Evaporation Device for Exhaust Gas with Electric Heating
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Solution Overview
Problem
Existing exhaust gas aftertreatment systems face challenges in achieving rapid heating of evaporation structures, leading to delayed urea solution injection and potential deposit formation due to low exhaust gas temperatures, especially during cold starts and low load conditions, which impairs the effectiveness of nitrogen oxide conversion.
Innovation Solution
The system incorporates electrically heated surface elements within the evaporation device, allowing for independent heating of the evaporation structures using resistance or PTC heating elements, and perpendicular fluid injection to enhance evaporation efficiency, minimizing pressure loss and ensuring timely urea solution evaporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If thermal convection heating from exhaust gas is used, then the structure is heated by the flowing exhaust gas, but the heating is directly dependent on exhaust gas temperature causing delayed injection during cold starts and low load conditions
Solution Approach 1:
The heating device is activated before the exhaust gas flow reaches the evaporation device, pre-heating the surface elements to the required temperature. This preliminary heating action ensures that the evaporation device is ready for immediate fluid injection, eliminating the delay that would otherwise occur during cold starts or low load conditions when exhaust gas temperature is insufficient.
Solution Approach 2:
An electric heating device is introduced as an intermediary between the exhaust gas and the surface elements. This heating device acts as a mediator that can independently control the temperature of the evaporation device without being directly dependent on the exhaust gas temperature, thereby enabling timely injection regardless of exhaust gas thermal conditions.
2Stress or pressure
If surface elements extend along the main flow direction, then pressure loss in the exhaust line is minimized, but heating of the surface elements becomes more difficult
Solution Approach 1:
The heating device is integrated directly with the surface elements, merging the heating function with the flow-guiding surface elements. This combination allows the surface elements to maintain their flow-optimized geometry (extending along the main flow direction to minimize pressure loss) while simultaneously receiving direct heating energy to overcome the reduced heating efficiency caused by their elongated shape.
Solution Approach 2:
The electric heating device serves as an intermediary energy source that compensates for the reduced thermal coupling between the exhaust gas and the surface elements. By introducing this external heating intermediary, the system can maintain effective heating of the surface elements even though their extended geometry along the flow direction reduces heat transfer efficiency from the exhaust gas.
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 enables faster and more efficient urea solution evaporation, facilitating earlier and complete exhaust gas aftertreatment, even during cold starts, by providing independent heating of evaporation structures and optimizing fluid distribution for enhanced reaction surfaces.
Implementation Method 1
evaporation device which can be electrically heated by a heating device
Implementation Method 2
the evaporation of the aqueous urea solution begins, releasing ammonia
Implementation Method 3
the structures used for evaporation are heated by thermal convection from the flowing exhaust gas
Implementation Method 4
the structures used for evaporation are heated by thermal convection from the flowing exhaust gas
Implementation Method 5
releasing ammonia, which in turn reacts with the nitrogen oxides to form nitrogen and water
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a device for cleaning exhaust gases, comprising a housing (1) through which exhaust gas can flow, an injection device (4) for metering a fluid, wherein the fluid can be metered into the region through which exhaust gas can flow, and an evaporation device which is arranged in the housing. The evaporation device has a plurality of surface elements (7) extending along the main flow direction (2) of the housing (1), and the fluid can be metered along a direction running perpendicularly to the main flow direction (2). The evaporation device can be electrically heated by a heating device (6, 10). The invention also relates to a method for operating the device.