Skip-Spark Engine Control for Load Shedding Stability
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Solution Overview
Problem
Rapid load shedding in pre-mixed spark-ignited and dual fuel engines leads to exhaust manifold over-pressure events and engine overspeeding, which can damage components and increase emissions.
Innovation Solution
A control strategy that dynamically adjusts the number of skipped combustion cycles and fuel injection to maintain exhaust air-fuel ratio within flammability limits, preventing uncombusted fuel from entering the exhaust system and minimizing engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional load shedding is used to reduce fuel consumption, then fuel efficiency improves, but engine stability deteriorates due to large torque fluctuations
Solution Approach 1:
The load shedding event is divided into multiple sequential phases: initial load reduction, skip-spark period with reduced or zero fuel injection, and recovery phase. This segmentation allows the engine to shed load gradually while maintaining stability through controlled transitions between phases, preventing the abrupt torque changes that would otherwise occur with conventional single-step load shedding.
Solution Approach 2:
The skip-spark strategy implements periodic cycles of spark ignition and non-spark (or reduced fuel) injection events. During the skip-spark period, the engine alternates between normal combustion cycles and skipped cycles, creating a periodic pattern that averages out torque fluctuations while maintaining reduced fuel consumption over the complete cycle.
2Use of energy by moving object
If load reduction is implemented to improve fuel efficiency, then energy consumption decreases, but torque delivery becomes inconsistent
Solution Approach 1:
Before implementing load shedding, the control system performs preliminary assessments of engine operating conditions, including torque requirements and stability margins. This preliminary action allows the system to determine optimal skip-spark timing and duration, ensuring that torque delivery remains adequate for the driving conditions while still achieving fuel savings.
Solution Approach 2:
The control system continuously monitors engine operating parameters including torque output, speed, and combustion characteristics during skip-spark operation. This feedback allows real-time adjustment of fuel injection timing and quantity, as well as spark timing, to maintain consistent torque delivery despite the periodic skipped cycles, thereby balancing fuel efficiency with power consistency.
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
Reduces exhaust manifold over-pressure events and engine overspeeding by controlling uncombusted fuel flow, thereby protecting components and reducing emissions.
Implementation Method 1
skip-spark/fuel strategy...cycles of spark and non-spark or reduced fuel injection events
Data Source
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AI summary
Systems, apparatus and methods include control techniques for controlling operation of pre-mixed internal combustion engines in response to a load shedding event. The control techniques determine, in response to the load shedding event, a number of cycles in which to skip combustion of the fuel in the at least one cylinder based on an air- fuel ratio limit in the exhaust flow, prevent combustion of the fuel in the at least one cylinder during the number of skipped cycles, and combust the fuel in the at least one cylinder each time the number of skipped cycles are complete.