Cam Phaser Control for Gaseous Engine Startup
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Solution Overview
Problem
Gaseous-fueled engines employing late inlet closing (LIC) timing face challenges with engine startup due to reduced charge in the cylinder, leading to inefficient combustion, and existing solutions like hydraulically controlled cam phasers complicate the engine and increase costs.
Innovation Solution
A control system with a variable valve timing device, including a sensor and controller, selectively switches between early and late Miller Cycle timings based on engine speed to optimize intake valve timing for reliable startup and high-speed efficiency, utilizing a hydraulically-actuated cam phaser to adjust valve timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If late inlet closing (LIC) timing is used to improve mechanical output and reduce emissions, then engine efficiency is improved, but engine startup reliability deteriorates due to reduced charge in the cylinder
Solution Approach 1:
The patent applies variable valve timing that dynamically adjusts the intake valve closing timing based on engine operating conditions. During startup, the valve closes early to maintain sufficient charge for reliable combustion. During normal operation, the valve closes late to improve mechanical output and reduce emissions, thus resolving the contradiction between startup reliability and operational efficiency
2Reliability
If an auxiliary hydraulic pump is added to enable valve timing adjustment for startup, then startup reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent employs a cam phaser that is self-actuating through hydraulic pressure generated by the engine's own operation. The cam phaser utilizes the engine's hydraulic system and operational pressure to automatically adjust valve timing, eliminating the need for an external electric motor-driven pump while maintaining the ability to optimize timing for both startup and operation
3Object-generated harmful factors
If intake valve closes later during LIC timing, then emissions are reduced, but charge amount in cylinder decreases
Solution Approach 1:
The variable valve timing system dynamically adjusts intake valve closing timing based on engine speed and load conditions. At low speeds during startup, the valve closes early to maintain sufficient charge amount for reliable combustion. At higher operating speeds, the valve closes late to reduce emissions, thus dynamically resolving the contradiction between charge amount and emissions control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables smooth and reliable engine startup with early Miller Cycle timing and high-speed efficiency using late Miller Cycle timing, improving mechanical output and reducing emissions without increasing complexity or cost.
Implementation Method 1
A cam phaser may be utilized to adjust the cyclical opening and closing timing of the intake valve
Data Source
AI summary
A control system for a gaseous-fueled engine is disclosed. The gaseous-fueled engine may have an intake valve mechanically driven by a camshaft. The control system may have a variable valve timing device configured to adjust a cyclical opening and closing timing of the intake valve. The control system may further have a sensor configured to generate a signal indicative of a speed of the engine and a controller in communication with the variable valve timing device and the sensor. In addition, the controller may be configured to selectively initiate a first Miller Cycle timing and a second Miller Cycle timing based on the signal.