Engine Valve Timing Control for Combustion Pressure Stability
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Solution Overview
Problem
Gaseous fuel-powered engines with lean-burn technology face challenges due to variations in combustion pressures between cylinders, leading to engine knock, reduced load rating, and undesirable torque and speed fluctuations, which existing control systems struggle to address effectively due to lag times in adjusting air/fuel mixtures.
Innovation Solution
A control system that includes a controller communicating with actuators to adjust the timing of engine valves based on engine speed signals, allowing for instantaneous regulation of air/fuel mixture delivery, thereby minimizing pressure variations and improving responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If throttle valves are adjusted to control air/fuel mixture delivery, then combustion pressure can be maintained, but lag time of 3-5 seconds occurs between adjustment and corresponding change in combustion pressure
Solution Approach 1:
The system performs preliminary action by adjusting the valve timing of the intake valve before combustion occurs. By controlling when the intake valve opens and closes, the system pre-determines the amount of air/fuel mixture entering the cylinder, which directly affects combustion pressure. This preliminary control of charge admission eliminates the lag time associated with throttle valve adjustment, as the valve timing can be changed instantaneously by the actuator without the 3-5 second delay inherent in throttle-based systems.
2Reliability
If margin of error is increased to accommodate pressure variations between cylinders, then engine reliability improves, but load rating must be reduced
Solution Approach 1:
The system applies local quality by independently controlling the valve timing for each cylinder through individual actuators. This allows each cylinder to be optimized for its specific combustion characteristics and pressure variations, rather than applying a uniform margin of error across all cylinders. By locally adjusting the intake valve timing in each cylinder based on its specific needs, the system can maintain reliable operation while maximizing the load rating of each individual cylinder, thereby increasing overall engine power output.
3Ease of operation
If conventional throttling systems are used to control air/fuel mixture, then engine speed and torque can be regulated, but significant lag time reduces responsiveness
Solution Approach 1:
The system replaces the mechanical throttling system with an actuated valve timing control system. Instead of using a mechanical throttle valve that requires physical adjustment and has inherent lag, the system uses an actuator to precisely control the timing of the intake valve. This substitution of the control mechanism eliminates the mechanical lag of throttling systems, as the actuator can instantaneously adjust valve timing in response to control signals, thereby significantly improving the response speed for engine speed and torque regulation while maintaining ease of operation.
Data Source
AI summary
A control system for an engine having a cylinder is disclosed having an engine valve movable to regulate a fluid flow of the cylinder and an actuator associated with the engine valve. The control system also has a controller in communication with the actuator. The controller is configured to receive a signal indicative of engine speed and compare the engine speed signal with a desired engine speed. The controller is also configured to selectively regulate the actuator to adjust a timing of the engine valve to control an amount of air/fuel mixture delivered to the cylinder based on the comparison.