Dynamic NOx Target Control for Diesel Depollution
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Solution Overview
Problem
Existing diesel engine depollution systems face challenges in effectively reducing NOx emissions when operating under non-nominal conditions, leading to excessive reducing agent flow rates that can exceed the capacity of pollution control devices, thereby reducing their lifespan.
Innovation Solution
A method that determines the target NOx quantity in exhaust gases based on external pressure, using a selective catalytic reduction system with an electronic control unit to adjust the injection of a reducing agent, ensuring compatibility with device limits and extending the system's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If large flows of reducing agent are injected to treat all NOx produced under non-nominal conditions, then NOx depollution effectiveness is improved, but the lifespan of the depollution device is reduced
Solution Approach 1:
The patent applies dynamics by making the target NOx quantity dynamic rather than fixed. The electronic control unit adjusts the target quantity based on real-time external pressure measurements, allowing the system to adapt to varying operating conditions. This dynamic adjustment prevents excessive reducing agent injection while maintaining effective NOx depollution across different environmental conditions.
Solution Approach 2:
The patent changes the parameter of target NOx quantity based on external pressure conditions. By measuring external pressure and adjusting the target quantity accordingly, the system optimizes reducing agent flow rates to match actual depollution needs, avoiding both over-injection (which reduces device lifespan) and under-injection (which reduces depollution effectiveness).
2Object-affected harmful factors
If the target quantity of NOx is set to handle maximum emissions under all conditions, then depollution effectiveness under non-nominal conditions is improved, but reducing agent flow rates exceed device capacity
Solution Approach 1:
The system dynamically adjusts the target NOx quantity based on external pressure measurements. Under non-nominal conditions (e.g., high altitude, low pressure), the target quantity is increased appropriately, but not to the maximum level that would cause excessive reducing agent flow. This dynamic parameter adjustment ensures effective depollution while keeping reducing agent flow rates within device capacity.
Solution Approach 2:
The electronic control unit implements feedback by continuously measuring external pressure and adjusting the target NOx quantity accordingly. This closed-loop control ensures that the reducing agent flow rate responds appropriately to actual environmental conditions, preventing both insufficient depollution and excessive reducing agent consumption that would exceed device capacity.
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 reduces NOx emissions under varying conditions while prolonging the service life of the pollution control device by optimizing reducing agent flow rates and adhering to emission standards.
Implementation Method 1
The document describes a selective catalytic reduction system which consists of injecting a NOx reducing solution, the injection being controlled dynamically in order to take into account the stoichiometric proportions defined by the following reactions
Implementation Method 2
4NH3 + 4NO + O2 → 4N2 + 6H2O; 2NH3 + NO + NO2 → 2N2 + 3H2O; 4NH3 + 2NO2 + O2 → 3N2 + 6H2O
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for removing NOx from an engine comprising an exhaust line, implemented in a catalyst, comprising the steps of: -determining a quantity (14) of NOx actually produced by the engine, -determining a target (16) of NOx not to be exceeded at the exhaust outlet, -comparing the quantity of NOx actually produced by the given engine with this target (16) of quantity of nitrogen oxides not to be exceeded, and if the quantity of NOx actually produced by the engine is greater than this target (16), treating the nitrogen oxides, as long as the quantity of NOx actually produced is greater than the target (16) not to be exceeded at the outlet of the line, characterized in that the target (16) of quantity of NOx in the exhaust gases not to be exceeded at the outlet of the line is determined as a function of the external pressure (Pext).