Library

2293 match your search

Many researchers have experimentally studied small (∼10–50 cm2), single cell PEMFC systems to understand the behavior and electrochemistry of PEMFC. Also, three-dimensional electrochemical models have been used to predict the distributions of current, temperature, and species mole fractions as a function of the operating conditions and geometry of small cells and these predictions have been compared with experimental data. However, the commercial viability of PEMFC systems depends on understanding the mass transport and electrochemistry of large-scale electrodes with reacting area on the...
Pneumatic conveying of solid materials is used in many process industries where solid particles are carried forward in pipes and channels by the fluid. The pressure drop in the system is dependent on a host of parameters such as particle and pipe diameters, particle and fluid properties, pipe roughness and orientation, etc. In this study, the commercial CFD software, STAR-CD is used to model pneumatic conveying in a horizontal pipe. A range of fluid flow rates is studied. Reasonable agreement is obtained between the predicted pressure drop and the experimental data of Marcus et al. (1990) for...
The Computational Fluid Dynamics analysis of the hydrodynamic performance of two America’s Cup design candidates is presented. Two fully appended hulls were tested in a free to sink and trim condition. The experimental data of one of the two hulls was known a priori and was used to investigate several computational parameters, which are discussed in the present paper. The validated numerical model was used to predict the performance of the second hull, whose experimental data were unknown a priori. The a posteriori numerical/experimental comparison showed that the numerical model was able to...
Property distribution and polarization characteristics of a proton exchange membrane fuel cell (PEMFC) under cathode starvation conditions were investigated numerically and experimentally for a unit cell. The polarization curves of a lab-scale PEMFC were measured with increasing current density for different cell temperatures (40°C, 50°C, and 60°C) at a relative humidity of 100%. To investigate the local temperature, water content and current density on the membrane, and gas velocity in the channel of the PEMFC, numerical studies using the es-pemfc module of the commercial flow solver STAR-CD...
Large-eddy simulation has been performed for a two-valve, four-stroke-cycle piston engine through 70 consecutive motored cycles, and proper orthogonal decomposition (POD) has been used to analyze the complex in-cylinder turbulent flow. Convergence of POD modes has been quantified, several POD variants have been explored, and sensitivity of results to using different subsets of engine cycles has been determined. In general, it has been found that conclusions that were drawn earlier from POD analysis of a simplified piston-cylinder assembly carry over to the much more complex flow in a real...
Aerodynamics plays an important role in ground vehicle design and optimization. With the worldwide interest in saving energy, drag reduction is one area where aerodynamics can help. The aerodynamics of pickup trucks is studied. The main objective is to understand the effect of the box configuration on the generated aerodynamic drag. In addition to that, the flow structures around the vehicle are analyzed. The CFD simulations of a generic pickup truck are performed using STAR-CCM+ package developed by CD-adapco. Several commonly used pickup truck configurations are presented including open-box...
Experiments were performed on two annular diffusers to characterize the flow separation and pressure recovery to create a foundation for future active flow control techniques. Both diffusers had the same fully developed inlet flow condition, however, the expansion of the two diffusers differed such that one diffuser replicated a typical compressor discharge diffuser found in a real machine while the other would create a naturally separated flow along the outer wall. Both diffusers were tested at two Reynolds numbers, 5x10 4 and 1x10 5 , with and without a vertical wall downstream of the exit...
In order to ascertain the required design parameters for a proposed micro aerial vehicle (MAV) a morphing mesh simulation based on a rigid wing approximation was conducted. The proposed vehicle is of the “X-wing” configuration popularized in 1985 by Frank Kiesler with his record setting, rubber band powered, “canard flapper.” This design attempts to take advantage of the “clap and fling” phenomenon, with multiple wing to wing interactions. The wing motion and placement was specified to adequately capture the complex physics without causing negative volume cells within the mesh. The...
A fuel cell based system's performance is mainly identified in the overall efficiency, strongly depending on the amount of power losses due to auxiliary devices to supply. In such a situation, everything that causes either a decrease of the available power output or an increment of auxiliary losses would determine a sensible overall efficiency reduction. This situation inevitably pops up in case of water flooding, a phenomenon that causes a reduction of the number of chemical reactions between reactants (O2 and H2) that can take place at the reaction sites, as liquid water would obstruct the...
Transported probability density function (PDF) methods are used to account for turbulent fluctuations in composition and temperature in simulations of liquid fuel injection (n-heptane), vaporization, mixing, autoignition, combustion and soot formation for a constant-volume combustion chamber. Both stochastic Lagrangian particle and stochastic Eulerian field methods are used to solve the modeled PDF transport equation. Model results are compared with experimental measurements from the Engine Combustion Network for nonreacting vaporizing sprays and for cases with autoignition and combustion...

Pages