HC Adsorbent and NOx Catalyst Temperature Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In engines with both a nitrogen oxide (NOx) catalyst and a hydrocarbon (HC) adsorbent and diesel oxidation catalyst in the exhaust passage, the purification performance of the NOx catalyst is compromised due to HC release during NOx removal, leading to excessive temperature increases and reduced catalyst effectiveness.
Innovation Solution
An exhaust emission control device with a first HC adsorbent that adsorbs HC at low temperatures and releases it at high temperatures, a NOx catalyst for storing and regenerating NOx, and a diesel oxidation catalyst, along with an HC controller that manages HC adsorption and release to prevent excessive temperature rises, ensuring the NOx catalyst's performance is maintained by injecting fuel to control HC release and using a selective catalytic reduction (SCR) catalyst downstream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the HC adsorbent and diesel oxidation catalyst are disposed in the exhaust passage together with the NOx catalyst, then the amount of HC discharged to the outside of the engine can be kept small, but the purification performance of the NOx catalyst may be declined
Solution Approach 1:
The exhaust passage is segmented into multiple functional zones: an upstream first purifying catalyst device containing HC adsorbent and diesel oxidation catalyst, and a downstream second purifying catalyst device containing NOx catalyst. This spatial segmentation allows HC to be adsorbed and oxidized upstream before reaching the NOx catalyst, preventing HC from interfering with NOx purification while maintaining separate functional optimization for each catalyst type.
2Reliability
If control for removing NOx from the NOx catalyst is performed by raising the temperature of the NOx catalyst, then NOx can be removed from the NOx catalyst, but a large amount of HC is released from the HC adsorbent and the temperature of the NOx catalyst is further raised, possibly declining the performance of the NOx catalyst
Solution Approach 1:
The HC adsorbent is pre-loaded with HC during cold start or low-temperature operation. When the NOx catalyst requires regeneration and temperature needs to be raised, the stored HC in the upstream HC adsorbent is released and immediately oxidized by the diesel oxidation catalyst, providing controlled heat release that raises the NOx catalyst temperature to the required level (300-400°C) without excessive temperature increase that would damage catalyst performance.
Solution Approach 2:
The diesel oxidation catalyst acts as an intermediary between the released HC and the NOx catalyst. It oxidizes the HC in a controlled manner, converting it to CO2 and H2O while releasing heat at a controlled rate. This intermediary oxidation process prevents direct uncontrolled combustion that would cause excessive temperature rise, thereby protecting the NOx catalyst from thermal damage while still achieving the necessary temperature for NOx removal.
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 configuration effectively suppresses HC and NOx emissions, maintains high NOx catalyst purification performance, and prevents excessive temperature increases, ensuring efficient engine exhaust treatment.
Implementation Method 1
a hydrocarbon (HC) adsorbent that adsorbs HC at a low temperature (e.g. 400° C., or less such as 300° C., 200° C. or lower) and releases HC at a high temperature
Implementation Method 2
a diesel oxidation catalyst capable of oxidizing HC
Implementation Method 3
a nitrogen oxide (NOx) catalyst capable of storing NOx contained in exhaust
Implementation Method 4
a NOx catalyst regenerator that regenerates the NOx catalyst while raising a temperature of the NOx catalyst
Implementation Method 5
the HC controller causes the fuel injector to inject the fuel into the cylinder in a first half of a combustion stroke and the fuel to burn in the cylinder
Data Source
AI summary
An exhaust emission control device for an engine is provided with a first purifying catalyst including an HC adsorbent that adsorbs HC at a low temperature and releases HC at a high temperature and a diesel oxidation catalyst capable of oxidizing HC, a second purifying catalyst including a NOx catalyst capable of storing NOx contained in exhaust, a NOx catalyst regenerator that regenerates the NOx catalyst while raising the temperature of the NOx catalyst, and HC controller that decides whether the amount of adsorbed HC that is HC adsorbed by the HC adsorbent is equal to or more than a preset reference amount and, when the amount of adsorbed HC is decided to be equal to or more than the reference amount, raises the temperature of the first purifying catalyst.