Nonlinear Controller for PCCI Combustion Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Diesel engines face challenges in achieving reduced NOx and PM emissions while maintaining high efficiency, due to the lack of a direct combustion trigger in advanced combustion modes like PCCI, which limits the effectiveness of traditional controllers.
Innovation Solution
A nonlinear model-based closed-loop controller is designed to control the combustion phasing of PCCI in diesel engines, utilizing oxygen fraction dynamics and flexible intake valve actuation, to provide robust control of the start of combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional non-model-based controllers are used in PCCI combustion, then the control structure is simpler, but the control effectiveness is limited due to nonlinear relationships between control inputs and combustion response
Solution Approach 1:
The patent transforms the combustion control problem from direct combustion parameter control to indirect control through oxygen fraction dynamics. By changing the controlled parameter from combustion timing directly to oxygen fraction in the intake manifold, the system achieves better control effectiveness while maintaining reasonable complexity. The nonlinear relationships are managed by controlling the oxygen fraction that governs the combustion process rather than directly controlling combustion timing.
Solution Approach 2:
The patent introduces oxygen fraction as an intermediary variable between the control inputs (intake valve actuation, fuel injection) and the combustion response. This intermediary allows the controller to indirectly influence combustion timing through the oxygen fraction dynamics, providing more effective control compared to direct combustion timing control while avoiding the complexity of directly measuring and controlling combustion parameters.
2Object-generated harmful factors
If advanced combustion modes like PCCI are used, then emissions are reduced, but the lack of direct combustion trigger limits control authority
Solution Approach 1:
The patent implements a closed-loop feedback control system that measures oxygen fraction in the intake manifold and uses this information to adjust control inputs (intake valve timing, fuel injection timing) to achieve desired combustion timing. This feedback mechanism provides the control authority needed for PCCI combustion without requiring direct combustion triggering, while maintaining the emission benefits of the advanced combustion mode.
Solution Approach 2:
The patent controls the oxygen fraction in advance of the combustion event by adjusting intake valve timing and fuel injection timing. By pre-controlling the oxygen fraction and charge composition before combustion occurs, the system establishes the conditions for desired combustion timing without needing direct combustion triggering, thereby maintaining both emission benefits and control authority.
3Manufacturing precision
If flexible intake valve actuation is used to control oxygen fraction dynamics, then combustion phasing control is improved, but device complexity increases
Solution Approach 1:
The patent makes the intake valve actuation system multi-functional by using it for both its traditional function (controlling intake flow) and an additional function (controlling oxygen fraction dynamics for combustion timing). By coordinating the intake valve timing with fuel injection timing, the system achieves precise combustion phasing control without requiring separate dedicated actuators, thereby improving control precision while limiting the increase in device complexity.
Data Source
AI summary
Advanced combustion modes, such as PCCI, operate near the system stability limits. In PCCI, the combustion event begins without a direct combustion trigger in contrast to traditional spark-ignited gasoline engines and direct-injected diesel engines. The lack of a direct combustion trigger encourages the usage of model-based controls to provide robust control of the combustion phasing. The nonlinear relationships between the control inputs and the combustion system response often limit the effectiveness of traditional, non-model-based controllers. Accurate knowledge of the system states and inputs is helpful for implementation of an effective nonlinear controller. A nonlinear controller is developed and implemented to control the engine combustion timing during diesel PCCI operation by targeting desired values of the in-cylinder oxygen concentration, pressure, and temperature during early fuel injection.