Secondary Air Oxidation for Exhaust Catalyst Temperature Maintenance
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Solution Overview
Problem
The existing technologies for warming up electrically heated catalysts in vehicles face challenges when battery charging is low, leading to insufficient warming and compromised exhaust gas purification performance at engine start-up.
Innovation Solution
A vehicle control method that supplies secondary air to an exhaust particulate filter when the engine is stopped, utilizing the heat from the oxidation reaction of accumulated fine exhaust particles to maintain the temperature of a downstream three-way catalyst, thereby preventing a deterioration in exhaust gas purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the electrically heated catalyst is warmed up by energizing it when the internal combustion engine is stopped, then the warming-up of the catalyst can be achieved, but the power consumption of the battery becomes large
Solution Approach 1:
The exhaust particulate filter performs self-heating through the oxidation reaction of accumulated fine exhaust particles. When secondary air is supplied to the filter during engine stop, the fine particles undergo oxidation that generates heat, which automatically warms the downstream three-way catalyst without requiring external electrical power. This converts the filter into a self-service heating device that utilizes its own accumulated particles as fuel.
Solution Approach 2:
The accumulated fine exhaust particles, which were previously considered harmful pollutants requiring purification, are converted into a beneficial heat source. By supplying secondary air to promote oxidation of these particles in the exhaust particulate filter, the harmful fine particles generate heat that warms the three-way catalyst, thereby converting a pollutant into a useful thermal energy source for maintaining catalyst temperature.
2Temperature
If the electrically heated catalyst is warmed up when battery charging amount is low, then the warming-up request is made, but the warming-up cannot be sufficiently carried out and exhaust gas purification performance cannot be ensured
Solution Approach 1:
The exhaust particulate filter serves dual functions: trapping fine exhaust particles during normal operation and generating heat through oxidation of these particles during engine stop. This self-service capability eliminates dependence on battery charge state for catalyst warming, ensuring reliable exhaust gas purification performance regardless of battery conditions.
Solution Approach 2:
The accumulated fine exhaust particles are transformed from a liability into an asset by using their oxidation reaction as a heat source. This ensures that the three-way catalyst maintains adequate temperature for effective exhaust gas purification even when battery power is insufficient, thereby guaranteeing reliable purification performance under all operating conditions.
3Loss of energy
If the internal combustion engine is stopped, then fuel consumption is reduced, but the temperature of the three-way catalyst drops and exhaust gas purification performance deteriorates
Solution Approach 1:
The oxidation of accumulated fine exhaust particles in the exhaust particulate filter generates heat that is transferred to the three-way catalyst. This converts the potentially harmful accumulated particles into a beneficial heat source that maintains catalyst temperature during engine stop, allowing fuel savings to be achieved without sacrificing purification performance.
Solution Approach 2:
The exhaust particulate filter acts as an intermediary thermal management device between the engine stop condition and the three-way catalyst. It accumulates fine particles during operation, then uses oxidation of these particles to generate heat that protects the downstream catalyst from temperature drop, thereby mediating between fuel economy and purification performance requirements.
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 method ensures the three-way catalyst remains warm, maintaining exhaust gas purification performance at engine start-up by using the heat generated from the oxidation reaction of fine exhaust particles, even when the battery is low on charge.
Implementation Method 1
an exhaust particulate filter which is capable of trapping fine exhaust particles in exhaust gas
Implementation Method 2
a three-way catalyst positioned on the downstream side of the exhaust particulate filter
Implementation Method 3
by the heat generated by the oxidation reaction (combustion) of the exhaust fine particles
Data Source
AI summary
An under-floor catalyst (33) includes a GPF (41) capable of trapping fine exhaust particles in exhaust gas, and a downstream-side catalyst (42) positioned on the downstream side of GPF (41). GPF (41) can be supplied with secondary air. When an internal combustion engine (10) is stopped during travel, the secondary air is supplied to GPF (41) in which the fine exhaust particles are accumulated. At this time, the temperature of GPF (41) is equal to or higher than a predetermined temperature. Thus, a deterioration in the exhaust gas purification performance of under-floor catalyst (33) at the time of the start of internal combustion engine (10) can be suppressed.