Development and Experimental Validation of a Control-Oriented Empirical Exhaust Gas Temperature Model 2020-24-0008

Modern turbo-charged downsized engines reach high values of specific power, causing a significant increase of the exhaust gas temperature. Such parameter plays a key role in the overall powertrain environmental impact because it strongly affects both the catalyst efficiency and the turbine durability. In fact, common techniques to properly manage the turbine inlet gas temperature are based on mixture enrichment, which causes both a steep increase in specific fuel consumption and a decrease of catalyst efficiency. At the test bench, exhaust gas temperature is typically measured using thermocouples that are not available for on-board application, and such information is processed to calibrate open-loop look-up-tables. A real-time, reliable, and accurate exhaust temperature model would then represent a strategic tool for improving the performance of the engine control system.

In this work, a novel analytical approach for the calculation of the exhaust gas temperature under steady-state conditions has been investigated and experimentally validated. An empirical control-oriented model has then been developed by incorporating the description of thermocouple dynamics, making it reliable for real-time application also under transient conditions.

At first, the control-oriented empirical model is introduced, describing how the polynomial approach used in a previous work of the authors has been applied to reproduce the steady-state thermocouple measurement. Then, a real-time compatible thermocouple dynamics model is proposed, and the calculated values are compared with the thermocouple signal under dynamic conditions.

In the last section of the paper the computational cost to execute the model is evaluated as the ratio between real and execution time. In this way the compatibility with on-board, real-time applications is finally demonstrated.