Diesel exhaust temperatures vary with engine load and speed thereby affecting the thermal behavior and thus performance of exhaust after-treatment systems. The determination of the transient temperature is needed to enable active-flow control after-treatment schemes that include parallel alternating flow, partial restricting flow, periodic flow reversal, and extended flow stagnation. The active schemes are found to be especially effective to treat engine exhausts that are difficult to cope with conventional passive-flow converters, by shifting the exhaust gas temperature, flow rate, and oxygen concentration to more favorable windows for the filtration, conversion, and regeneration processes. This paper reports a thermal-response model that uses the temperature data obtained with two high-inertia thermocouples of different sizes to estimate the diesel engine transient exhaust gas temperature. The thermal inertial difference of the two thermocouples is critical in predicting the transient temperature through a mathematical procedure. To validate the model, the exhaust gas temperature was simultaneously measured with a third thermocouple of high sensitivity that acquired temperature data approximating the real-time value.

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