Pub Date : 2019-09-24DOI: 10.3389/fmech.2019.00058
N. Zacharof, O. Özener, Muammer Özkan, Abdullah Kilicaslan, G. Fontaras
Heavy-duty vehicles constitute a significant contributor to road CO2 emissions, despite accounting for only a low share of the vehicle fleet. CO2 Emissions certification and monitoring are performed using vehicle simulation software designed for the purpose (VECTO). The European Union currently regulates rigid truck and tractor-trailer CO2 emissions and subsequently will proceed to buses and other heavy-duty vehicle categories. The current study investigated the use of VECTO on a city bus by modelling the on-road operating conditions of a vehicle in an urban route in Istanbul. The simulation results showed a difference with the on-road measurements in the range of -1.6% to 3.2%, depending on the direction of the route. The difference was attributed to the influence of the total elevation change, and the use of auxiliaries. The latter comprise a significant part of energy consumption in buses, and for this reason, VECTO includes a dedicated bus auxiliary module. The use of the module was also explored, and it was found to improve the results in some cases. The findings highlight the need to assess the operation of auxiliary components in city buses accurately, and to consider the provision of more precise, auxiliary-component specific, information when running actual real-world CO2 simulations of these vehicles.
{"title":"Simulating City-Bus On-Road Operation With VECTO","authors":"N. Zacharof, O. Özener, Muammer Özkan, Abdullah Kilicaslan, G. Fontaras","doi":"10.3389/fmech.2019.00058","DOIUrl":"https://doi.org/10.3389/fmech.2019.00058","url":null,"abstract":"Heavy-duty vehicles constitute a significant contributor to road CO2 emissions, despite accounting for only a low share of the vehicle fleet. CO2 Emissions certification and monitoring are performed using vehicle simulation software designed for the purpose (VECTO). The European Union currently regulates rigid truck and tractor-trailer CO2 emissions and subsequently will proceed to buses and other heavy-duty vehicle categories. The current study investigated the use of VECTO on a city bus by modelling the on-road operating conditions of a vehicle in an urban route in Istanbul. The simulation results showed a difference with the on-road measurements in the range of -1.6% to 3.2%, depending on the direction of the route. The difference was attributed to the influence of the total elevation change, and the use of auxiliaries. The latter comprise a significant part of energy consumption in buses, and for this reason, VECTO includes a dedicated bus auxiliary module. The use of the module was also explored, and it was found to improve the results in some cases. The findings highlight the need to assess the operation of auxiliary components in city buses accurately, and to consider the provision of more precise, auxiliary-component specific, information when running actual real-world CO2 simulations of these vehicles.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"219 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85596665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-18DOI: 10.3389/fmech.2019.00049
Muhammad A. Santoso, Eirik G. Christensen, Jiuling Yang, G. Rein
Wildfires are the occurrence of uncontrolled combustion in the natural environment (forest, grassland, or peatland). The frequency and size of these fires are expected to increase globally due to climate change, land use, and population movement, posing a significant threat to populations living at the wildland urban interface (WUI), as well as to habitats and the environment. Wildfires can be broadly divided into two types, smouldering (heterogeneous combustion) and flaming (homogeneous combustion). Both are important in wildfires and despite being characteristically different, one can lead to the other. The smouldering-to-flaming (STF) transition is considered threatening because it represents a sudden increase in spread rate, power, and hazard. STF transition is a sudden initiation of homogeneous gas-phase ignition preceded by smouldering combustion, and needs sufficient oxygen supply, thermal energy production, and pyrolysis products. Its unpredictable occurrence, temporally and spatially, poses an additional challenge in wildfire prevention and mitigation. For example, flaming fire may reignite through the STF transition of an undetected smouldering fire, or the transition from ember. The current understanding of the mechanisms leading to the transition is poor. Strong oxidation of char is a plausible mechanism due to its high exothermicity, acting both as heat source in driving gaseous fuel production and ignition source of the gaseous fuel. Broadly, the literature has identified two variables that govern the STF transition, i.e. oxygen supply and heat flux, on samples ranging from 0.1 to 1.22 m. Airflow velocity has competing effects. It increases oxygen supply to the reaction zone, thus increasing the reaction rate of oxygen-limited spread, but simultaneously increases convective cooling. Permeability of a fuels and fuel ability to remain consolidated (maintain its integrity) during burning influences the propagation of smouldering. Permeability controls the oxygen penetration into the fuel, and consolidation allows the formation of internal pores where STF can take place. Considering the high complexity of the STF transition problem, more studies are needed on different types of fuel, especially on wildland fuels. This review synthesizes the research and identifies regions for further research as well as informs on various STF transition mechanisms in the literature.
{"title":"Review of the Transition From Smouldering to Flaming Combustion in Wildfires","authors":"Muhammad A. Santoso, Eirik G. Christensen, Jiuling Yang, G. Rein","doi":"10.3389/fmech.2019.00049","DOIUrl":"https://doi.org/10.3389/fmech.2019.00049","url":null,"abstract":"Wildfires are the occurrence of uncontrolled combustion in the natural environment (forest, grassland, or peatland). The frequency and size of these fires are expected to increase globally due to climate change, land use, and population movement, posing a significant threat to populations living at the wildland urban interface (WUI), as well as to habitats and the environment. Wildfires can be broadly divided into two types, smouldering (heterogeneous combustion) and flaming (homogeneous combustion). Both are important in wildfires and despite being characteristically different, one can lead to the other. The smouldering-to-flaming (STF) transition is considered threatening because it represents a sudden increase in spread rate, power, and hazard. STF transition is a sudden initiation of homogeneous gas-phase ignition preceded by smouldering combustion, and needs sufficient oxygen supply, thermal energy production, and pyrolysis products. Its unpredictable occurrence, temporally and spatially, poses an additional challenge in wildfire prevention and mitigation. For example, flaming fire may reignite through the STF transition of an undetected smouldering fire, or the transition from ember. The current understanding of the mechanisms leading to the transition is poor. Strong oxidation of char is a plausible mechanism due to its high exothermicity, acting both as heat source in driving gaseous fuel production and ignition source of the gaseous fuel. Broadly, the literature has identified two variables that govern the STF transition, i.e. oxygen supply and heat flux, on samples ranging from 0.1 to 1.22 m. Airflow velocity has competing effects. It increases oxygen supply to the reaction zone, thus increasing the reaction rate of oxygen-limited spread, but simultaneously increases convective cooling. Permeability of a fuels and fuel ability to remain consolidated (maintain its integrity) during burning influences the propagation of smouldering. Permeability controls the oxygen penetration into the fuel, and consolidation allows the formation of internal pores where STF can take place. Considering the high complexity of the STF transition problem, more studies are needed on different types of fuel, especially on wildland fuels. This review synthesizes the research and identifies regions for further research as well as informs on various STF transition mechanisms in the literature.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"37 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87459762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-13DOI: 10.3389/fmech.2019.00054
Shaorun Lin, Xinyan Huang, J. Urban, S. McAllister, C. Fernandez-Pello
Recent mega wildfires have become one of the most dangerous and devastating hazards, with a wide range of negative impacts on the economy, society and environment. As cylindrical shrubs and twigs are typical fuel loads in wildfires, it is important to understand how the diameter and arrangement of cylindrical fuels affect ignition behaviors. In this work, the piloted ignition of cylindrical wood rods with different diameters (3.2 ~15.9 mm) are conducted under the irradiation up to 50 kW/m2. Three fuel groups are tested: (I) single vertical rod, (II) single horizontal rod, and (III) horizontal rod bed attached to the ground. For a single vertical rod, the measured ignition time decreases as the diameter is decreased from 15.9 mm to 6.4 mm, showing a thermally-thin behavior. However, the ignition of the 3.2-mm rod is more difficult than the 9.5-mm rod, because of the enhanced convective cooling by the smaller curvature. Nevertheless, when the rod fuels are placed horizontally on the ground, the curvature-enhanced convective cooling becomes limited. For a single rod, when both the fuel diameter and the irradiation are small, only smoldering ignition occurs, and eventually the sample collapses. For the rod bed, flaming ignition always occurs, and it is easier to ignite because of a smaller convective cooling. For both horizontal configurations, the fuel ignition temperature increases almost linearly with the diameter from 270℃ (3.2 mm) to 330℃ (15.9 mm) but is insensitive to the irradiation level. This research quantifies the effect of fuel diameter and arrangement on the piloted ignition and reveals that the traditional classification of thermally thin and thick fuel for flat materials may not be suitable for cylindrical wildland fuels.
{"title":"Piloted Ignition of Cylindrical Wildland Fuels Under Irradiation","authors":"Shaorun Lin, Xinyan Huang, J. Urban, S. McAllister, C. Fernandez-Pello","doi":"10.3389/fmech.2019.00054","DOIUrl":"https://doi.org/10.3389/fmech.2019.00054","url":null,"abstract":"Recent mega wildfires have become one of the most dangerous and devastating hazards, with a wide range of negative impacts on the economy, society and environment. As cylindrical shrubs and twigs are typical fuel loads in wildfires, it is important to understand how the diameter and arrangement of cylindrical fuels affect ignition behaviors. In this work, the piloted ignition of cylindrical wood rods with different diameters (3.2 ~15.9 mm) are conducted under the irradiation up to 50 kW/m2. Three fuel groups are tested: (I) single vertical rod, (II) single horizontal rod, and (III) horizontal rod bed attached to the ground. For a single vertical rod, the measured ignition time decreases as the diameter is decreased from 15.9 mm to 6.4 mm, showing a thermally-thin behavior. However, the ignition of the 3.2-mm rod is more difficult than the 9.5-mm rod, because of the enhanced convective cooling by the smaller curvature. Nevertheless, when the rod fuels are placed horizontally on the ground, the curvature-enhanced convective cooling becomes limited. For a single rod, when both the fuel diameter and the irradiation are small, only smoldering ignition occurs, and eventually the sample collapses. For the rod bed, flaming ignition always occurs, and it is easier to ignite because of a smaller convective cooling. For both horizontal configurations, the fuel ignition temperature increases almost linearly with the diameter from 270℃ (3.2 mm) to 330℃ (15.9 mm) but is insensitive to the irradiation level. This research quantifies the effect of fuel diameter and arrangement on the piloted ignition and reveals that the traditional classification of thermally thin and thick fuel for flat materials may not be suitable for cylindrical wildland fuels.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"21 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85629814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-13DOI: 10.3389/fmech.2019.00053
Houzhi Wang, Philip J. van Eyk, P. Medwell, C. Birzer, Z. Tian, M. Possell, Xinyan Huang
Fuel on the ground, such as leaves, twigs and decomposing matter, accumulate over time and account for a large percentage of the total fuel load in forests. In fire events, material on the ground is often referred to as a fuel bed. The air permeability of a fuel bed is a critical factor that influences fire behaviour because it controls the amount of air or oxygen available for combustion within the fuel bed. The aim of this study is to provide a better understanding of the air permeability of the fuel beds in forests. The air permeability for different fuel beds were determined using experimental and theoretical methods. The pressure drop across the fuel bed samples were experimentally measured using a verified permeability testing rig. The air permeability was then calculated using Darcy's Law or the Forchheimer equation from the pressure drop measurements, depending on the Reynolds number. The particles in the fuel beds were characterised in terms of particle size and shape. Based on the particle characterisation, the air permeability of the fuel beds was also calculated using the Kozeny-Carman equation. The results show that the experimental method is preferred when determining the air permeability for natural forest fuel beds due to the variability in the size and shape of the particles. The effect of Reynolds number on effective permeability was aslo investigated, and it was found that the transition from Darcian to non- Darcian flow occur at different Reynolds numbers for different fuel particles. For example, the transition occurs at 5 and 15 for gum bark and decomposing matter, respectively. The significance of this study is that it increases the ability to predict the air permeability of fuel beds in forests, which is essential for modelling wildland fire behaviours involving in porous fuel beds. All the samples were dried at 105 OC to remove moisture in the samples.
{"title":"Air Permeability of the Litter Layer in Broadleaf Forests","authors":"Houzhi Wang, Philip J. van Eyk, P. Medwell, C. Birzer, Z. Tian, M. Possell, Xinyan Huang","doi":"10.3389/fmech.2019.00053","DOIUrl":"https://doi.org/10.3389/fmech.2019.00053","url":null,"abstract":"Fuel on the ground, such as leaves, twigs and decomposing matter, accumulate over time and account for a large percentage of the total fuel load in forests. In fire events, material on the ground is often referred to as a fuel bed. The air permeability of a fuel bed is a critical factor that influences fire behaviour because it controls the amount of air or oxygen available for combustion within the fuel bed. The aim of this study is to provide a better understanding of the air permeability of the fuel beds in forests. The air permeability for different fuel beds were determined using experimental and theoretical methods. The pressure drop across the fuel bed samples were experimentally measured using a verified permeability testing rig. The air permeability was then calculated using Darcy's Law or the Forchheimer equation from the pressure drop measurements, depending on the Reynolds number. The particles in the fuel beds were characterised in terms of particle size and shape. Based on the particle characterisation, the air permeability of the fuel beds was also calculated using the Kozeny-Carman equation. The results show that the experimental method is preferred when determining the air permeability for natural forest fuel beds due to the variability in the size and shape of the particles. The effect of Reynolds number on effective permeability was aslo investigated, and it was found that the transition from Darcian to non- Darcian flow occur at different Reynolds numbers for different fuel particles. For example, the transition occurs at 5 and 15 for gum bark and decomposing matter, respectively. The significance of this study is that it increases the ability to predict the air permeability of fuel beds in forests, which is essential for modelling wildland fire behaviours involving in porous fuel beds. All the samples were dried at 105 OC to remove moisture in the samples.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"17 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82990619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-13DOI: 10.3389/fmech.2019.00057
Xiuling Ji, Hongyu Zhang
Osteoarthritis (OA) is a leading cause of disability in elderly individuals. As a common chronic degenerative joint disease, OA is typically characterized by articular cartilage degeneration, subchondral bone sclerosis and concomitant synovium inflammation. As such, the structural and functional alterations in the articular cartilage and subchondral bone become the focus of research during progression of OA. Similarly, the molecular mechanism regulating articular cartilage lubrication and the cellular communication controlling metabolic status of subchondral bone cells promote innovative strategies for prevention and treatment of early stage OA. The current therapeutic options for OA are aimed at keeping the associated pain, inflammation and degeneration of synovial joint tissues manageable in order to minimize the structural and symptomatic progression. These include, but are not limited to, synergetic therapy combining lubrication and drug intervention, regulatory balance between bone resorption and formation, and exercise therapy. In this mini review, we focus on the up-to-date research progress on these novel strategies for OA treatment.
{"title":"Current Strategies for the Treatment of Early Stage Osteoarthritis","authors":"Xiuling Ji, Hongyu Zhang","doi":"10.3389/fmech.2019.00057","DOIUrl":"https://doi.org/10.3389/fmech.2019.00057","url":null,"abstract":"Osteoarthritis (OA) is a leading cause of disability in elderly individuals. As a common chronic degenerative joint disease, OA is typically characterized by articular cartilage degeneration, subchondral bone sclerosis and concomitant synovium inflammation. As such, the structural and functional alterations in the articular cartilage and subchondral bone become the focus of research during progression of OA. Similarly, the molecular mechanism regulating articular cartilage lubrication and the cellular communication controlling metabolic status of subchondral bone cells promote innovative strategies for prevention and treatment of early stage OA. The current therapeutic options for OA are aimed at keeping the associated pain, inflammation and degeneration of synovial joint tissues manageable in order to minimize the structural and symptomatic progression. These include, but are not limited to, synergetic therapy combining lubrication and drug intervention, regulatory balance between bone resorption and formation, and exercise therapy. In this mini review, we focus on the up-to-date research progress on these novel strategies for OA treatment.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"60 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87641741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-03DOI: 10.3389/fmech.2019.00055
E. Ciulli
There is an increasing diffusion of the industry 4.0 concept today. The fourth industrial revolution, following three other previous industrial revolutions, is considered related to the introduction of modern information and communication technologies in production. Tribological concepts are much older than industry. Tribology has always been connected to industrial problems from the birth of industry. It was strongly connected with the previous industrial revolutions and it is surely related to industry 4.0. In this work, the main aspects of the four industrial revolutions and the main evolutions of tribology are firstly reviewed from a historical point of view. The relationships between tribology and industry are described with particular attention to the aspects that relate the modern tribology 4.0 to industry 4.0. Tribology can have in particular a big impact on the industrial needs to reduce losses and wastes, for instance with the development of new tribological components and materials also in connection with electronic smart systems and taking advantage of the information and communication technologies.
{"title":"Tribology and Industry: From the Origins to 4.0","authors":"E. Ciulli","doi":"10.3389/fmech.2019.00055","DOIUrl":"https://doi.org/10.3389/fmech.2019.00055","url":null,"abstract":"There is an increasing diffusion of the industry 4.0 concept today. The fourth industrial revolution, following three other previous industrial revolutions, is considered related to the introduction of modern information and communication technologies in production. Tribological concepts are much older than industry. Tribology has always been connected to industrial problems from the birth of industry. It was strongly connected with the previous industrial revolutions and it is surely related to industry 4.0. In this work, the main aspects of the four industrial revolutions and the main evolutions of tribology are firstly reviewed from a historical point of view. The relationships between tribology and industry are described with particular attention to the aspects that relate the modern tribology 4.0 to industry 4.0. Tribology can have in particular a big impact on the industrial needs to reduce losses and wastes, for instance with the development of new tribological components and materials also in connection with electronic smart systems and taking advantage of the information and communication technologies.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"1 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74533000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-21DOI: 10.3389/fmech.2019.00050
Jeanette Cobian-Iñiguez, Amirhessam Aminfar, D. Weise, M. Princevac
Flame geometry plays a key role in shaping fire behavior as it can influence flame spread, radiative heat transfer and fire intensity. For wildland fire, a thorough understanding of relationships between flame geometry including flame length, flame height and flame tilt can help advance the derivation of comprehensive models of wildfire behavior. Within the fire community, a classical flame modeling approach has been the development of semi-empirical models. Many of these models have been derived for surface fuels or for pool fire configurations. However, few have sought to model flame behavior in chaparral crown fires. Thus, the objective of this study was to assess the applicability of existing semi-empirical models on observed chaparral crown fire geometry. Semi-empirical models of flame tilt, flame height and flame length were considered. Comparison with experimental observation of crown fuel layer flame height showed good agreement between two-fifths power law that relates flame height to heat release rate. Predictions of flame tilt were obtained from application of semi-empirical power-law correlations relating flame tilt angle to Froude number. Observed flame tilt values exhibited low correlation with predicted values. Thus, two new power-law correlations were proposed. Coefficients for new models were obtained from regression analysis.
{"title":"On the Use of Semi-empirical Flame Models for Spreading Chaparral Crown Fire","authors":"Jeanette Cobian-Iñiguez, Amirhessam Aminfar, D. Weise, M. Princevac","doi":"10.3389/fmech.2019.00050","DOIUrl":"https://doi.org/10.3389/fmech.2019.00050","url":null,"abstract":"Flame geometry plays a key role in shaping fire behavior as it can influence flame spread, radiative heat transfer and fire intensity. For wildland fire, a thorough understanding of relationships between flame geometry including flame length, flame height and flame tilt can help advance the derivation of comprehensive models of wildfire behavior. Within the fire community, a classical flame modeling approach has been the development of semi-empirical models. Many of these models have been derived for surface fuels or for pool fire configurations. However, few have sought to model flame behavior in chaparral crown fires. Thus, the objective of this study was to assess the applicability of existing semi-empirical models on observed chaparral crown fire geometry. Semi-empirical models of flame tilt, flame height and flame length were considered. Comparison with experimental observation of crown fuel layer flame height showed good agreement between two-fifths power law that relates flame height to heat release rate. Predictions of flame tilt were obtained from application of semi-empirical power-law correlations relating flame tilt angle to Froude number. Observed flame tilt values exhibited low correlation with predicted values. Thus, two new power-law correlations were proposed. Coefficients for new models were obtained from regression analysis.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"B4 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85209856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-21DOI: 10.3389/fmech.2019.00052
K. Vos, G. Shaver, A. Ramesh, J. McCarthy
Cylinder deactivation (CDA) and cylinder cutout are different operating strategies for diesel engines. CDA includes the deactivation of both the valve motions and the fuel injection of select cylinders, while cylinder cutout incorporates only fuel injection deactivation in select cylinders. This study compares diesel engine aftertreatment thermal management improvements possible via CDA and cylinder cutout at curb idle operation (800 RPM and 1.3 bar BMEP). Experiments and analysis demonstrated that both CDA and cylinder cutout enable improved fuel efficient “stay warm” thermal management compared to a stock thermal calibration on a Clean Idle Certified engine. At curb idle, this stock calibration depends on elevated exhaust manifold pressure to increase the required fueling (for thermal management) and to drive EGR. The study described here demonstrates that CDA does not require an elevated exhaust manifold pressure for thermal management or EGR delivery control, whereas cylinder cutout does. In addition to achieving engine-out NOx levels no higher than the stock thermal calibration, both cylinder cutout and CDA enable up to 55% and 80% reductions in particulate matter (PM), respectively. Cylinder cutout demonstrates 17% fuel savings, while CDA demonstrates 40% fuel savings, over the stock six-cylinder thermal calibration. These fuel efficiency improvements primarily result from reductions in pumping work via reduced air flow through the engine. Cylinder cutout reduces the air flow rate via elevated amounts of recirculated gases which are also required to regulate engine-out NOx, resulting in a larger delta pressure across the engine and consequently more pumping work than CDA. CDA reduces the air flow rate by deactivating cylinders, which reduces the charge flow rate and enables a small delta pressure between the intake and exhaust manifolds, resulting in less pumping work by the cylinders. As a result, CDA is more efficient than cylinder cutout. Furthermore, the thermal merits of cylinder cutout require high exhaust manifold pressures, and are subject to the configuration of the exhaust manifold and the exhaust gas recirculation (EGR) path.
{"title":"Impact of Cylinder Deactivation and Cylinder Cutout via Flexible Valve Actuation on Fuel Efficient Aftertreatment Thermal Management at Curb Idle","authors":"K. Vos, G. Shaver, A. Ramesh, J. McCarthy","doi":"10.3389/fmech.2019.00052","DOIUrl":"https://doi.org/10.3389/fmech.2019.00052","url":null,"abstract":"Cylinder deactivation (CDA) and cylinder cutout are different operating strategies for diesel engines. CDA includes the deactivation of both the valve motions and the fuel injection of select cylinders, while cylinder cutout incorporates only fuel injection deactivation in select cylinders. This study compares diesel engine aftertreatment thermal management improvements possible via CDA and cylinder cutout at curb idle operation (800 RPM and 1.3 bar BMEP). Experiments and analysis demonstrated that both CDA and cylinder cutout enable improved fuel efficient “stay warm” thermal management compared to a stock thermal calibration on a Clean Idle Certified engine. At curb idle, this stock calibration depends on elevated exhaust manifold pressure to increase the required fueling (for thermal management) and to drive EGR. The study described here demonstrates that CDA does not require an elevated exhaust manifold pressure for thermal management or EGR delivery control, whereas cylinder cutout does. In addition to achieving engine-out NOx levels no higher than the stock thermal calibration, both cylinder cutout and CDA enable up to 55% and 80% reductions in particulate matter (PM), respectively. Cylinder cutout demonstrates 17% fuel savings, while CDA demonstrates 40% fuel savings, over the stock six-cylinder thermal calibration. These fuel efficiency improvements primarily result from reductions in pumping work via reduced air flow through the engine. Cylinder cutout reduces the air flow rate via elevated amounts of recirculated gases which are also required to regulate engine-out NOx, resulting in a larger delta pressure across the engine and consequently more pumping work than CDA. CDA reduces the air flow rate by deactivating cylinders, which reduces the charge flow rate and enables a small delta pressure between the intake and exhaust manifolds, resulting in less pumping work by the cylinders. As a result, CDA is more efficient than cylinder cutout. Furthermore, the thermal merits of cylinder cutout require high exhaust manifold pressures, and are subject to the configuration of the exhaust manifold and the exhaust gas recirculation (EGR) path.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"83 3 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77185553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-06DOI: 10.3389/fmech.2019.00046
Jason Liu, James Peck, K. Yazawa, T. Fisher, T. Shih
Surface coolers are heat exchangers with fins on the air side. When air approaches the fins, a portion is diverted away (bypass) because of the adverse pressure gradients induced by the fins. Also, for the air that does flow between the fins, a portion exits (loss) because of pressure rise along the fins due to friction Both bypass and loss reduce the effectiveness of surface coolers to transfer heat to the air. In this study, steady RANS with the SST model (with and without conjugate heat transfer) were performed to examine how geometric and operating parameters affect bypass, loss, pressure drop, and heat transfer in two surface coolers commonly used in aircraft applications. Of the surface coolers, one has continuous fins, and the other has staggered or non-staggered segmented fins. Geometric parameter examined include: spacing between the fins (S/H = 0.2,0.4,0.6,0.8), thickness of the fins (t/H = 0.1, 0.2, 0.4), length of the fins (L/H = 1, 5, 10), and the height of the channel, where the surface cooler is placed (C/H = 2.5, 5, 10, 20, 40 cm), where H is the height of the fin, and C is the half the height of the channel. Operating parameters examined include: velocity (Vin = 32.5, 65, 97.5, and 135 m/s) and temperature (Tin = 300 and 473 K) of flow approaching the surface cooler, the fins’ wall temperature (Tw = 300, 320, 350, 375, 400, 493 K). Results obtained show C/H to significantly affect bypass and loss until C/H reaches about 20. Bypass, loss, and pressure drop all increase monotonically as the blockage created by the fins, t/(S+t), increases. The ratio of the Nusselt number to the pressure coefficient is a maximum when t/(S+t) = 0.33 for the conjugate cases and 0.5 for the isothermal cases. Vin, Tin and Tw were found to have negligible effects on bypass, but have appreciable effects on loss when spacing between the fins is small. For the geometries studied, segmenting the fins was found to increase loss, resulting in the worst heat-transfer rate and highest pressure drop.
{"title":"Bypass, Loss, and Heat Transfer in Aircraft Surface Coolers","authors":"Jason Liu, James Peck, K. Yazawa, T. Fisher, T. Shih","doi":"10.3389/fmech.2019.00046","DOIUrl":"https://doi.org/10.3389/fmech.2019.00046","url":null,"abstract":"Surface coolers are heat exchangers with fins on the air side. When air approaches the fins, a portion is diverted away (bypass) because of the adverse pressure gradients induced by the fins. Also, for the air that does flow between the fins, a portion exits (loss) because of pressure rise along the fins due to friction Both bypass and loss reduce the effectiveness of surface coolers to transfer heat to the air. In this study, steady RANS with the SST model (with and without conjugate heat transfer) were performed to examine how geometric and operating parameters affect bypass, loss, pressure drop, and heat transfer in two surface coolers commonly used in aircraft applications. Of the surface coolers, one has continuous fins, and the other has staggered or non-staggered segmented fins. Geometric parameter examined include: spacing between the fins (S/H = 0.2,0.4,0.6,0.8), thickness of the fins (t/H = 0.1, 0.2, 0.4), length of the fins (L/H = 1, 5, 10), and the height of the channel, where the surface cooler is placed (C/H = 2.5, 5, 10, 20, 40 cm), where H is the height of the fin, and C is the half the height of the channel. Operating parameters examined include: velocity (Vin = 32.5, 65, 97.5, and 135 m/s) and temperature (Tin = 300 and 473 K) of flow approaching the surface cooler, the fins’ wall temperature (Tw = 300, 320, 350, 375, 400, 493 K). Results obtained show C/H to significantly affect bypass and loss until C/H reaches about 20. Bypass, loss, and pressure drop all increase monotonically as the blockage created by the fins, t/(S+t), increases. The ratio of the Nusselt number to the pressure coefficient is a maximum when t/(S+t) = 0.33 for the conjugate cases and 0.5 for the isothermal cases. Vin, Tin and Tw were found to have negligible effects on bypass, but have appreciable effects on loss when spacing between the fins is small. For the geometries studied, segmenting the fins was found to increase loss, resulting in the worst heat-transfer rate and highest pressure drop.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"39 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85440113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-08-02DOI: 10.3389/fmech.2019.00047
R. Pohrt, V. Popov
{"title":"Editorial: Friction and Wear: From Elementary Mechanisms to Macroscopic Behavior","authors":"R. Pohrt, V. Popov","doi":"10.3389/fmech.2019.00047","DOIUrl":"https://doi.org/10.3389/fmech.2019.00047","url":null,"abstract":"","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"88 4 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78609203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：