Extra-Stroke Engine Cycles for Fuel Efficiency and Exhaust Heat
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Solution Overview
Problem
Existing internal combustion engines operating in a single four-stroke cycle are inefficient at lower torque levels, producing sub-optimal exhaust temperatures and burning fuel at a high rate, and existing methods like the six-stroke cycle do not account for multiple modes of operation or include decompression strokes.
Innovation Solution
Implementing an extra-stroke engine cycle that includes intake, compression, decompression, and power strokes, with a controller transitioning the engine between four-stroke and extra-stroke modes based on engine and aftertreatment system conditions to optimize efficiency and exhaust temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single four-stroke engine cycle is used at all torque levels, then the engine structure remains simple, but fuel efficiency deteriorates and exhaust temperature becomes sub-optimal at lower torque levels
Solution Approach 1:
The engine dynamically switches between four-stroke and extra-stroke modes based on operating conditions such as torque level and aftertreatment system temperature requirements. This dynamic adaptation allows the engine to optimize fuel efficiency at lower torque levels while maintaining simple structure through conditional operation rather than permanent structural modification
Solution Approach 2:
The engine changes operational parameters by introducing an additional stroke (decompression stroke) between compression and power strokes at specific operating conditions. This parameter change enables better control over combustion timing and exhaust temperature without fundamentally altering the engine's basic four-stroke architecture
2Loss of energy
If a six-stroke engine cycle is used, then fuel efficiency improves, but the method does not account for multiple modes of operation or include decompression strokes
Solution Approach 1:
The engine implements dynamic mode switching between four-stroke and extra-stroke cycles based on real-time operating conditions. This allows the engine to adapt to varying torque requirements and aftertreatment temperature needs, providing versatility that fixed six-stroke designs cannot achieve
Solution Approach 2:
The engine design provides multi-functionality by capable of operating in both traditional four-stroke mode and extended extra-stroke mode. This universal operation capability allows the same engine to serve different operating conditions optimally, whether high torque or low torque, without requiring separate engine designs
3Temperature
If the exhaust valve is opened frequently, then exhaust is efficiently removed, but exhaust temperature decreases and aftertreatment system performance deteriorates
Solution Approach 1:
The exhaust valve operation follows a periodic pattern where it remains closed for extended periods during extra-stroke cycles, allowing exhaust temperature to accumulate and increase. This periodic opening strategy balances exhaust removal with temperature maintenance for aftertreatment system effectiveness
Solution Approach 2:
By keeping the exhaust valve closed during the additional decompression and power strokes, the system maintains continuous heat accumulation in the exhaust stream. This continuity of thermal energy ensures sufficient exhaust temperature reaches the aftertreatment system without requiring frequent valve openings that would cool the exhaust
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
Improves fuel efficiency and increases exhaust temperatures, enhancing the operation of aftertreatment systems by adapting engine cycles to varying conditions.
Implementation Method 1
a first compression stroke, immediately subsequent to the intake stroke, in which the mass of air within the combustion chamber is compressed
Implementation Method 2
a decompression stroke, immediately subsequent to the first compression stroke, in which the mass of air within the combustion chamber is decompressed
Implementation Method 3
a second compression stroke, in which the mass of air within the combustion chamber is recompressed
Implementation Method 4
a power stroke, in which an air-fuel mixture including the mass of air and a mass of fuel within the combustion chamber is ignited
Data Source
AI summary
In one instance, disclosed herein is a controller configured for operating an engine in an extra-stroke mode, the controller comprising: a processor; and a memory storing instructions that, when executed by the processor, cause the electronic control module to generate commands for operations including: transitioning operation of the engine from a four-stroke mode to the extra-stroke mode or from the extra-stroke mode to the four-stroke mode, wherein the four-stroke mode includes an intake stroke, a compression stroke, a power stroke, and an exhaust stroke, and wherein the extra-stroke mode includes at least six strokes of a piston disposed within a combustion chamber of an engine cylinder of the engine, during which an exhaust valve of the engine cylinder is opened only once, during or immediately preceding a final upward stroke of the at least six strokes.