<p>The SAAB variable compression engine is a new engine concept that enables the fuel consumption to be radically cut by varying the compression ratio. A challenge with this new engine concept is that the compression ratio has a direct influence on the output torque, which means that a change in compression ratio also leads to a change in the torque. A torque change may be felt as a jerk in the movement of the car, and this is an undesirable effect since the driver has no control over the compression ratio. </p><p>The aim of this master's thesis work is to develop a torque control strategy for the SAAB variable compression engine. Where the main control objective is to make the output torque behave in a desirable way despite the influence of compression ratio changes. </p><p>The controller is developed using a design method called Internal Model Control, which is a straightforward way of both configuring a controller and determining its parameters. The controller has been implemented and evaluated in a real engine, and has proved to be able to reduce the effect of compression ratio disturbance.</p>

<p>Knock is a phenomenon that limits how effciently an engine can operate. Severe knock is harmful to the engine and must therefore be avoided. Controlling the knock intensity is complicated by a phenomenon called cycle to cycle variations. Because of these variations, the knock intensity must be considered a stochastic variable and the control is made on a mean value from a large number of cycles. </p><p>The SVC (Saab Variable Compression) concept adds the compression ratio as an extra degree of freedom. At Vehicular systems, research is done on how to put this additional variable to its best use. </p><p>A controller is developed that control the engine to a desired knock intensity and torque, using the ignition angle and the pedal position. The controller is implemented as two separate controllers in Matlab and Simulink. These are merged together with a Stateflow chart. A confidence interval calculation is implemented for the mean value of the knock intensity. A program is also developed to process a large number of operating points and make measurements in all of them. </p><p>The conclusion is that the basic construction of the controller and the script are fi;lling their functions but that there are some improvements left to be done. The controller is rather slow and the calculations of the confi;dence interval needs further refi;nement.</p>

The SAAB variable compression engine is a new engine concept that enables the fuel consumption to be radically cut by varying the compression ratio. A challenge with this new engine concept is that the compression ratio has a direct influence on the output torque, which means that a change in compression ratio also leads to a change in the torque. A torque change may be felt as a jerk in the movement of the car, and this is an undesirable effect since the driver has no control over the compression ratio. The aim of this master's thesis work is to develop a torque control strategy for the SAAB variable compression engine. Where the main control objective is to make the output torque behave in a desirable way despite the influence of compression ratio changes. The controller is developed using a design method called Internal Model Control, which is a straightforward way of both configuring a controller and determining its parameters. The controller has been implemented and evaluated in a real engine, and has proved to be able to reduce the effect of compression ratio disturbance.

Knock is a phenomenon that limits how effciently an engine can operate. Severe knock is harmful to the engine and must therefore be avoided. Controlling the knock intensity is complicated by a phenomenon called cycle to cycle variations. Because of these variations, the knock intensity must be considered a stochastic variable and the control is made on a mean value from a large number of cycles. The SVC (Saab Variable Compression) concept adds the compression ratio as an extra degree of freedom. At Vehicular systems, research is done on how to put this additional variable to its best use. A controller is developed that control the engine to a desired knock intensity and torque, using the ignition angle and the pedal position. The controller is implemented as two separate controllers in Matlab and Simulink. These are merged together with a Stateflow chart. A confidence interval calculation is implemented for the mean value of the knock intensity. A program is also developed to process a large number of operating points and make measurements in all of them. The conclusion is that the basic construction of the controller and the script are fi;lling their functions but that there are some improvements left to be done. The controller is rather slow and the calculations of the confi;dence interval needs further refi;nement.

Recently, some new technologies (e.g., downsizing, turbocharging) have been widely used in spark-ignition (SI) engines to achieve higher efficiencies and less emissions. However, the improved power density and in-cylinder pressure promote more engine knock, causing violent pressure oscillations and threatening engine integrity. Therefore, it is imperative to study engine knocking combustion more than ever; In-depth understandings of knock mechanism and characteristics are of utmost importance for controlling knock. With this emphasis, this thesis implements systematic studies to bridge the gap between knocking combustion characteristics and knock suppressing strategies. To investigate knock with optical and laser diagnostics, an optical compression-ignition (CI) engine was modified to operate under SI mode. A home-made metal liner with multiple spark plugs was used to trigger more controllable knock events via different spark strategies. Up to six pressure sensors were installed to collect the pressure signals from different sides. Next, the relationships between in-cylinder pressure, knock intensity, pressure fluctuation, heat release, and measurement location are analyzed to study the knock mechanism, influential factors, and measurement methods. The findings indicate a trade-off between the mass fraction and temperature of end-gas. The effects of compression ratio and fuel octane number are also explored. Moreover, the multichannel pressure monitoring is synchronized with high-speed imaging to investigate the flame propagation and knock development processes regarding the different spark strategies. The results give insights into the in-cylinder temperature inhomogeneity and how it affects the spatial distribution of auto-ignition sites. Furthermore, a new method is proposed to detect the local pressure fluctuations by setting a series of virtual flame monitors instead of pressure sensors. The results validate that this method provides a convenient and reliable way to study knock oscillations. Finally, this study presents a hydraulically actuated VCR (variable compression ratio) piston design to address knock challenges. The numerical simulation results show this VCR piston has a good adaptability and could help achieve high engine efficiencies, while keeping reasonable peak pressure to avoid heavy knock at high loads. However, more analysis work still needs to be implemented on its practical applications, e.g., the thermal stress and frictions under different operating conditions.

[pt] No presente trabalho foi realizada a construção, montagem, revisão de projeto e avaliação experimental preliminar de um novo motor a combustão interna rotativo por ignição por centelha, que pode ser classificado como cat-and-mouse engine ou Twin-Rotor Piston Engine. Nesse motor, dois pares de deslocadores são montados sobre dois rotores, que giram em velocidade variável em dentro de uma câmara cilindrica, de forma a conferir uma variação da posição angular relativa entre deslocadores e, assim, formar quatro câmaras de volumes variáveis com o tempo, a fim de se realizar processos termodinâmicos equivalentes aos de um motor alternativo de quatro tempos. Esse motor destaca-se por possuir um sistema inovador que permite a mudança do movimento dos rotores e deslocadores, de forma a aumentar o volume deslocado e a taxa de compressão das câmaras onde ocorrem os processos termodinâmicos. Tal dispositivo permite alterar e otimizar a taxa de compressão para diferentes combustíveis. Os componentes do motor foram usinados de acordo com o projeto e o protótipo foi montado, revisado e ajustado, de forma a garantir a operacionalidade do equipamento. Posteriormente, o motor foi montado em uma bancada para se efetuar testes preliminares de acionamento externo, afim de se medir vazão volumétrica, potência fornecida e pressão de compressão no ponto morto superior em função da velocidade angular. A revisão bibliográfica do trabalho contém definições úteis na classificação de motores rotativos, além de discutir suas especificidades características. / [en] The present work describes the construction, assembly, project revision and preliminary experimental evaluation of an innovative rotary spark ignition internal combustion engine. First, a literature survey was carried out. Some useful definitions were found for rotary engines classification as well as some of their specific characteristics were discussed. The engine can be classified as cat-andmouse engine or Twin-Rotor Piston Engine. It is characterized by two pairs of displacers, assembled over two rotors, which rotate at a variable rotational speed within a cylindrical cavity. The driving mechanism is such that the relative distance between each pair of displacers varies continuously, thus providing the positive displacement effect. Therefore, the engine has four chambers, each one with its own time varying volume, so that thermodynamic processes, equivalent to those of a four-stroke reciprocating internal combustion engine, can take place. This engine presents a unique and innovative mechanism by which the compression ratio can be varied during operation, thus optimizing engine efficiency a for a given fuel. Engine components, designed in an effort previous to the present one, were fabricated according to the original project. A prototype was assembled, with all components following a routine of project revision, including measurements, uncertainties and adjustments. The engine was then placed on a test bench where preliminary non-firing external driving tests were carried out. They included: volumetric flow rate, driving (frictional) power and cylinder maximum pressure with displacer at the top dead center, all these parameters in terms of the primary shaft angular velocity.