The paper reviews an infrared (IR) thermographic study that was implemented to evaluate the performance of a catalytic converter in a 1.6 liter fuel-injected spark ignition gasoline engine from Renault.
Part of a 10-year ongoing research and development effort, this collaboration involves the research center IMST within the Department of the Universidad
Politécnica de Valencia and the engineering center of Renault in Valladolid, Spain.
Experimental tests were carried out at the engine test bench using an infrared camera. Infrared thermography data made it possible to compare the actual internal temperature of the exhaust gases at different engine speeds and loads with values calculated using heat transfer theory, and corresponding correlations of external free convection, external radiation, and internal forced convection into the
catalyst.
The comparison between theoretical calculations and the experimental exhaust gas temperatures shows striking consistency. It proved possible to develop some interesting conclusions about the flow of exhaust gases in the interior of the catalytic converter as a function of the exhaust mass flow rate. A major finding
was that the distribution of the exhaust gases inside the catalytic converter is not uniform, but flows mostly through the central part of the device, so the rest of the swept volume acts as insulating material, where relatively still exhaust gases remain in the cells of the structure, depending on the load and the
engine speed.
The paper emphasizes the use of thermal imaging techniques in two aspects of particular interest in this engineering field:
• The estimation of the internal temperature of the gas flowing through pipes or ducts
• The use of temperature measurements to complete the energy balance of the engine
Some basic heat transfer concepts necessary to analyze these aspects are also briefly described.
related words: Engines, internal gas temperature, catalytic converter, energy balance, infrared, IR, and thermal imaging.
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