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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...
Theemission composition is measured for a prototype burner while varyingthe equivalence ratio in discrete portions of the burner. Theburner is a three sector system, consisting of a separateigniter, pilot/stabilizer and main burner. The design allows for discretecontrol of equivalence ratio in each of the three sectors.The ignition sector, designated RPL (Rich-Pilot-Lean), operates from rich tolean equivalence values, and serves to ignite the pilot sector,which, in turn, stabilizes the main combustion sector. All threeburner sections are premixed. The burner is operated at atmosphericpressure...
In this paper, effect of geometric parameters of a centrifugal fan with backward- and forward-curved blades has been investigated. Centrifugal fans are used for enhancing the heat dissipation from the IC engine surfaces. In the process, the fan consumes power generated from the engine. As a first step, an experimental setup was developed and prototypes of fans were made to carry out measurements of flow and power consumed by the fan. The fan mounting setup was such that fan with uniform blades can be tested. Generally, fans have cut blades on the vehicle due to mounting accessories. We...
We present the results from the 3-D numerical simulations on the optimization of the fan-cooling system in a two-wheeler 4-stroke single cylinder engine. Objective was to optimize the flow rate and distribution of flow over the engine surfaces to keep the maximum temperature of engine oil and engine surfaces well within the lubrication and material limit respectively at the expense of minimum increase in fan power. This work aimed at reducing the engine oil temperature by 20°C. Combined flow and heat transfer analysis (Conjugate analysis) was conducted with the engine head and block modeled...

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