Este trabalho tem como objetivo propor e avaliar um novo método para controle antissurto de compressores dinâmicos. É sabido que compressores dinâmicos são sujeitos ao fenômeno de surto, o qual pode danificar gravemente os componentes do compressor e provocar distúrbios de produção. O surto pode surgir a partir da ocorrência de distúrbios (por exemplo, fechamento da válvula de descarga do compressor) os quais, sem ação antissurto, fariam com que o ponto de operação se deslocasse para uma região de baixas vazões delimitada por uma linha conhecida como linha de surto. Portanto, compressores dinâmicos sempre são equipados com mecanismos antissurto: tipicamente uma válvula de reciclo de ação rápida controlada por um controlador PI antissurto. Dado que o surto se desenvolve extremamente rápido, usualmente não se permite que o compressor opere muito próximo da linha de surto. Esse objetivo de controle (manter o compressor afastado da linha de surto) é conflitante com objetivos de eficiência energética, pois os pontos de maior eficiência estão localizados próximos a essa linha. Logo, é desejável operar o compressor utilizando a mínima margem de surto que ainda garanta que a ação antissurto seja efetiva. Este trabalho propõe um método para ativação da ação antissurto no compressor com o objetivo de atingir uma ação mais rápida que o controle PI tradicional. O método proposto se baseia no cálculo offline das aberturas necessárias para a válvula de reciclo para cada possível combinação das posições dos atuadores do sistema, considerando um conjunto discreto pré-definido de valores dentro da faixa de valores de cada atuador. Esse processo gera uma tabela auxiliar para uso online. Os valores da tabela auxiliar são utilizados para gerar valores de referência para um controlador por realimentação, o qual é responsável por garantir que a trajetória do sistema irá do estado inicial no momento da ativação do controle antissurto para o estado estacionário desejado. Diversos cenários de distúrbio são simulados para diferentes controladores por realimentação e comparados com o controle antissurto PI tradicional. Os resultados mostram que a estratégia proposta é um candidato para melhorias na prática atual de controle antissurto, mas um controle por realimentação adequado deve ser selecionado e avaliado também considerando o aspecto de robustez, o qual é brevemente considerado no escopo deste trabalho. / This work aims at proposing and evaluating a novel method for anti-surge control of dynamic compressors. Dynamic compressors are known to suffer from surge, which can severely damage compressor components and disturb production. Surge may arise by the occurrence of disturbances (e.g. compressor discharge valve closure) that would bring its operating point to a region at low flows delimited by the so called surge line. Therefore, dynamic compressors are always equipped with anti-surge mechanisms: typically a fast actuating recycle valve controlled by a PI anti-surge controller. Since surge develops extremely fast, the compressor is usually not allowed to operate too close from the surge line. This control objective (keep the compressor away from the surge line) is conflicting with energy efficiency requirements, since higher efficiency operating points are located close to the surge line. Therefore, it is desirable to operate the compressor using the smallest possible surge margin that still guarantees anti-surge action is effective. This work proposes a method for triggering the compressor anti-surge action, aiming at a faster action than traditional PI control. The proposed anti-surge control method relies on an offline computation of necessary recycle valve openings for each possible combination of the system actuators positions, considering a predefined discrete set of values from the actuators positioning ranges. This generates a look-up table for online use. The values from the look-up table are used to identify the necessary compressor flow set-point for a feedback controller, which is responsible for ensuring that the system trajectory goes from the state upon anti-surge activation to the desired steady state. Several disturbance scenarios are simulated for different feedback controllers and compared to the traditional PI anti-surge controller. Results show that the proposed strategy is a candidate for improvements in current anti-surge control practice but an adequate feedback control strategy must be chosen and evaluated also under the consideration of robustness, which is slightly considered in the scope of this work.

Este trabalho tem como objetivo propor e avaliar um novo método para controle antissurto de compressores dinâmicos. É sabido que compressores dinâmicos são sujeitos ao fenômeno de surto, o qual pode danificar gravemente os componentes do compressor e provocar distúrbios de produção. O surto pode surgir a partir da ocorrência de distúrbios (por exemplo, fechamento da válvula de descarga do compressor) os quais, sem ação antissurto, fariam com que o ponto de operação se deslocasse para uma região de baixas vazões delimitada por uma linha conhecida como linha de surto. Portanto, compressores dinâmicos sempre são equipados com mecanismos antissurto: tipicamente uma válvula de reciclo de ação rápida controlada por um controlador PI antissurto. Dado que o surto se desenvolve extremamente rápido, usualmente não se permite que o compressor opere muito próximo da linha de surto. Esse objetivo de controle (manter o compressor afastado da linha de surto) é conflitante com objetivos de eficiência energética, pois os pontos de maior eficiência estão localizados próximos a essa linha. Logo, é desejável operar o compressor utilizando a mínima margem de surto que ainda garanta que a ação antissurto seja efetiva. Este trabalho propõe um método para ativação da ação antissurto no compressor com o objetivo de atingir uma ação mais rápida que o controle PI tradicional. O método proposto se baseia no cálculo offline das aberturas necessárias para a válvula de reciclo para cada possível combinação das posições dos atuadores do sistema, considerando um conjunto discreto pré-definido de valores dentro da faixa de valores de cada atuador. Esse processo gera uma tabela auxiliar para uso online. Os valores da tabela auxiliar são utilizados para gerar valores de referência para um controlador por realimentação, o qual é responsável por garantir que a trajetória do sistema irá do estado inicial no momento da ativação do controle antissurto para o estado estacionário desejado. Diversos cenários de distúrbio são simulados para diferentes controladores por realimentação e comparados com o controle antissurto PI tradicional. Os resultados mostram que a estratégia proposta é um candidato para melhorias na prática atual de controle antissurto, mas um controle por realimentação adequado deve ser selecionado e avaliado também considerando o aspecto de robustez, o qual é brevemente considerado no escopo deste trabalho. / This work aims at proposing and evaluating a novel method for anti-surge control of dynamic compressors. Dynamic compressors are known to suffer from surge, which can severely damage compressor components and disturb production. Surge may arise by the occurrence of disturbances (e.g. compressor discharge valve closure) that would bring its operating point to a region at low flows delimited by the so called surge line. Therefore, dynamic compressors are always equipped with anti-surge mechanisms: typically a fast actuating recycle valve controlled by a PI anti-surge controller. Since surge develops extremely fast, the compressor is usually not allowed to operate too close from the surge line. This control objective (keep the compressor away from the surge line) is conflicting with energy efficiency requirements, since higher efficiency operating points are located close to the surge line. Therefore, it is desirable to operate the compressor using the smallest possible surge margin that still guarantees anti-surge action is effective. This work proposes a method for triggering the compressor anti-surge action, aiming at a faster action than traditional PI control. The proposed anti-surge control method relies on an offline computation of necessary recycle valve openings for each possible combination of the system actuators positions, considering a predefined discrete set of values from the actuators positioning ranges. This generates a look-up table for online use. The values from the look-up table are used to identify the necessary compressor flow set-point for a feedback controller, which is responsible for ensuring that the system trajectory goes from the state upon anti-surge activation to the desired steady state. Several disturbance scenarios are simulated for different feedback controllers and compared to the traditional PI anti-surge controller. Results show that the proposed strategy is a candidate for improvements in current anti-surge control practice but an adequate feedback control strategy must be chosen and evaluated also under the consideration of robustness, which is slightly considered in the scope of this work.

<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>

<p>Mean Value Engine Modeling (MVEM) is used to make engine control development less expensive. With more and more cars equipped with turbocharged engines good turbo MVEM models are needed. A turbocharger consists of two major parts: turbine and compressor. Whereas the turbine is relatively durable, there exist phenomenons on the compressor that can destroy the turbocharger. One of these is surge.</p><p>Several compressor models are developed in this thesis. Methods to determine the compressor model parameters are proposed and discussed both for the stable operating range as well as for the surge region of a compressor map. For the stationary region methods to automatically parameterize the compressor model are developed. For the unstable surge region methods to get good agreement for desired surge properties are discussed. The parameter sensitivity of the different surge properties is also discussed. A validation of the compressor model shows that it gives good agreement to data, both for the stationary region as well as the surge region.</p><p>Different open loop and closed loop controllers as well as different performance variables are developed and discussed. A benchmark is developed, based on a measured vehicle acceleration, and the control approaches are compared using this benchmark. The best controller is found to be a open loop controller based on throttle and surge valve mass flow.</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. 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.

Mean Value Engine Modeling (MVEM) is used to make engine control development less expensive. With more and more cars equipped with turbocharged engines good turbo MVEM models are needed. A turbocharger consists of two major parts: turbine and compressor. Whereas the turbine is relatively durable, there exist phenomenons on the compressor that can destroy the turbocharger. One of these is surge. Several compressor models are developed in this thesis. Methods to determine the compressor model parameters are proposed and discussed both for the stable operating range as well as for the surge region of a compressor map. For the stationary region methods to automatically parameterize the compressor model are developed. For the unstable surge region methods to get good agreement for desired surge properties are discussed. The parameter sensitivity of the different surge properties is also discussed. A validation of the compressor model shows that it gives good agreement to data, both for the stationary region as well as the surge region. Different open loop and closed loop controllers as well as different performance variables are developed and discussed. A benchmark is developed, based on a measured vehicle acceleration, and the control approaches are compared using this benchmark. The best controller is found to be a open loop controller based on throttle and surge valve mass flow.