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In an effort to define the desirable airfoil characteristics for large variable-speed wind turbines, a systematic study was performed using a series of airfoils designed to have similar aerodynamic properties, except for the amount of lift, which varied over a wide range. For several airfoil combinations, blade shapes were designed for a 750-kW wind turbine with a 48.8-m diameter rotor using the optimization code PROPGA together with PROPID, which is an inverse design method for horizontalaxis wind turbines. Roughness effects, including the consideration of dirty-blade performance in the blade-shape optimization process, were also considered and are discussed. The results and conclusions reveal practical design implications that should aid in the aerodynamic blade design of not only large but also other sizes of variable-speed wind turbines.

In an effort to define the desirable airfoil characteristics for large variable-speed wind turbines, a systematic study was performed using a series of airfoils designed to have similar aerodynamic properties, except for the amount of lift, which varied over a wide range. For several airfoil combinations, blade shapes were designed for a 750-kW wind turbine with a 48.8-m diameter rotor using the optimization code PROPGA together with PROPID, which is an inverse design method for horizontalaxis wind turbines. Roughness effects, including the consideration of dirty-blade performance in the blade-shape optimization process, were also considered and are discussed. The results and conclusions reveal practical design implications that should aid in the aerodynamic blade design of not only large but also other sizes of variable-speed wind turbines.

Ultrarich filtration combustion of ethane is studied in a porous medium composed of alumina spheres with the aim to achieve optimized conversion to hydrogen and syngas. Temperature, velocities, and...

Ultrarich filtration combustion of ethane is studied in a porous medium composed of alumina spheres with the aim to achieve optimized conversion to hydrogen and syngas. Temperature, velocities, and...

Abstract The oxidation characteristics of several small methyl and ethyl esters with carbon number less than six were investigated in laminar flames. The kinetics of such fuels are subsets of those of larger alkyl esters that are constituents of practical biodiesel fuels. A total of seven fuels, namely methyl formate, methyl acetate, methyl propionate, methyl butanoate, ethyl formate, ethyl acetate, and ethyl propionate were considered. Experiments were conducted at atmospheric pressure, elevated reactant temperatures, and over a wide range of equivalence ratios. Laminar flame speeds were determined in the counterflow configuration in which flow velocities were measured using particle image velocimetry. Several detailed kinetic models were tested against the experimental data, and insight was provided into the high-temperature combustion kinetics of the aforementioned fuels. Based on comparisons between experimental and computed results it became apparent that the chemistry of alkyl-ester combustion chemistry is evolving and much needs to be done in order to derive improved rate constants for a wide range of elementary steps.

Abstract The oxidation characteristics of several small methyl and ethyl esters with carbon number less than six were investigated in laminar flames. The kinetics of such fuels are subsets of those of larger alkyl esters that are constituents of practical biodiesel fuels. A total of seven fuels, namely methyl formate, methyl acetate, methyl propionate, methyl butanoate, ethyl formate, ethyl acetate, and ethyl propionate were considered. Experiments were conducted at atmospheric pressure, elevated reactant temperatures, and over a wide range of equivalence ratios. Laminar flame speeds were determined in the counterflow configuration in which flow velocities were measured using particle image velocimetry. Several detailed kinetic models were tested against the experimental data, and insight was provided into the high-temperature combustion kinetics of the aforementioned fuels. Based on comparisons between experimental and computed results it became apparent that the chemistry of alkyl-ester combustion chemistry is evolving and much needs to be done in order to derive improved rate constants for a wide range of elementary steps.

The paper presents an experimental study on the formation process of burden surface texture on the blast furnace throat and its influence on the radial distribution of gas flow. The study was performed with the application of blast furnaces equipped with a bell-type charging device using radio-isotope means for the control of burden surface texture (profile) and burden surface level, i.e., gamma locators for burden surface texture. The study was carried out under the conditions of an operating blast furnace in an iron and steel plant using a unique GEOTAPS system for automated control of geometric and temperature parameters of burden material surface on the blast furnace throat. The influence of the surface texture on the gas flow distribution was also investigated. The possibility of a self-stabilization effect for burden surface texture and gas flow in an operating blast furnace under suitable conditions was experimentally proven. As a result of the experimental study performed, four ways of energy-saving technology implementation were determined for the control of blast furnace melting based on the data on the burden surface texture and previously unknown regularities of surface layer formation of burden material on the throat of an operating blast furnace with a bell-type charging device. The main idea of the paper is the development of automated control for the radial distribution of burden material and gas flow using actual or predicted surface texture parameters as important intermediate factors that both describe the process and have a significant simultaneous influence on it.

The paper presents an experimental study on the formation process of burden surface texture on the blast furnace throat and its influence on the radial distribution of gas flow. The study was performed with the application of blast furnaces equipped with a bell-type charging device using radio-isotope means for the control of burden surface texture (profile) and burden surface level, i.e., gamma locators for burden surface texture. The study was carried out under the conditions of an operating blast furnace in an iron and steel plant using a unique GEOTAPS system for automated control of geometric and temperature parameters of burden material surface on the blast furnace throat. The influence of the surface texture on the gas flow distribution was also investigated. The possibility of a self-stabilization effect for burden surface texture and gas flow in an operating blast furnace under suitable conditions was experimentally proven. As a result of the experimental study performed, four ways of energy-saving technology implementation were determined for the control of blast furnace melting based on the data on the burden surface texture and previously unknown regularities of surface layer formation of burden material on the throat of an operating blast furnace with a bell-type charging device. The main idea of the paper is the development of automated control for the radial distribution of burden material and gas flow using actual or predicted surface texture parameters as important intermediate factors that both describe the process and have a significant simultaneous influence on it.

Abstract The effect of the thermal environment on performance and productivity has been a focus of interest among indoor environmental researchers for nearly a century, but most of that work has been conducted in relative isolation from the cognate disciplines of human performance evaluation. The present review examines thermal environmental effects on cognitive performance research conducted across multiple disciplines. After differentiating performance from productivity, we compare the two dominant conceptual models linking thermal stress to performance; (1) the inverted-U concept and (2) the extended-U relationship. The inverted-U specifies a single optimum temperature (or its corresponding subjective thermal sensation) at which performance is maximised. In contrast, the extended-U model posits a broad central plateau across which there is no discernible thermal effect on cognitive performance. This performance plateau is bounded by regions of progressive performance decrements in more extreme thermal conditions. The contradictions between these opposing conceptual models might derive from various confounding factors at play in their underlying research bases. These include, inter alia, environment-related, task-related, and performer-related factors, as well as their associated two-way and three-way interaction effects. Methodological discrepancies that might also contribute to the divergence of these conceptual models are evaluated, along with the proposed causal mechanisms underlying the two models. The weight of research evidence reviewed in this paper suggests that the extended-U hypothesis fits the relationship between moderate thermal environments and cognitive performance. In contrast to the inverted-U relationship, implemention of the extended-U in indoor climate control implies substantial reductions in building energy demand, since it permits the heating and cooling setpoint deadband to expand across the full width of the thermal comfort zone, or even slightly further during emergencies such as peak demand events on the electricity grid. Use of personal comfort systems can further extend the thermostat setpoint range beyond the comfort zone.