Validation of a GT-Power Model for a Volvo D13 Heavy Duty Engine

Abstract

The increasing amount of challenges to modern internal combustion engines, particularly regarding fuel consumption and exhaust-gas emissions, requires many efforts in research and development. In this context, the usage of engine-simulation software, like e.g. GT-Power, becomes more important since it helps to optimize the efficient use of experimental work, which is generally expensive in both cost and time. This work describes the validation of a GT-Power model for a Volvo D13 heavy duty engine based on experimental results from a similar engine installed on a test rig. The validation work focused on the 12 engine operating points according to the European Stationary Cycle (ESC). Before defining the model as validated, a careful calibration procedure on the engine model was performed. Several components, subsystems and parameters were modified with the purpose to match the experimental data. The first modification was the adaption of the gas exchange system in the model according to the one present in the engine laboratory, but this did not show any important effect on the engine performance. Later, the calibration of the Charge Air Cooler (CAC) and the Exhaust Gas Cooler (EGC) was accomplished by matching the temperatures in the cold side of the flow system and in this way obtaining a considerable effect on all the other temperatures in the flow system. Once the heat exchangers were calibrated, the consequent work focused on the turbocharger calibration. Since the turbocharger uses a Variable Geometry Turbine (VGT), the implementation of a PID control on the VGT rack position and the correction of the turbine efficiency multiplier allowed the gauge pressure matching over the entire system. After that, by measuring the dynamic pressure in cylinder 6 and the connected intake and exhaust runners respectively, the analysis of the rate of the heat release was carried out for evaluating the actual burn rate. In this way the new cumulative burn rate was defined and directly implemented in the GT-Power model. This evaluation gave as results simulated cylinder pressure traces which were very close to experimental ones with a considerable change of the outlet cylinder temperatures. Finally, the exhaust-gas temperature in the GT-Power model was better understood after comparing it with the measured values under consideration of the energy balance on the thermocouple probe. In fact, thanks to this last analysis it was seen that a difference of up to 30 °C was present between the actual gas temperature and the measured temperature.