An extended calculation approach of exhaust thermocouple temperatures in one-dimensional gas exchange simulation for turbocharged gasoline direct-injection engines

Abstract

A new model approach is presented to determine exhaust thermocouple temperatures in gas exchange calculations for turbocharged gasoline direct-injection engines. Since the measured thermocouple temperature at turbine inlet is typically used as a criterion to fix the required fuel enrichment for turbocharger protection, an accurate prediction of this value is decisive in the development of future engine concepts. Therefore, a detailed one-dimensional thermocouple model has been developed which captures the measurement principle by a physical approach. The major advantage of this approach is the integration of detailed data of convective heat transfer along the thermocouple protrusion length from three-dimensional computational fluid dynamic exhaust flow simulations. Detailed investigations by means of three-dimensional and one-dimensional simulations are presented for steady-state flow as well as in full and part load operations of four turbocharged gasoline direct-injection engines. For further verification, the test carriers have been equipped with special temperature measurement technology like various thermocouple penetration lengths and profile thermocouples. A comparison with measured temperatures shows that at turbine inlet, a prediction deviation of less than 10 K can be achieved with the detailed one-dimensional model.