Exhaust System Dual Heating for Rapid Catalyst Light-Off
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Solution Overview
Problem
Existing exhaust systems for internal combustion engines face challenges in quickly reaching operating temperatures for catalytic converters during cold starts, limiting the effectiveness of emissions reduction, especially since catalytic converters require a specific light-off temperature to function efficiently.
Innovation Solution
The exhaust system incorporates a combination of a burner and an electrical heating device downstream of the first exhaust gas purification device, allowing for rapid heating of the second exhaust gas purification device, which is positioned remotely from the engine, thereby enabling quick activation and efficient conversion of pollutants with high heating output, independent of engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If catalytic converters are used in the exhaust system, then emissions conversion is effective, but the light-off temperature is not reached immediately after cold start
Solution Approach 1:
The exhaust system performs preliminary heating actions before the catalytic converter needs to operate. A heating device (burner or electric heater) is activated during cold start to preheat the exhaust gas and catalyst, ensuring the light-off temperature is reached quickly. This preliminary thermal preparation allows the catalytic converter to become effective immediately after engine start.
2Temperature
If heating devices are installed to raise exhaust gas temperature, then light-off temperature is achieved, but heating output is limited and tied to certain operating conditions
Solution Approach 1:
The system uses self-service heating where the exhaust gas itself serves as the heating medium. The heating device injects fuel into the exhaust stream, and the exothermic combustion of this fuel directly heats the exhaust gas and catalyst. This self-heating approach eliminates dependence on external power sources and provides high heating output independent of engine operating conditions.
3Reliability
If a second exhaust gas purification device is positioned remotely from the engine, then emissions conversion is enhanced, but heating time is extended due to distance from heat source
Solution Approach 1:
A heating device is introduced as an intermediary between the engine exhaust and the remote second purification device. This heating device actively heats the exhaust gas stream as it travels through the exhaust system, compensating for the thermal loss over distance. The intermediary heating ensures that even though the second catalyst is positioned remotely for better emissions conversion, it still receives sufficiently heated exhaust gas to achieve rapid light-off.
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 solution allows the second exhaust gas purification device to reach its light-off temperature rapidly, reducing starting emissions and enabling efficient conversion performance, even with large catalyst volumes, while maintaining aging stability and allowing for adjustable heating output and lambda control.
Implementation Method 1
The second exhaust gas purification device has an electric heating device for heating the second exhaust gas purification device
Implementation Method 2
a burner arranged in the exhaust gas flow path downstream of the first exhaust gas cleaning device and upstream of the second exhaust gas cleaning device, which is configured to be operated with a fuel and an oxidizing gas stream in order to heat the gas stream by combustion of the fuel
Implementation Method 3
catalytic converters used in the exhaust systems of internal combustion engines in vehicles require an operating temperature to be effective
Data Source
Figure 1~2
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AI summary
The invention relates to an exhaust system (2) for an internal combustion engine (10), comprising a first exhaust gas purification device (21) located close to the engine and a second exhaust gas purification device (22) located further away from the engine, wherein the second exhaust gas purification device (22) can be heated by a combination of an upstream burner (27) and an electric heating device (29). To heat the exhaust gas purification devices (21, 22) after an engine start, the internal combustion engine (10) is operated with at least one in-engine measure to increase the exhaust gas temperature, and the burner (27) and the electric heating device (28) are activated simultaneously or sequentially to heat the second exhaust gas purification device (22), whereby a mixed gas entering the second exhaust gas purification device (22) is adjusted to a stoichiometric lambda value.The invention enables accelerated heating of the exhaust gas purification devices and thus a reduction of start-up emissions.