EGR Freeze Prevention Through Engine Output Limiting
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Solution Overview
Problem
Existing engine systems face challenges in maintaining exhaust performance when outside air temperature is low, particularly due to water freezing in the EGR passage, leading to insufficient exhaust gas return and increased NOx discharge.
Innovation Solution
An engine system with an integrated control apparatus that adjusts engine output parameters and EGR valve operations based on outside air and purification apparatus temperatures, prohibiting EGR when freezing is likely and reducing engine torque to prevent water freezing and NOx discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the intake air amount is decreased to reduce harmful substance discharge, then exhaust performance is improved, but engine output is reduced
Solution Approach 1:
The control apparatus dynamically adjusts the upper limit value of engine output parameter based on purification apparatus temperature and outside air temperature. When purification apparatus temperature is low, the upper limit is set lower to reduce exhaust gas volume and harmful substance discharge. When outside air temperature is low, an even lower upper limit is applied to prevent freezing in the EGR passage while still allowing some engine output.
2Object-generated harmful factors
If the EGR passage is used to return exhaust gas to improve exhaust performance, then exhaust gas recirculation is enhanced, but water freezing occurs in the EGR passage when outside air temperature is low
Solution Approach 1:
The control apparatus applies preliminary anti-action by setting a lower upper limit value for engine output parameter when outside air temperature is low, before freezing actually occurs. This preventive measure reduces the temperature and volume of exhaust gas flowing through the EGR passage, preventing water freezing and maintaining EGR passage reliability.
Solution Approach 2:
The system uses a composite control strategy combining temperature-based upper limit setting with EGR valve control. The control apparatus integrates purification apparatus temperature and outside air temperature information to determine appropriate upper limit values, creating a multi-layered protection system against freezing.
3Object-generated harmful factors
If the upper limit value of engine output parameter is set lower when purification apparatus temperature is low, then harmful substance discharge is reduced, but engine torque is restricted
Solution Approach 1:
The control apparatus changes the operating parameters by setting different upper limit values for engine output parameter based on purification apparatus temperature. When the purification apparatus temperature is below a predetermined threshold, the upper limit is set lower than the maximum value, reducing both harmful substance discharge and engine torque. This dynamic parameter adjustment allows the system to optimize exhaust performance while adapting to varying thermal conditions of the purification apparatus.
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 maintains proper exhaust performance by preventing water freezing in the EGR passage and reducing NOx discharge, even at low temperatures, ensuring efficient engine operation.
Implementation Method 1
when the outside air temperature is low, water in the exhaust gas may freeze in the EGR passage
Data Source
AI summary
An engine system is provided with an adjustment apparatus, which adjusts an engine output parameter; and an exhaust gas recirculation (EGR) passage, which connects an exhaust passage on a downstream side relative to exhaust gas purification apparatuses with an intake passage, and returns EGR gas as a part of exhaust gas to the intake passage. Restriction control is carried out to control the adjustment apparatus such that when a purification apparatus temperature is lower than a predetermined reference temperature, an upper limit value of the engine output parameter is set to lower than a maximum value and the engine output parameter has a value equal to or lower than the upper limit value, such that when the outside air temperature is low, the upper limit value is set to a lower value than when the outside air temperature is high.