Hydrogen Engine Controller Urea Deposition SCR
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Solution Overview
Problem
Hydrogen engines with urea SCR systems face challenges in maintaining adequate exhaust gas temperature for effective urea deposition control, leading to increased frequency of burning control due to lower exhaust gas temperatures compared to diesel engines.
Innovation Solution
A controller for a hydrogen engine that adjusts the urea addition amount and air-fuel ratio to suppress urea deposition in the SCR device, by setting a higher urea addition start temperature and implementing a lean-burn limiting process when deposition exceeds a specified value, and performing burning control when necessary to raise the SCR device temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If urea SCR system is employed in hydrogen engine, then NOx reduction is achieved, but urea deposition in SCR device increases due to lower exhaust gas temperature
Solution Approach 1:
The controller changes the urea addition amount parameter based on the estimated urea deposition amount. When deposition is detected to be at or above a threshold, the controller reduces the urea addition amount to a lower level, thereby preventing excessive deposition while maintaining effective NOx reduction.
2Reliability
If burning control is performed frequently to remove deposited urea, then SCR device temperature is maintained, but engine performance and fuel efficiency deteriorate
Solution Approach 1:
The controller continuously monitors the estimated urea deposition amount and uses this feedback to adjust urea addition accordingly. By implementing feedback control, the system can prevent excessive deposition without requiring frequent burning control, thus maintaining SCR reliability while preserving engine performance.
3Object-generated harmful factors
If urea addition amount is increased to improve NOx reduction, then NOx emissions decrease, but urea deposition in SCR device accelerates
Solution Approach 1:
The controller dynamically adjusts the urea addition amount based on real-time estimation of urea deposition. The system transitions between different urea addition levels (normal addition when deposition is low, reduced addition when deposition is high), creating a dynamic control strategy that balances NOx reduction with deposition prevention.
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
Effectively suppresses urea deposition in the SCR device, reduces NOx emissions, and minimizes the frequency and duration of burning control, thereby optimizing engine performance and fuel efficiency.
Implementation Method 1
an SCR device, which reduces nitrogen oxide (NOx) in the exhaust gas through selective catalytic reduction
Implementation Method 2
the controller performs a burning control for burning the deposited urea by increasing the temperature of the exhaust gas
Data Source
AI summary
A controller for a hydrogen engine controls a hydrogen engine including a selective catalytic reduction (SCR) device installed in an exhaust passage and a urea addition valve that adds urea to exhaust gas flowing through a portion of the exhaust passage upstream of the SCR device. Processing circuitry of the controller executes a reduction process that causes a urea addition amount of the urea addition valve to be smaller when a urea deposition amount of the SCR device is greater than or equal to a prescribed value than when the urea deposition amount is less than the prescribed value. The processing circuitry executes a lean-burn limiting process that sets an air-fuel ratio of an air-fuel mixture to be burned in the hydrogen engine to a value less than or equal to a prescribed lean-burn limiting value while the reduction process is reducing the urea addition amount.