Electric Machine Generator Heating for Early EGR Activation
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Solution Overview
Problem
Early introduction of exhaust gas recirculation (EGR) in engines after a cold start can cause combustion instability and potentially damage compressor blades due to condensation formation, especially in forced induction engines.
Innovation Solution
A method that uses an electric machine as a generator to increase engine and exhaust gas temperatures, allowing for the earlier and safer introduction of EGR by activating it only when temperatures are sufficient to prevent instability and condensation, utilizing an electronic controller to monitor and control the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If exhaust gas recirculation is introduced early after cold start to reduce NOx emissions, then emission compliance is improved, but combustion stability deteriorates due to low gas temperature
Solution Approach 1:
The patent applies preliminary action by using the electric machine to heat the exhaust gas and engine components before EGR is activated. This pre-heating ensures that when EGR is introduced, the gas temperatures are already sufficient to maintain combustion stability, thus allowing early EGR operation without the usual stability penalties.
Solution Approach 2:
The patent changes the temperature parameter of the exhaust gas and inducted gas by using the electric machine as a heater. By actively controlling and increasing these temperatures to specific thresholds before EGR activation, the system enables early EGR operation while maintaining combustion stability that would otherwise be compromised at cold start conditions.
2Object-generated harmful factors
If low pressure exhaust gas recirculation is used early in forced induction engines, then NOx emissions are reduced, but compressor blade damage occurs due to condensation formation
Solution Approach 1:
The patent uses preliminary action by heating the exhaust gas and engine components before LPEGR is activated. This ensures that the temperature remains above the dew point throughout the LPEGR process, preventing condensation formation that would otherwise damage compressor blades during early operation after cold start.
Solution Approach 2:
The patent changes the temperature parameter to maintain it above the dew point threshold. By using the electric machine to actively control and increase temperatures before and during LPEGR operation, the system prevents the temperature drop that would lead to condensation and subsequent compressor blade damage.
3Loss of time
If the electric machine is used as a generator to increase engine load and temperature, then EGR can be activated earlier, but energy consumption increases
Solution Approach 1:
The patent applies multi-functionality by using the electric machine in dual roles: as a starter motor for engine start-up and as a generator for heating the exhaust gas and engine components. This eliminates the need for a separate heating system, and the energy used for heating can be recovered through regenerative braking, thereby reducing overall energy consumption while enabling early EGR activation.
Solution Approach 2:
The system applies self-service by using the electric machine to generate the heat required for early EGR operation. The same component that starts the engine also provides the heating function, and any excess energy can be stored in the battery for later use, making the system self-sufficient without requiring additional external energy sources.
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
Enables the reduction of NOx emissions after a cold start without causing combustion instability or damaging condensation issues, effectively utilizing EGR to improve engine performance and emissions control.
Implementation Method 1
using an electric machine as a generator to apply a load to the engine to increase the rate at which the engine temperature and the exhaust gas temperature increase
Implementation Method 2
an exhaust gas recirculation system to recirculate exhaust gas from an exhaust side of the engine to an intake side of the engine
Data Source
AI summary
A system and method for increasing engine heating rate to facilitate early introduction of exhaust gas recirculation after a cold start include operating an electric machine connect to the engine to apply a load to the engine. The electric machine may be operated as a generator to produce an increased engine torque demand and increase the rate of engine heating until an engine temperature and an exhaust temperature exceed corresponding thresholds. Operation of the electric machine as a generator may be stopped in response to a battery state of charge exceeding a threshold, or engine load exceeding a threshold.