Model Based Control of Combustion Timing and Load in HCCI Engines

• Author / Creator

  Ebrahimi, Khashayar

• Different model based control strategies are developed for combustion timing and load control in a single cylinder Homogeneous Charge Compression Ignition (HCCI) engine. In HCCI engines, a lean homogeneous air-fuel mixture auto-ignites due to compression and the resulting combustion occurs at lower temperatures compared to spark ignition or diesel engines. The low HCCI combustion temperatures result in low Nitrogen Oxides (NOX) levels but high unburnt Hydrocarbons (HC) and Carbon Monoxide (CO) levels. High HCCI thermal efficiency occurs when the combustion efficiency is high and the combustion timing is appropriate. In this thesis, the effects of fueling rate and valve timing on HCCI engine performance and energy distribution are described. This analysis indicates that Variable Valve Timing (VVT) with Symmetric Negative Valve Overlap (SNVO) is an effective actuator for combustion timing control. In addition, combustion timing affects combustion efficiency which has an important role in engine energy distribution. Next, a detailed multi-zone model with fuel specific kinetics is developed for HCCI engine performance analysis that captures valve timing and fueling rate dynamics. The multi-zone physics based model has 483 states, 5 inputs and 4 outputs. PI controller gains are first tuned using the detailed multi-zone model in simulation and then the controller is implemented on a single cylinder engine. Combustion timing is used as feedback to the controller and valve timing is the main actuator. Then a Feedforward/Feedback (Fdfwd/Fdbk) strategy is developed for HCCI combustion timing control. The Fdfwd/Fdbk controller is based on a model that relates combustion timing to valve timing and it is combined with an integrator feedback to zero the steady state error. A Model Predictive Control (MPC) strategy is then developed for HCCI combustion timing and load control that takes into account actuator and output constraints. A physics based approach is used for model order reduction of the detailed multi-zone model and a discrete nonlinear control oriented model is obtained with 4 states, 2 inputs and 2 outputs. This model is linearized around one operating point and the MPC is designed based on the linearized version of the 4-state control oriented model. The MPC is then implemented on the single cylinder engine and the results are compared to the PI and Fdfwd/Fdbk controller. The MPC exhibits good tracking performance for combustion timing and load. Finally, a new control oriented model is developed for combustion timing and load control considering combustion efficiency. This model can be used for future MPC design which consider combustion efficiency constraints.

• Subjects / Keywords

  • Modeling
  • Control
  • HCCI
  • MPC

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3MW28P0F

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.