Hydrogen Engine ASC Regeneration Using H2-Rich Exhaust
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Solution Overview
Problem
Existing hydrogen combustion engine systems face challenges in efficiently regenerating the ammonia slip catalyst (ASC) due to the formation of NOx during high-temperature combustion, necessitating an effective exhaust aftertreatment system (EATS) that requires periodic maintenance or regeneration.
Innovation Solution
A method for controlling the hydrogen combustion engine system that identifies a regeneration time window based on temperature criteria and operates in an H2 exhaust excess mode to regenerate the ASC using unburnt H2, achieving a regeneration temperature of at least 500°C by injecting H2 during specific engine cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the hydrogen combustion engine operates at high temperature to improve combustion efficiency, then power output increases, but NOx formation increases and ASC regeneration becomes more difficult
Solution Approach 1:
The system alternates between normal operation mode and H2 exhaust excess mode periodically. During normal operation, the engine operates efficiently for power generation. When ASC soot accumulation reaches a threshold, the system switches to H2 exhaust excess mode to perform ASC regeneration, then returns to normal operation. This periodic switching resolves the contradiction by allowing high-temperature efficient combustion during normal operation while periodically addressing the NOx and ASC regeneration issues.
Solution Approach 2:
The system changes the H2 concentration parameter in the exhaust gas by operating the engine at different load points. In H2 exhaust excess mode, the engine operates at a specific load point that produces exhaust with H2 concentration above 1.5 mol%, which is sufficient for ASC regeneration. This parameter change allows the system to achieve both power output and ASC regeneration by selecting appropriate operating conditions.
2Reliability
If the ASC is regenerated frequently to maintain emission reduction performance, then emission control reliability improves, but system complexity and maintenance requirements increase
Solution Approach 1:
The system uses its own H2 exhaust gas to regenerate the ASC, eliminating the need for external regeneration equipment or additional chemicals. The H2 already present in the exhaust (at ≥1.5 mol% concentration) is utilized to burn off soot from the ASC, making the regeneration process self-contained and simple. This self-service approach maintains emission control reliability while avoiding increased system complexity.
3Reliability
If the engine operates in H2 exhaust excess mode continuously to ensure ASC regeneration, then ASC performance is maintained, but fuel consumption increases
Solution Approach 1:
The system operates in H2 exhaust excess mode only periodically when ASC soot accumulation reaches a predetermined threshold, not continuously. The control unit monitors ASC soot load and switches to H2 exhaust excess mode only when regeneration is needed, then returns to normal efficient operation mode. This periodic operation maintains ASC performance while minimizing fuel consumption by avoiding unnecessary H2 excess operation during periods when regeneration is not required.
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
The method efficiently regenerates the ASC by burning H2, effectively removing particles and pollutants, thereby enhancing the performance and reducing the need for frequent maintenance of the EATS.
Implementation Method 1
During the regeneration of the ASC, H2 is burned in the ASC resulting in the increased temperature, whereby regeneration of the ASC is achieved.
Implementation Method 2
an exhaust aftertreatment system, EATS, configured to reduce emissions of the engine exhausts, the EATS comprising a selective catalyst reduction, SCR, catalyst
Implementation Method 3
an ammonia slip catalyst, ASC, arranged downstream of the SCR catalyst
Data Source
AI summary
A method for controls the operation of a hydrogen combustion engine system of a vehicle including a hydrogen combustion engine and an exhaust aftertreatment system, EATS, to reduce emissions in the engine exhausts. The EATS comprises a selective catalyst reduction, SCR, catalyst and an ammonia slip catalyst, ASC, arranged downstream of the SCR catalyst. The method includes: identifying a regeneration time window for performing regeneration of the ASC; in response of identifying the regeneration time window, operating the hydrogen combustion engine in an H2 exhaust excess mode defined by an amount of unburnt H2 of at least 1.5 mol % in the engine exhaust and regenerating the ASC by using the unburnt H2 in the engine exhausts and reaching a regeneration temperature of at least 500° C.