Dedicated EGR Engine Fueling Control for Catalyst Durability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Water gas shift catalysts used in dedicated exhaust gas recirculation engines experience rapid deactivation due to catalyst coking from constant exposure to rich exhaust gases, leading to a loss in reactivity and efficiency.
Innovation Solution
Implementing a fueling strategy that alternates between rich and lean engine cycles to prevent coke buildup on the catalyst surface, with the dedicated cylinder being leaned out every 8 to 10 engine cycles to produce excess oxygen and burn off carbon deposits, and adjusting spark timing and fuel injection to maintain optimal combustion conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dedicated cylinder operates continuously at rich fuel-to-air equivalence ratios to produce hydrogen through water gas shift reaction, then hydrogen production and combustion stability are improved, but the water gas shift catalyst rapidly deactivates due to coke buildup
Solution Approach 1:
The system alternates between rich and lean operating modes in a periodic cycle. The dedicated cylinder operates at rich equivalence ratios for a first number of cycles to produce hydrogen, then switches to lean operation for a second number of cycles to regenerate the catalyst by burning off coke deposits. This periodic switching resolves the contradiction by allowing the catalyst to remain durable while still producing hydrogen during the rich phases.
Solution Approach 2:
The system temporarily sacrifices hydrogen production during lean cycles to recover catalyst activity. By deliberately operating in a lean mode, the system burns off accumulated coke on the catalyst surface, restoring its ability to facilitate the water gas shift reaction. This recovery process enables long-term sustained hydrogen production rather than continuous operation leading to complete deactivation.
2Duration of action of stationary object
If the dedicated cylinder is leaned out every 8 to 10 engine cycles to burn off carbon deposits, then catalyst life is extended, but combustion efficiency and power output decrease during lean cycles
Solution Approach 1:
The system implements periodic lean operation at predetermined intervals (every 8-10 cycles) to maintain catalyst health. During these brief lean phases, power output is temporarily reduced, but the majority of cycles operate at rich conditions for optimal power and hydrogen production. This periodic maintenance approach extends catalyst service life while minimizing impact on overall engine performance.
Solution Approach 2:
The system dynamically changes the fuel-to-air equivalence ratio parameter between rich and lean states. By adjusting this fundamental combustion parameter, the system enables the dedicated cylinder to switch between power-producing rich mode and catalyst-regenerating lean mode. The electronic control unit modifies injection timing and duration to achieve the desired equivalence ratio changes, balancing power output with catalyst durability.
3Stability of the object's composition
If rich operation is maintained to maximize hydrogen production, then combustion stability improves, but coke deposits accumulate on the catalyst surface reducing reactivity
Solution Approach 1:
The system employs periodic switching between rich and lean operation to maintain both combustion stability and catalyst reactivity. During rich phases, hydrogen production and combustion stability are maximized. During lean phases, the catalyst is regenerated by oxidizing coke deposits. This periodic action ensures that the catalyst maintains its reactivity over time while still providing the combustion stability benefits of rich operation during the majority of cycles.
Solution Approach 2:
The system maintains continuous useful action by ensuring that hydrogen production during rich cycles compensates for the temporary reduction during lean cycles. The overall hydrogen production remains positive and useful, while the catalyst reactivity is continuously restored through periodic lean operation. This approach ensures that neither combustion stability nor catalyst reactivity are permanently compromised.
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 strategy effectively prolongs the life of the water gas shift catalyst by preventing complete deactivation, maintaining hydrogen production and improving engine efficiency and combustion stability.
Implementation Method 1
The water gas shift reaction has been employed in industrial processes to produce H2 from water vapor and carbon monoxide. The basic water gas shift reaction is set forth in Equation 1, provided below. CO+H2O ⇄CO2+H2
Implementation Method 2
The air and fuel in the main and dedicated cylinders are combusted
Implementation Method 3
Each of the main cylinder and the dedicated cylinder comprises an intake valve, an exhaust valve and a spark plug
Data Source
AI summary
A method of operating an dedicated exhaust gas recirculation engine including a water gas shift catalyst by supplying ambient air and fuel to a dedicated cylinder at a first fuel to air equivalence ratio in the range of greater than 1.0 to 1.6 for a first number of engine cycles and, for a second number of engine cycles, supplying ambient air and fuel to the dedicated cylinder at a second fuel to air equivalence ratio in the range of 0.7 to less than 1.0. During the second number of cycles, spark timing of the dedicated cylinder is adjusted and a time delay when exhaust recirculated from the dedicated cylinder will be inducted into the cylinders is determined. At the end of the time delay, a second spark timing of the main cylinder is adjusted and the amount of fuel supplied to the main cylinders is increased.