Impact of Pressure Pulsations on Diesel Air Path Control and Compensation Measures
Abstract: Stricter pollution norms have led to increased efforts to achieve lower emissions. Exhaust Gas Re-circulation (EGR) is a well known measure to reduce NOx internally in the engine. In order to achieve better performance of an engine in terms of emissions it is very essential to control the flow of exhaust gases through EGR valve. Generally, an Engine Control Unit (ECU) uses mean value models or map-based approaches to calculate the mass flow through EGR valve. The main driving factor of the mass flow through an EGR valve i.e. the exhaust gas pressure is continuously fluctuating throughout an engine cycle. This continuous change in the pressure lead to variations in the mass flow through EGR valve, thus introducing inaccuracies in the desired flow through EGR valve, thereby affecting the engine performance greatly. Hence it is very essential to consider the pulsations in a combustion cycle. In this thesis an EGR valve model is developed in Matlab/Simulink environment. The model is able to consider the effect of exhaust pressure pulsations and is found to be more accurate than the mean value models used in the ECU.
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