S.H. Chan

A complete polarization model of a solid oxide fuel cell and its sensitivity to the change of cell component thickness

Abstract This paper presents a complete polarization model of a solid oxide fuel cell (SOFC) that eliminates the ambiguity of the suitability of such model when used under different design and operating conditions. The Butler–Volmer equation is used in the model to describe the activation overpotential instead of using simplified expressions such as the Tafel equation and the linear current–potential equation. In the concentration overpotential, both ordinary and Knudsen diffusions are considered to cater for different porous electrode designs. Sensitivity tests are then conducted to show the effect of the thickness of the respective fuel cell components on the drop in cell voltage. Results show that the performance of an anode-supported fuel cell is superior to that using cathode as the support under elevated operating pressure in the cathode compartment. The former can achieve an improved operating range of current density under normal atmospheric conditions.

Heat transfer and chemical reactions in exhaust system of a cold-start engine

Abstract Modelling of cold-start engine exhaust behaviour is a difficult task as it involves complicated heat transfer processes and chemical reactions at both the exhaust manifold/pipe and catalytic converter. This paper presents a model that is capable of predicting the exhaust gas temperatures along the exhaust pipe and across the catalyst monolith, both spatially and temporally. The dew point temperature platform, due to water condensation and subsequent evaporation, at catalysts downstream immediately after engine cold-start is successfully predicted. The conversions of toxic carbon monoxide and unburned hydrocarbons to harmless carbon dioxide and water at the catalytic converter are also validated satisfactorily by the experimental data.

Catalyst Layer Models for Proton Exchange Membrane Fuel Cells

This paper presents two simple catalyst layer models – the macro-homogeneous model and the agglomerate model for the proton exchange membrane (polymer) fuel cell using hydrogen gas as the feedstock. The former is solved analytically whereas the latter is solved numerically. The emphasis of this research is to parameterize factors affecting the performance of the fuel cell with simple approach without going into detailed catalyst layer modeling.

A Thermodynamic View of Partial Oxidation, Steam Reforming, and Autothermal Reforming on Methane

Abstract Thermodynamic analysis on three thermo-chemical reforming processes, i.e., partial oxidation (POX), steam reforming (STR), and autothermal reforming (ATR) with methane as the feedstock fuel are conducted in this study. The focus of this article is to show the effect of air-fuel (AF) ratio, water-fuel (WF) ratio, temperature and pressure on hydrogen (H2) yield, hydrogen/carbon monoxide (H2/CO) ratio, carbon (C), and carbon monoxide (CO) formation. Optimal operating conditions under no solid carbon formation in the reaction are recommended for each thermochemical reforming technique.

Heat transfer and chemical kinetics in the exhaust system of a cold-start engine fitted with a three-way catalytic converter

Abstract Modelling of cold-start engine exhaust behaviour is a difficult task as it involves complicated heat transfer processes associated with water condensation and evaporation at the walls of the exhaust manifold/pipe and monolith cells, and the chemical reactions of CO/HC/NO in the three-way catalytic converter. This paper presents a model that is capable of predicting the exhaust gas temperatures along the exhaust system and across the catalyst monolith, both spatially and temporally, from the moment when the engine is cranked. The conversions of CO/HC/NO to harmless carbon dioxide, water and nitrogen at the catalytic converter downstream have been validated satisfactorily by the experimental data. The distortion of measured NO emission data/signals due to the dynamic behaviour of the chemiluminescence analyser has been reconstructed by means of a signal inference technique before these signals were used to validate the predictive capability of the model developed.

Chemical Reactions in the Exhaust System of a Cold-start Engine

Transient heat transfer and water condensation in the engine exhaust system have a strong influence on the conversion of carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO x ) in the three-way catalytic converter (TWC) of an engine cold-start. This paper presents the theoretical modeling of heat transfer and chemical reactions of CO, HC, and NO associated with the effects of catalyst surface water vapor condensation, and water evaporation in the entire engine exhaust system fitted with a TWC. The predictive capability of the model is validated successfully with the experimental data.