Modelisation of the engine coolant warming-up behavior

Abstract: This master thesis report describes the development of a physically based modelwhich can predict the coolant temperature of an internal combustion engine during itswarm-up phase. The model is used to detect if the thermostat in the cooling systemis functioning correctly which is a requirement for present day On-Board DiagnosticsII (OBD II). The model uses information available within the Engine Control Unit(ECU) and needs little calibration work. Thereby, the model can easily be extendedwith extra features to remain applicable with future power train applications. Thetemperature prediction capability has been tested for steady state conditions as wellas for ”real-world” driving and regulated driving cycles, thereby the model has beentested on a vehicle with a start-stop system. The model includes a diagnostic functionwhich is performed at the most accurate prediction of the model. The sensitivityof the temperature prediction to sensor input errors and varying parameters (like fuelquality) has been investigated in a sensitivity study. Finally, a threshold value is proposedfor the diagnostic function by determining when an invalid faulty thermostatis detected or a faulty thermostat is not detected.