Intake Valve Timing Control for Lean-Burn Engine Emissions
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Solution Overview
Problem
Lean-burn internal combustion engines fueled with gaseous fuels face high unburned hydrocarbon emissions, particularly at low engine loads due to low equivalence ratios and cylinder temperatures, which existing techniques have not effectively addressed.
Innovation Solution
Adjusting the timing of the intake valve closure in lean-burn internal combustion engines, either by advancing or retarding it, to maintain an equivalence ratio between 0.4 and 0.95, and employing variable valve actuation systems to control the timing of intake and exhaust valves, thereby reducing unburned hydrocarbon emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the equivalence ratio is reduced to control engine load in lean-burn engines, then fuel economy and efficiency are improved, but unburned hydrocarbon emissions increase
Solution Approach 1:
The patent changes the timing parameter of intake valve closure to control the equivalence ratio. By advancing or retarding the intake valve closure timing, the engine can maintain higher equivalence ratios (0.4-0.95) even at low loads, which improves combustion completeness and reduces unburned hydrocarbon emissions while maintaining fuel economy benefits of lean operation
Solution Approach 2:
The patent employs dynamic adjustment of intake valve closure timing based on operating conditions. The variable valve actuation system allows the engine to adapt the equivalence ratio dynamically across different load and speed conditions, optimizing the balance between fuel economy and emissions reduction
2Object-generated harmful factors
If the cylinder temperature is increased to reduce unburned hydrocarbon emissions, then combustion completeness is improved, but NOx emissions and thermal stress increase
Solution Approach 1:
Instead of changing temperature directly, the patent changes the equivalence ratio parameter through intake valve timing control. By maintaining higher equivalence ratios (0.4-0.95) via variable valve actuation, the system improves combustion completeness and reduces unburned hydrocarbons without the need for temperature increase, thereby avoiding NOx emission increases
3Object-generated harmful factors
If variable valve actuation is implemented to control equivalence ratio, then unburned hydrocarbon emissions are reduced, but device complexity increases
Solution Approach 1:
The variable valve actuation system performs multiple functions: it controls equivalence ratio to reduce unburned hydrocarbon emissions, maintains boost pressure for transient performance, and reduces turbo-lag. By making the valve actuation system multi-functional, the patent justifies the increased device complexity through multiple performance benefits
4Object-generated harmful factors
If intake valve closure timing is advanced to reduce emissions, then equivalence ratio is improved, but volumetric efficiency decreases
Solution Approach 1:
The patent uses dynamic adjustment of intake valve closure timing rather than a fixed advanced timing. The system advances or retards timing based on real-time operating conditions, allowing the engine to maintain high volumetric efficiency at most operating points while achieving emission reductions when needed through localized timing adjustments
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
This approach effectively maintains unburned hydrocarbon emissions below a predetermined level by optimizing the equivalence ratio and volumetric efficiency, even at low engine loads, and improves transient engine performance by maintaining boost pressure and reducing turbo-lag.
Implementation Method 1
adjusting the timing for closing of an intake valve as a function of engine operating conditions
Implementation Method 2
combust a mixture of the air and gaseous fuel to generate a power output and a flow of exhaust
Implementation Method 3
maintaining boost pressure
Data Source
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AI summary
It is a challenge to reduce unburned hydrocarbon emissions for gaseous fuelled engines, especially at low engine load conditions, to meet demanding emission regulation targets. A method for reducing unburned hydrocarbon emissions in a lean- burn internal combustion engine that is fuelled with a gaseous fuel comprises adjusting the timing for closing of an intake valve as a function of engine operating conditions by one of advancing timing for closing of the intake valve and closing the intake valve earlier during an intake stroke; and retarding timing for closing of the intake valve and closing the intake valve later during a compression stroke. The volumetric efficiency of the internal combustion engine is reduced and unburned hydrocarbon emissions are maintained below a predetermined level.