The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform
Jacqueline H Chen - One of the best experts on this subject based on the ideXlab platform.
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direct numerical simulation of flame stabilization assisted by autoignition in a reheat gas turbine combustor
Proceedings of the Combustion Institute, 2019Co-Authors: Konduri Aditya, Andrea Gruber, Alex Krisman, Mirko Ruben Bothien, Jacqueline H ChenAbstract:Abstract A three-dimensional direct numerical simulation (DNS) is performed for a turbulent hydrogen-air flame, represented with detailed chemistry, stabilized in a model gas-turbine combustor. The combustor geometry consists of a mixing duct followed by a sudden expansion and a combustion chamber, which represents a geometrically simplified version of Ansaldo Energia’s GT26/GT36 sequential combustor Design. In this configuration, a very lean blend of hydrogen and vitiated air is prepared in the mixing duct and convected into the combustion chamber, where the residence time from the inlet of the mixing duct to the combustion chamber is Designed to coincide with the ignition delay time of the mixture. The results show that when the flame is stabilized at its Design Position, combustion occurs due to both autoignition and flame propagation (deflagration) modes at different locations within the combustion chamber. A chemical explosive mode analysis (CEMA) reveals that most of the fuel is consumed due to autoignition in the bulk-flow along the centerline of the combustor, and lower amounts of fuel are consumed by flame propagation near the corners of the sudden expansion, where the unburnt temperature is reduced by the thermal wall boundary layers. An unstable operating condition is also identified, wherein periodic auto-ignition events occur within the mixing duct. These events appear upstream of the intended stabilization Position, due to positive temperature fluctuations induced by pressure waves originating from within the combustion chamber. The present DNS investigation represents the initial step of a comprehensive research effort aimed at gaining detailed physical insight into the rate-limiting processes that govern the sequential combustor behavior and avoid the insurgence of the off-Design auto-ignition events.
Nesreen Ghaddar - One of the best experts on this subject based on the ideXlab platform.
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Effectiveness of contaminant confinement in office spaces equipped with ceiling personalized ventilation system
Building Simulation, 2018Co-Authors: Sorour Alotaibi, Walid Chakroun, Charbel Habchi, Kamel Ghali, Nesreen GhaddarAbstract:Creating a micro-environment around infected occupants constitutes an effective strategy in reducing contaminants spread insuring a relatively clean macroclimate decreasing the risk of infection for occupants circulating in an office space. In this work, the ability of ceiling personalized ventilation (CPV) system assisted by desk fans (DF) or chair fans (CF) was studied with respect to confining contaminants spread in typical office space while considering possible occupant shift. A 3D computational fluid dynamics (CFD) model was developed to simulate particle spread. The developed model was validated experimentally with respect to concentration values using a thermal manikin in a climatic chamber with controlled particle generation. A parametric study was followed to determine the effect of the occupant shift from CPV Design Position, the CPV+DF or CF configuration, and the canopy angle on confinement performance for minimal particle spread in the space. The CPV jet and diffusers’ flow canopy favored particle dePosition within the microclimate region leading to their removal from indoor air. For no occupant shift, assisting the CPV jet by DF or CF was very efficient in particle confinement. However, in the cases of critical backward occupant shift, flow asymmetry was formed around the occupant leading to particle spread and leading to asymmetry attenuation when operated with CF. The highest particle confinement was obtained for a canopy angle of 45° for the case of CPV assisted by CF due to forming a recirculation zone between the CPV and jet diffusers; hence trapping particles and reducing their spread to the macroclimate. It was found that a total supply flow rate of 60 L/s for MV is required compared to 43.5 L/s for the optimal CPV Design, for equivalent average particle concentration within the macroclimate zone at the critical generation plane, leading to 62% reduction in power consumption of the supply fan.
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Effect of shifts from occupant Design Position on performance of ceiling personalized ventilation assisted with desk fan or chair fans
Energy and Buildings, 2016Co-Authors: Charbel Habchi, Walid Chakroun, Sorour Alotaibi, Kamel Ghali, Nesreen GhaddarAbstract:Recently, personalized ventilation systems have gained popularity since they consist on localizing the occupant needs in terms of thermal comfort and indoor air quality (IAQ). Localized ventilation systems are Designed on the basis of fixed occupant Position. Since people move and do not remain in same Position, it is of interest to study personalized ventilation system performance with respect to shifts from occupant Design Position. The aim of this work is to study and compare the performance of ceiling personalized ventilation (CPV) when aided with desk fans (DF) versus chair fans (CF) in crowded office spaces for shifts from seated occupant chair Position with respect to the CPV jet. A computational fluid dynamics (CFD) model for particle transport and dePosition was developed to simulate a two-station office ventilated by CPV system to predict particle transport and to assess ventilation effectiveness. The CFD model was coupled with a bio-heat model to predict segmental and overall sensation and comfort in addition to segmental skin temperatures. In this work, experiments were conducted to validate the CFD model accuracy in capturing the effect of the CF on particle transport. The use of CF allowed the reduction of CPV flow rate by 22.72% resulting in energy savings of 14.87% for the case where the occupant was beneath the jet. Installing CFs allowed maintaining good performance of the system when chair shift due to movement of person occurred while installing DFs resulted in largely degrading the system performance at equal chair shift from the CPV center.
Shaun Lawson - One of the best experts on this subject based on the ideXlab platform.
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Funology, 2nd ed. - Reorienting Geolocation Data Through Mischievous Design
Human–Computer Interaction Series, 2018Co-Authors: Ben Kirman, Conor Linehan, Shaun LawsonAbstract:The increasing capability of smart mobile devices to use geolocation and networking has resulted in a proliferation of digital mobile computing services that respond to the social and physical places we visit as we move through the world. This chapter reports and comments on a series of four provocative Design projects undertaken in order to better understand location data as material comprising complex social, psychological, and physical properties, and to problematise the growing trend of services uncritically built upon these data. We describe how approaching these goals in a playful and mischievous manner allowed us to explore surprising, jarring or under-reported qualities of geolocation data. In each project, the Design process began with ideation around the subversion of stereotypical uses of this data. Working prototypes were Designed and implemented using contemporary hardware and software services. Through playing, using, or reading about these prototypes in the media, participants raised new questions and new concerns about how location data is mediated by smart devices, which were developed further in subsequent projects. We believe that this series of projects highlights the value of mischief and fun as a valid Design Position through which to explore sociocultural aspects of new technologies.
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reorienting geolocation data through mischievous Design
Funology 2nd ed., 2018Co-Authors: Ben Kirman, Conor Linehan, Shaun LawsonAbstract:The increasing capability of smart mobile devices to use geolocation and networking has resulted in a proliferation of digital mobile computing services that respond to the social and physical places we visit as we move through the world. This chapter reports and comments on a series of four provocative Design projects undertaken in order to better understand location data as material comprising complex social, psychological, and physical properties, and to problematise the growing trend of services uncritically built upon these data. We describe how approaching these goals in a playful and mischievous manner allowed us to explore surprising, jarring or under-reported qualities of geolocation data. In each project, the Design process began with ideation around the subversion of stereotypical uses of this data. Working prototypes were Designed and implemented using contemporary hardware and software services. Through playing, using, or reading about these prototypes in the media, participants raised new questions and new concerns about how location data is mediated by smart devices, which were developed further in subsequent projects. We believe that this series of projects highlights the value of mischief and fun as a valid Design Position through which to explore sociocultural aspects of new technologies.
Konduri Aditya - One of the best experts on this subject based on the ideXlab platform.
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direct numerical simulation of flame stabilization assisted by autoignition in a reheat gas turbine combustor
Proceedings of the Combustion Institute, 2019Co-Authors: Konduri Aditya, Andrea Gruber, Alex Krisman, Mirko Ruben Bothien, Jacqueline H ChenAbstract:Abstract A three-dimensional direct numerical simulation (DNS) is performed for a turbulent hydrogen-air flame, represented with detailed chemistry, stabilized in a model gas-turbine combustor. The combustor geometry consists of a mixing duct followed by a sudden expansion and a combustion chamber, which represents a geometrically simplified version of Ansaldo Energia’s GT26/GT36 sequential combustor Design. In this configuration, a very lean blend of hydrogen and vitiated air is prepared in the mixing duct and convected into the combustion chamber, where the residence time from the inlet of the mixing duct to the combustion chamber is Designed to coincide with the ignition delay time of the mixture. The results show that when the flame is stabilized at its Design Position, combustion occurs due to both autoignition and flame propagation (deflagration) modes at different locations within the combustion chamber. A chemical explosive mode analysis (CEMA) reveals that most of the fuel is consumed due to autoignition in the bulk-flow along the centerline of the combustor, and lower amounts of fuel are consumed by flame propagation near the corners of the sudden expansion, where the unburnt temperature is reduced by the thermal wall boundary layers. An unstable operating condition is also identified, wherein periodic auto-ignition events occur within the mixing duct. These events appear upstream of the intended stabilization Position, due to positive temperature fluctuations induced by pressure waves originating from within the combustion chamber. The present DNS investigation represents the initial step of a comprehensive research effort aimed at gaining detailed physical insight into the rate-limiting processes that govern the sequential combustor behavior and avoid the insurgence of the off-Design auto-ignition events.
Charbel Habchi - One of the best experts on this subject based on the ideXlab platform.
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Effectiveness of contaminant confinement in office spaces equipped with ceiling personalized ventilation system
Building Simulation, 2018Co-Authors: Sorour Alotaibi, Walid Chakroun, Charbel Habchi, Kamel Ghali, Nesreen GhaddarAbstract:Creating a micro-environment around infected occupants constitutes an effective strategy in reducing contaminants spread insuring a relatively clean macroclimate decreasing the risk of infection for occupants circulating in an office space. In this work, the ability of ceiling personalized ventilation (CPV) system assisted by desk fans (DF) or chair fans (CF) was studied with respect to confining contaminants spread in typical office space while considering possible occupant shift. A 3D computational fluid dynamics (CFD) model was developed to simulate particle spread. The developed model was validated experimentally with respect to concentration values using a thermal manikin in a climatic chamber with controlled particle generation. A parametric study was followed to determine the effect of the occupant shift from CPV Design Position, the CPV+DF or CF configuration, and the canopy angle on confinement performance for minimal particle spread in the space. The CPV jet and diffusers’ flow canopy favored particle dePosition within the microclimate region leading to their removal from indoor air. For no occupant shift, assisting the CPV jet by DF or CF was very efficient in particle confinement. However, in the cases of critical backward occupant shift, flow asymmetry was formed around the occupant leading to particle spread and leading to asymmetry attenuation when operated with CF. The highest particle confinement was obtained for a canopy angle of 45° for the case of CPV assisted by CF due to forming a recirculation zone between the CPV and jet diffusers; hence trapping particles and reducing their spread to the macroclimate. It was found that a total supply flow rate of 60 L/s for MV is required compared to 43.5 L/s for the optimal CPV Design, for equivalent average particle concentration within the macroclimate zone at the critical generation plane, leading to 62% reduction in power consumption of the supply fan.
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Effect of shifts from occupant Design Position on performance of ceiling personalized ventilation assisted with desk fan or chair fans
Energy and Buildings, 2016Co-Authors: Charbel Habchi, Walid Chakroun, Sorour Alotaibi, Kamel Ghali, Nesreen GhaddarAbstract:Recently, personalized ventilation systems have gained popularity since they consist on localizing the occupant needs in terms of thermal comfort and indoor air quality (IAQ). Localized ventilation systems are Designed on the basis of fixed occupant Position. Since people move and do not remain in same Position, it is of interest to study personalized ventilation system performance with respect to shifts from occupant Design Position. The aim of this work is to study and compare the performance of ceiling personalized ventilation (CPV) when aided with desk fans (DF) versus chair fans (CF) in crowded office spaces for shifts from seated occupant chair Position with respect to the CPV jet. A computational fluid dynamics (CFD) model for particle transport and dePosition was developed to simulate a two-station office ventilated by CPV system to predict particle transport and to assess ventilation effectiveness. The CFD model was coupled with a bio-heat model to predict segmental and overall sensation and comfort in addition to segmental skin temperatures. In this work, experiments were conducted to validate the CFD model accuracy in capturing the effect of the CF on particle transport. The use of CF allowed the reduction of CPV flow rate by 22.72% resulting in energy savings of 14.87% for the case where the occupant was beneath the jet. Installing CFs allowed maintaining good performance of the system when chair shift due to movement of person occurred while installing DFs resulted in largely degrading the system performance at equal chair shift from the CPV center.