Dynamic EGR Control for SCR Efficiency and Fuel Economy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing exhaust gas recirculation (EGR) systems in supercharged engines, combined with selective catalytic reduction (SCR) systems, face challenges in optimizing fuel consumption and emissions due to inefficient SCR operation, unsteady temperature thresholds, and increased energy losses from continuous recirculation, leading to higher emissions and fuel costs.
Innovation Solution
The EGR recirculation system calculates exhaust gas mappings and urea-based additive flow rates using a cost minimization function based on unit costs of fuel and additive, allowing for adjustable recirculation rates from 1-2% to 45% to maximize vehicle range and reduce maintenance costs, while compensating for SCR efficiency decay and avoiding negative pumping work, using a twin-scroll turbine with variable geometry to maintain engine boost pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous EGR recirculation is maintained at minimum 20% rate to ensure SCR efficiency, then SCR pollutant reduction is maintained, but negative pumping work increases and fuel consumption rises
Solution Approach 1:
The EGR recirculation rate is made dynamically adjustable rather than fixed at minimum 20%. The system varies the recirculation rate between 1-2% and 45% based on real-time SCR efficiency measurements, allowing optimization of fuel consumption while maintaining pollutant reduction standards.
Solution Approach 2:
The system changes the EGR recirculation rate parameter based on SCR efficiency decay and operating conditions. By adjusting this parameter dynamically, the system resolves the contradiction between maintaining SCR efficiency and minimizing fuel consumption from negative pumping work.
2Reliability
If SCR temperature is raised to 250°C threshold using post-injections or exhaust choking, then SCR efficiency is improved, but fuel consumption and unburned hydrocarbon emissions increase
Solution Approach 1:
The system uses feedback from SCR efficiency measurements and temperature sensors to determine when and how to adjust EGR recirculation rate. This feedback mechanism allows the system to maintain SCR efficiency without resorting to harmful methods like post-injections or exhaust choking that increase hydrocarbon emissions.
Solution Approach 2:
The EGR system serves the dual purpose of both cooling exhaust gases for SCR efficiency and managing temperature naturally through recirculation adjustments, eliminating the need for additional fuel-based heating methods.
3Power
If EGR scroll is made smaller to avoid excessive counterpressure and energy transfer to turbine, then waste-gate valve activation is delayed, but negative pumping work is still performed by all cylinders
Solution Approach 1:
The EGR scroll size or geometry is made dynamically adjustable, allowing the system to optimize the balance between counterpressure generation for EGR recirculation and energy transfer to the turbine. This dynamic adjustment resolves the contradiction by adapting to different operating conditions.
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 optimizes fuel consumption and emissions, extends vehicle range, reduces maintenance costs, and improves engine performance by up to 3-5% with reduced fuel usage and emissions, while maintaining efficient pollutant reduction and engine power delivery.
Implementation Method 1
the SCR may fully replace the EGR technique... a chemical reactor which uses a reducing agent... aqueous urea solution injected upstream of the SCR... the SCR efficiency, which exceeds a threshold value and, in particular, 95% of a nominal value
Implementation Method 2
a branch (54) connecting the exhaust manifold (5) to the intake manifold (4)... recirculating, in a variable percentage... said exhaust gas
Data Source
Figure 1
Figure 2~3
AI summary
System for exhaust gas recirculation in a supercharged engine equipped with an ATS device, the engine (E) comprising an intake manifold (4), exhaust manifolds (5, 5'); wherein at least one of the exhaust manifolds is connected to the intake manifold (4) to recirculate an exhaust gas flow rate (EGR), according to predetermined operating conditions (rpm, T) of the engine (E), means for injecting, in the ATS, an aqueous additive for the reduction of pollutant emissions, processing means configured to control said exhaust gas recirculation and said aqueous additive injection, minimizing a cost function based on the unit costs of the additive and of the fuel and/or maximizing a function of a distance that can be covered based on residual quantities of the fuel and of the additive.