Exhaust Gas Reducing Agent Supply System
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Solution Overview
Problem
Internal combustion engines with a lambda value greater than 1, commonly used for fuel efficiency, experience increased nitrogen oxide emissions due to insufficient exhaust gas temperatures for urea conversion into ammonia, leading to high electrical energy consumption and reduced efficiency in existing reducing agent supply methods.
Innovation Solution
A method that dynamically adjusts the feed state and chemical composition of the reducing agent, such as urea or urea-water solutions, based on exhaust gas parameters and energy availability, ensuring efficient conversion into ammonia by optimizing the form (gaseous or liquid) and location (internal or external) of the conversion process, using sensors and adjustable flow paths with contact heaters and hydrolysis catalytic converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If urea conversion is performed externally with electrical heaters, then complete conversion of reducing agent is achieved, but electrical energy consumption increases significantly
Solution Approach 1:
The exhaust gas itself is used as the heating medium to convert urea into ammonia. The hot exhaust gas flows through the converter where urea is converted, eliminating the need for external electrical heaters. This self-service approach uses the available thermal energy in the system rather than requiring additional energy input.
Solution Approach 2:
The system determines in advance whether the exhaust gas temperature is sufficient for urea conversion before initiating the conversion process. Based on this preliminary assessment, the control unit decides whether to perform external conversion or rely on internal exhaust gas heating, optimizing energy usage before the conversion actually occurs.
2Ease of operation
If reducing agent is supplied in liquid form, then storage and handling are simplified, but conversion efficiency decreases at low exhaust gas temperatures
Solution Approach 1:
The system dynamically changes the physical state parameter of the reducing agent based on exhaust gas temperature conditions. At high temperatures, liquid urea is supplied directly. At low temperatures, the system switches to supplying gaseous ammonia or pre-heats/atomizes the liquid to ensure complete vaporization and conversion, thus adapting the physical state to match the thermal conditions.
Solution Approach 2:
The reducing agent supply system is made dynamic by allowing switching between different supply forms (liquid urea, gaseous ammonia, atomized spray) based on real-time exhaust gas temperature conditions. This dynamic adaptation ensures optimal conversion efficiency across varying operating conditions while maintaining ease of storage and handling.
3Adaptability or versatility
If multiple flow paths with different treatments are provided, then adapting to varying operating conditions is improved, but device complexity increases
Solution Approach 1:
The reducing agent supply system is divided into separate flow paths, each optimized for specific operating conditions. One path handles liquid urea supply with atomization capabilities, another path handles gaseous ammonia supply, and a third path provides pre-heating treatment. This segmentation allows the system to adapt to different conditions by activating only the relevant flow path.
Solution Approach 2:
The multiple flow paths are designed to be universally applicable across different operating conditions. Each flow path can serve multiple functions - for example, the liquid urea path can operate in both atomized and non-atomized modes depending on temperature. This multi-functionality reduces the need for completely separate systems for different conditions.
4Reliability
If exhaust gas temperature is increased to enable urea conversion, then conversion efficiency improves, but fuel consumption increases
Solution Approach 1:
The system continuously monitors exhaust gas temperature and provides feedback to the control unit. Based on this feedback, the control unit determines whether the temperature is sufficient for urea conversion and adjusts the reducing agent supply strategy accordingly. This feedback mechanism prevents unnecessary fuel consumption by avoiding conversion attempts when temperatures are inadequate.
Solution Approach 2:
Instead of maintaining high exhaust gas temperatures continuously, the system changes operational parameters based on actual temperature conditions. When temperatures are low, it switches to supplying gaseous ammonia or pre-heats the urea locally. When temperatures are sufficient, it uses standard liquid urea injection. This parameter adaptation avoids the need for continuous high-temperature 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 ensures complete conversion of the reducing agent with reduced energy expenditure, improving engine efficiency by adapting to varying operating conditions and maintaining effective nitrogen oxide reduction across different engine states.
Implementation Method 1
contact heaters
Implementation Method 2
hydrolysis catalytic converters
Implementation Method 3
Ammonia is then generated from the urea through the use of thermolysis and/or hydrolysis
Data Source
AI summary
A method for feeding reducing agent or reducing agent precursor into exhaust systems of mobile internal combustion engines and an exhaust system are preferably used for internal combustion engines with high nitrogen oxide compound emissions. A feed time is established. An exhaust parameter and/or necessary quantity of reducing agent is determined and a feed state of the reducing agent is defined. The reducing agent is treated if the feed state does not correspond to a stored state. The reducing agent feed to the exhaust system takes place last. The steps are repeated multiple times. This permits reducing agent to be fed into an exhaust system in a state suitable for the exhaust temperature, so that complete conversion of reducing agent takes place and selectively catalytic reduction is also ensured. This reduces the quantity of electrical energy necessary for converting reducing agent. A motor vehicle having the system is also provided.