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Reducing the fuel consumption of today's vehicle fleet is of great importance due to the environmental impact of using fossil-based fuels. The turbocharged compression ignition (CI) engine is widely used for trucks. The CI engine efficiency is dependent on the operating point, in terms of rotational speed and load. The selection of load point can be controlled by selecting suitable gears, but remains a challenging task during dynamic driving, due to the turbocharger dynamics which introduces a lag in the system. Electric turbocharger technologies can improve the engine response time, but developing efficient control strategies can be challenging. Due to turbocharger lag, all conditions that are reachable in stationary operation for the turbocharged CI engine are not always reachable during dynamic events, for example after an up-shift where the engine speed and torque demand changes rapidly. In this work the fuel saving potential of electric turbocharging for a heavy-duty truck performing a long-haulage driving mission is investigated. An electric turbocharger control strategy is proposed and evaluated. The results show that the fuel consumption can be reduced using the electric turbocharger, when comparing to a conventional turbocharged CI truck performing a long-haulage driving mission. A turbocharged CI engine model suitable for optimal control of transient behavior is developed. Sub-models are validated using data describing the components, and the model suitability for optimal control is shown with a tip-in example. To increase the model accuracy, the torque model is extended with a further dependence on the air-fuel ratio and operating point dependent losses. The complete engine model is parameterized for a set of stationary load points. The model is validated using data from a dynamic engine test, where it is shown that both the stationary and dynamic features in the data is represented well by the model. The developed engine model is used as a foundation in an optimal control problem setup to solve fuel optimal accelerations including gear changes. The setup is used to investigate the impact of driveshaft flexibility on the optimal control results, when compared to a stiff driveshaft model. Apart from a slight increase in fuel consumption, the driveshaft flexibility is shown to have minor effects on the fuel optimal control signals, in terms of general torque output and gear shift characteristics. The hybrid electric vehicle (HEV) technology can potentially reduce the consumption of diesel fuel, but how to design and control the system, consisting of several degrees of freedom remains a challenging task. Energy optimal accelerations of a CI parallel HEV with electric turbocharger is investigated using the optimal control problem setup. The results show that the electric turbocharger is used when the electrical energy cost is high, and the usage of the crank shaft motor is increasing with decreasing electric energy cost. To summarize, the developed models and problem setups enable investigations of different powertrain configurations and optimal control of these. One conclusion is that the energy savings using an electric turbocharger and crank shaft motor during accelerations are significant. Funding agencies: Linköping Center of Informatics; Control LINK-SIC

The diesel engine remains one of the key components in the global economy, transporting most of the worlds goods. To cope with stricter regulations and the continuous demand for lower fuel consumption, optimization is a key method. To enable mathematical optimization of the diesel engine, appropriate models need to be developed. These are preferably continuously differentiable, in order to be used with a gradient-based optimization solver. Demonstration of the optimization-based methodology is also necessary in order for the industry to adapt it. The paper presents a complete mean value engine model structure, tailored for optimization and simulation purposes. The model is validated using measurements on a heavyduty diesel engine. The validated model is used to study the transient performance during a time-optimal tip-in, the results validate that the model is suitable for simulation and optimization studies.

The thesis is about investigating the inlet and outlet pipes effect on the compressors measured performance. From measurements made in a gas stand, a thermodynamic model is to be created and the compressor efficiency further investigated. The temperatures and pressures entering and leaving the compressor does not have to be the same as the temperatures measured in the gasstand, because of the thermodynamics of the pipes that connects the measurement equipment and the compressor. During a gasstand test the turbocharger is connected in a test bench, it is connected with pipes on both the compressor and turbine side, to simulate the hot exhaust gases from the car engine and the pressure increase over the compressor. The air entering and leaving the turbocharger through the different pipes is controlled and all the entering and leaving temperatures and pressures are measured. Gasstand data from different tests are available during the thesis, one specific turbocharger is used as references during the modeling. Models of the inlet and outlet pipes are created and connected to a compressor model. The model is controlled to give the same mass flow as the measured data, to ensure that the work cycle is followed. The effects of the non ideal inlet and outlet pipes on measured compressor efficiency is studied with help of this model and the main impacts on the measured compressor efficiency are discovered. The result shows that the measured values used to calculate the compressor efficiency could change, depending on the measurement positions on the inlet and outlet pipes.