No description available.

Homogeneous Charge Compression Ignition (HCCI) is a promising method for combustion engines to provide a substantial reduction in fuel consumption and formation of both nitrogen oxides and soot pollutants in automotive and stationary engines. Control of HCCI combustion timing is essential for the successful integration of the HCCI concept in real applications. This thesis concentrates on control oriented modeling and experimental study of HCCI combustion for control of ignition timing in HCCI engines. A detailed experimental study of HCCI with over 600 operating points on two different engines is done to characterize the complex relationship among the engine variables, the ignition timing and the exhaust temperature. This leads to identifying regions with distinct patterns of cyclic variation for HCCI ignition timing. In addition, main influential factors on the variations of ignition timing and exhaust temperature in HCCI engines are determined. A dynamic full-cycle physics based Control Oriented Model(COM) is derived from using the experimental data and simulations from an HCCI thermo-kinetic model. The COM is validated with a large number of transient and steady-state experimental points. The validation results show that the COM captures the key HCCI dynamics with a high degree of accuracy for control applications. The COM is computationally efficient and all inputs of the model can be readily measured or estimated on a real engine. This makes the COM simple and fast enough for use as an off-line simulation bed to design and evaluate different strategies for physics-based control of combustion timing in HCCI engines.

No description available.

Zugl.: Karlsruhe, Univ., Diss., 2007

Stuttgart, Univ., Diss., 2007.

[pt] Uma bancada experimental foi desenhada e desenvolvida para realizar ensaios experimentais de um motor de ciclo Diesel utilizando gasolina como combustível. O motor (originalmente de ciclo diesel) foi adequado com diferentes dispositivos para funcionar em modo HCCI. Estas modificações não afetaram as condições originais do motor, podendo em qualquer momento voltar ao modo diesel. A instrumentação inclui medição de: temperatura (gases de escapamento, entrada da carga de admissão, óleo lubrificante), pressão (entrada do ar de admissão, entrada da gasolina, câmara de combustão), torque, rotação, vazão de ar, vazão de combustível. O motor foi submetido a diversas condições de operação e parâmetros de controle para estudar e analisar os efeitos da rotação do motor, da relação ar-combustível e da temperatura da mistura (ar-gasolina) de entrada na combustão HCCI. Os resultados indicam que as variações na quantidade de combustível e na temperatura de admissão têm um efeito direto na combustão HCCI. Maiores temperaturas ou quantidades de combustível provocam um avanço da fase de ignição, que teria uma influência direta no início da combustão e nas máximas pressões no interior da câmara de combustão. Os resultados também indicam que, incrementando a quantidade de combustível e variando a temperatura de admissão, mais energia útil é gerada até atingir o limite da zona de detonação, obtendo os melhores resultados para a temperatura de 75 Graus C com uma eficiência térmica de 34,2 por cento na rotação de 1900 RPM. Pequenos ganhos na eficiência de combustão são traduzidos em economias significativas de energia, reduzindo também os níveis de poluição dos gases de escapamento. / [en] An experimental device was designed and developed to perform experimental tests of a Diesel cycle engine using gasoline as fuel. The engine (originally Diesel cycle) was adequated with different devices to operate in HCCI mode. These modifications did not affect the original conditions of the engine, making it able return to the diesel mode at any moment. The instrumentation included measurement of: temperature (exhaust gases, intake charge admission, lubricating oil), pressure (inlet ar admission, injector nozzle, combustion chamber), torque, engine speed, crankshaft angle, air flow and fuel rate. The engine was submitted to various operating conditions and control parameters to study and analyze the effects of the engine speed, the air-fuel ratio and the temperature of the mixture (air-gasoline) in the HCCI combustion. The results indicate that variations in the amount of fuel and the intake temperature have a direct effect on HCCI combustion. High temperatures or amounts of fuel cause an advanced ignition, which would have a direct influence on the combustion timing and in the maximum pressure inside the combustion chamber. The results also indicate that increasing the amount of fuel and varying the inlet temperature, more useful energy is generated until it reaches the zone of detonation, getting the best results for the temperature of 75 C Degrees with a thermal efficiency of 34,2 percent at 1900 RPM. Small gains in combustion efficiency are translated into significant energy savings, reducing also the pollution levels caused by exhaust gases.

Zugl.: München, Techn. Univ., Diss., 2009

Argon replacing nitrogen has been examined as a new engine cycle to reach high efficiency. Experiments were carried out under Homogeneous Charge Compression Ignition (HCCI) conditions using a single cylinder variable compression ratio Cooperative Fuel Research (CFR) engine. Isooctane has been used as the fuel for this study. All the parameters were kept fixed but the compression ratio to make the combustion phasing constant. Typical engine outputs and emissions were compared to conventional cycles with both air and synthetic air. It has been found that the compression ratio of the engine must be significantly reduced while using argon due to its higher specific heat ratio. The resulting in-cylinder pressure was lower but combustion remains aggressive. However, greater in-cylinder temperatures were reached. To an end, argon allows gains in fuel efficiency, in unburned hydrocarbon and carbon monoxide, as well as in indicated efficiency. A higher nitrogen oxide concentration while replacing nitrogen by argon was observed but the origin remains to be identified. The concept should therefore be able to reach zero-NOx emissions as no nitrogen should be present.

Zugl.: Aachen, Techn. Hochsch., Diss., 2009

No description available.