The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Kaoru Maruta - One of the best experts on this subject based on the ideXlab platform.
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development and scale effects of small swiss roll Combustors
31st International Symposium on Combustion, 2007Co-Authors: Nam Il Kim, Satoshi Aizumi, Takeshi Yokomori, Soichiro Kato, Toshiro Fujimori, Kaoru MarutaAbstract:Abstract The configuration of Swiss-roll was adopted as a promising structure for the development of sub-millimetre scale Combustors. In this study, the scaling effects are investigated both experimentally and analytically. Based on our first proto-type (64 mm in diameter), scaled-down Combustors (45 mm) with different design parameters were fabricated; diameter of the combustor, top plate thickness, channel size and combustor material. A simple one-dimensional analytical model was constructed to interpret the combustion characteristics of the Swiss-roll Combustors. Two energy equations for combustor body and mixture, along with species equations employing two-step global reaction model were solved. In spite of the simplicity of the present model, important characteristics of the Combustors such as upper and lower flammability limits, effect of cap thickness on flammability limits were predicted well. Based on the analytical results, several smaller coin-size Combustors (diameter 26 and 20 mm) were additionally developed and their characteristics were investigated. This study shows that the effects of design parameters are important in the practical development of smaller Combustors.
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flame stabilization and emission of small swiss roll Combustors as heaters
Combustion and Flame, 2005Co-Authors: Nam Il Kim, Takeshi Yokomori, Toshiro Fujimori, Souichiro Kato, Takuya Kataoka, Shigenao Maruyama, Kaoru MarutaAbstract:Abstract The characteristics of small Swiss-roll Combustors were investigated experimentally in detail. Three types of Swiss-roll Combustors of different designs and two cases of heat transfer conditions were studied. The effects of design parameters on the performance of these Combustors were examined. Each combustor consisted of a combustion region at the center (called the combustion room) and double spiral-shaped channels, the widths of which were smaller than the minimum quenching distance of a propane premixed flame at a normal state. Flames could be stabilized successfully for a wide range of equivalence ratios and mean velocities by using the recirculated heat from the burned gas, and blow-off was not observed. Temperature distributions of the Combustors, variation of gas temperature, and the concentrations of the exhaust gas from the Combustors were also investigated. Mean temperatures of the Combustors were found to be governed by both the radiant heat loss from the Combustors and the total chemical energy liberated by the Combustors. Efficiencies of the Combustors as heaters were evaluated. As a combustor became smaller, its thermal efficiency as a heater increased and its NOx emission decreased, while the emission of CO increased. By adding a catalytic reactor at the exhaust port, it was found that the emission of CO could be eliminated. This study provides new experimental results for a small Swiss-roll combustor, which represents an essential step toward the development of a microcombustor.
Ian A. Waitz - One of the best experts on this subject based on the ideXlab platform.
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Impact of Manufacturing Variability on Combustor Liner Durability
Journal of Engineering for Gas Turbines and Power, 2009Co-Authors: Sean D. Bradshaw, Ian A. WaitzAbstract:This paper presents a probability-based systems-level approach for assessing the impact of manufacturing variability on combustor liner durability. Simplified models are used to link combustor life, liner temperature variability, and the effects of manufacturing variability. A probabilistic analysis is then applied to the simplified models to estimate the combustor life distribution. The typical combustor life was found to be approximately 20% less than the estimate life using deterministic methods for these Combustors, and the probability that a randomly selected combustor will fail earlier than expected using deterministic methods is approximately 80%. The application of a sensitivity analysis to a surrogate model for the life identified the leading drivers of the minimum combustor life and the typical combustor life as the material property variability and the circumferential variability of turbulent mixing rates, respectively.
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high power density silicon combustion systems for micro gas turbine engines
ASME Turbo Expo 2002: Power for Land Sea and Air, 2002Co-Authors: Christopher M. Spadaccini, A Mehra, Stephen P. Lukachko, Ian A. Waitz, Xin ZhangAbstract:As part of an effort to develop a micro-scale gas turbine engine for power generation and micro-propulsion applications, this paper presents the design, fabrication, experimental testing, and modeling of the combustion system. Two radial inflow combustor designs were examined; a single-zone arrangement and a primary and dilution-zone configuration. Both Combustors were micro-machined from silicon using Deep Reactive Ion Etching (DRIE) and aligned fusion wafer bonding. Hydrogen-air and hydrocarbon-air combustion was stabilized in both devices, each with chamber volumes of 191 mm3 . Exit gas temperatures as high as 1800 K and power densities in excess of 1100 MW/m3 were achieved. For the same equivalence ratio and overall efficiency, the dual-zone combustor reached power densities nearly double that of the single-zone design. Because diagnostics in micro-scale devices are often highly intrusive, numerical simulations were used to gain insight into the fluid and combustion physics. Unlike large-scale Combustors, the performance of the micro-Combustors was found to be more severely limited by heat transfer and chemical kinetics constraints. Important design trades are identified and recommendations for micro-combustor design are presented.Copyright © 2002 by ASME
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Combustors for micro gas turbine engines
Journal of Fluids Engineering-transactions of The Asme, 1998Co-Authors: Ian A. Waitz, Gautam Gauba, Yangsheng TzengAbstract:The development ofa hydrogen-air microcombustor is described. The combustor is intended for use in a 1 mm 2 inlet area, micro-gas turbine engine. While the size of the device poses several difficulties, it also provides new and unique opportunities. The combustion concept investigated is based upon introducing hydrogen and premixing it with air upstream of the combustor. The wide flammability limits of hydrogen-air mixtures and the use of refractory ceramics enable combustion at lean conditions, obviating the need for both a combustor dilution zone and combustor wall cooling. The entire combustion process is carried out at temperatures below the limitations set by material properties, resulting in a significant reduction of complexity when compared to larger-scale gas turbine Combustors. A feasibility study with initial design analyses is presented, followed by experimental results from 0.13 cm 3 silicon carbide and steel microCombustors. The Combustors were operated for tens of hours, and produced the requisite heat release for a microengine application over a range of fuel-air ratios, inlet temperatures, and pressures up to four atmospheres. Issues of flame stability, heat transfer, ignition and mixing are addressed. A discussion of requirements for catalytic processes for hydrocarbon fuels is also presented.
Jun Li - One of the best experts on this subject based on the ideXlab platform.
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fundamental flame characteristics of premixed h2 air combustion in a planar porous micro combustor
Chemical Engineering Journal, 2016Co-Authors: Jun Li, Qingqing Li, Yuantao WangAbstract:Micro-/meso-scale combustion represents a great potential in generating portable power in an efficient way. Heat recirculation is regarded as the most important factor that influences the combustion process in micro-Combustors. Adding porous medium to a free flame micro-combustor is able to enhance thermal energy transport, thus allowing more heat recirculation. A CFD study on fundamental flame characteristics of premixed H2–air combustion in a planar porous micro-combustor is carried out. Thermal radiation is not considered in order to focus on the contribution of enhanced thermal conduction. The effects of flow conditions and properties of the porous medium on the wall temperature, species concentration, flame temperature, flame location, and flame speed are examined individually. The numerical results indicate that a porous micro-combustor gives a higher wall temperature and a lower flame temperature than a free flame counterpart. In the presence of porous medium, temperature distribution as well as species (OH) concentration becomes more uniform. Flame locations in a porous micro-combustor exhibit a U-shaped pattern against the change of the inlet flow velocity. Choosing the porous material properly to have the effective thermal conductivity and the wall thermal conductivity in the same order of magnitude is helpful to localize flames. Finally, the flame speed is found to be in a linear relation with the inlet flow velocity. It is noted that the blocking effect incurred by the solid matrix renders some conclusions of free flame micro-Combustors ineffective in explaining the results of the porous micro-combustor, which requires further studies or more sophisticated models.
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study on premixed combustion in cylindrical micro Combustors transient flame behavior and wall heat flux
Experimental Thermal and Fluid Science, 2009Co-Authors: Jun Li, Guangbin Huang, S K Chou, Wenming Yang, Zicong LiAbstract:Abstract The micro combustor is a key component of the micro thermophotovoltaic (TPV) system. Improving the wall temperature of the micro combustor is an effective way to elevate the system efficiency. An experimental study on the wall temperature and radiation heat flux of a series of cylindrical micro Combustors (with a backward-facing step) was carried out. For the micro Combustors with d = 2 mm, the regime of successful ignition (under the cold wall condition) was identified for different combustor lengths. Acoustic emission was detected for some cases and the emitted sound was recorded and analyzed. Under the steady-state condition, the effects of the combustor diameter ( d ), combustor length ( L ), flow velocity ( u 0 ) and fuel–air equivalence ratio ( Ф ) on the wall temperature distribution were investigated by measuring the detailed wall temperature profiles. In the case that the micro combustor is working as an emitter, the optimum efficiency was found at Ф ≈ 0.8, independent of the combustor dimensions ( d and L ) and the flow velocity. Under the experimental conditions employed in the present study, the positions of the peak wall temperature were found to be about 8–11 mm and 4–6 mm from the step for the d = 3 mm and d = 2 mm micro Combustors, respectively, which are 8–11 and 8–12 times of their respective step heights. This result suggests that the backward-facing step employed in the combustor design is effective in stabilizing the flame position.
Nam Il Kim - One of the best experts on this subject based on the ideXlab platform.
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development and scale effects of small swiss roll Combustors
31st International Symposium on Combustion, 2007Co-Authors: Nam Il Kim, Satoshi Aizumi, Takeshi Yokomori, Soichiro Kato, Toshiro Fujimori, Kaoru MarutaAbstract:Abstract The configuration of Swiss-roll was adopted as a promising structure for the development of sub-millimetre scale Combustors. In this study, the scaling effects are investigated both experimentally and analytically. Based on our first proto-type (64 mm in diameter), scaled-down Combustors (45 mm) with different design parameters were fabricated; diameter of the combustor, top plate thickness, channel size and combustor material. A simple one-dimensional analytical model was constructed to interpret the combustion characteristics of the Swiss-roll Combustors. Two energy equations for combustor body and mixture, along with species equations employing two-step global reaction model were solved. In spite of the simplicity of the present model, important characteristics of the Combustors such as upper and lower flammability limits, effect of cap thickness on flammability limits were predicted well. Based on the analytical results, several smaller coin-size Combustors (diameter 26 and 20 mm) were additionally developed and their characteristics were investigated. This study shows that the effects of design parameters are important in the practical development of smaller Combustors.
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flame stabilization and emission of small swiss roll Combustors as heaters
Combustion and Flame, 2005Co-Authors: Nam Il Kim, Takeshi Yokomori, Toshiro Fujimori, Souichiro Kato, Takuya Kataoka, Shigenao Maruyama, Kaoru MarutaAbstract:Abstract The characteristics of small Swiss-roll Combustors were investigated experimentally in detail. Three types of Swiss-roll Combustors of different designs and two cases of heat transfer conditions were studied. The effects of design parameters on the performance of these Combustors were examined. Each combustor consisted of a combustion region at the center (called the combustion room) and double spiral-shaped channels, the widths of which were smaller than the minimum quenching distance of a propane premixed flame at a normal state. Flames could be stabilized successfully for a wide range of equivalence ratios and mean velocities by using the recirculated heat from the burned gas, and blow-off was not observed. Temperature distributions of the Combustors, variation of gas temperature, and the concentrations of the exhaust gas from the Combustors were also investigated. Mean temperatures of the Combustors were found to be governed by both the radiant heat loss from the Combustors and the total chemical energy liberated by the Combustors. Efficiencies of the Combustors as heaters were evaluated. As a combustor became smaller, its thermal efficiency as a heater increased and its NOx emission decreased, while the emission of CO increased. By adding a catalytic reactor at the exhaust port, it was found that the emission of CO could be eliminated. This study provides new experimental results for a small Swiss-roll combustor, which represents an essential step toward the development of a microcombustor.
Yetao Shao - One of the best experts on this subject based on the ideXlab platform.
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three dimensional numerical investigations of the rotating detonation engine with a hollow combustor
Combustion and Flame, 2015Co-Authors: Xinmeng Tang, Jianping Wang, Yetao ShaoAbstract:Abstract The aim of this work is to numerically verify a new model of the rotating detonation engine (RDE) combustor. The new model, which we call the hollow combustor, has no inner wall and is hollow. It is presented to solve the problem of engine heating that arises in RDEs with the co-axial annular combustor. Using the one-step chemistry kinetic model and the Euler equations in cylindrical coordinates, a series of three-dimensional (3D) numerical simulations are performed to find out whether detonation waves can propagate in such Combustors. The results show that this new RDE combustor model can realize energy conversion in rotating detonation. The fuel-based specific impulse can reach around 7000 s. By comparing the results of hollow and annular Combustors, some important differences are observed though general behaviors in these two RDE combustor models are similar. One is that there is no repeated reflection of shock waves in the hollow model. Another is that in the center of the cylinder part of fresh gas rolls inward into the region r R inner and here the RDE experiences some non-detonation burning. Also, through the comparison and analysis, roles of the outer and inner walls are presented. Without the restriction of the inner wall, burnt gas flows a little more divergently.