Pre-DOC Exhaust Purification System Multistage Injection Control
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Solution Overview
Problem
Existing exhaust gas purification systems face challenges in improving NOx purification rates at low temperatures and preventing unburned hydrocarbon (HC) slip, which leads to white smoke generation, especially in diesel engines, due to inadequate activation of catalysts and inefficient temperature control.
Innovation Solution
The system incorporates a pre-stage oxidation catalyst (Pre-DOC) upstream of the main exhaust gas purification device, with a control mechanism for multistage temperature rise injection and post-injection to ensure the pre-DOC is activated early, oxidizing HC and raising exhaust gas temperatures efficiently, thereby enhancing NOx purification and DPF regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature rise control is executed to activate the catalyst, then NOx purification rate is improved, but unburned hydrocarbon slip increases causing white smoke generation
Solution Approach 1:
The pre-oxidation catalyst is positioned upstream of the main exhaust gas purification device to preliminarily oxidize unburned hydrocarbons before they reach the main catalyst. This preliminary action prevents HC slip while the main catalyst is being activated by temperature rise control, resolving the contradiction between improving NOx purification and preventing white smoke generation.
2Loss of time
If multistage temperature rise injection is performed to raise exhaust gas temperature, then catalyst activation is expedited, but fuel consumption increases
Solution Approach 1:
The pre-oxidation catalyst utilizes the heat from multistage temperature rise injection to oxidize unburned hydrocarbons, converting chemical energy to thermal energy that then serves to activate the main catalyst. This self-service mechanism reduces the additional fuel injection needed for catalyst activation, thereby reducing overall fuel consumption while maintaining rapid catalyst activation.
3Object-generated harmful factors
If the pre-stage oxidation catalyst is positioned upstream, then HC oxidation is enhanced, but system complexity increases
Solution Approach 1:
The pre-oxidation catalyst is integrated into the existing exhaust gas purification system architecture, merging its function with the main catalyst system. This combining approach enhances HC oxidation capability while minimizing the increase in system complexity by utilizing the existing structural framework and control mechanisms.
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 prevents HC slip and improves NOx purification rates and DPF regeneration efficiency, even at low temperatures, by ensuring the pre-DOC is activated early and maintaining optimal temperatures for catalyst activity.
Implementation Method 1
a pre-oxidation catalyst... oxidizing HC and raising exhaust gas temperatures efficiently
Implementation Method 2
oxidizing HC and raising exhaust gas temperatures efficiently
Data Source
AI summary
Exhaust gas of an internal combustion engine is made to pass through an exhaust gas purification device after passing through a pre-oxidation catalyst. When a first temperature of the exhaust gas on an upstream side of the device is lower than a first set temperature, multistage temperature rise injection is performed. When the first temperature becomes the first set temperature or more, post injection is performed in addition to the multistage temperature rise injection, and feedback control of the post injection is executed so that a second temperature of the exhaust gas on a downstream side of the exhaust gas purification device becomes a second set temperature.