Fanning the Optimal Breeze with an Abanico

2017

We study the flow generated when a handheld fan is waved. This fluid-structure interaction problem is investigated through precision experiments, using an oscillating semi-circular elastic plate as a reduced analog model. The aerodynamic performance of the fans is systematically characterized for a variety of geometric and material parameters, as well as the amplitude of the periodic driving. We demonstrate that the bending stiffness of the structure can be tuned to maximize the output of the generated airflow, while simultaneously minimizing the input power. A design guideline is established for this optimal conditions based on matching the driving and the natural frequencies of the plate. Closer to the handheld fans, we then consider a discrete analog model comprising an array of overlapping strips. Unlike homogeneous plates, these discrete designs deform passively into shapes with finite Gaussian curvature and further enhance the generated flow. Finally, we explored the effect of...

2010

NASA's next generation space suit system will place new demands on the fan used to circulate breathing gas through the ventilation loop of the portable life support system. Long duration missions with frequent extravehicular activities (EVAs), the requirement for significant increases in reliability and durability, and a mission profile that imposes strict limits on weight, volume and power create the basis for a set of requirements that demand more performance than is available from existing fan designs. This paper describes the development of a new fan to meet these needs. A centrifugal fan was designed with a normal operating speed of approximately 39,400 rpm to meet the ventilation flow requirements while also meeting the aggressive minimal packaging, weight and power requirements. The prototype fan also operates at 56,000 rpm to satisfy a second operating condition associated with a single fan providing ventilation flow to two spacesuits connected in series. This fan incorp...

Procedia Manufacturing, 2019

The lack of standards for industrial fan sizing forces companies to size its products under strong influence of precious experience, based, mostly, in empiric data. This can lead to the oversizing of the fans and, thus, increase the costs of the final product unnecessarily. The scope of the work is the computational fluid dynamics analysis of radial fans, using qualitative and quantitative results. The study was conducted in bench scale using a prototype. The characteristic data from the fan was collected and inserted in the ANSYS FLUENT software. The preliminary results, using the original geometry will enable the project optimization, increasing the product's efficiency via the elimination of supersizing and assessing the feasibility of computational simulations in the industry.

Applied Sciences, 2017

To meet humans' need of enhancing the quality of life, the high-performance stand fan has become an essential appliance in every family. On the other hand, energy saving can not only solve the problem of environment protection, but also can reduce the cost of energy consumption. However, the aerodynamic performance and flow characteristics of the stand fan are rarely investigated and analyzed in a systematical manner. Therefore, this research intends to investigate the physical mechanism of the flow pattern and identify the design parameters of the stand fan by combining numerical and experimental methods. First of all, both the structure and performance of a commercial 14-inch stand fan are chosen for analysis and are set as the reference for the fan. The stand fan can be divided into the impeller and the protective cover. Clearly, the impeller blades have a great influence on the fan performance, so they are the first design target. In this work, CFD (computational fluid dynamics) software Fluent (version 14.5, ANSYS Inc., Canonsburg, PA, USA, 2012) is used to analyze and observe the corresponding influences on flow fields and aerodynamic performance by changing the design parameters such as the setting, twist, and inclination angles. Then, the protective cover is studied, improved and integrated with the designed impeller to further enhance the performance of the fan. The protective cover is modified by varying the spacing between the blade tip and cover, as well as varying the shape and angle of ribs to improve the fan's flow field and performance. Finally, the optimal fan mockup is made via CNC (computer numerical control) technology. Also, its acoustics and performance have been measured to validate the accuracy and reliability of the numerical simulation. The testing results show that the optimally designed stand fan is better than the reference fan with a significant 54% increase in max flow rate. In addition, it has more uniform velocity distribution compared with the reference fan to achieve a comfortable feeling for the human body. In summary, this research successfully establishes a reliable and systematic scheme to design the stand fan. Also, the corresponding performance influences caused by those important parameters are analyzed and summarized to serve as the design reference for the stand fan.

The paper presents a historical overview of the developments of aerodynamic design methods for low-speed axial-flow fans. This historical overview starts from the first fan applications, dating back to the 16th century, and arrives to the modern times of computer-based design techniques, passing through the pioneering times of aerodynamic theories and the times of designing before computers. The overview shows that the major achievements in the axial fan design discipline have actually been related to other technological fields, such as marine and aeronautical propulsion, as well as to the development of wind tunnels. At the end of the paper, the reader will have acquired a complete panorama of how the historical developments of the discipline have brought us to the current state of the art.

ISRN Mechanical Engineering, 2013

Members of the aerospace fan community have systematically developed computational methods over the last five decades. The complexity of the developed methods and the difficulty associated with their practical application ensured that, although commercial computational codes date back to the 1980s, they were not fully exploited by industrial fan designers until the beginning of the 2000s. The application of commercial codes proved to be problematic as, unlike aerospace fans, industrial fans include electrical motors and other components from which the flow will invariably separate. Consequently, industrial fan designers found the application of commercial codes challenging. The decade from 2000 to 2010 was focused on developing techniques that would facilitate converged solutions that predicted the fans' performance characteristics over the stable part of their operating range with reasonable accuracy, using a practical computational effort. In this paper, we focus on elucidating aspects of the flow physics that one cannot easily study in a laboratory environment, discussing the challenges involved and the relative merits of the available modelling techniques. The paper ends with a discussion of the practical problems associated with the use of commercial codes in a development environment and finally the legislation that is driving the need for aerospace style computation methods.

2020

Natural wind movement is impeded by dense urban fabric in the tropics causing thermal discomfort and aggravating pollution. Research suggests that if average wind velocity cannot be improved, the airflow fluctuation frequency can be used as a control factor to provide a sensation of thermal cooling for pedestrians. Therefore, this paper introduces the novel application of actuated travelling waves as a façade retrofit that alters the fluctuation frequency of the stagnant airflow field to improve thermal comfort. Nine case studies were simulated to optimise the movement of the travelling wave, and the best-case scenario had a 72% improvement in velocity values compared to the initial base case. This combination of travelling wave with 34.85m wavelength and wave speed of 18m/s produced a consistent air velocity with a targeted frequency of 0.22 Hz, which is within the range of frequencies that provides a strong cooling sensation.

Sensors and Actuators A: Physical, 2018

Piezoelectric fans offer an intriguing alternative to conventional rotary fans for thermal management of portable and wearable electronics due to their scalability, low power consumption and simple mechanical construct. We report a combined experimental and modeling study to help elucidate power dissipation mechanisms in piezoelectric fans. To analyze contributions from these different mechanisms, mathematical models that account for mechanical hysteresis, dielectric loss and viscous damping from generated air flows are used in conjunction with vibration amplitudes and power consumption data obtained experimentally from piezoelectric fans of different blade lengths, thicknesses and mass distributions. In parallel, we perform experiments on convective heat transfer coefficients and aerodynamic forces acting on surfaces that are oriented perpendicular with respect to fan-induced air flows. These experiments establish that the portion of power dissipation ascribed to air flows correlates well with the heat transfer performance and aerodynamic force. A power ratio, defined as the fraction of the air flow power to the total power dissipation, is then proposed as a useful indicator of the power efficiency of the piezoelectric fans. We show that the power efficiency exhibits a peak at a bias voltage amplitude that balances parasitic power dissipation, due in particular to mechanical hysteresis loss and the dielectric loss, with power dissipation directly linked to actual air flow generation. Lastly, we relate the air flow power to the blade's geometrical parameters to facilitate systematic optimization of the blades for both cooling performance and power efficiency.

Prefacio del editor norteamericano Unas palabras del autor 1. Los pensamientos son cosas El hombre que "pensó" la manera de asociarse con Thomas A. Edison El inventor y el vagabundo Los inesperados disfraces de la oportunidad A un metro del oro "Nunca me detendrá porque me digan: NO" Una lección de perseverancia de cincuenta centavos El extraño poder de una niña Todo lo que usted necesita es una buena idea El "imposible" motor V8 de Ford Por qué es usted "el dueño de su destino" Principios que pueden cambiar su destino 2. El deseo El punto inicial de todo logro El hombre que quemó sus naves El incentivo que conduce a la riqueza Seis maneras de convertir el deseo en oro ¿Puede imaginarse que es usted millonario? El poder de los grandes sueños Cómo hacer que lo ssueños despeguen de la plataforma de lanzamiento El deseo lleva ventaja sobre la madre naturaleza Un "accidente" que cambió una vida Ganó un mundo nuevo con seis centavos El niño sordo que oyó Ideas que obran milagros La "química mental" hace magia

Acta Semiotica, 2021

La culture est la transcendance humaine de la nature. L’enseignement est le sacerdoce d’une telle transcendance. Et la salle de classe est son temple.