I completed all my education at Seikei University Japan in 1980. My professional career started at UCSD as a postgraduate engineer (1980-1981), a researcher at Princeton University (1981-1986), and faculty at University of Kentucky (1986 - present). Currently I am the Tennessee valley Authority Professor in Mechanical Engineering and the founding Director of the Institute of Research for Technology Development (IR4TD). My research interest includes combustion, fire research, scale modeling and Monozukuri.
The authors are a team of fire whirl researchers who have been actively studying whirls and large... more The authors are a team of fire whirl researchers who have been actively studying whirls and large-scale wildland fires by directly observing them through fire-fighting efforts and applying theory, scale modeling, and numerical simulations in fire research. This multidisciplinary research-background team previously conducted scale model experiments to reconstruct hazardous large-scale fires in the laboratory, then conducted numerical simulations and developed fundamental theories to translate these findings into a basic understanding of combustion science and fluid dynamics. This article, a mix of reviews of the state of art experiments, theories, numerical modeling and artificial intelligence, and two case studies, is intended to address some safety concerns and raise awareness of large-scale fire whirls and forest fires with knowledge of thermodynamics, chemical kinetics, fluid dynamics, design, and practical fire-fighting experience, offering gaps that should be filled and future ...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2017
Automotive spray painting is among the most sophisticated and controlled industrial painting oper... more Automotive spray painting is among the most sophisticated and controlled industrial painting operations currently performed. Nevertheless, improvements in it are still sought in efforts to minimize the costs, the energy use and the environmental impacts. One compelling aspect of improvement is the paint transfer efficiency, i.e. the amount of paint that remains on a vehicle relative to the amount supplied to the paint applicator during coating operations, because currently it has been estimated that the overall paint transfer efficiency in the automotive industry is between 50% and 60%. Hence, this review assesses current automotive spray coating technologies with respect to their transfer efficiencies and discusses the fundamental and operational parameters that influence it. A comprehensive characterization of paint spray applicators (air sprayers, high-volume low-pressure sprayers, airless sprayers, air-assisted airless sprayers, rotary bell atomizers, electrostatic sprayers, and...
A volume of fluid (VOF) numerical study is presented in which new pi number-based criteria are di... more A volume of fluid (VOF) numerical study is presented in which new pi number-based criteria are discussed that identify and separate three different regimes for a droplet-on-demand (DOD) print-head system. A trailing filament coalesces into the main droplet while the filament breaks into one or multiple satellite droplet(s). The numerical simulation results are compared with published large-scale experimental results that used a 2 mm diameter inkjet nozzle head, roughly 50 times larger than the actual diameter of inkjet outlets. Liquid filament break-up behavior is predicted using a combination of two pi-numbers, including either Weber (We)-Ohnesorge (Oh) number couplets or Reynolds (Re)-Weber (We) number couplets that are dependent only on the ejected liquid properties and the velocity waveform at the print-head inlet. These new criteria have merit over the currently existing ones that require accurate measurements of actual droplets to determine filament physical features like length and diameter [1].
Abstract The paper aims to solve drawbacks associated with Gas Turbine GT by integrating a novel ... more Abstract The paper aims to solve drawbacks associated with Gas Turbine GT by integrating a novel cascaded system into a combined cycle simultaneously. Parabolic trough collectors preheat the air at the combustion chamber inlet, then drive an absorption inlet-air cooling cycle that controls the ambient-air temperature at the compressor's inlet. This study uses the 2nd law of thermodynamics to estimate the maximum available energy, calculate the electric exergy efficiency, and explore the maximum irreversible exergy destruction in the system's components. Artificial Neural Network was employed to develop a multi-objective optimization by linking data collected from equations in the Engineering Equation Solver software with Matlab. Spider diagrams investigated the effect of varying several key operating parameters on the performance of the system, identifying gas turbine as the highest irreversibility sub-unit and the solar field parabolic trough collectors as the second. Design improvement for the combustion chamber can reduce 303.6 MW, and for parabolic trough collectors field reduce 58.9 MW. Artificial neural networks with multi-objective optimization maximized the electric exergy destruction to 46.19% and minimized the exergy destruction to 489.4 MW, relative to the corresponding values from the simple design point.
Abstract Live foliage for some tree and shrub species can support flaming fire spread at much hig... more Abstract Live foliage for some tree and shrub species can support flaming fire spread at much higher moisture content than dead fuel materials. However, the role of live fuels in forest fires has been controversial in the past decades. Although ignition and spread statistical data for live and dead fuels exist in the literature, a clear understanding of the fundamental difference in the burning behavior is missing. To illuminate the role of live fuel on forest fire spreading, a laboratory ignition experiment was designed to examine the burning behavior of live Norway spruce needles. A Schlieren-Infrared combined measurement apparatus was developed with a spatial resolution of 0.75 mm and a time resolution of 0.0025 s, to visualize/measure the ignition behavior of live fuels. Schlieren and IR images revealed that the ejection of live fuel volatiles can alter the flame direction and induce previously unaccounted heating of the nearby fuel. Depending on the conditions, these interferences could heat and modify the heat flux received by the adjacent fuels. To analyze each of these outcomes, a scaling analysis using the law approach was performed. First, theoretical equations were developed and validated against a set of previously published experimental data. After the characteristic equations were verified, we used them to assess the volatile ejection phenomenon. We found that adjacent fuels were preheated by hot volatiles ejected from the heated live needle, and direct flame contact ignited the adjacent fuels. Our IR experiments confirmed the outcomes of the scaling analysis. The rapid ejection of volatiles was also found to propel burning needles far from the burning branch, resulting in micro-spotting.
The authors are a team of fire whirl researchers who have been actively studying whirls and large... more The authors are a team of fire whirl researchers who have been actively studying whirls and large-scale wildland fires by directly observing them through fire-fighting efforts and applying theory, scale modeling, and numerical simulations in fire research. This multidisciplinary research-background team previously conducted scale model experiments to reconstruct hazardous large-scale fires in the laboratory, then conducted numerical simulations and developed fundamental theories to translate these findings into a basic understanding of combustion science and fluid dynamics. This article, a mix of reviews of the state of art experiments, theories, numerical modeling and artificial intelligence, and two case studies, is intended to address some safety concerns and raise awareness of large-scale fire whirls and forest fires with knowledge of thermodynamics, chemical kinetics, fluid dynamics, design, and practical fire-fighting experience, offering gaps that should be filled and future ...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2017
Automotive spray painting is among the most sophisticated and controlled industrial painting oper... more Automotive spray painting is among the most sophisticated and controlled industrial painting operations currently performed. Nevertheless, improvements in it are still sought in efforts to minimize the costs, the energy use and the environmental impacts. One compelling aspect of improvement is the paint transfer efficiency, i.e. the amount of paint that remains on a vehicle relative to the amount supplied to the paint applicator during coating operations, because currently it has been estimated that the overall paint transfer efficiency in the automotive industry is between 50% and 60%. Hence, this review assesses current automotive spray coating technologies with respect to their transfer efficiencies and discusses the fundamental and operational parameters that influence it. A comprehensive characterization of paint spray applicators (air sprayers, high-volume low-pressure sprayers, airless sprayers, air-assisted airless sprayers, rotary bell atomizers, electrostatic sprayers, and...
A volume of fluid (VOF) numerical study is presented in which new pi number-based criteria are di... more A volume of fluid (VOF) numerical study is presented in which new pi number-based criteria are discussed that identify and separate three different regimes for a droplet-on-demand (DOD) print-head system. A trailing filament coalesces into the main droplet while the filament breaks into one or multiple satellite droplet(s). The numerical simulation results are compared with published large-scale experimental results that used a 2 mm diameter inkjet nozzle head, roughly 50 times larger than the actual diameter of inkjet outlets. Liquid filament break-up behavior is predicted using a combination of two pi-numbers, including either Weber (We)-Ohnesorge (Oh) number couplets or Reynolds (Re)-Weber (We) number couplets that are dependent only on the ejected liquid properties and the velocity waveform at the print-head inlet. These new criteria have merit over the currently existing ones that require accurate measurements of actual droplets to determine filament physical features like length and diameter [1].
Abstract The paper aims to solve drawbacks associated with Gas Turbine GT by integrating a novel ... more Abstract The paper aims to solve drawbacks associated with Gas Turbine GT by integrating a novel cascaded system into a combined cycle simultaneously. Parabolic trough collectors preheat the air at the combustion chamber inlet, then drive an absorption inlet-air cooling cycle that controls the ambient-air temperature at the compressor's inlet. This study uses the 2nd law of thermodynamics to estimate the maximum available energy, calculate the electric exergy efficiency, and explore the maximum irreversible exergy destruction in the system's components. Artificial Neural Network was employed to develop a multi-objective optimization by linking data collected from equations in the Engineering Equation Solver software with Matlab. Spider diagrams investigated the effect of varying several key operating parameters on the performance of the system, identifying gas turbine as the highest irreversibility sub-unit and the solar field parabolic trough collectors as the second. Design improvement for the combustion chamber can reduce 303.6 MW, and for parabolic trough collectors field reduce 58.9 MW. Artificial neural networks with multi-objective optimization maximized the electric exergy destruction to 46.19% and minimized the exergy destruction to 489.4 MW, relative to the corresponding values from the simple design point.
Abstract Live foliage for some tree and shrub species can support flaming fire spread at much hig... more Abstract Live foliage for some tree and shrub species can support flaming fire spread at much higher moisture content than dead fuel materials. However, the role of live fuels in forest fires has been controversial in the past decades. Although ignition and spread statistical data for live and dead fuels exist in the literature, a clear understanding of the fundamental difference in the burning behavior is missing. To illuminate the role of live fuel on forest fire spreading, a laboratory ignition experiment was designed to examine the burning behavior of live Norway spruce needles. A Schlieren-Infrared combined measurement apparatus was developed with a spatial resolution of 0.75 mm and a time resolution of 0.0025 s, to visualize/measure the ignition behavior of live fuels. Schlieren and IR images revealed that the ejection of live fuel volatiles can alter the flame direction and induce previously unaccounted heating of the nearby fuel. Depending on the conditions, these interferences could heat and modify the heat flux received by the adjacent fuels. To analyze each of these outcomes, a scaling analysis using the law approach was performed. First, theoretical equations were developed and validated against a set of previously published experimental data. After the characteristic equations were verified, we used them to assess the volatile ejection phenomenon. We found that adjacent fuels were preheated by hot volatiles ejected from the heated live needle, and direct flame contact ignited the adjacent fuels. Our IR experiments confirmed the outcomes of the scaling analysis. The rapid ejection of volatiles was also found to propel burning needles far from the burning branch, resulting in micro-spotting.
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Papers by Kozo Saito