Internal Combustion Engine EGR Control via Dynamic Valve Timing
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Solution Overview
Problem
Internal combustion engines face challenges in reducing nitrogen oxide (NOx) emissions effectively while maintaining fuel efficiency, particularly under stringent regulations like IMO Tier III, where traditional methods such as exhaust gas recirculation (EGR) and Miller cycles require early intake valve closing, leading to decreased cylinder fill and increased specific fuel oil consumption (SFOC).
Innovation Solution
The method employs a turbocharged internal combustion engine with a by-pass duct and valve system that allows for controlled internal EGR and water injection, using different valve overlap durations and the by-pass valve to regulate EGR rates, avoiding the need for extremely early Miller timing and maintaining fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If early intake valve closing timing is used to achieve high EGR rate and lower NOx emissions, then NOx emissions are reduced, but cylinder fill decreases and specific fuel oil consumption increases
Solution Approach 1:
The patent applies variable valve timing to dynamically adjust intake valve closing timing based on operating conditions. During low load operation, early intake valve closing is used to achieve high EGR rates and low NOx emissions. During high load operation, the timing is optimized to maintain cylinder fill and power output, thereby avoiding excessive SFOC increases while still achieving emission reductions when needed.
Solution Approach 2:
The patent changes the timing parameter of intake valve closing dynamically. By adjusting the crank angle position of intake valve closing based on load conditions, the system achieves high EGR rates during low load (reducing NOx) while maintaining adequate cylinder fill during high load (preventing excessive SFOC increase).
2Object-generated harmful factors
If very early intake valve closing is used to achieve high EGR rate, then NOx emissions are reduced, but power output decreases
Solution Approach 1:
The patent uses dynamic valve timing control to apply very early intake valve closing only during low load operation when power output requirements are minimal. During high load operation, the intake valve closing timing is adjusted to a less extreme position to maintain adequate cylinder fill and power output, while still achieving sufficient EGR rates through the coordinated action of exhaust valve timing.
Solution Approach 2:
The patent employs periodic adjustment of valve timing parameters based on operating cycle conditions. The valve timing is optimized periodically according to load demands, allowing very early closing during low load periods for maximum EGR and NOx reduction, while transitioning to more conventional timing during high load periods to maintain power output.
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 achieves low NOx emissions without compromising fuel efficiency by controlling EGR rates through valve overlap and by-pass valve adjustments, allowing for flexible operation modes to meet varying NOx emission limits, such as IMO Tier II and Tier III requirements.
Implementation Method 1
water is injected into the exhaust ports for cooling the recirculated exhaust gas
Implementation Method 2
water is injected into the exhaust ports for cooling the recirculated exhaust gas
Implementation Method 3
at least one turbocharger, which comprises a turbine and a compressor
Implementation Method 4
at least one turbocharger, which comprises a turbine and a compressor
Data Source
Figure 1
AI summary
The method for operating an internal combustion engine (1) comprises at least two different operating modes. In at least one operating mode the intake valves (12) are closed during the intake stroke before bottom dead center for lowering the pressure in the cylinders (3), and internal exhaust gas recirculation (EGR) is used by reopening the exhaust valves (13) after the closing of the intake valves and before bottom dead center for allowing exhaust gas recirculation from the exhaust duct (4) into the cylinders (3). Water is injected into exhaust ports (4a) for cooling the recirculated exhaust gas. Different valve overlap durations are used in different operating modes for regulating the amount of the exhaust gas that is trapped within the cylinders (3) and in at least one operating mode the amount of the recirculated exhaust gas is regulated by means of a by-pass valve (7) that is arranged between an intake duct (2) and an exhaust duct (4) of the engine (1).