Shape optimization of a Savonius wind rotor with different convex and concave sides

Reliability improvement of wind turbine power generation using model-based fault detection and fault tolerant control: A review

Urban-wildland fires have plagued the United States for centuries. Recent urban-wildland fires include the 2002 Hayman Fire, the 2000 Los Alamos Fire, and the 1991 Oakland Hills Fire [1]. Fires in the urban wildland interface can have a devastating effect on human life, property loss, and local economies. Embers or firebrands are produced as trees and other objects burn in urban-wildland fires. These firebrands are entrained in the atmosphere and may be carried by winds over long distances. Hot firebrands ultimately come to rest and may ignite fuels far removed from the fire, resulting in fire spread. This process is commonly referred to as spotting. Understanding how these hot firebrands can ignite surrounding fuels is an important consideration in mitigating fire spread in communities. A major advance in urban-wildland fire research would be the development of a model to predict the ignitability of materials due to firebrand impact [2]. The lack of a detailed theory on the ability of firebrands to ignite remote objects limits the utility of detailed computational fluid dynamic models (CFD) that could be used to predict fire spread by firebrands [2]. Detailed experimental ignition studies of fuel beds typically found in the urban-wildland interface due to firebrand impact are required to validate such models. Consequently, an experimental apparatus has been built to investigate the ignition of fuel beds as a result of impact with burning firebrands. The apparatus allowed for the ignition and deposition of firebrands onto the target fuel bed. The moisture content of the fuel beds used was varied and the fuels considered were pine needle beds and shredded paper beds. Pine needle beds were intended to simulate gutters filled with pine needles. Shredded paper beds were used as a surrogate for typical cellulosic fuels that would be found in attic spaces. Firebrands were simulated by machining wood (pinus ponderosa) into small disks of uniform geometry. The firebrand ignition apparatus was installed into the Fire Emulator/Detector Evaluator (FE/DE) to investigate the influence of an air flow on the ignition propensity of fuel beds. Results of this study are presented.

Urban-Wildland Fires: On the Ignition of Fuel Beds by Firebrands. (POSTER ABSTRACTS) | NIST

Optimal shape of thick blades for a hydraulic Savonius turbine

Review of savonius wind turbine design and performance

Australian bushfires have killed many people and caused severe damage; like as any other type of disaster. Previous studies have identified direct flame contact and radiant heat as the main cause of fatalities.The role of screens in limiting the radiation exposure on an object by fire on the other side of the screen is well-known, but still it has not been experimentally determined. A screen between a radiation source and an object divides the radiant heat flux into two parts. The first part is direct radiant heat flux that passes directly through the screen without any interaction. The second part is indirect radiation heat flux, which includes both emitted and reflected radiant heat fluxes by the heated screen. This experimental study deals with the direct radiant heat flux, which depends on the screen porosity and is independent of the material composition or the surface quality of the screen. The experimental results of four square cell,plain woven screens with porosities ranging from 41% to 66% show that the passing ratios of direct radiant heat flux through screens are less than those suggested by their porosity. Four empirical equations have been developed to determine the passing ratio of the direct radiation through screens, and tunnel vision angles of the screens.

Experimental Measurement of Direct Thermal Radiation Through Single-Layer Square-Cell Plain Woven Screens

When compared with other wind turbines, drag driven vertical axis Savonius wind turbine offers lower power coefficient due to its slow turning speed. However, they have many advantages over others, such as simplicity of manufacturing, ability to operate in any wind direction, and having a good starting torque at low wind speed. They are well suited to be integrated in urban environment as small scale power generating wind mills. 
Waste heats or naturally available heat sources such as geothermal and solar energy can be utilized to produce swirling flow when there is a source of angular momentum. Previous computational work suggests that the performance of Savonius turbine can be improved by providing a hot swirling flow inside the turbine chamber. The swirling flow can be induced by a design similar to that of split channels, which includes one or a few vertical slits, and is currently used to onset fire whirls in the laboratories. 
In the present experimental study, the influence of blade overlap, blade arc angle and the diameter of the hot air inlet hole on the torque and power coefficient have been investigated. The results indicate that the maximum power coefficient for a 258 mm diameter rotor occurs at 28 mm blade overlap, '195°' blade angle and 9 mm diameter of hot air inlet hole.

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Influence of blade overlap and blade angle on the aerodynamic coefficients in vertical axis swirling type Savonius wind turbine

[]: Estimating the drag force on a metal mesh is important if the installed metal mesh area is large and wind speeds are moderate Such a situation may arise if a metal mesh is used to protect a property from ember attacks in a bushfire prone area In this work, computational simulations are used to correlate the drag coefficient of a metal mesh in terms of its porosity and the Reynolds number for 10 ≤ Re ≤ 1000 A benchmarking exercise suggests that the computational simulations may be in error by up to 13 % error for the level of discretization that could be achieved due to computer memory limitations The drag coefficient correlation we have obtained has a maximum error of only 65 % with respect to the results from the simulations

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Computational simulation of the wind-force on metal meshes

A computational technique is used to establish a view factor correlation for the target-object — screen — bushfire arrangement for aligned, double-layered screens consisting of woven wire, square-celled elements. The results indicate that the average view factor between an infinite fire and a target object of the same size as the square cell is related to the porosity of screens. The spacing of two layers only affects the view factor if two screen layers are very close. The results also show that it is possible to block up to about 98% of the direct radiant heat flux by using a low porosity (25%) double-layered screen.

Double-layered metal mesh screens to contain or exclude thermal radiation from bush fires

The positioning of a metal mesh between a property and a wildfire not only reduces the threat of ember attack, but can also be effective in reducing the radiation heat flux from the fire to the property. A computational technique is used to establish a view factor correlation for the object-screen-wildfire arrangement for screens consisting of woven wire, square-celled elements. The view factor between the object and fire is calculated separately for each square-celled element of the screen and the results are added. The results indicate that the average view factor between an infinite fire and an object of the same size as the square cell is only related to the porosity of screen and is independent of distance of the object from the screen (when the object is in the proximity of the mesh). The results also show the view factor is less than screen porosity, particularly at lower porosities.

Ahmad Sharifian

Papers

Experimental Measurement of Direct Thermal Radiation Through Single-Layer Square-Cell Plain Woven Screens

Influence of blade overlap and blade angle on the aerodynamic coefficients in vertical axis swirling type Savonius wind turbine

Computational simulation of the wind-force on metal meshes

Double-layered metal mesh screens to contain or exclude thermal radiation from bush fires

Direct radiation from wildfires through square woven screens