The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Siew Hwa Chan - One of the best experts on this subject based on the ideXlab platform.
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Sensitivity analysis of anode overpotential during Start-up process of a high temperature proton exchange membrane fuel cell
Electrochimica Acta, 2015Co-Authors: Raj Kamal, Siew Hwa ChanAbstract:Abstract This paper investigates the sensitivity of Start-up parameters during the Start-up or warm-up process of a high temperature proton exchange membrane fuel cell (HT-PEMFC), where carbon monoxide (CO) contaminated hydrogen is used as fuel. The heating strategy considered in this study involves external heating of the HT-PEMFC to an Initial Start-up temperature (above 100 °C), after which current is extracted, where the external heating still remains. A transient three-dimensional isothermal anode model is developed to determine the sensitivity of operational Start-up parameters such as temperature increase rate, Initial Start-up temperature, CO volume fraction and extracted current density, on the anode overpotential during the Start-up process. The results indicate that having a low Initial Start-up temperature is the key reason that makes the other parameters such as the current density, CO mole fraction and temperature increase rate, sensitive, especially at 108 °C. In addition, temperature range of 130 ± 5 °C is most critical as the sensitivity reaches a peak for all parameters at the three considered Initial Start-up temperatures. In addition, a system-level energy analysis considered for the Start-up process of a 1-kW stack, suggests that having low Initial Start-up temperature can reduce warm-up time and energy consumption.
Fangxi Xie - One of the best experts on this subject based on the ideXlab platform.
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Effect of Initial Start conditions on combustion and rotation characteristics of first firing cycle during direct-Start process for a GDI engine
Applied Thermal Engineering, 2017Co-Authors: Zhong Bing, Wei Hong, Fangxi XieAbstract:Abstract The first cycle combustion is important for the Start process of spark ignition engines and plays an important potential role in the direct-Start process. In the experimental work, the effects of Initial Start conditions, such as Initial piston position (IPP), coolant temperature (CT) and fuel injection pressure (FIP), on the combustion and rotation characteristics of the first firing cycle during direct-Start process had been investigated. For different IPPs and CTs, the combustion efficiency (CE) increased obviously with the improved excess air coefficient (λ). The most advanced combustion process and fastest heat release velocity appeared for the IPP of 90 and 100°CA. With the λ of 0.7–1.0, the CE was gradually improved for the IPP changed from 40 to 90°CA and the difference was not obvious for the IPPs of 90–120°CA. During the IPP range of 60–110°CA, the engine could get higher peak rotation speed in a relatively wide λ range of 0.6–0.9 and only when the λ was too large or too small, the peak rotation speed decreased obviously. The peak in-cylinder pressure and heat release rate improved, the combustion duration shortened, the heat release velocity increased and the CE enhanced with the CT and FIP improvement. However, the engine still could get bigger peak rotation speed using a relatively smaller λ when the CT and FIP were low. Compared with the two direct-Start modes, the IPP range for successful direct-Start had a certain overlap and also some differences. The range expanded to 85–130°CA with combined using two direct-Start modes and increased and then narrowed with the enhanced CT, but the effect of FIP on it was weak. Controlling the temperature near 70 °C made the successful realization range biggest.
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Study on Optimization of Control Parameters for the Second Cycle during Forward Rotation Direct-Start Process at a GDI Engine
Applied Mechanics and Materials, 2015Co-Authors: Wen Xu Sun, Wei Hong, Fangxi XieAbstract:To get better Starting performance for GDI engine forward rotation direct-Starting without Starter, the optimized choices of fuel injection and ignition control parameters under different Initial Start conditions was carried out in a wall-guided GDI engine. The results showed that the ignition timing and injection timing have been less affected by the Initial Start conditions. When the ignition timing is kept near its compression TDC and the injection timing is kept within the scope of 2-10 °CA after the crankshaft rotation, the engine all can get higher rotation speed under different Initial Start conditions. When the fuel pressures and cooling water temperature are lower, the richer mixture was needed for obtaining higher rotation speed.
D Sales - One of the best experts on this subject based on the ideXlab platform.
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dry thermophilic anaerobic digestion of organic fraction of the municipal solid waste focusing on the inoculum sources
Bioresource Technology, 2007Co-Authors: T Forstercarneiro, L I Romero, M. Pérez, D SalesAbstract:Abstract The effect of inoculum source on anaerobic thermophilic digestion of separately collected organic fraction of municipal solid wastes (SC_OFMSW) has been studied. Performance of laboratory scale reactors (V: 1.1 L) were evaluated using six different inoculums sources: (1) corn silage (CS); (2) restaurant waste digested mixed with rice hulls (RH_OFMSW); (3) cattle excrement (CATTLE); (4) swine excrement (SWINE); (5) digested sludge (SLUDGE); and (6) SWINE mixed with SLUDGE (1:1) (SWINE/SLUDGE). The SC_OFMSW was separately and collected from university restaurant. The selected conditions were: 25% of inoculum, 30% of total solid and 55 °C of temperature, optimum in the thermophilic range. The six inoculum sources showed an Initial Start-up phase in the range between 2 and 4 days and the Initial methane generation began over 10 days operational process. Results indicated that SLUDGE is the best inoculum source for anaerobic thermophilic digestion of the treatment of organic fraction of municipal solid waste at dry conditions (30% TS). Over 60 days operating period, it was confirmed that SLUDGE reactor can achieve 44.0% COD removal efficiency and 43.0% VS removal. In stabilization phase, SLUDGE reactor showed higher volumetric biogas generated of 78.9 mL/day (or 35.6 mL CH 4 /day) reaching a methane yield of 0.53 L CH 4 /g VS. Also, SWINE/SLUDGE and SWINE were good inoculums at these experimental conditions.
Ilya O. Ryzhov - One of the best experts on this subject based on the ideXlab platform.
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Winter Simulation Conference - An empirical sensitivity analysis of the Kiefer-Wolfowitz algorithm and its variants
2013 Winter Simulations Conference (WSC), 2013Co-Authors: Marie Chau, Ilya O. RyzhovAbstract:We investigate the mean-squared error (MSE) performance of the Kiefer-Wolfowitz (KW) stochastic approximation (SA) algorithm and two of its variants, namely the scaled-and-shifted KW (SSKW) in Broadie, Cicek, and Zeevi (2011) and Kesten's rule. We conduct a sensitivity analysis of KW with various tuning sequences and Initial Start values and implement the algorithms for two contrasting functions. From our numerical experiments, SSKW is less sensitive to Initial Start values under a set of pre-specified parameters, but KW and Kesten's rule outperform SSKW if they begin with well-tuned parameter values. We also investigate the tightness of an MSE bound for quadratic functions, a relevant issue for determining how long to run an SA algorithm. Our numerical experiments indicate the MSE bound for quadratic functions for the KW algorithm is sensitive to the noise level.
Raj Kamal - One of the best experts on this subject based on the ideXlab platform.
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Sensitivity analysis of anode overpotential during Start-up process of a high temperature proton exchange membrane fuel cell
Electrochimica Acta, 2015Co-Authors: Raj Kamal, Siew Hwa ChanAbstract:Abstract This paper investigates the sensitivity of Start-up parameters during the Start-up or warm-up process of a high temperature proton exchange membrane fuel cell (HT-PEMFC), where carbon monoxide (CO) contaminated hydrogen is used as fuel. The heating strategy considered in this study involves external heating of the HT-PEMFC to an Initial Start-up temperature (above 100 °C), after which current is extracted, where the external heating still remains. A transient three-dimensional isothermal anode model is developed to determine the sensitivity of operational Start-up parameters such as temperature increase rate, Initial Start-up temperature, CO volume fraction and extracted current density, on the anode overpotential during the Start-up process. The results indicate that having a low Initial Start-up temperature is the key reason that makes the other parameters such as the current density, CO mole fraction and temperature increase rate, sensitive, especially at 108 °C. In addition, temperature range of 130 ± 5 °C is most critical as the sensitivity reaches a peak for all parameters at the three considered Initial Start-up temperatures. In addition, a system-level energy analysis considered for the Start-up process of a 1-kW stack, suggests that having low Initial Start-up temperature can reduce warm-up time and energy consumption.