The purpose of this master thesis is to investigate the possibility to refine the control system of turbochargers in petrol engines by introducing turbo speed measurement. This thesis also investigates possible control enhancement from an electric wastegate actuator compared with a traditional pneumatic actuator. During the thesis work the control problem is divided into 3 sub systems: boost pressure controller, turbo speed controller, and electric actuator controller. The design procedure of the controllers follows model-based method in which a simulation model for engine and a simulation model for electric actuator are used. The designed controller is then implemented and evaluated in an engine test cell. The result of the thesis work shows that the electric wastegate actuator is preferred as it delivers consistent actuation speed and accurate positioning which favours model-based design that requires exact wastegate position. Although the purposed controller structure that uses turbo speed measurement cannot yet achieve faster generation of boost pressure by the end of the thesis work, the use of turbo speed sensor as controller feedback still shows potential to enhance the boost controller and ease the controller design, as the turbo speed measurement can reflect the boost pressure faster and is less sensitive to the disturbances in the air flow.

<p>In some turbochargers, boost pressure is reduced by opening the wastegate valve. In a modern turbo charged car, the most common way for opening the wastegate is with a pneumatic actuator and an air control solenoid, controlled by the ECU. In the control systems studied the ECU utilizes a static feedforward and a PID controller, for the purpose of making the boost pressure follow its reference value. With no systematic method for tuning the controller, this can be time consuming, and a set of well defined experiments to determine PID parameters are desired.When test time in a real engine is limited or expensive, it is advantageousto work in a simulation environment before doing live tests. A model for thewastegate actuator and air control solenoid is developed in the thesis. This is used to simulate controller performance before any tests in a real car is performed.In the thesis a tuning method for the PID controller based on step responsesis proposed. The tuning method evaluated is the IMC-choice of controller fora second order system, and it has a single design parameter not given by theexperiments. The controller is shown to give desired behavior when the staticfeedforward is correct or has small error.</p>

In some turbochargers, boost pressure is reduced by opening the wastegate valve. In a modern turbo charged car, the most common way for opening the wastegate is with a pneumatic actuator and an air control solenoid, controlled by the ECU. In the control systems studied the ECU utilizes a static feedforward and a PID controller, for the purpose of making the boost pressure follow its reference value. With no systematic method for tuning the controller, this can be time consuming, and a set of well defined experiments to determine PID parameters are desired.When test time in a real engine is limited or expensive, it is advantageousto work in a simulation environment before doing live tests. A model for thewastegate actuator and air control solenoid is developed in the thesis. This is used to simulate controller performance before any tests in a real car is performed.In the thesis a tuning method for the PID controller based on step responsesis proposed. The tuning method evaluated is the IMC-choice of controller fora second order system, and it has a single design parameter not given by theexperiments. The controller is shown to give desired behavior when the staticfeedforward is correct or has small error.

No description available.

The aim of master’s thesis was to put forward calculation methodology of wastegate turbocharger bypass channel discharge coefficient. Designed methodology was based on discharge coefficient analysis conducted utilizing CFD simulations of turbocharger turbine-side parametric model. It was achieved to propose a calculation, which differentiates relatively in average 1,4% from CFD data. New methodology improves the accuracy bypass channel design and helps to choose appropriate wastegate valve actuator.

<p>Since measurements in engine test cells are closely coupled with high costs it is of interest to use physically interpretable engine models instead of engine maps. Such engine models can also be used to do off-line tests of how new or altered components affects engine performance.</p><p>In the thesis an existing mean value engine model will be extended with a model of a compressor bypass valve. A controller for that valve will also be developed. The purpose with that controller is to save torque and boost pressure but at the same time avoid having the compressor entering surge during fast closing transients in the throttle position.</p><p>Both the extension and controller is successfully developed and implemented. The extension lowers the pressure after the compressor and increases the pressure before the compressor when the bypass valve is being opened and the controller shows better results in simulations than the controller used in the research lab. By using the proposed controller, as much as 5 percent higher torque can be achieved in simulations.</p><p>Finally there is a discussion on wastegate control alternatives and the use of TOMOC for optimization of wastegate control.</p>

A turbo system is driven by the excess energy in the exhaust gases.  As a result, variation in exhaust temperature cause variations in  boost pressure. By using the information about the available exhaust  energy in the turbo controller directly through a feedforward  controller, an unexpected variation in turbo boost can be avoided. A  model based controller is developed that calculates the desired  turbine power from the boost pressure reference and then, by  observing the available exhaust energy, controls the generated  turbine power to match the desired power. A Mean Value Engine Model  has been used to make simulation with the developed controller  implemented. Steps between different boost pressure references are  used to evaluate controller performance. Tests in a car have also  been made to make sure the simulation results are consistent in a  real environment. / Turbosystem drivs av överskottsenergin i motorns avgaser. Dettainnebär att temperaturvariationer i avgaserna orsakar variationer igenererad turbineffekt och därmed ökat laddtryck från turbosystemet.Används informationen om den tillgängliga energin i avgaserna när manstyr turbinen så kan man motverka oväntade laddtrycksförändringar. Idenna rapport har en modellbaserad turboregulator med en framkopplingsom beräknar en önskad turbineffekt från givet referenstryckutvecklats. Sedan tas en styrsignal fram till turbinen som, genom attanvända informationen om den observerade energin i avgaserna, matcharden önskade turbineffekten. En model av en medelvärdesmotor haranvänds för att validera prestandan i regulatorn via stegsvar mellanolika referenstryck. Det har även utförts tester i bil för att avgöraom resultatet blir detsamma under verkliga förhållanden.

Since measurements in engine test cells are closely coupled with high costs it is of interest to use physically interpretable engine models instead of engine maps. Such engine models can also be used to do off-line tests of how new or altered components affects engine performance. In the thesis an existing mean value engine model will be extended with a model of a compressor bypass valve. A controller for that valve will also be developed. The purpose with that controller is to save torque and boost pressure but at the same time avoid having the compressor entering surge during fast closing transients in the throttle position. Both the extension and controller is successfully developed and implemented. The extension lowers the pressure after the compressor and increases the pressure before the compressor when the bypass valve is being opened and the controller shows better results in simulations than the controller used in the research lab. By using the proposed controller, as much as 5 percent higher torque can be achieved in simulations. Finally there is a discussion on wastegate control alternatives and the use of TOMOC for optimization of wastegate control.

Tato diplomová práce se zabývá turbodmychadly a CFD simulací turbodmychadla s integrovaným přepouštěcím ventilem pro benzínový motor. Cílem je poskytnout všeobecný přehled o přeplnování a konstrukci turbodmychadel. Práce popisuje proces tvorby 3-rozměrného virtuálního modelu sestavy turbínové skříně, extrakci negativního objemu plynů, tvorbu meshe a nastavení počítačové CFD simulace, která je v závěru práce vyhodnocena. Výsledky simulace slouží pro návrh odlišného provedení turbínové skříně za účelem zlepšení rozložení teplot výfukových plynů na výstupu a zkrácení aktivační doby výfukového katalyzátoru.

The high demands on low fuel consumption and low emissions on the combustion engines of both today, and the future, is highly dependent on advanced control systems in order to fulfill these demands. The control systems and strategies are based on models which describe the physical system. The more accuratly the models describe the real world system, the more accurate the control will be, leading to better fuel economy and lower emissions. This master's thesis investigates and improves the mass flow model used for a compressible restriction, such as over the throttle valve, EGR valve, or the wastegate valve, for example. The standard model is evaluated and an improvement is proposed which does not assume isentropic flow. This seems to explain the deviation from the isentropic Psi-function shown in earlier research such as (Andersson:2005). Furthermore a throttle valve is analyzed in ANSYS in order to show the generation of entropy. The presence of pressure pulsations in a combustion engine is also evaluated, especially how they effect the otherwise assumed steady flow model. It is tested if a mean value pressure is sufficient or if one needs to take the pulsations in to account, and the result shows that a mean pressure is sufficient, at least for the throttle when typical intake manifold pulsations is present. A dynamic flow model is also derived which can be useful for pressure ratios close to one. The dynamic flow model is based on the standard equation but with an extra dynamic term, however it is not implemented and tested due to complexity and time limitation. The proposed new non-isentropic flow model has proven promising and can hopefully lead to lower emissions and better fuel economy.