach is first validated against laminar counter flow diffusion ethylene/air flames and then applied to a 3D turbulent non-premixed ethylene/air combustor operated at Cambridge University. Comparison with measurements confirm the validity of the approach for the prediction of PAH.
{"title":"On the inclusion of preferential diffusion effects for PAH tabulation in turbulent non-premixed ethylene/air sooting flames","authors":"Alexandre Coudray, Eleonore Riber, Bénédicte Cuenot","doi":"10.1016/j.proci.2024.105607","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105607","url":null,"abstract":"Soot is an unwelcome by-product of combustion that not only raises public health issues but also plays a role in climate change and, more practically, deteriorates engine performances. Although critical for the design of low-soot burners, the numerical prediction of soot phenomena remains a challenge. Among other, one major difficulty is linked to the numerous chemical species involved in the chemistry of gaseous soot precursors (PAHs). In this paper, an improved modeling methodology is proposed to describe PAHs, which relaxes standard assumptions on transport properties and number of PAHs, two aspects which play a major role on the PAH evolution. To do so, a hybrid method has been developed, coupling semi-detailed chemistry integration for the accurate flame structure description, with pre-tabulated quantities issued from prior simple calculations for gaseous soot precursors modeling. In addition the classical flamelet approach has been extended to account for non-unity Lewis numbers. The proposed modeling approach is first validated against laminar counter flow diffusion ethylene/air flames and then applied to a 3D turbulent non-premixed ethylene/air combustor operated at Cambridge University. Comparison with measurements confirm the validity of the approach for the prediction of PAH.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"17 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258993","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 : 2024-09-11DOI: 10.1016/j.proci.2024.105533
Sean C. Coburn, Nicolas Harris, Elijah A. Miller, Stefan Droste, Kevin Knabe, Gregory B. Rieker
Gas flaring is used as an alternative to venting when waste gases cannot be captured from industrial processes such as oil and natural gas production, chemical processing, and waste management. In the oil and natural gas production sector alone, an estimated 3.5 % of total global natural gas production is flared. Survey studies have shown that the methane destruction efficiency (DE) of flares is lower than expected due to real-world conditions (weather and equipment malfunction) and estimate that improving flare efficiency is a 0.5 Tg/yr methane emissions reduction opportunity. Continuous monitoring of flare DE would provide the opportunity for feedback to lower emissions; however, there are currently no technologies used at scale that can provide such a measurement. Here we present a method for measuring the operational methane DE from flares by monitoring methane levels in flares using dual-frequency comb spectroscopy. This method leverages the temperature-dependent absorption fingerprint of methane to differentiate heated and ambient methane. We assess the capabilities of this technique through a set of laboratory-based experiments utilizing a partially premixed methane flame. We estimate the limit of detection (LOD) and sensitivity of the measurements for directly monitoring a flame, and monitoring a flame from a distance of 1 km in the presence of ambient methane. For our configuration, a targeted monitoring scenario (direct flame measurement) results in the ability to distinguish methane DE up to 99.9 %; whereas in the presence of a 1 km background methane signal, the approach is able to quantify methane DE to 97.5 %. These performance metrics could be improved through an updated high-temperature spectral absorption database for methane, however the current estimated performance could already substantially impact flare emissions by closing the gap between the flare design specifications and what research studies estimate from actual in-field performance.
{"title":"Measuring methane destruction efficiency in gas flares with dual comb spectroscopy","authors":"Sean C. Coburn, Nicolas Harris, Elijah A. Miller, Stefan Droste, Kevin Knabe, Gregory B. Rieker","doi":"10.1016/j.proci.2024.105533","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105533","url":null,"abstract":"Gas flaring is used as an alternative to venting when waste gases cannot be captured from industrial processes such as oil and natural gas production, chemical processing, and waste management. In the oil and natural gas production sector alone, an estimated 3.5 % of total global natural gas production is flared. Survey studies have shown that the methane destruction efficiency (DE) of flares is lower than expected due to real-world conditions (weather and equipment malfunction) and estimate that improving flare efficiency is a 0.5 Tg/yr methane emissions reduction opportunity. Continuous monitoring of flare DE would provide the opportunity for feedback to lower emissions; however, there are currently no technologies used at scale that can provide such a measurement. Here we present a method for measuring the operational methane DE from flares by monitoring methane levels in flares using dual-frequency comb spectroscopy. This method leverages the temperature-dependent absorption fingerprint of methane to differentiate heated and ambient methane. We assess the capabilities of this technique through a set of laboratory-based experiments utilizing a partially premixed methane flame. We estimate the limit of detection (LOD) and sensitivity of the measurements for directly monitoring a flame, and monitoring a flame from a distance of 1 km in the presence of ambient methane. For our configuration, a targeted monitoring scenario (direct flame measurement) results in the ability to distinguish methane DE up to 99.9 %; whereas in the presence of a 1 km background methane signal, the approach is able to quantify methane DE to 97.5 %. These performance metrics could be improved through an updated high-temperature spectral absorption database for methane, however the current estimated performance could already substantially impact flare emissions by closing the gap between the flare design specifications and what research studies estimate from actual in-field performance.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"82 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258995","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 : 2024-09-11DOI: 10.1016/j.proci.2024.105760
Giovanni Tretola, Paul McGinn, Daniel Fredrich, Konstantina Vogiatzaki
In this paper, an artificial neural network (ANN) is trained with large eddy simulation (LES) data to predict the droplet size distribution (DSD) from the primary atomisation of a liquid jet in gaseous cross-flow (JIC), in terms of the Weber number (), momentum flux ratio () and density ratio. The JIC is simulated considering three (250, 500, 1000), (1, 5, 10), and density ratios (10, 100, 1000), respectively. The accuracy of the simulations is enhanced by including the injector geometry as well. The training data are obtained using LES with a stochastic fields transported-probability density function (PDF) method. We initially provide a physical analysis of the droplet distributions observed. We find that for lower density ratios, the resulting spray is mostly dominated by , influencing the main mechanisms governing the break-up process, which change the DSD shape. This dual mechanism is not present when increasing the density ratio. In the second part of the work, we build an ANN model (based on a multi-layered perceptron) using the DSDs from the LES as a train-and-test dataset, to predict at the end the full DSD for the JIC given as input the three non-dimensional parameters. The DSD from the trained ANN is found to be a good fit for the range investigated, predicting both the stochastic nature and change in shape of the droplet populations upon varying the input parameters. The developed model is intended to enhance future simulations of secondary atomisation in Eulerian-Lagrangian frameworks by providing the initial DSDs.
本文利用大涡模拟（LES）数据训练了一个人工神经网络（ANN），从韦伯数（）、动量通量比（）和密度比的角度预测气态横流（JIC）中液体射流一次雾化的液滴粒度分布（DSD）。模拟 JIC 时分别考虑了三个（250、500、1000）、（1、5、10）和密度比（10、100、1000）。通过将喷射器的几何形状也考虑在内，提高了模拟的准确性。训练数据是通过采用随机场传输概率密度函数 (PDF) 方法的 LES 获得的。我们首先对观察到的液滴分布进行了物理分析。我们发现，在密度比较低的情况下，所产生的喷雾主要是由"...... "主导，影响着改变液滴分布形状的主要破裂机制。当密度比增加时，这种双重机制就不存在了。在工作的第二部分，我们使用来自 LES 的 DSD 作为训练和测试数据集，建立了一个 ANN 模型（基于多层感知器），在输入三个非维度参数的情况下，最终预测 JIC 的完整 DSD。结果发现，经过训练的 ANN 所得出的 DSD 与所研究的范围非常吻合，既能预测液滴群的随机性，又能预测输入参数变化时液滴群形状的变化。所开发的模型旨在通过提供初始 DSD 增强未来欧拉-拉格朗日框架中二次雾化的模拟。
{"title":"Machine learning assisted characterisation and prediction of droplet distributions in a liquid jet in cross-flow","authors":"Giovanni Tretola, Paul McGinn, Daniel Fredrich, Konstantina Vogiatzaki","doi":"10.1016/j.proci.2024.105760","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105760","url":null,"abstract":"In this paper, an artificial neural network (ANN) is trained with large eddy simulation (LES) data to predict the droplet size distribution (DSD) from the primary atomisation of a liquid jet in gaseous cross-flow (JIC), in terms of the Weber number (), momentum flux ratio () and density ratio. The JIC is simulated considering three (250, 500, 1000), (1, 5, 10), and density ratios (10, 100, 1000), respectively. The accuracy of the simulations is enhanced by including the injector geometry as well. The training data are obtained using LES with a stochastic fields transported-probability density function (PDF) method. We initially provide a physical analysis of the droplet distributions observed. We find that for lower density ratios, the resulting spray is mostly dominated by , influencing the main mechanisms governing the break-up process, which change the DSD shape. This dual mechanism is not present when increasing the density ratio. In the second part of the work, we build an ANN model (based on a multi-layered perceptron) using the DSDs from the LES as a train-and-test dataset, to predict at the end the full DSD for the JIC given as input the three non-dimensional parameters. The DSD from the trained ANN is found to be a good fit for the range investigated, predicting both the stochastic nature and change in shape of the droplet populations upon varying the input parameters. The developed model is intended to enhance future simulations of secondary atomisation in Eulerian-Lagrangian frameworks by providing the initial DSDs.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"1 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258822","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}
Understanding flame propagation in a gasoline/air mixture with reaction progress is necessary to understand flame propagation in the cylinder and improve the combustion performance in spark-ignition engines. In this study, numerical simulations were performed to discuss the mechanisms of laminar flame speed evolution of flames propagating in gasoline/air mixtures with reaction progress. The simulation was conducted for stoichiometric and fuel-lean mixtures under high temperature and pressure conditions considering the in-cylinder condition of spark-ignition engines. Two reactors in Ansys Chemkin-Pro software were coupled. The first reactor simulates a homogeneous, adiabatic, isochoric reaction progress for a finite designated time. The pressure increase in the reaction progress period was taken into account as observed in practical engines. Then, the output of the first reactor was used as the inlet condition of the second reactor, which simulates a steady one-dimensional planar flame propagation. As a result, the laminar flame speed increased despite the pressure increase caused by the reaction progress in the first reactor. However, the rate of change in the laminar flame speed with respect to the reaction progress varied depending on the conditions, and a greater rate of increase was observed in fuel-lean conditions than in stoichiometric conditions. Also, the trend was related to low temperature chemistry. A comparative study was conducted to examine the thermal, pressure, and chemical effects of reaction progress on the laminar flame speed, and the temperature increase by reaction progress had the dominant increase effect, while pressure increase and reduced chemical enthalpy by chemical composition change had negative impacts on flame propagation. Furthermore, sensitivity analysis was conducted to investigate how the reaction in the flame changes as a result of reaction progress. The results indicate that the increase in pressure and compositional change influenced the flame chemistry and resulting changes in the laminar flame speed, and the equivalence ratio had a significant impact on the trend of sensitivity.
{"title":"Effects of reaction progress on the laminar flame speed of gasoline/air mixtures under engine-relevant conditions","authors":"Haruki Tajima, Takuya Tomidokoro, Takeshi Yokomori","doi":"10.1016/j.proci.2024.105734","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105734","url":null,"abstract":"Understanding flame propagation in a gasoline/air mixture with reaction progress is necessary to understand flame propagation in the cylinder and improve the combustion performance in spark-ignition engines. In this study, numerical simulations were performed to discuss the mechanisms of laminar flame speed evolution of flames propagating in gasoline/air mixtures with reaction progress. The simulation was conducted for stoichiometric and fuel-lean mixtures under high temperature and pressure conditions considering the in-cylinder condition of spark-ignition engines. Two reactors in Ansys Chemkin-Pro software were coupled. The first reactor simulates a homogeneous, adiabatic, isochoric reaction progress for a finite designated time. The pressure increase in the reaction progress period was taken into account as observed in practical engines. Then, the output of the first reactor was used as the inlet condition of the second reactor, which simulates a steady one-dimensional planar flame propagation. As a result, the laminar flame speed increased despite the pressure increase caused by the reaction progress in the first reactor. However, the rate of change in the laminar flame speed with respect to the reaction progress varied depending on the conditions, and a greater rate of increase was observed in fuel-lean conditions than in stoichiometric conditions. Also, the trend was related to low temperature chemistry. A comparative study was conducted to examine the thermal, pressure, and chemical effects of reaction progress on the laminar flame speed, and the temperature increase by reaction progress had the dominant increase effect, while pressure increase and reduced chemical enthalpy by chemical composition change had negative impacts on flame propagation. Furthermore, sensitivity analysis was conducted to investigate how the reaction in the flame changes as a result of reaction progress. The results indicate that the increase in pressure and compositional change influenced the flame chemistry and resulting changes in the laminar flame speed, and the equivalence ratio had a significant impact on the trend of sensitivity.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"14 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180281","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 : 2024-09-05DOI: 10.1016/j.proci.2024.105587
Md Maksudur Rahman, Yun Yu, Hongwei Wu
This study investigates the formation of primary volatiles obtained from fast pyrolysis of waste tyre using a wire mesh reactor (WMR) at a temperature of 300‒600 °C and a heating rate of 1000 °C/s. The unique design of WMR allows the collection of primary volatiles with minimized secondary reactions in the vapour phase. Using a recently developed method, this study successfully quantified all major products in the primary volatiles (condensed as oil product) by gas chromatography-mass spectrometry (GC‒MS). The waste tyre pyrolysis can start at a low temperature of ∼250 °C, and the char yield reduces but the oil yield increases with pyrolysis temperature and holding time. At 600 °C, the char yield rapidly reaches a stable value of ∼35 % due to the presence of carbon black in the waste tyre. The oil yield at a holding time of 100 s increases from ∼20 % at 350 °C to a maximum of ∼47 % at 600 °C. The oil products mainly include limonene, isoprene, toluene, ethylbenzene, and p-xylene. Among these major products, limonene has the highest selectivity of ∼60‒65 % depending on the pyrolysis conditions, while isoprene, p-xylene, ethylbenzene, and toluene contribute to ∼9‒13 %, ∼7‒10 %, ∼6‒8 %, ∼6‒8 % of the oil products, respectively. The total selectivity of the quantified compounds in the oil products is about ∼94‒97 %, indicating that almost all compounds in the oil products are quantified. During pyrolysis, limonene and isoprene are mainly produced from natural rubber, while aromatic products such as toluene, p-xylene and ethylbenzene are more likely produced from synthetic rubber. The tyre sample exhibits melting behaviour at ≥400 °C, forming a molten liquid phase that may promote the secondary reactions of isoprene to form limonene via monomer recombination. Overall, these results provide new insights into the primary pyrolysis mechanism of waste tyre.
本研究利用钢丝网反应器（WMR），在 300-600 °C 的温度和 1000 °C/s 的加热速率下，研究了废轮胎快速热解过程中一次挥发物的形成。WMR 的独特设计可以收集初级挥发物，并最大限度地减少气相中的二次反应。本研究采用最新开发的方法，通过气相色谱-质谱法（GC-MS）成功地量化了一次挥发物（凝结为油产品）中的所有主要产品。废轮胎热解可以在 250 ℃ 以下的低温开始，随着热解温度和保温时间的增加，炭产量降低，但油产量增加。在 600 °C 时，由于废轮胎中炭黑的存在，炭产量迅速达到稳定值 35%。保温时间为 100 秒时，产油量从 350 °C 时的∼20 % 增加到 600 °C 时的∼47 %。油产品主要包括柠檬烯、异戊二烯、甲苯、乙苯和对二甲苯。在这些主要产物中，根据热解条件的不同，柠檬烯的选择性最高，可达 60-65 %，而异戊二烯、对二甲苯、乙苯和甲苯分别占油类产物的 9-13 %、7-10 %、6-8 % 和 6-8 %。油产品中定量化合物的总选择性约为∼94-97 %，表明油产品中几乎所有化合物都得到了定量。在热解过程中，柠烯和异戊二烯主要由天然橡胶产生，而甲苯、对二甲苯和乙苯等芳香族产品则更有可能由合成橡胶产生。轮胎样品在温度≥400 °C时出现熔化现象，形成熔融液相，这可能会促进异戊二烯的二次反应，通过单体重组形成柠烯。总之，这些结果为了解废轮胎的初级热解机理提供了新的视角。
{"title":"Formation of primary volatiles during fast pyrolysis of waste tyre in a wire mesh reactor","authors":"Md Maksudur Rahman, Yun Yu, Hongwei Wu","doi":"10.1016/j.proci.2024.105587","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105587","url":null,"abstract":"This study investigates the formation of primary volatiles obtained from fast pyrolysis of waste tyre using a wire mesh reactor (WMR) at a temperature of 300‒600 °C and a heating rate of 1000 °C/s. The unique design of WMR allows the collection of primary volatiles with minimized secondary reactions in the vapour phase. Using a recently developed method, this study successfully quantified all major products in the primary volatiles (condensed as oil product) by gas chromatography-mass spectrometry (GC‒MS). The waste tyre pyrolysis can start at a low temperature of ∼250 °C, and the char yield reduces but the oil yield increases with pyrolysis temperature and holding time. At 600 °C, the char yield rapidly reaches a stable value of ∼35 % due to the presence of carbon black in the waste tyre. The oil yield at a holding time of 100 s increases from ∼20 % at 350 °C to a maximum of ∼47 % at 600 °C. The oil products mainly include limonene, isoprene, toluene, ethylbenzene, and p-xylene. Among these major products, limonene has the highest selectivity of ∼60‒65 % depending on the pyrolysis conditions, while isoprene, p-xylene, ethylbenzene, and toluene contribute to ∼9‒13 %, ∼7‒10 %, ∼6‒8 %, ∼6‒8 % of the oil products, respectively. The total selectivity of the quantified compounds in the oil products is about ∼94‒97 %, indicating that almost all compounds in the oil products are quantified. During pyrolysis, limonene and isoprene are mainly produced from natural rubber, while aromatic products such as toluene, p-xylene and ethylbenzene are more likely produced from synthetic rubber. The tyre sample exhibits melting behaviour at ≥400 °C, forming a molten liquid phase that may promote the secondary reactions of isoprene to form limonene via monomer recombination. Overall, these results provide new insights into the primary pyrolysis mechanism of waste tyre.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"59 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180282","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}
Co-firing green ammonia and coal in power plants is expected as an attractive method to phase down coal power. During the co-firing process, the ignition and combustion of pulverized coal particles are comprehensively affected by coal rank and particle size. However, the influences of coal rank and particle size on ammonia/coal stream ignition are unknown. In this study, the coal ignition process of different coal ranks (lignite, sub-bituminous, bituminous, and anthracite) and particle sizes (ranging from 63 to 120 µm) were investigated using a novel two-stage flat flame burner at various co-firing ratios. Multi-optical methods, including CH and NH chemiluminescence and high-speed backlight videography, were used to characterize the ignition process. Co-firing ammonia in the hot gas environment has both positive and negative effects on subsequent pulverized coal combustion. The positive effect is the elevated ambience temperature, while the negative effect is the consumption of oxygen in the reaction zone due to the ammonia reaction. Due to the positive effect, co-firing with ammonia in hot gas environment can induce the transition of the ignition mode. For high rank coal (e.g., anthracite) and large coal particles, the ignition mode transitions from heterogeneous ignition dominance to hetero-homogeneous joint ignition dominance. In contrast, For low-rank coal and small coal particles, co-firing ammonia further enhances the homogenous ignition and combustion. These findings contributes to the further application of the ammonia-coal co-firing technology.
{"title":"Comprehensive effect of the coal rank and particle size on ammonia/coal stream ignition","authors":"Peng Ma, Qian Huang, Ziqiu Wu, Tong Si, Zhou Lv, Shuiqing Li","doi":"10.1016/j.proci.2024.105464","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105464","url":null,"abstract":"Co-firing green ammonia and coal in power plants is expected as an attractive method to phase down coal power. During the co-firing process, the ignition and combustion of pulverized coal particles are comprehensively affected by coal rank and particle size. However, the influences of coal rank and particle size on ammonia/coal stream ignition are unknown. In this study, the coal ignition process of different coal ranks (lignite, sub-bituminous, bituminous, and anthracite) and particle sizes (ranging from 63 to 120 µm) were investigated using a novel two-stage flat flame burner at various co-firing ratios. Multi-optical methods, including CH and NH chemiluminescence and high-speed backlight videography, were used to characterize the ignition process. Co-firing ammonia in the hot gas environment has both positive and negative effects on subsequent pulverized coal combustion. The positive effect is the elevated ambience temperature, while the negative effect is the consumption of oxygen in the reaction zone due to the ammonia reaction. Due to the positive effect, co-firing with ammonia in hot gas environment can induce the transition of the ignition mode. For high rank coal (e.g., anthracite) and large coal particles, the ignition mode transitions from heterogeneous ignition dominance to hetero-homogeneous joint ignition dominance. In contrast, For low-rank coal and small coal particles, co-firing ammonia further enhances the homogenous ignition and combustion. These findings contributes to the further application of the ammonia-coal co-firing technology.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223751","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 : 2024-09-05DOI: 10.1016/j.proci.2024.105412
Patrick A. Meagher, Xinyu Zhao
3D high-fidelity simulations of non-ideal detonations in narrow channels are conducted in this study to assess the numerical resolution requirement for capturing both viscous and thermal wall losses. 3D simulations are complimented with auxiliary 2D simulations of the narrow dimension of the channel. A comprehensive convergence study, with grid resolutions ranging from 11 to 357 cells per ZND induction length was performed. A brief scale analysis was performed using Mirels’ boundary layer solution, which provides a framework for estimating the resolution requirements for a non-ideal detonation simulation. The impact of grid resolution and boundary condition was quantitatively assessed through measurement of the average detonation wave speed, analysis of average boundary layer profiles, and comparison of the effective local volumetric momentum and heat loss terms. By filtering Mirels’ solution, the loss terms from simulation were accurately recreated. This provides a mechanism to predict the error in detonation wave speed based on grid resolution. Using the filtered Mirels’ model, a simulation resolution criterion is proposed, requiring the grid resolution to be at least the momentum thickness evaluated at one induction length after the lead shock.
{"title":"Grid resolution considerations for simulating non-ideal cellular detonations","authors":"Patrick A. Meagher, Xinyu Zhao","doi":"10.1016/j.proci.2024.105412","DOIUrl":"https://doi.org/10.1016/j.proci.2024.105412","url":null,"abstract":"3D high-fidelity simulations of non-ideal detonations in narrow channels are conducted in this study to assess the numerical resolution requirement for capturing both viscous and thermal wall losses. 3D simulations are complimented with auxiliary 2D simulations of the narrow dimension of the channel. A comprehensive convergence study, with grid resolutions ranging from 11 to 357 cells per ZND induction length was performed. A brief scale analysis was performed using Mirels’ boundary layer solution, which provides a framework for estimating the resolution requirements for a non-ideal detonation simulation. The impact of grid resolution and boundary condition was quantitatively assessed through measurement of the average detonation wave speed, analysis of average boundary layer profiles, and comparison of the effective local volumetric momentum and heat loss terms. By filtering Mirels’ solution, the loss terms from simulation were accurately recreated. This provides a mechanism to predict the error in detonation wave speed based on grid resolution. Using the filtered Mirels’ model, a simulation resolution criterion is proposed, requiring the grid resolution to be at least the momentum thickness evaluated at one induction length after the lead shock.","PeriodicalId":408,"journal":{"name":"Proceedings of the Combustion Institute","volume":"16 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142180283","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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