Pub Date : 2025-04-16DOI: 10.1016/j.expthermflusci.2025.111493
Jonathan Lukas Stober , Maurizio Santini , Kathrin Schulte
This study experimentally investigates oblique droplet impacts on thin wall films, providing new insights into crown formation, splashing types, and threshold modelling. Different splashing types were identified by varying the impact angle and Weber number , keeping the film thickness and fluid (isopropanol) constant. The splashing types include secondary droplet ejection only from the front or only from the sides of the crown, splashing caused by crown-film interaction, and 90°-like splashing. Combinations of these mechanisms, such as simultaneous front and side splashing, were also observed, as their triggering mechanisms are independent and allow for a superposition of regimes. A regime map and threshold formulations were developed to describe the distinct splashing types. The front splashing limit lies at , which reveals that the is the relevant physical quantity beside the Weber number. Side splashing depends solely on the wall-normal Weber number (). Crown-film interactions occur below if the Weber number is high enough, while splashing similar to that seen when is observed if the impact angle exceeds .
{"title":"Characterization of splashing and regime thresholds for oblique droplet impact on thin wall films","authors":"Jonathan Lukas Stober , Maurizio Santini , Kathrin Schulte","doi":"10.1016/j.expthermflusci.2025.111493","DOIUrl":"10.1016/j.expthermflusci.2025.111493","url":null,"abstract":"<div><div>This study experimentally investigates oblique droplet impacts on thin wall films, providing new insights into crown formation, splashing types, and threshold modelling. Different splashing types were identified by varying the impact angle <span><math><mi>α</mi></math></span> and Weber number <span><math><mrow><mi>W</mi><mi>e</mi></mrow></math></span>, keeping the film thickness <span><math><mrow><mi>δ</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>22</mn></mrow></math></span> and fluid (isopropanol) constant. The splashing types include secondary droplet ejection only from the front or only from the sides of the crown, splashing caused by crown-film interaction, and 90°-like splashing. Combinations of these mechanisms, such as simultaneous front and side splashing, were also observed, as their triggering mechanisms are independent and allow for a superposition of regimes. A regime map and threshold formulations were developed to describe the distinct splashing types. The front splashing limit lies at <span><math><mrow><mo>cos</mo><mrow><mo>(</mo><mi>α</mi><mo>)</mo></mrow><mspace></mspace><mi>W</mi><mi>e</mi><mo>=</mo><mn>128</mn></mrow></math></span>, which reveals that the <span><math><mrow><mo>cos</mo><mrow><mo>(</mo><mi>α</mi><mo>)</mo></mrow></mrow></math></span> is the relevant physical quantity beside the Weber number. Side splashing depends solely on the wall-normal Weber number (<span><math><mrow><mi>W</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>=</mo><mn>425</mn></mrow></math></span>). Crown-film interactions occur below <span><math><mrow><mi>α</mi><mo><</mo><mn>60</mn><mo>°</mo></mrow></math></span> if the Weber number is high enough, while splashing similar to that seen when <span><math><mrow><mi>α</mi><mo>=</mo><mn>90</mn><mo>°</mo></mrow></math></span> is observed if the impact angle exceeds <span><math><mrow><mi>α</mi><mo>></mo><mn>81</mn><mo>°</mo></mrow></math></span>.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111493"},"PeriodicalIF":2.8,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143855075","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 : 2025-04-11DOI: 10.1016/j.expthermflusci.2025.111491
C. Sandoval , C. Treviño , A. Alvarez , D. Matuz , J. Lizardi , L. Martínez-Suástegui
In this work, two-dimensional time-resolved particle image velocimetry (TR-PIV) measurements are carried out to study the flow structure and impinging interactions of two turbulent submerged isothermal circular impinging water jets. In this configuration, the uphill and downhill jets impinge obliquely and normally onto a flat target surface, respectively. A comprehensive parametric study is carried out for values of the jets’ exit Reynolds number of and 8000, jets’-to-surface target distances of and 5, and inclination angles of the uphill oblique jet-to-impingement surface of (30°, 45°, 60°). For all the experiments, the jet-to-jet spacing distances were varied for each impingement angle of the oblique jet so that the impingement point of both jets coincide at the geometric intersection of the jets’ axes. Flow visualization images showing ensemble-averaged and instantaneous flow distributions and turbulent characteristics for equal and non-equal Reynolds numbers of the jets are presented. Velocity profiles and Reynolds shear stress distributions of the downhill wall jet development and its corresponding dimensionless shedding frequencies are also obtained. A proper orthogonal decomposition (POD) analysis reveals the spatial structure of the dominant fluctuation motions of the turbulent flow as well as their respective contributions to the total kinetic energy. Our results show that the jets’ exit Reynolds numbers, the oblique impingement angle of the uphill jet and the jets’-to-surface distance play a major role on the complex flow structure and dynamics, location of the stagnation point and entrainment characteristics of the turbulent flow field of the twin jets.
{"title":"Flow field analysis of submerged oblique and normally impinging twin jets at varying impinging angles","authors":"C. Sandoval , C. Treviño , A. Alvarez , D. Matuz , J. Lizardi , L. Martínez-Suástegui","doi":"10.1016/j.expthermflusci.2025.111491","DOIUrl":"10.1016/j.expthermflusci.2025.111491","url":null,"abstract":"<div><div>In this work, two-dimensional time-resolved particle image velocimetry (TR-PIV) measurements are carried out to study the flow structure and impinging interactions of two turbulent submerged isothermal circular impinging water jets. In this configuration, the uphill and downhill jets impinge obliquely and normally onto a flat target surface, respectively. A comprehensive parametric study is carried out for values of the jets’ exit Reynolds number of <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>j</mi></mrow></msub><mo>=</mo><mn>5000</mn></mrow></math></span> and 8000, jets’-to-surface target distances of <span><math><mrow><mi>H</mi><mo>/</mo><mi>D</mi><mo>=</mo><mn>3</mn></mrow></math></span> and 5, and inclination angles of the uphill oblique jet-to-impingement surface of (<span><math><mrow><msub><mrow><mi>θ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>=</mo></mrow></math></span>30°, 45°, 60°). For all the experiments, the jet-to-jet spacing distances were varied for each impingement angle of the oblique jet so that the impingement point of both jets coincide at the geometric intersection of the jets’ axes. Flow visualization images showing ensemble-averaged and instantaneous flow distributions and turbulent characteristics for equal and non-equal Reynolds numbers of the jets are presented. Velocity profiles and Reynolds shear stress distributions of the downhill wall jet development and its corresponding dimensionless shedding frequencies are also obtained. A proper orthogonal decomposition (POD) analysis reveals the spatial structure of the dominant fluctuation motions of the turbulent flow as well as their respective contributions to the total kinetic energy. Our results show that the jets’ exit Reynolds numbers, the oblique impingement angle of the uphill jet and the jets’-to-surface distance play a major role on the complex flow structure and dynamics, location of the stagnation point and entrainment characteristics of the turbulent flow field of the twin jets.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111491"},"PeriodicalIF":2.8,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143833432","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 : 2025-04-08DOI: 10.1016/j.expthermflusci.2025.111487
K.J. Price, A. Martin, S.C.C. Bailey
An arc-jet campaign conducted in the Aerodynamic Heating Facility at NASA Ames was conducted to investigate the spallation of thermal protection system materials by estimating the size of particles ejected from these materials, as well as the corresponding mass loss. Particle sizes were determined both from analysis of particle tracking velocimetry, utilizing a force balance on the particulates, and by direct measurement of particles captured through targeted design of the test articles. Analysis of the captured particles revealed that they took on different geometries consisting of fine particulates, individual fibers, and clumps of multiple fibers. Different methods were required for each particle sizing approach to determine particle quantities, and corresponding mass loss. However, similar values for mass loss were determined using both techniques. In addition, it was found that the particle size distributions were independent of surface heat flux, and whether the carbon preform contained additional phenolic resin. It was found, however, that the presence of phenolic resin caused a measurable reduction in the rate of particle production, potentially due to its pyrolysis reducing the diffusion of oxygen from the free stream into the sample.
{"title":"Measurement of particulates formed during thermal protection system spallation in an arc-jet environment","authors":"K.J. Price, A. Martin, S.C.C. Bailey","doi":"10.1016/j.expthermflusci.2025.111487","DOIUrl":"10.1016/j.expthermflusci.2025.111487","url":null,"abstract":"<div><div>An arc-jet campaign conducted in the Aerodynamic Heating Facility at NASA Ames was conducted to investigate the spallation of thermal protection system materials by estimating the size of particles ejected from these materials, as well as the corresponding mass loss. Particle sizes were determined both from analysis of particle tracking velocimetry, utilizing a force balance on the particulates, and by direct measurement of particles captured through targeted design of the test articles. Analysis of the captured particles revealed that they took on different geometries consisting of fine particulates, individual fibers, and clumps of multiple fibers. Different methods were required for each particle sizing approach to determine particle quantities, and corresponding mass loss. However, similar values for mass loss were determined using both techniques. In addition, it was found that the particle size distributions were independent of surface heat flux, and whether the carbon preform contained additional phenolic resin. It was found, however, that the presence of phenolic resin caused a measurable reduction in the rate of particle production, potentially due to its pyrolysis reducing the diffusion of oxygen from the free stream into the sample.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111487"},"PeriodicalIF":2.8,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143821567","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 : 2025-04-08DOI: 10.1016/j.expthermflusci.2025.111494
Jianghong Li , Songbai Yao , Ying Lei , Jingtian Yu , Yeqi Zhou , Wenwu Zhang
In this short communication, we explore the feasibility of using renewable ethanol fuel for the rotating detonation engine (RDE) and examine the behavior of the two-phase rotating detonation wave under varying working conditions. The liquid ethanol is injected at ambient temperature, while oxygen-enriched air (60 % oxygen by mass) is supplied at mass flow rates ranging from 90 to 200 g/s. The operation of the RDE is examined under fuel-lean conditions with equivalence ratios ranging from 0.4 to 0.9. At lower mass flow rates, the rotating detonation can still be initiated but remains highly unstable. As the mass flow rate increases, the stability of the ethanol-fueled RDE improves, premature extinction becomes less frequent, and the velocity deficit of the rotating detonation wave decreases.
{"title":"Experimental investigation of rotating detonation engine fueled by liquid ethanol and oxygen-enriched air","authors":"Jianghong Li , Songbai Yao , Ying Lei , Jingtian Yu , Yeqi Zhou , Wenwu Zhang","doi":"10.1016/j.expthermflusci.2025.111494","DOIUrl":"10.1016/j.expthermflusci.2025.111494","url":null,"abstract":"<div><div>In this short communication, we explore the feasibility of using renewable ethanol fuel for the rotating detonation engine (RDE) and examine the behavior of the two-phase rotating detonation wave under varying working conditions. The liquid ethanol is injected at ambient temperature, while oxygen-enriched air (60 % oxygen by mass) is supplied at mass flow rates ranging from 90 to 200 g/s. The operation of the RDE is examined under fuel-lean conditions with equivalence ratios ranging from 0.4 to 0.9. At lower mass flow rates, the rotating detonation can still be initiated but remains highly unstable. As the mass flow rate increases, the stability of the ethanol-fueled RDE improves, premature extinction becomes less frequent, and the velocity deficit of the rotating detonation wave decreases.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111494"},"PeriodicalIF":2.8,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828237","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 : 2025-04-06DOI: 10.1016/j.expthermflusci.2025.111489
Qiansen Wang , Yunfei Zheng , Shuochen Yang , Xiongwei Yang , Huimin Cui , Qingkuan Liu
To examine the impact of mutual interference between buildings on the wind loads acting on disturbed structures, a study was conducted using two identical square-section ultrahigh-rise buildings with a height-to-width ratio of 6:1. The wind tunnel pressure test considering aeroelastic effect was carried out. The results indicate that the influence of the aeroelastic effect is significant when the interfering building is positioned obliquely upstream or in a juxtaposed configuration. Then, the presence of upstream buildings reduces the mean pressure coefficient (CP, mean) of the disturbed building. However, when the interfering building is positioned directly upstream, the interference effect leads to an increase in the root mean square of the pressure coefficient (CP, rms) at most corner points of the disturbed building. Regardless of how the wind angle changes, except for some locations upstream of the interfering building, the extreme value of the wind pressure coefficient of the disturbed building often appears near the corner of the windward side of the building. The interference from different positions has varying effects on the mean aerodynamic force coefficients. Specifically, interference from an upstream oblique position increases the mean lift coefficient (CL, mean) of the disturbed building, whereas interference from a downstream oblique position increases the mean drag coefficient (CD, mean). The power spectrum of the aerodynamic force coefficients is most notably influenced by a building positioned directly upstream. Furthermore, as the wind direction angle increases, the changes in the power spectrum become more pronounced.
{"title":"Experimental study on the wind load characteristics of high-rise buildings considering the aeroelastic effect of interference","authors":"Qiansen Wang , Yunfei Zheng , Shuochen Yang , Xiongwei Yang , Huimin Cui , Qingkuan Liu","doi":"10.1016/j.expthermflusci.2025.111489","DOIUrl":"10.1016/j.expthermflusci.2025.111489","url":null,"abstract":"<div><div>To examine the impact of mutual interference between buildings on the wind loads acting on disturbed structures, a study was conducted using two identical square-section ultrahigh-rise buildings with a height-to-width ratio of 6:1. The wind tunnel pressure test considering aeroelastic effect was carried out. The results indicate that the influence of the aeroelastic effect is significant when the interfering building is positioned obliquely upstream or in a juxtaposed configuration. Then, the presence of upstream buildings reduces the mean pressure coefficient (<em>C<sub>P</sub></em><sub>, mean</sub>) of the disturbed building. However, when the interfering building is positioned directly upstream, the interference effect leads to an increase in the root mean square of the pressure coefficient (<em>C<sub>P</sub></em><sub>, rms</sub>) at most corner points of the disturbed building. Regardless of how the wind angle changes, except for some locations upstream of the interfering building, the extreme value of the wind pressure coefficient of the disturbed building often appears near the corner of the windward side of the building. The interference from different positions has varying effects on the mean aerodynamic force coefficients. Specifically, interference from an upstream oblique position increases the mean lift coefficient (<em>C<sub>L</sub></em><sub>, mean</sub>) of the disturbed building, whereas interference from a downstream oblique position increases the mean drag coefficient (<em>C<sub>D</sub></em><sub>, mean</sub>). The power spectrum of the aerodynamic force coefficients is most notably influenced by a building positioned directly upstream. Furthermore, as the wind direction angle increases, the changes in the power spectrum become more pronounced.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111489"},"PeriodicalIF":2.8,"publicationDate":"2025-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143821568","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 : 2025-04-06DOI: 10.1016/j.expthermflusci.2025.111492
Rongying Tian, Agisilaos Kourmatzis, Yilong Zhang, Assaad R. Masri
This paper employs blends of water and hexane to study the flash-assisted atomization of immiscible two-fluid sprays without the use of surfactants. Equal volumes of each fluid are heated separately to the same temperature above the boiling point of hexane (69 °C), mixed quicky and ejected through a small nozzle to the atmospheric environment. The results are compared with those obtained for single fluids of hexane and water. High-speed imaging and phase Doppler particle analyser (PDPA) measurements at different downstream and radial locations were taken to map the spray morphology and droplet characteristics. A puffing phenomenon was observed in the near field of the spray when temperatures exceed the boiling point of the single fluid or one of the fluids in the blend. This phenomenon significantly widens the spray, with the spray width and liquid core length of the immiscible water-hexane falling between those for pure hexane and water. A novel finding from the PDPA results indicate that the puffing phenomenon induces instabilities in the immiscible blend as the explosions of hexane bubbles promote spray mixing, decreasing the droplet size and increasing the droplet velocity. Micro-explosion of bubbles from the evaporating component underlies the mechanism of flash-assisted atomization and this, in immiscible blends, results in additional instabilities through spray puffing induced pulsating breakup which eventually improves the breakup and fragmentation of both components in the mixture, producing clusters of fine droplets at a certain frequency. The results provide the potential of utilizing the immiscibility between fluids to further assist the atomization of a superheated spray.
{"title":"On the flash-assisted atomization of a two-component immiscible mixture spray","authors":"Rongying Tian, Agisilaos Kourmatzis, Yilong Zhang, Assaad R. Masri","doi":"10.1016/j.expthermflusci.2025.111492","DOIUrl":"10.1016/j.expthermflusci.2025.111492","url":null,"abstract":"<div><div>This paper employs blends of water and hexane to study the flash-assisted atomization of immiscible two-fluid sprays without the use of surfactants. Equal volumes of each fluid are heated separately to the same temperature above the boiling point of hexane (69 °C), mixed quicky and ejected through a small nozzle to the atmospheric environment. The results are compared with those obtained for single fluids of hexane and water. High-speed imaging and phase Doppler particle analyser (PDPA) measurements at different downstream and radial locations were taken to map the spray morphology and droplet characteristics. A puffing phenomenon was observed in the near field of the spray when temperatures exceed the boiling point of the single fluid or one of the fluids in the blend. This phenomenon significantly widens the spray, with the spray width and liquid core length of the immiscible water-hexane falling between those for pure hexane and water. A novel finding from the PDPA results indicate that the puffing phenomenon induces instabilities in the immiscible blend as the explosions of hexane bubbles promote spray mixing, decreasing the droplet size and increasing the droplet velocity. Micro-explosion of bubbles from the evaporating component underlies the mechanism of flash-assisted atomization and this, in immiscible blends, results in additional instabilities through spray puffing induced pulsating breakup which eventually improves the breakup and fragmentation of both components in the mixture, producing clusters of fine droplets at a certain frequency. The results provide the potential of utilizing the immiscibility between fluids to further assist the atomization of a superheated spray.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111492"},"PeriodicalIF":2.8,"publicationDate":"2025-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143844340","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 : 2025-04-04DOI: 10.1016/j.expthermflusci.2025.111484
Qing Chen , Kun Zhao , Bin Li , Dan Zhang , Rhoda Afriyie Mensah , Oisik Das , Lifeng Xie , Yongxu Wang
As the infrastructure for piped hydrogen, including long tube trailers, urban utility tunnels, and hydrogen fuel cell vehicles, expands, the risk of hydrogen explosions increases. To enhance safety technologies and minimize accident risks, this paper presents a study where hydrogen venting tests were conducted with concentrations ranging from 30 % to 60 % in a 2.25-meter-long shock tube with an inner diameter of 70 mm. The effects of different vented areas and different vented shapes on the overpressure propagation law and flame characteristics were investigated. The results indicated that higher hydrogen concentrations increase vent flame temperature, but not pressure proportionally, with 40 % H2 producing the highest pressure peaks under all vented conditions. Smaller vented areas reduce the secondary explosion's impact on internal piping and the sensitivity of venting effectiveness to concentration. The distribution of pressure peaks on the outside of the pipe is highly dependent on the vented area. The vented shape has little effect on pressure, but has a slight effect on flame characteristics at R=2/5 or 1/5. In addition, the mechanism behind pressure peak generation during pipeline venting and a brief consequence analysis of the most hazardous scenario of secondary explosions has been provided.
{"title":"Effect of hydrogen concentration, vented area, and vented shape on vented hydrogen-air explosions and its consequence analysis","authors":"Qing Chen , Kun Zhao , Bin Li , Dan Zhang , Rhoda Afriyie Mensah , Oisik Das , Lifeng Xie , Yongxu Wang","doi":"10.1016/j.expthermflusci.2025.111484","DOIUrl":"10.1016/j.expthermflusci.2025.111484","url":null,"abstract":"<div><div>As the infrastructure for piped hydrogen, including long tube trailers, urban utility tunnels, and hydrogen fuel cell vehicles, expands, the risk of hydrogen explosions increases. To enhance safety technologies and minimize accident risks, this paper presents a study where hydrogen venting tests were conducted with concentrations ranging from 30 % to 60 % in a 2.25-meter-long shock tube with an inner diameter of 70 mm. The effects of different vented areas and different vented shapes on the overpressure propagation law and flame characteristics were investigated. The results indicated that higher hydrogen concentrations increase vent flame temperature, but not pressure proportionally, with 40 % H<sub>2</sub> producing the highest pressure peaks under all vented conditions. Smaller vented areas reduce the secondary explosion's impact on internal piping and the sensitivity of venting effectiveness to concentration. The distribution of pressure peaks on the outside of the pipe is highly dependent on the vented area. The vented shape has little effect on pressure, but has a slight effect on flame characteristics at R=2/5 or 1/5. In addition, the mechanism behind pressure peak generation during pipeline venting and a brief consequence analysis of the most hazardous scenario of secondary explosions has been provided.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"167 ","pages":"Article 111484"},"PeriodicalIF":2.8,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143850282","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 : 2025-04-03DOI: 10.1016/j.expthermflusci.2025.111472
Xiaokang Liu , Dongbin Wang , Shen Fang , Siyi Zhang , Lijun Yang , Jingxuan Li
This study introduces a novel passive control method for mitigating thermoacoustic instabilities by adding iron nanopowder to the flame within a Rijke tube. A comprehensive experimental setup was designed to investigate how varying nanopowder concentrations influence self-excited oscillations at different Rijke tube lengths. Results show that even small amounts of iron nanopowder can suppress certain high-frequency instability modes or induce nonlinear behavior, such as mode switching from higher to lower modes. At higher concentrations, thermoacoustic instabilities can be almost entirely eliminated. Detailed analysis reveals that iron nanopowder mitigates thermoacoustic instabilities by extending the flame length, which reduces the heat release rate gain to the system, and by enhancing particle-induced acoustic damping.
{"title":"Mitigating thermoacoustic instabilities in a Rijke tube burner using iron nanopowder additives","authors":"Xiaokang Liu , Dongbin Wang , Shen Fang , Siyi Zhang , Lijun Yang , Jingxuan Li","doi":"10.1016/j.expthermflusci.2025.111472","DOIUrl":"10.1016/j.expthermflusci.2025.111472","url":null,"abstract":"<div><div>This study introduces a novel passive control method for mitigating thermoacoustic instabilities by adding iron nanopowder to the flame within a Rijke tube. A comprehensive experimental setup was designed to investigate how varying nanopowder concentrations influence self-excited oscillations at different Rijke tube lengths. Results show that even small amounts of iron nanopowder can suppress certain high-frequency instability modes or induce nonlinear behavior, such as mode switching from higher to lower modes. At higher concentrations, thermoacoustic instabilities can be almost entirely eliminated. Detailed analysis reveals that iron nanopowder mitigates thermoacoustic instabilities by extending the flame length, which reduces the heat release rate gain to the system, and by enhancing particle-induced acoustic damping.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111472"},"PeriodicalIF":2.8,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143785893","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 : 2025-04-02DOI: 10.1016/j.expthermflusci.2025.111490
Fangfang Zhang , Shuyan Che , Hao Yin , Xiangyu Li , Chuangyao Zhao
The 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) ionic liquid aqueous solution is a promising absorbent used in absorption refrigeration technology. In this paper, the falling film flow pattern transition of the [EMIm]Ac ionic liquid aqueous solution was experimentally studied. The findings reveal that the critical Reynolds number for flow pattern transitions rises with increases in tube spacing, inlet liquid temperature, and circulating liquid temperature. In comparison to deionized water, the ionic liquid aqueous solution exhibits much smaller critical Reynolds numbers, and provides a more stable liquid film, and produces much smoother and clearer interfaces between liquid and gas. Additionally, hysteresis in flow pattern transitions is observed, and it generally increases with increasing tube spacing, inlet liquid temperature, and circulating liquid temperature. Criteria for flow pattern transitions are developed, and flow pattern maps are constructed for conditions with increasing and decreasing film flow rates, respectively.
{"title":"Falling film flow pattern transition of ionic liquid aqueous solution on horizontal tube bundles","authors":"Fangfang Zhang , Shuyan Che , Hao Yin , Xiangyu Li , Chuangyao Zhao","doi":"10.1016/j.expthermflusci.2025.111490","DOIUrl":"10.1016/j.expthermflusci.2025.111490","url":null,"abstract":"<div><div>The 1-ethyl-3-methylimidazolium acetate ([EMIm]Ac) ionic liquid aqueous solution is a promising absorbent used in absorption refrigeration technology. In this paper, the falling film flow pattern transition of the [EMIm]Ac ionic liquid aqueous solution was experimentally studied. The findings reveal that the critical Reynolds number for flow pattern transitions rises with increases in tube spacing, inlet liquid temperature, and circulating liquid temperature. In comparison to deionized water, the ionic liquid aqueous solution exhibits much smaller critical Reynolds numbers, and provides a more stable liquid film, and produces much smoother and clearer interfaces between liquid and gas. Additionally, hysteresis in flow pattern transitions is observed, and it generally increases with increasing tube spacing, inlet liquid temperature, and circulating liquid temperature. Criteria for flow pattern transitions are developed, and flow pattern maps are constructed for conditions with increasing and decreasing film flow rates, respectively.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111490"},"PeriodicalIF":2.8,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143785854","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 : 2025-04-02DOI: 10.1016/j.expthermflusci.2025.111476
Jaime Gimeno, Pedro Martí-Aldaraví, Marcos Carreres, César Carvallo
Spray-wall interaction (SWI) plays a crucial role in spray-based processes, influencing atomization, mixing, combustion efficiency, and pollutant formation. This study investigates SWI by analyzing spray morphology and key geometrical parameters, including spray penetration, spray area, spreading behavior on a quartz wall, and post-impingement spray thickness. Three optical visualization techniques were employed to study the effects of varying injection and ambient pressures, fuel and ambient temperatures, and injector tip-to-wall distance. The impact of cold-start and other evaporative engine conditions on spray morphology was analyzed. An increase in the injection pressure, an increase in wall-to-tip distance, and a decrease in ambient back-pressure delay the start of the spray-wall interaction. Higher injection pressure leads to greater spray spreading over the wall. Regarding extinction profiles, a higher injection pressure and ambient temperature result in lower liquid concentration in the spray.
{"title":"Gasoline direct injection spray-wall impingement: Macroscopic characterization and optical analysis","authors":"Jaime Gimeno, Pedro Martí-Aldaraví, Marcos Carreres, César Carvallo","doi":"10.1016/j.expthermflusci.2025.111476","DOIUrl":"10.1016/j.expthermflusci.2025.111476","url":null,"abstract":"<div><div>Spray-wall interaction (SWI) plays a crucial role in spray-based processes, influencing atomization, mixing, combustion efficiency, and pollutant formation. This study investigates SWI by analyzing spray morphology and key geometrical parameters, including spray penetration, spray area, spreading behavior on a quartz wall, and post-impingement spray thickness. Three optical visualization techniques were employed to study the effects of varying injection and ambient pressures, fuel and ambient temperatures, and injector tip-to-wall distance. The impact of cold-start and other evaporative engine conditions on spray morphology was analyzed. An increase in the injection pressure, an increase in wall-to-tip distance, and a decrease in ambient back-pressure delay the start of the spray-wall interaction. Higher injection pressure leads to greater spray spreading over the wall. Regarding extinction profiles, a higher injection pressure and ambient temperature result in lower liquid concentration in the spray.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"166 ","pages":"Article 111476"},"PeriodicalIF":2.8,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767705","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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