Pub Date : 2024-09-17DOI: 10.1177/09576509241282747
Malinee Sriariyanun, Elaiyarasan U, Sakthivel R, Baranitharan P, Atthasit Tawai, Arunkumar T
Biofuel is an alternative fuel for diesel engines which is necessary to reduce exhaust emissions and helps to balance the depletion of fossil fuels. This study details the synthesis of bio-diesel and bio-oil from stone apple seeds ( Aegle marmelos) through transesterification, direct oxygenate additive, and pyrolysis processes. The diesel engine is powered by the resulting stone apple methyl ester bio-diesel/diesel and bio-oil/diesel mixtures. In a test engine rig, the effectiveness and emission uniqueness of test fuel mixes were examined at various engine loads (EL = 3 kg–12 kg) and compression ratios (CR = 16–17.5) while maintaining a steady speed of 1500 r/min. Furthermore, engine performance and emissions for bio-diesel and bio-oil are measured and compared. The oxides of nitrogen (NOx) emission by bio-diesel and bio-oil opus were higher than neat diesel (FD). Also, carbon monoxide (CO) and hydrocarbon (HC) emissions were measured to be lower. The improvements of BTE by 4.87% and decrement of CO by 18.8%, HC by 13.26% were observed with the trans-esterified bio-diesel/diesel opus compared to diesel at a higher CR and rated load conditions. The engine analysis responses revealed that the FBD blend showed enhanced performance and lower emissions except NOx compared to diesel fuel. Hence, trans-esterified bio-diesel is a greater diesel alternative than FBDE and FBO.
{"title":"Studies on fuels and engine attributes powered by bio-diesel and bio-oil derived from stone apple seed (Aegle marmelos) for bioenergy","authors":"Malinee Sriariyanun, Elaiyarasan U, Sakthivel R, Baranitharan P, Atthasit Tawai, Arunkumar T","doi":"10.1177/09576509241282747","DOIUrl":"https://doi.org/10.1177/09576509241282747","url":null,"abstract":"Biofuel is an alternative fuel for diesel engines which is necessary to reduce exhaust emissions and helps to balance the depletion of fossil fuels. This study details the synthesis of bio-diesel and bio-oil from stone apple seeds ( Aegle marmelos) through transesterification, direct oxygenate additive, and pyrolysis processes. The diesel engine is powered by the resulting stone apple methyl ester bio-diesel/diesel and bio-oil/diesel mixtures. In a test engine rig, the effectiveness and emission uniqueness of test fuel mixes were examined at various engine loads (EL = 3 kg–12 kg) and compression ratios (CR = 16–17.5) while maintaining a steady speed of 1500 r/min. Furthermore, engine performance and emissions for bio-diesel and bio-oil are measured and compared. The oxides of nitrogen (NOx) emission by bio-diesel and bio-oil opus were higher than neat diesel (FD). Also, carbon monoxide (CO) and hydrocarbon (HC) emissions were measured to be lower. The improvements of BTE by 4.87% and decrement of CO by 18.8%, HC by 13.26% were observed with the trans-esterified bio-diesel/diesel opus compared to diesel at a higher CR and rated load conditions. The engine analysis responses revealed that the FBD blend showed enhanced performance and lower emissions except NOx compared to diesel fuel. Hence, trans-esterified bio-diesel is a greater diesel alternative than FBDE and FBO.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"188 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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: 10.1177/09576509241283129
Mario Carta, Shahrokh Shahpar, Tiziano Ghisu
In the field of design and optimization of sophisticated geometries such as film-cooled turbine blades of modern jet engines, Computational Fluid Dynamics (CFD) simulation is commonly employed. As the pursuit for higher turbine entry temperatures intensifies, it becomes crucial for computational analyses to offer accurate predictions of metal temperatures and heat transfer coefficients on these critical components. This study investigates the impact of key physical factors that characterize the operation of these components on the accuracy of the computational model. In particular, the effects of including the exchange of thermal energy between the fluid and solid domains, as well as modelling the unsteady interaction between the rotor and stator are studied. The research focuses on a fully featured one-and-a-half stage high-pressure turbine of a commercial jet engine, utilizing proprietary software for conducting 3D Reynolds-Averaged Navier-Stokes flow simulations. To model the fluid-solid thermal interaction, steady-state Conjugate Heat Transfer (CHT) simulations are performed. The CHT results are then compared with experimental data obtained from a thermal paint test, achieving good levels of agreement. Additionally, phase-lag simulations are executed under adiabatic-wall conditions to evaluate the influence of stator-rotor interaction on near-wall gas temperatures. This work shows that, by modelling the periodic unsteadiness at the stator-rotor interface with a phase-lag technique, the maximum near-wall gas temperature prediction is significantly increased, sometimes more than 100K, with respect to the steady-state model one. Findings from this work also suggest that simplified “strip” source terms used to model the presence of film cooling hole rows on the surface of a blade can be used with satisfactory accuracy only for nominal conditions. The mass flows delivered by each source strip should not be linearly scaled based on mainstream quantities for use in different conditions, but they should be recalculated from scratch for the new conditions.
{"title":"Analysis of the aerothermal performance of modern commercial high-pressure turbine rotors using different levels of fidelity","authors":"Mario Carta, Shahrokh Shahpar, Tiziano Ghisu","doi":"10.1177/09576509241283129","DOIUrl":"https://doi.org/10.1177/09576509241283129","url":null,"abstract":"In the field of design and optimization of sophisticated geometries such as film-cooled turbine blades of modern jet engines, Computational Fluid Dynamics (CFD) simulation is commonly employed. As the pursuit for higher turbine entry temperatures intensifies, it becomes crucial for computational analyses to offer accurate predictions of metal temperatures and heat transfer coefficients on these critical components. This study investigates the impact of key physical factors that characterize the operation of these components on the accuracy of the computational model. In particular, the effects of including the exchange of thermal energy between the fluid and solid domains, as well as modelling the unsteady interaction between the rotor and stator are studied. The research focuses on a fully featured one-and-a-half stage high-pressure turbine of a commercial jet engine, utilizing proprietary software for conducting 3D Reynolds-Averaged Navier-Stokes flow simulations. To model the fluid-solid thermal interaction, steady-state Conjugate Heat Transfer (CHT) simulations are performed. The CHT results are then compared with experimental data obtained from a thermal paint test, achieving good levels of agreement. Additionally, phase-lag simulations are executed under adiabatic-wall conditions to evaluate the influence of stator-rotor interaction on near-wall gas temperatures. This work shows that, by modelling the periodic unsteadiness at the stator-rotor interface with a phase-lag technique, the maximum near-wall gas temperature prediction is significantly increased, sometimes more than 100K, with respect to the steady-state model one. Findings from this work also suggest that simplified “strip” source terms used to model the presence of film cooling hole rows on the surface of a blade can be used with satisfactory accuracy only for nominal conditions. The mass flows delivered by each source strip should not be linearly scaled based on mainstream quantities for use in different conditions, but they should be recalculated from scratch for the new conditions.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"47 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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: 10.1177/09576509241283612
Huan Li, Shuguang Zuo, Siyue Chen
The integrated two-stage electric centrifugal compressors are most widely used in the present fuel cell vehicles. Air compressors influence the efficiency of fuel cell systems significantly, so it is crucial to improve the energy efficiency of centrifugal compressors. However, there is a lack of centrifugal compressor performance models that can reflect the thermodynamic characteristics of two-stage compression system, which is the main focus of this paper. In this paper, an analytical model of two-stage centrifugal compressor performance considering the thermodynamic characteristics of two-stage compression was first derived and experimentally validated. The single-stage centrifugal compressor model (SSCCM) can be treated as a lumped parameter model of the two-stage centrifugal compressor to predict the compressor performance. Therefore, the SSCCM and the two-stage centrifugal compressor model (TSCCM) were compared. The results show that the TSCCM is more accurate and robust. Furthermore, a novel compressor structure equipped with an intercooler in the inter-stage piping was proposed to improve the energy efficiency of the centrifugal compressor. Based on this novel structure, the TSCCM was modified. Finally, a quantitative analysis was performed to study the effect of an inter-stage intercooler on compressor efficiency. Compared to the original compressor without the inter-stage intercooler, the efficiency improvement by the inter-stage intercooler can be in the range of 3.29–3.97%, with power savings of 0.332–0.635 kW. The study can be used to support engineers and researchers in fast identifying effective solutions in terms of design for the next generation of centrifugal compressors.
{"title":"Analytical modeling and performance improvement of an electric two-stage centrifugal compressor for fuel cell vehicles","authors":"Huan Li, Shuguang Zuo, Siyue Chen","doi":"10.1177/09576509241283612","DOIUrl":"https://doi.org/10.1177/09576509241283612","url":null,"abstract":"The integrated two-stage electric centrifugal compressors are most widely used in the present fuel cell vehicles. Air compressors influence the efficiency of fuel cell systems significantly, so it is crucial to improve the energy efficiency of centrifugal compressors. However, there is a lack of centrifugal compressor performance models that can reflect the thermodynamic characteristics of two-stage compression system, which is the main focus of this paper. In this paper, an analytical model of two-stage centrifugal compressor performance considering the thermodynamic characteristics of two-stage compression was first derived and experimentally validated. The single-stage centrifugal compressor model (SSCCM) can be treated as a lumped parameter model of the two-stage centrifugal compressor to predict the compressor performance. Therefore, the SSCCM and the two-stage centrifugal compressor model (TSCCM) were compared. The results show that the TSCCM is more accurate and robust. Furthermore, a novel compressor structure equipped with an intercooler in the inter-stage piping was proposed to improve the energy efficiency of the centrifugal compressor. Based on this novel structure, the TSCCM was modified. Finally, a quantitative analysis was performed to study the effect of an inter-stage intercooler on compressor efficiency. Compared to the original compressor without the inter-stage intercooler, the efficiency improvement by the inter-stage intercooler can be in the range of 3.29–3.97%, with power savings of 0.332–0.635 kW. The study can be used to support engineers and researchers in fast identifying effective solutions in terms of design for the next generation of centrifugal compressors.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"6 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142201272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-08-27DOI: 10.1177/09576509241277578
Xin Yan, Haibo Wang, Kun He
The periodic-cell model was proposed to simulate the successive contacts between the labyrinth fin and multiple honeycomb cells. With the experimental data, the finite-element-analysis (FEA) method with the periodic-cell model was validated. The effects of incursion parameters (i.e. incursion depth, incursion rate and sliding velocity) on the contact force, frictional temperature, material loss, and worn geometry of the honeycomb seal during the incursion process were studied. With the predicted worn geometry, the sealing performance degradation in the honeycomb seal was analyzed. The results showed that the proposed periodic-cell model has an excellent accuracy in predicting the wear behavior of honeycomb seal in rubbing events. The contact force between the honeycomb liner and labyrinth fin is pronounced especially at low sliding velocity and high incursion rate conditions, which increases the possibility of wear damage in the rotor part. At low sliding velocity and low incursion rate conditions, the frictional heat transferring to rotor part is increased, which increases the thermal stress near the contact region of the rotor part. As the clearance gap of honeycomb seal increases from 0.6 mm to 0.9 mm in the rubbing event, the leakage rate is increased by about 12%, and the carry-over effects downstream of the worn cells are increased.
{"title":"Investigations into rubbing wear behavior of honeycomb land against labyrinth fin with periodic-cell model","authors":"Xin Yan, Haibo Wang, Kun He","doi":"10.1177/09576509241277578","DOIUrl":"https://doi.org/10.1177/09576509241277578","url":null,"abstract":"The periodic-cell model was proposed to simulate the successive contacts between the labyrinth fin and multiple honeycomb cells. With the experimental data, the finite-element-analysis (FEA) method with the periodic-cell model was validated. The effects of incursion parameters (i.e. incursion depth, incursion rate and sliding velocity) on the contact force, frictional temperature, material loss, and worn geometry of the honeycomb seal during the incursion process were studied. With the predicted worn geometry, the sealing performance degradation in the honeycomb seal was analyzed. The results showed that the proposed periodic-cell model has an excellent accuracy in predicting the wear behavior of honeycomb seal in rubbing events. The contact force between the honeycomb liner and labyrinth fin is pronounced especially at low sliding velocity and high incursion rate conditions, which increases the possibility of wear damage in the rotor part. At low sliding velocity and low incursion rate conditions, the frictional heat transferring to rotor part is increased, which increases the thermal stress near the contact region of the rotor part. As the clearance gap of honeycomb seal increases from 0.6 mm to 0.9 mm in the rubbing event, the leakage rate is increased by about 12%, and the carry-over effects downstream of the worn cells are increased.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"4 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142201273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-08-26DOI: 10.1177/09576509241275778
Awais Junejo, Sergio Chapela, Jacobo Porteiro, Yasir M. Al-Abdeli
Air staging in solid fuel combustion features widely in small scale domestic boilers to large scale moving grate combustors. Whilst the effects of air staging on the combustion characteristics of these systems are generally known, there is very little insight available into the role of secondary air on the flow and temperature field in the freeboard of batch-type fixed bed biomass combustors. Three-dimensional gas phase simulations using the Transition 𝑘kl-𝜔 and Finite Rate/Eddy Dissipation models were validated against freeboard temperatures and emissions (CO2 and O2) measured on the same set-up. Results show that secondary air at Qs/Qt ≥0.25 induces two recirculation zones, upstream and downstream of its injection point with maximum freeboard temperatures generally observed around these recirculation zones, if Qs/Qt drops to 0.12-0.18 only an upstream recirculation zone is observed until it diminishes by Qs/Qt = 0.06. However, there is a trade-off caused by what appears to be a cooling effect if Qs/Qt is increased between 0.25 and 0.71. Modelling results show that in reacting cases, unlike non-reacting modelling on the same geometry, the strength of the secondary air induced upstream recirculation zone appears significantly stronger.
{"title":"Secondary air induced flow structures and their interplay with the temperature field in fixed bed combustors","authors":"Awais Junejo, Sergio Chapela, Jacobo Porteiro, Yasir M. Al-Abdeli","doi":"10.1177/09576509241275778","DOIUrl":"https://doi.org/10.1177/09576509241275778","url":null,"abstract":"Air staging in solid fuel combustion features widely in small scale domestic boilers to large scale moving grate combustors. Whilst the effects of air staging on the combustion characteristics of these systems are generally known, there is very little insight available into the role of secondary air on the flow and temperature field in the freeboard of batch-type fixed bed biomass combustors. Three-dimensional gas phase simulations using the Transition 𝑘kl-𝜔 and Finite Rate/Eddy Dissipation models were validated against freeboard temperatures and emissions (CO<jats:sub>2</jats:sub> and O<jats:sub>2</jats:sub>) measured on the same set-up. Results show that secondary air at Q<jats:sub>s</jats:sub>/Q<jats:sub>t</jats:sub> ≥0.25 induces two recirculation zones, upstream and downstream of its injection point with maximum freeboard temperatures generally observed around these recirculation zones, if Q<jats:sub>s</jats:sub>/Q<jats:sub>t</jats:sub> drops to 0.12-0.18 only an upstream recirculation zone is observed until it diminishes by Q<jats:sub>s</jats:sub>/Q<jats:sub>t</jats:sub> = 0.06. However, there is a trade-off caused by what appears to be a cooling effect if Q<jats:sub>s</jats:sub>/Q<jats:sub>t</jats:sub> is increased between 0.25 and 0.71. Modelling results show that in reacting cases, unlike non-reacting modelling on the same geometry, the strength of the secondary air induced upstream recirculation zone appears significantly stronger.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"17 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142201205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-08-22DOI: 10.1177/09576509241277241
Chang’an Wang, Yuanmao Chen, Maoyun Luo, Lin Zhao, Pengbo Zhao, Defu Che
Due to the deep stage of oxygen, the pulverized coal cannot be burned completely in the primary combustion zone, resulting in a high content of residual carbon. The residual carbon in ash has a potential effect on the melting characteristics of ash, while there is a lack of specific research on the effects of residual carbon on ash fusion characteristics of high-alkali coals. In the present study, synthetic ash was blended with residual carbon to study the impacts of residual carbon content, graphitization level of the carbon, and atmospheric condition on ash fusion characteristics. Thermogravimetric analyzers and ash melting point testers were used to study the thermogravimetric behavior of ash and the characteristic temperatures of ash fusion, and then analyze the changes in the mineral composition and micromorphology of slag using X-ray diffractometers and scanning electron microscopy. The experimental results reveal that the change in residual char content exerts a minor influence on the type of crystalline minerals within the ash, while it affects the relative content of various minerals. The softening temperature of the ash blended with activated carbon and graphite are 1234°C and 1242°C, respectively. The blending of activated carbon greatly promotes the generation of gehlenite (Ca2Al2SiO7, 1593°C) and inhibits the generation of merwinite (Ca3MgSi2O8, 1550°C), increasing the ash melting temperature. The ash fusion characteristic temperatures of the pure synthetic ash decrease with the enhancement of the reductive atmosphere. However, the ash fusion characteristic temperatures of the ash blended with carbon in strong reducing atmosphere are increased compared to those in weak reducing atmosphere because part of the carbon acts as a skeleton or reacts to form a carbon-silicon compound. The present study can offer improved knowledge to provide fundamental support for the combustion and utilization of high-alkali Zhundong coal under deep oxygen-staged conditions.
由于氧气阶段较深，煤粉在一次燃烧区不能完全燃烧，导致残炭含量较高。灰渣中的残炭对灰渣的熔融特性有潜在的影响，而残炭对高碱煤灰渣熔融特性的影响还缺乏专门的研究。本研究将合成灰与残炭混合，研究残炭含量、残炭石墨化程度和大气条件对灰熔融特性的影响。使用热重分析仪和灰熔点测试仪研究了灰的热重行为和灰熔融的特征温度，然后使用 X 射线衍射仪和扫描电子显微镜分析了矿渣矿物成分和微观形态的变化。实验结果表明，残炭含量的变化对灰渣中结晶矿物种类的影响较小，而对各种矿物相对含量的影响较大。掺入活性炭和石墨的灰的软化温度分别为 1234°C 和 1242°C。活性炭的掺入极大地促进了gehlenite（Ca2Al2SiO7，1593°C）的生成，抑制了merwinite（Ca3MgSi2O8，1550°C）的生成，从而提高了灰熔化温度。纯合成灰的灰熔融特征温度随着还原气氛的增强而降低。然而，与弱还原气氛相比，在强还原气氛中掺入碳的灰熔融特性温度会升高，这是因为部分碳起到了骨架的作用，或发生反应形成了碳硅化合物。本研究可为高碱准东煤在深氧阶段条件下的燃烧和利用提供基础支持。
{"title":"Experimental study on the effects of residual carbon on ash fusion characteristics of high-alkali Zhundong coal under deep oxygen-staged condition","authors":"Chang’an Wang, Yuanmao Chen, Maoyun Luo, Lin Zhao, Pengbo Zhao, Defu Che","doi":"10.1177/09576509241277241","DOIUrl":"https://doi.org/10.1177/09576509241277241","url":null,"abstract":"Due to the deep stage of oxygen, the pulverized coal cannot be burned completely in the primary combustion zone, resulting in a high content of residual carbon. The residual carbon in ash has a potential effect on the melting characteristics of ash, while there is a lack of specific research on the effects of residual carbon on ash fusion characteristics of high-alkali coals. In the present study, synthetic ash was blended with residual carbon to study the impacts of residual carbon content, graphitization level of the carbon, and atmospheric condition on ash fusion characteristics. Thermogravimetric analyzers and ash melting point testers were used to study the thermogravimetric behavior of ash and the characteristic temperatures of ash fusion, and then analyze the changes in the mineral composition and micromorphology of slag using X-ray diffractometers and scanning electron microscopy. The experimental results reveal that the change in residual char content exerts a minor influence on the type of crystalline minerals within the ash, while it affects the relative content of various minerals. The softening temperature of the ash blended with activated carbon and graphite are 1234°C and 1242°C, respectively. The blending of activated carbon greatly promotes the generation of gehlenite (Ca2Al2SiO7, 1593°C) and inhibits the generation of merwinite (Ca3MgSi2O8, 1550°C), increasing the ash melting temperature. The ash fusion characteristic temperatures of the pure synthetic ash decrease with the enhancement of the reductive atmosphere. However, the ash fusion characteristic temperatures of the ash blended with carbon in strong reducing atmosphere are increased compared to those in weak reducing atmosphere because part of the carbon acts as a skeleton or reacts to form a carbon-silicon compound. The present study can offer improved knowledge to provide fundamental support for the combustion and utilization of high-alkali Zhundong coal under deep oxygen-staged conditions.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"15 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142201206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The volute-free centrifugal fans in ventilation applications are used to exhaust a large amount of air under the effect of the head loss in the ventilation pipeline system, thus, a high static pressure rise at a large flow rate of the fans is anticipated. The shroud of the conventional volute-free centrifugal fans has an axisymmetric geometry, that is, the height of the fan outlet is constant over the whole circumference. Considering the non-uniform flow in the blade passages, the shroud of a wavy geometry might help in improving the static pressure rise and efficiency of the fans at a large flow rate condition. In this work, we performed a numerical investigation on the internal flow of a volute-free centrifugal fan with a wavy shroud. The effect of the geometry of the wavy shroud, as quantified by the maximum height and profile, on the aerodynamic performance of the fan is explored, and the flow physics leading to the performance improvement are demonstrated through a detailed analysis of the patterns of the internal flow. The numerical results showed that compared with the baseline fan with an axisymmetric shroud, the fan with a wavy shroud could substantially improve the static pressure rise and efficiency at the large flow rate. The wavy shroud regulates the near-wall flow especially at the fan outlet; the fluctuation of the radial velocity, secondary flow, and reversed flow is greatly weakened, producing a uniform flow at the fan outlet. The fluctuation of the static pressure in the blade passages and on the shroud side of the fan outlet greatly decreases. Further analysis of the acoustic power level field indicates that the wavy shroud increases the acoustic power at the fan inlet but does not have a notable influence on that near the outlet.
{"title":"Improvement of aerodynamic performance of a volute-free centrifugal fan at a large flow rate using a wavy shroud","authors":"Hengjun Qin, Haijiang He, Ping Luo, Zhenli Zhang, Zhengdao Wang, Hui Yang, Yikun Wei, Wei Zhang","doi":"10.1177/09576509241272863","DOIUrl":"https://doi.org/10.1177/09576509241272863","url":null,"abstract":"The volute-free centrifugal fans in ventilation applications are used to exhaust a large amount of air under the effect of the head loss in the ventilation pipeline system, thus, a high static pressure rise at a large flow rate of the fans is anticipated. The shroud of the conventional volute-free centrifugal fans has an axisymmetric geometry, that is, the height of the fan outlet is constant over the whole circumference. Considering the non-uniform flow in the blade passages, the shroud of a wavy geometry might help in improving the static pressure rise and efficiency of the fans at a large flow rate condition. In this work, we performed a numerical investigation on the internal flow of a volute-free centrifugal fan with a wavy shroud. The effect of the geometry of the wavy shroud, as quantified by the maximum height and profile, on the aerodynamic performance of the fan is explored, and the flow physics leading to the performance improvement are demonstrated through a detailed analysis of the patterns of the internal flow. The numerical results showed that compared with the baseline fan with an axisymmetric shroud, the fan with a wavy shroud could substantially improve the static pressure rise and efficiency at the large flow rate. The wavy shroud regulates the near-wall flow especially at the fan outlet; the fluctuation of the radial velocity, secondary flow, and reversed flow is greatly weakened, producing a uniform flow at the fan outlet. The fluctuation of the static pressure in the blade passages and on the shroud side of the fan outlet greatly decreases. Further analysis of the acoustic power level field indicates that the wavy shroud increases the acoustic power at the fan inlet but does not have a notable influence on that near the outlet.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"15 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141969294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Refrigeration technology contributes to 10∼15% of global energy consumption, resulting in significant carbon emission. Solar-driven ejection-compression refrigeration system is promising for reducing electricity consumption and carbon emissions. However, existing solar ejection-compression refrigeration systems suffer from drawbacks of low heat utilization efficiency, oversized solar collectors, and thermal leakage due to large temperature differences of storage devices. Addressing these challenges, this study proposes and investigates a new solar-assisted ejector-compressor hybrid refrigeration system with subcooling storage coupled at intermediate temperatures. The system model is established, and the ejector model is experimentally validated. Through system modelling, an energetic and exergetic performance comparative analyses are conducted. The results indicate that the COP of the proposed system is 9.7% higher than that of traditional system combinations, producing the same cooling capacity with the same generating heat. Moreover, considering the stored cooling energy can be fully converted to cooling energy at evaporating temperatures, the COPh of the new system reaches 8.29, 24.5% higher than traditional systems. The cooling storage at 15°C with 0.325 ejector entrainment ratio suggests a reduction of approximately two-thirds in energy storage, lower temperature differences, and reduced thermal leakage, leading to decreased space and economic costs and improved energy performance. Additionally, as the COPh, COPgh, and ηex of MCS mode consistently outperform those of ZCS and HCS modes, the MCS mode is prioritized in system operation. This study underscores that the new system offers superior overall energy efficiency and requires smaller storage devices compared to traditional systems, revealing its promising practical applications.
{"title":"Performance evaluation and comparative study on a novel solar-heat-driven ejection-compression hybrid cooling system with subcooling storage","authors":"Yingjie Xu, Yongjun Ling, Zhiwei Wang, Yaobo Zheng, Zhe Sun, Xiaopo Wang","doi":"10.1177/09576509241272788","DOIUrl":"https://doi.org/10.1177/09576509241272788","url":null,"abstract":"Refrigeration technology contributes to 10∼15% of global energy consumption, resulting in significant carbon emission. Solar-driven ejection-compression refrigeration system is promising for reducing electricity consumption and carbon emissions. However, existing solar ejection-compression refrigeration systems suffer from drawbacks of low heat utilization efficiency, oversized solar collectors, and thermal leakage due to large temperature differences of storage devices. Addressing these challenges, this study proposes and investigates a new solar-assisted ejector-compressor hybrid refrigeration system with subcooling storage coupled at intermediate temperatures. The system model is established, and the ejector model is experimentally validated. Through system modelling, an energetic and exergetic performance comparative analyses are conducted. The results indicate that the COP of the proposed system is 9.7% higher than that of traditional system combinations, producing the same cooling capacity with the same generating heat. Moreover, considering the stored cooling energy can be fully converted to cooling energy at evaporating temperatures, the COP<jats:sub>h</jats:sub> of the new system reaches 8.29, 24.5% higher than traditional systems. The cooling storage at 15°C with 0.325 ejector entrainment ratio suggests a reduction of approximately two-thirds in energy storage, lower temperature differences, and reduced thermal leakage, leading to decreased space and economic costs and improved energy performance. Additionally, as the COP<jats:sub>h</jats:sub>, COP<jats:sub>gh</jats:sub>, and η<jats:sub>ex</jats:sub> of MCS mode consistently outperform those of ZCS and HCS modes, the MCS mode is prioritized in system operation. This study underscores that the new system offers superior overall energy efficiency and requires smaller storage devices compared to traditional systems, revealing its promising practical applications.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"46 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141945126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2024-08-02DOI: 10.1177/09576509241270837
Ping Liu, Shiming Sang, Lianghong Hu, Guangfeng Liu, Weihua Wang
Nanofluid was frequent technique which solved microscale heat and mass transport problems to intensify pool boiling heat transfer. This paper had investigated the effect of nanofluid, ultrasonic field and ribs surfaces on cooperative heat transfer enhancement in pool boiling. A two-step method was applied to prepare Al2O3 nanofluids of different kinds of concentrations and diameters. Group experiments were examined the influences of nanofluid concentration and diameter, ultrasonic power and distance and rib surface type on heat transfer characteristics, respectively. The heat flux and convection heat transfer coefficient were used the performance parameters. The results showed that the concentration and diameter of the Al2O3 nanofluid effected the heat transfer performance on the pool boiling. The Al2O3 nanofluid with an average diameter of 80 nm had the most significant enhancement effect on the pool boiling heat transfer performance, but the Al2O3 with a diameter of 30 nm had the weakest enhancement effect, when the concentration of Al2O3 nanofluid was 0.01 wt%. Meanwhile, the generated acoustic streaming effect and cavitation effect by ultrasonic field can promote the energy accumulation, rupture and regeneration of the bubbles at low superheat stage on nanofluid pool boiling. The heat transfer coefficient (HTC) gradually enhances as the ultrasonic field changes. At an ultrasonic power of 528 W and a distance of 50 mm, the nanofluid pool boiling increased by 44.34% compared to no ultrasonic field HTC. Compared with No rib, the boiling point of the Al2O3 nanofluidic pool boiling of Rib II was reduced by 2°C under the ultrasonic field. The nanofluid pool boiling with ultrasonic field of p = 528 W and Rib II had the best heat transfer effect, and HTC improved more than 50%. This is due to the addition of more nucleation points for bubbles on the heated surface of the Rib II.
纳米流体是解决微尺度传热和传质问题以强化池沸腾传热的常用技术。本文研究了纳米流体、超声波场和肋片表面对池水沸腾传热协同强化的影响。采用两步法制备了不同浓度和直径的 Al2O3 纳米流体。分组实验分别考察了纳米流体浓度和直径、超声功率和距离以及肋片表面类型对传热特性的影响。热通量和对流传热系数是性能参数。结果表明，Al2O3 纳米流体的浓度和直径对池沸腾的传热性能有影响。当 Al2O3 纳米流体的浓度为 0.01 wt% 时，平均直径为 80 nm 的 Al2O3 纳米流体对水池沸腾传热性能的增强效果最显著，而直径为 30 nm 的 Al2O3 纳米流体的增强效果最弱。同时，超声波场产生的声流效应和空化效应可促进纳米流体池沸腾低过热阶段气泡的能量积累、破裂和再生。传热系数（HTC）随着超声场的变化而逐渐增大。在超声波功率为 528 W、距离为 50 mm 时，纳米流体池沸腾比无超声波场 HTC 提高了 44.34%。与无肋相比，肋 II 的 Al2O3 纳米流体池沸点在超声场下降低了 2°C。超声波场 p = 528 W 和肋骨 II 的纳米流体池沸腾的传热效果最好，HTC 提高了 50%以上。这是因为在 Rib II 的受热表面上增加了更多的气泡成核点。
{"title":"Effect of ultrasonic field on pool boiling heat transfer to Al2O3 nanofluid on ribbed surfaces","authors":"Ping Liu, Shiming Sang, Lianghong Hu, Guangfeng Liu, Weihua Wang","doi":"10.1177/09576509241270837","DOIUrl":"https://doi.org/10.1177/09576509241270837","url":null,"abstract":"Nanofluid was frequent technique which solved microscale heat and mass transport problems to intensify pool boiling heat transfer. This paper had investigated the effect of nanofluid, ultrasonic field and ribs surfaces on cooperative heat transfer enhancement in pool boiling. A two-step method was applied to prepare Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> nanofluids of different kinds of concentrations and diameters. Group experiments were examined the influences of nanofluid concentration and diameter, ultrasonic power and distance and rib surface type on heat transfer characteristics, respectively. The heat flux and convection heat transfer coefficient were used the performance parameters. The results showed that the concentration and diameter of the Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> nanofluid effected the heat transfer performance on the pool boiling. The Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> nanofluid with an average diameter of 80 nm had the most significant enhancement effect on the pool boiling heat transfer performance, but the Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> with a diameter of 30 nm had the weakest enhancement effect, when the concentration of Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> nanofluid was 0.01 wt%. Meanwhile, the generated acoustic streaming effect and cavitation effect by ultrasonic field can promote the energy accumulation, rupture and regeneration of the bubbles at low superheat stage on nanofluid pool boiling. The heat transfer coefficient (HTC) gradually enhances as the ultrasonic field changes. At an ultrasonic power of 528 W and a distance of 50 mm, the nanofluid pool boiling increased by 44.34% compared to no ultrasonic field HTC. Compared with No rib, the boiling point of the Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> nanofluidic pool boiling of Rib II was reduced by 2°C under the ultrasonic field. The nanofluid pool boiling with ultrasonic field of p = 528 W and Rib II had the best heat transfer effect, and HTC improved more than 50%. This is due to the addition of more nucleation points for bubbles on the heated surface of the Rib II.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"52 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141881646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The blades of an axial fan are optimized using artificial neural networks and genetic algorithms in this paper. In first, a parametric axial fan blade model is established with constraints imposed on several parameters. The chord length, maximum camber, maximum camber position, blade thickness, and airfoil stagger angle are considered as an optimization parameter of axial fan. The static pressure efficiency and static pressure of axial fan are regarded as the optimization objectives. An optimization calculation of an axial fan blade is carried out based on the combination of artificial neural network and genetic algorithm. The objective aim of optimization is to improve the static pressure efficiency, the static pressure of axial fan and to reduce the flow loss of axial fan. Numerical results of axial fan demonstrate that the pressure distribution gradient and turbulent kinetic energy contour maps of the optimized axial fan are effectively suppressed within the impeller region compared with that of original axial fan. Furthermore, the internal flow stability of the optimized axial fan also is significantly improved by studying the pressure fluctuation and the Fast Fourier Transform (FFT) of pressure fluctuation. Experimental results of axial fan aerodynamic performance further demonstrate that the static pressure of the optimized axial fan rises as much as 90.93 Pa and the improved static pressure efficiency is effectively improved as much as 7.43% at the design flow rates compared with that of the original axial fan. The application of optimized axial flow fans is of great significance in energy-saving of energy equipment.
{"title":"Aerodynamic performance and flow optimization of axial fan based on the neural network and genetic algorithm","authors":"Tianyi Sun, Xiaoming Wu, Kejun Mao, Zhengdao Wang, Hui Yang, Yikun Wei","doi":"10.1177/09576509241267857","DOIUrl":"https://doi.org/10.1177/09576509241267857","url":null,"abstract":"The blades of an axial fan are optimized using artificial neural networks and genetic algorithms in this paper. In first, a parametric axial fan blade model is established with constraints imposed on several parameters. The chord length, maximum camber, maximum camber position, blade thickness, and airfoil stagger angle are considered as an optimization parameter of axial fan. The static pressure efficiency and static pressure of axial fan are regarded as the optimization objectives. An optimization calculation of an axial fan blade is carried out based on the combination of artificial neural network and genetic algorithm. The objective aim of optimization is to improve the static pressure efficiency, the static pressure of axial fan and to reduce the flow loss of axial fan. Numerical results of axial fan demonstrate that the pressure distribution gradient and turbulent kinetic energy contour maps of the optimized axial fan are effectively suppressed within the impeller region compared with that of original axial fan. Furthermore, the internal flow stability of the optimized axial fan also is significantly improved by studying the pressure fluctuation and the Fast Fourier Transform (FFT) of pressure fluctuation. Experimental results of axial fan aerodynamic performance further demonstrate that the static pressure of the optimized axial fan rises as much as 90.93 Pa and the improved static pressure efficiency is effectively improved as much as 7.43% at the design flow rates compared with that of the original axial fan. The application of optimized axial flow fans is of great significance in energy-saving of energy equipment.","PeriodicalId":20705,"journal":{"name":"Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy","volume":"7 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141779382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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