Engine Torque Limiting by SCR Temperature and Ammonia Adsorption
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Solution Overview
Problem
Existing engine systems face challenges in achieving consistent exhaust performance due to the varying purification capabilities of selective reduction catalysts based on temperature and ammonia adsorption levels, leading to inadequate reduction of NOx emissions.
Innovation Solution
An engine system with a control apparatus that adjusts engine output and torque by setting a lower upper limit value when the selective reduction catalyst is at a low temperature or has a small initial ammonia adsorption amount, ensuring proper exhaust performance by optimizing NOx purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the intake air amount is decreased to reduce harmful substance discharge, then the discharge amount of harmful substance can be decreased, but the purification capability of the selective reduction catalyst cannot be sufficiently utilized when the engine is started
Solution Approach 1:
The control apparatus dynamically adjusts the upper limit value of engine output or torque based on two key parameters: catalyst temperature and initial ammonia adsorption amount. When the catalyst temperature is below a predetermined threshold or the initial ammonia adsorption amount is small, the upper limit value is set to a lower value, thereby optimizing the balance between harmful substance discharge and purification capability.
2Temperature
If the engine is stopped in a state where the temperature of the selective reduction catalyst is high, then the ammonia adsorption amount becomes small, but the purification capability at engine start becomes low
Solution Approach 1:
The control apparatus uses feedback from the initial ammonia adsorption amount (determined by the catalyst's temperature history) to adjust the upper limit value of engine output or torque. This feedback mechanism ensures that when the catalyst temperature was high during the previous operation (resulting in low ammonia adsorption), the engine output is restricted at startup to compensate for the reduced purification capability.
3Device complexity
If the intake air amount is changed only in accordance with the catalyst temperature, then the control is simple, but proper exhaust performance cannot be achieved when the ammonia adsorption amount varies
Solution Approach 1:
The control apparatus considers two parameters (catalyst temperature and initial ammonia adsorption amount) to determine the upper limit value of engine output or torque. By incorporating the initial ammonia adsorption amount as an additional parameter, the system achieves better exhaust performance without significantly increasing control complexity, as the initial ammonia adsorption amount can be estimated based on the catalyst temperature at the time of engine stop.
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 system effectively reduces NOx emissions by preventing excessive discharge and maintaining optimal engine output, even when catalyst temperatures and ammonia adsorption vary, thereby enhancing overall exhaust performance.
Implementation Method 1
a selective reduction catalyst which adsorbs ammonia and thereby reduces NOx
Implementation Method 2
a selective reduction catalyst which adsorbs ammonia and thereby reduces NOx in exhaust gas by using the ammonia
Data Source
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AI summary
An adjustment apparatus (9) which adjusts an engine output or engine torque and selective reduction catalysts (42 and 43) which adsorb ammonia and reduce NOx in exhaust gas by using the ammonia are provided, restriction control for controlling the adjustment apparatus is carried out such that in a case where temperatures of the selective reduction catalysts are lower than a predetermined determination catalyst temperature, an upper limit value of the engine output or the engine torque is set to a lower value than a maximum value and the engine output or the engine torque has a value equal to or lower than the upper limit value, and in carrying out the restriction control, the upper limit value is set to a lower value when an initial adsorption amount is small than when that is large.