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

High concentrations of toxic gases discharged from chimneys are a health hazard. Previous study shows that a split chimney is capable of lowering the concentration of the smoke and harmful gases within the configuration before ejection to the environment but there might be leakages from its sides. The effect of low-speed wind at different directions on a split chimney with an arbitrary geometry is modeled. The results show that the leak can be eliminated by proper positioning of the configuration.

The effect of direction of low speed winds on the performance of a split chimney

Australia is considered as the most fire-prone country in the world. Spotting ignition by lofted firebrands is the main mechanism of fire spread. Many experimental studies have been conducted to evaluate the effect of the firebrand attacks on structures and to identify possible solutions. The experimental facility consists of a firebrand generator coupled to a wind tunnel. The wind speed in the firebrand generator is relatively low, in order to assure a quality continuous flow of glowing firebrands. On the contrary, the wind speed in the wind tunnel is high to duplicate actual firebrand attacks. Previous works show a highly turbulent region above the entrance of firebrands to the wind tunnel which is formed because of the velocity difference and penetration of firebrand entrance hose into the wind tunnel. The penetration is required to provide a uniform firebrand distribution along the height of the test section. In this computational work, the influence of the height of the entrance hose, its orientation respect to the tunnel and the distance between the coupling port and the test section are analyzed. The optimized results are presented and discussed for a variety of wind speeds within the wind tunnel and the firebrand generator.

/pdf/optimizing-the-coupling-of-a-firebrand-generator-to-a-3369ll6r6c.pdf

Optimizing the Coupling of a Firebrand Generator to a Horizontal Wind Tunnel

In this paper, the boiling flow inside a nanochannel with 700000 argon particle has been simulated by molecular dynamics (MD) simulation. This approach has been employed to analyse the superheated flow and its heat transfer pattern as well. For all simulations, an external thrust force varying from 1 PN to 12 PN is exerted on inlet nanoparticles along the channel to have the forced annular boiling flow. Computations reveal that increase of saturation condition and superheated region have significant impacts on the liquid-vapor interface. Furthermore, because of the major influence of surface tension throughout the nanochannel, the x-velocity of liquid film and vapor core has no considerable fluctuations and stay smooth. Results show the behaviors of what significantly similar with the author’s previous published simulation with 700000 solid particles.

/pdf/simulation-of-boiling-process-in-a-nanochannel-with-700000-17ri1yofru.pdf

Simulation of Boiling Process in a Nanochannel with 700000 Argon Particles by Molecular Dynamics

Hydrocarbon refrigerants are environmentally friendly and many countries have started using them in refrigeration and air-conditioner systems. Propane, a typical hydrocarbon, does not damage the ozone layer and its effect on global warming is very small. Use of propane as a refrigerant is gaining favour, especially in systems designed for R-22. The main drawback of using propane as a refrigerant is its flammability. To reduce the risk posed by propane, the total mass of propane in the system should be minimized without degrading the system performance. This work deals with how the mass of propane within a capillary tube can be reduced without compromising the system performance. In the first step, the mass flow rate and inlet and outlet conditions of the refrigerant within the capillary tube of a commercial propane air-conditioner under normal working conditions were measured. In the next step, a parametric MATLAB code was developed to determine the required length and volume of the capillary tube, and the velocity and mass of the propane within the capillary tube. The input parameters of the code are the inside diameter, roughness, shape, mass flow rate, and inlet and outlet conditions. The script was run for sixteen common types of capillary tubes, including the one in our laboratory. According to the results, it is possible to considerably reduce the propane mass within the capillary tube using a small inside diameter helical capillary tube with a decreased coil diameter. However, the results should not be extended to an air-conditioner in which the distance between the outlet of the condenser and the inlet of evaporator is fixed and longer than the calculated length.

Reducing the mass of the refrigerant in the capillary tube of a propane air-conditioner

Flow characteristics in the onset of vortex shedding and heat transfer pattern over a single and two same-sized square prisms placed in tandem are studied numerically. All simulations are carried out for Reynolds numbers range varying from 1 to 200 and spacing between the prisms in the order of five widths of prism for in tandem configuration. The calculations are done employing a finite volume in-house computer program according to semi-implicit method for pressure linked equations-consistent (SIMPLEC) numerical procedure and nonstaggered mesh in 2-dimensional, steady/unsteady and incompressible flow regimes. The instantaneous and time-averaged streamlines as well as iso-therm pattern for different Reynolds numbers are analysed. Furthermore, the influence of Reynolds number and the onset of vortex shedding on the flow pattern are studied in detail. Three distinct patterns namely fully-attached, trailing-edge separation and leading-edge separation were observed.

Ahmad Sharifian

Papers

The effect of direction of low speed winds on the performance of a split chimney

Optimizing the Coupling of a Firebrand Generator to a Horizontal Wind Tunnel

Simulation of Boiling Process in a Nanochannel with 700000 Argon Particles by Molecular Dynamics

Reducing the mass of the refrigerant in the capillary tube of a propane air-conditioner

Time-averaged heat transfer and vortex shedding of asingular and twin heated bluff bodies in cross flow