Particulate Filter Regeneration Using Ram-Air Bypass
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Solution Overview
Problem
Turbocharged direct-injection engines generate increased soot due to inadequate air-fuel mixing at high speeds and loads, leading to challenges in particulate filter regeneration in spark-ignition engines, particularly concerning NOx emissions and excess oxygen saturation in three-way catalysts.
Innovation Solution
The method involves directing exhaust to a three-way catalyst and then to a particulate filter during combustion, and using ram-air to regenerate the filter during non-combustion engine conditions, while adjusting operations during and after shutdown to manage excess oxygen levels and reduce NOx emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If excess oxygen is supplied to the particulate filter for regeneration, then the filter can be regenerated effectively, but the three-way catalyst becomes saturated with oxygen and NOx emissions increase
Solution Approach 1:
The exhaust flow is segmented into two separate paths: one path directs oxygen-depleted exhaust to the three-way catalyst for emission control, while another path introduces ram-air to provide oxygen for particulate filter regeneration. This segmentation allows independent control of oxygen levels at each device, preventing catalyst saturation while enabling effective filter regeneration.
Solution Approach 2:
Ram-air acts as an intermediary substance that introduces oxygen to the particulate filter without passing through the three-way catalyst. The ram-air inlet is positioned to draw in fresh air that bypasses the catalyst, serving as a mediator that supplies regeneration oxygen independently of the catalyst's oxygen storage capacity.
2Power
If the engine operates at high speed and high load to meet power demands, then vehicle performance is improved, but air-fuel mixing becomes inadequate and soot generation increases
Solution Approach 1:
The system converts the harmful soot generated during high-power operation into a manageable byproduct that can be periodically removed through regeneration. Rather than attempting to prevent soot formation during high-load operation, the system allows soot accumulation and then uses controlled oxygen introduction to burn off the particulates, transforming the harmful effect into a controlled regeneration process.
Solution Approach 2:
The system allows soot to accumulate in the particulate filter during normal high-power operation, then periodically discards the accumulated soot through controlled combustion during regeneration events. The filter captures and holds the harmful particulates, then enables their removal through oxygen-supplied burning, effectively discarding the harmful byproduct while maintaining continuous power output.
3Reliability
If the particulate filter is regenerated during engine shutdown, then the three-way catalyst is protected from oxygen saturation, but the vehicle is stationary and ram-air flow is limited
Solution Approach 1:
The system dynamically adjusts the ram-air inlet positioning based on vehicle operating conditions. During vehicle motion, the inlet is positioned to maximize ram-air flow for regeneration. During stationary conditions or when regeneration is not required, the inlet position is adjusted to prevent catalyst saturation while maintaining stoichiometric operation at the catalyst.
Solution Approach 2:
The system changes the operational parameters of the ram-air inlet, including its position and opening degree, based on real-time detection of vehicle speed, engine load, and oxygen levels. This parameter adjustment allows the system to optimize between maximizing oxygen supply during motion and preventing catalyst saturation during stationary or low-speed operation.
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 regenerates the particulate filter while minimizing the impact on three-way catalyst emission control, reducing NOx emissions and maintaining efficient emission control operations.
Implementation Method 1
directing exhaust from the engine to a three-way catalyst
Implementation Method 2
particulate filter positioned downstream of the three-way catalyst
Implementation Method 3
directing fresh ram-air to the particulate filter to regenerate the particulate filter
Data Source
AI summary
Systems and methods for controlling regeneration of a particulate filter positioned downstream of an engine in a vehicle are provided herein. One exemplary method includes, during combusting engine conditions, directing exhaust from the engine to a three-way catalyst and then to the particulate filter, and during non-combusting engine conditions and while the vehicle is in motion, directing fresh ram-air to between the particulate filter and the catalyst to regenerate the particulate filter. Thus, vehicle motion may be used to introduce the ram-air.