Multi Zone Modeling Of A Primary Reference Fuel Hcci Engine

Author : Varun Tandra
Publisher :
ISBN 13 :
Total Pages : 218 pages
Book Rating : 4.:/5 (841 download)

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Download or read book Modeling and Control of Single Cylinder HCCI Engine written by Varun Tandra and published by . This book was released on 2009 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: With growing environmental concern, energy consumption has become a key element in the current debate on global warming. Over the past two decades, Homogeneous Charge Compression Ignition (HCCI) engine technology has aroused a great deal of interest in the automotive sector owing to its fuel flexibility and ability to generate ultra-low exhaust emissions. One of the strategies to achieve ultra-low emissions in HCCI engines is to retain some exhaust gas/burnt products in the cylinder by dynamically actuating/varying valve opening and closing timings and lifts. This can be achieved by recent advancements in microprocessor, actuators and controller technologies. The first step in the synthesis of control algorithms involves developing simple system-level mathematical models. This thesis presents two such mathematical models of HCCI combustion. In the first part of this thesis, a control-oriented two-zone thermo-kinetic model of a single cylinder HCCI engine is presented. Earlier control laws were derived using single zone mathematical models of HCCI combustion; however, such models fail to accurately capture the combustion dynamics of an HCCI engine owing to the assumption of homogeneous composition and temperature in the cylinder. Certain multi-zone models of HCCI engines emphasizing the shortcomings of these single zone models have also been reported in literature. However, such models are far too complex and unwieldy for the development of fast and efficient controllers for HCCI engines. The present work outlines the modeling approach of a physics based two-zone model of a single-cylinder HCCI engine by incorporating the first law of thermodynamics and the temperature and concentration inhomogeneities within the cylinder in order to better predict emissions, peak pressures, and timing. A comparative analysis between the single zone and two-zone models is also discussed. The nonlinear model was linearized about an operating point to facilitate the development of an effective LQR regulator. The model inputs include variable valve timing to effectively control peak pressures, exhaust temperatures and ignition timing. In the second part of the thesis we address the shortcomings of control analysis which to date has been done by developing models that are engine specific, such models often rely on extensive parameters which are to be experimentally identified. Moreover, further investigation revealed that these models were valid only for a narrow operating range. Therefore, a detailed mathematical model of an HCCI engine, which is fuel flexible and valid for transitions in engine speed, is developed based on ideal gas laws and basic thermodynamics and conservation principles. The different engine subsystems and engine phenomena discretized into eight stages are modeled in a "control-oriented sense" to address the combustion timing, peak pressure and heat release rate control issues. The model has been implemented in MATLAB® to facilitate simulation studies and requires minimum tuning parameters to be experimentally recognized. Model validation is based on three sets of engine data, obtained from literature. The validation suggests that the model, once tuned properly, shows a fair agreement between the simulation and experimental data for a given engine and operating conditions.