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HCCI Modeling and Control Strategies Utilizing Water Injection
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- Author / Creator
- Gordon, David
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Homogeneous Charge Compression Ignition (HCCI) has the potential to significantly reduce oxides of nitrogen NOx emissions, while maintaining a high fuel efficiency compared to existing lean-burn spark ignition engines. HCCI is characterized by compression induced autoignition of a lean homogeneous air-fuel mixture. The challenge with HCCI combustion is the high cyclic variation due to the lack of direct ignition control leading to cycles with high emissions. Combustion timing is highly dependent on the in-cylinder state including pressure, temperature and trapped mass. To control HCCI combustion it is necessary to have an accurate representation of the gas exchange process. Currently, microprocessor based engine control units require that the gas exchange process is simplified to meet very limited calculation time allowances. However, using a Field Programmable Gate Array (FPGA) a detailed simulation of the physical gas exchange process can be implemented in real-time. This thesis outlines the process of converting physical governing equations to an online real-time capable FPGA based model. This development process is described and the online model is experimentally validated using a single cylinder research engine with electromagnetic valves. The real-time FPGA gas exchange results are recorded and compared to the offline reference. The FPGA model is able to accurately calculate the cylinder temperature, air mass, fuel mass and heat released at 0.1 deg crank angle (CA) intervals during the gas exchange process for a range of negative valve overlap, boost pressures and engine speed making the model useful for real-time control applications. An operating region variation is performed on the engine to determine the effect of the negative valve overlap on the HCCI combustion process. The impact of direct water injection on HCCI is also investigated by varying water injection timing and quantity. Using the results of the water injection testing, a feed-forward direct water injection controller is developed and experimentally validated. The low latency and rapid calculation rate of the FPGA is utilized to calculate the gas exchange process and the required control interaction within 0.1 deg CA. The maximum cylinder pressure during negative valve overlap, heat released during combustion and residual fuel mass are the three control inputs which are tested with the feedforward controller. This controller prevents early rapid combustion following a late combustion cycle by using direct water injection to cool the cylinder charge and counter the additional thermal energy from any residual fuel that is transferred between cycles. By cooling the trapped cylinder mass the upcoming combustion phasing can be delayed to the desired setpoint. The controller was tested at several operating points and showed an improvement in the combustion stability as shown by a reduction in the standard deviation of both combustion phasing and indicated mean effective pressure.
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- Graduation date
- Spring 2019
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.