EGR Cooling via AC Loop and Thermal Storage
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Solution Overview
Problem
Current methods for cooling intake gases in diesel engines to reduce NOx emissions are energy-intensive and require costly post-treatment systems, often relying on engine coolant for cooling, which limits temperature reduction and lacks efficient cold storage and adaptive control strategies.
Innovation Solution
A motor vehicle system utilizing a dual hydraulic cooling circuit with a storage heat exchanger, integrating the air conditioning loop to cool recirculated exhaust gases, allowing for adaptive control of compressor displacement and cold storage, balancing engine power gain with air conditioning consumption, and incorporating a bypass system for efficient cold management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If engine coolant is used to cool recirculated exhaust gases, then cooling function is provided, but temperature reduction is limited and energy consumption increases
Solution Approach 1:
The system pre-cools recirculated exhaust gases using the second hydraulic circuit before they enter the combustion chamber. By performing cooling in advance through a dedicated circuit with lower temperature coolant, the system achieves greater temperature reduction without excessive energy consumption during critical combustion phases.
Solution Approach 2:
The cooling system is divided into two separate hydraulic circuits: a first circuit using engine coolant for general cooling, and a second circuit with lower temperature coolant specifically for pre-cooling recirculated exhaust gases. This segmentation allows each circuit to operate independently with optimized temperature levels, achieving better overall cooling efficiency.
2Temperature
If air conditioning loop is used to cool recirculated gases, then temperature reduction is improved, but engine power consumption increases
Solution Approach 1:
A second hydraulic circuit acts as an intermediary between the air conditioning loop and the recirculated exhaust gases. Instead of directly coupling the air conditioning system to cool gases (which would cause high power consumption), the second hydraulic circuit serves as a mediator, using a pump-driven coolant loop to transfer cooling capacity efficiently, thereby reducing the direct power burden on the engine.
3Object-generated harmful factors
If costly post-treatment systems are used to reduce NOx emissions, then emission standards are met, but vehicle cost increases
Solution Approach 1:
The system performs preliminary cooling of recirculated exhaust gases to lower temperatures before they enter the combustion chamber. By pre-cooling the gases, the system reduces the formation of nitrogen oxides at the source, thereby meeting emission standards without requiring expensive downstream post-treatment systems such as selective catalytic reduction (SCR) or diesel particulate filters (DPF).
Solution Approach 2:
The invention converts the typically harmful hot recirculated exhaust gases into a beneficial cooling medium. By using these gases as the fluid to be cooled in the heat exchanger, the system transforms what would otherwise be waste heat into a useful cooling resource, reducing NOx formation while eliminating the need for additional post-treatment equipment.
4Temperature
If additional dedicated cooling circuit is used to obtain lower temperatures, then cooling efficiency is improved, but system complexity increases
Solution Approach 1:
The second hydraulic circuit is designed with multi-functionality, serving both as a cooling circuit for recirculated exhaust gases and as a thermal energy storage system. The circuit includes a thermal energy storage unit that can store cold energy during periods of low demand and release it when needed, allowing the same infrastructure to handle varying cooling requirements without requiring separate dedicated systems for each function.
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 effectively reduces NOx emissions and extends the life of NOx traps while minimizing energy consumption, enabling efficient cold storage and instantaneous thermal management, thus optimizing engine performance and emissions control.
Implementation Method 1
a storage heat exchanger allowing heat exchange between the coolant of the second hydraulic circuit and the refrigerant of the air conditioning circuit
Implementation Method 2
an evaporator in which a refrigerant fluid circulates
Implementation Method 3
a heat exchanger for said recirculated exhaust gases comprising a first high temperature stage and a second low temperature stage
Data Source
Figure 1~2
Figure 3~5
Figure 6~7
AI summary
In a motor vehicle having exhaust-gas recirculation, the fluid of the air-conditioning circuit is used to cool the coolant of a dedicated hydraulic circuit, which in turn cools the recirculated exhaust gases in a two-stage (HT,LT EGR) heat exchanger, thus increasing engine gain by replenishing in order to reduce NOx emissions. The method comprises differentiated control strategies for these circuits, as a function of vehicle driving conditions, continuous modes and transient braking and acceleration modes, in order to compensate for the consumption of the compressor (C) of the air-conditioning circuit. The circuits comprise a heat exchanger (EXCH STORE) for heat exchange between the air-conditioning fluid and coolant, provided with a bypass, capable of accumulating and releasing cold energy, and, optionally, a line for condensing the water vapour of the exhaust gases and for reinjecting the condensed water to the intake.