Examensarbeten för masterexamen // Master Theses
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- PostDynamic Temperature Model of an Automatic Transmission(2019) Berglund, Oscar; Zhang, Yao; Chalmers tekniska högskola / Extern; Chalmers University of Technology / ExternalThis report presents the development of a dynamic temperature model for an automatic transmission in a Volvo Cars passenger vehicle. The model should simulate the oil to cooler temperature and flow from the transmission. A mathematical approach to use lumped masses for different parts of the transmission was used. These lumped masses were the oil, moving parts and house. To tune the response of the lumped masses and heat transfer coefficients, temperature measurements were used. Some existing measurements at Volvo Cars were tested, but these measurements were not accurate enough. New improved measurements on a vehicle in a chassis dyno were then performed. A decision to do measurements on all eight gears were made since the power losses were different on every gear. However the torque converter was open on the first gear, and could not be closed, which led to the decision to only test the remaining gears since the first gear will only be used during short times during most driving scenarios. To verify the model, simple drive cycles were performed with temperature measurement in the same chassis dyno and on the same vehicle. The verification on the model shows that the model can simulate the behaviour of a transmission with an error of 2.5 °C during normal behaviour and 6.5 °C for a few minutes, when a sudden change in the temperature from the cooler have a large transient increase. Because of this, the model is considered to be fairly accurate. However, in order to make the model compatible with Volvo Cars existing simulation software, Vsim, a "cooler model" has to be created.
- PostMild Hybrid Electro-Thermal Battery Modelling(2016) Biswas, Akik; Yao, Xuming; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentIn this thesis an electro-thermal battery pack model has been developed for a 48 V Mild Hybrid vehicle application to predict the pack temperature under different loading cases which have been verified with experiments. Both the joule and the entropic heat play significant roles in the total heat generation process. Furthermore, the entropic heat can be both endothermic and exothermic and these processes have also been verified. The contribution of entropic heat to the thermal dynamic behavior was verified through simulations using GTSUITE software and experiment. For the electrical battery pack model it was found that the 2 RC circuit model captured the electrical dynamic behavior which was in good agreement with the experiment data, whereas the 0 RC circuit model failed to do so. The 2 RC circuit model produced an error of 1.5 %, whereas the 0 RC circuit model gave an error of 3.2 %. Experiments were carried out both at the battery pack for temperature measurements and at the cell level to determine the internal battery cell parameters such as R0, R1, R2, C1, C2, specific heat and the entropic heat. Moreover, the experiments were carried out over a wide range of state of charge (SOC) levels and temperatures restricted between 5 C and 45 C.