Exhaust Mixing Device With Electric Heating For Low-Temperature Reactant Decomposition
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Solution Overview
Problem
Existing exhaust systems for internal combustion engines face inefficiencies in mixing reactants with exhaust gas, particularly at low operating and ambient temperatures, leading to inadequate ammonia formation for selective catalytic reduction, especially at high metering rates.
Innovation Solution
A mixing device with a double-walled configuration, featuring an electrically energizable heating device and heat transfer rib formation, ensures efficient thermal conditions for reactant evaporation and decomposition by providing thermal energy through heating elements and enlarged heat transfer surfaces, minimizing heat loss and optimizing heat distribution along the mixing section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the exhaust gas temperature is low, then the thermal energy available for reactant evaporation and decomposition is insufficient, but increasing the exhaust gas temperature directly is not feasible
Solution Approach 1:
An electrically energizable heating device is introduced as an intermediary to transfer thermal energy to the exhaust gas and reactant, enabling reactant evaporation and decomposition even when exhaust gas temperature is insufficient
Solution Approach 2:
The heating device changes the thermal parameter (temperature) of the exhaust gas and reactant to enable efficient reactant evaporation and decomposition under low-temperature operating conditions
2Quantity of substance
If the reactant metering rate is high, then the amount of reactant to be mixed and decomposed increases, but the available thermal energy and mixing time remain constant, leading to incomplete decomposition
Solution Approach 1:
The heating device pre-heats the reactant and exhaust gas before they enter the mixing section, creating favorable thermal conditions in advance for efficient reactant evaporation and decomposition even at high metering rates
Solution Approach 2:
The heating device ensures continuous thermal energy supply throughout the mixing section, maintaining the temperature conditions necessary for complete reactant decomposition across varying metering rates
3Device complexity
If the mixing section length is short, then the device complexity and space requirements are reduced, but the reactant and exhaust gas do not have sufficient time and distance for efficient mixing and decomposition
Solution Approach 1:
The heating device changes the thermal parameters of the reactant and exhaust gas to accelerate evaporation and decomposition reactions, achieving complete mixing and decomposition in a shorter mixing section length
Solution Approach 2:
The heating device dynamically adjusts thermal energy input to optimize the mixing and decomposition process within the available mixing section length, ensuring complete reactant decomposition regardless of section length variations
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
The solution ensures efficient mixing and decomposition of reactants, enhancing ammonia formation and nitrogen oxide reduction, even at low temperatures and high metering rates, by actively introducing heat and maintaining uniform thermal interaction within the mixing device.
Implementation Method 1
an electrically energizable heating device is provided at the inner wall
Implementation Method 2
a heat transfer rib formation is provided at the inner wall... the heat transfer rib formation and the enlarged interaction surface thus provided for heating the reactant
Implementation Method 3
the reactant evaporates and is thermally decomposed in the process and ammonia will essentially be formed
Implementation Method 4
the reactant evaporates and is thermally decomposed in the process and ammonia will essentially be formed
Data Source
AI summary
A mixing device for an exhaust system of an internal combustion engine includes a mixing section (14) with a mixing section inlet area (20) to be positioned downstream in relation to a reactant introduction device (12). A mixing section outlet area (22) is positioned upstream in relation to a catalytic converter device (16). The mixing section (14) includes an inner wall (26) surrounding an inner volume (28), through which exhaust gas (A) or/and reactant (R) can flow, and an outer wall (24) surrounding the inner wall (26). An outer volume (30) surrounds the inner volume (28) in a ring-shape, formed between the inner wall and the outer wall (24). An electrically energizable heating device (34) is provided at the inner wall (26), or/and a heat transfer rib formation (54) is provided at the inner wall (26).