Exhaust Gas Recirculation Flow Mixer and Cooler
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Solution Overview
Problem
Existing engine systems face challenges in achieving low mixed gas intake manifold temperature differentials to maximize engine power density and minimize pollutant emissions, particularly due to the difficulty in cooling recirculated exhaust gas and the high cost and weight of stainless steel heat exchangers used in exhaust gas recirculation systems.
Innovation Solution
The engine system employs a flow mixer to combine uncooled exhaust gas with cooled charge air, using a mixed gas heat exchanger to cool the mixture to a low temperature, eliminating the need for stainless steel heat exchangers by using aluminum alloys and ambient air cooling, and optionally incorporating a waste heat recovery Rankine cycle to further reduce intake manifold temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If recirculated exhaust gas is cooled using conventional heat exchangers, then the temperature is reduced to decrease NOx formation, but the system requires expensive and heavy stainless steel materials
Solution Approach 1:
The cooling process is divided into two independent stages: first, the exhaust gas is cooled in an exhaust gas recirculation cooler; second, the charge air is cooled in a charge air cooler. This segmentation allows each cooler to be optimized for its specific temperature range, enabling the use of lighter aluminum materials instead of stainless steel.
Solution Approach 2:
The exhaust gas recirculation cooler acts as an intermediary device that pre-cools the hot exhaust gas before it enters the recirculation system. This intermediate cooling step reduces the thermal load on subsequent components, allowing them to use lighter materials while still achieving the required final temperature.
2Object-generated harmful factors
If recirculated exhaust gas is cooled to reduce peak combustion temperature, then NOx concentration decreases, but the system complexity and cost increase due to stainless steel heat exchangers
Solution Approach 1:
The cooling system is segmented into two separate coolers handling different temperature ranges. The exhaust gas recirculation cooler handles high-temperature exhaust gas, while the charge air cooler handles the mixed gas at lower temperatures. This segmentation simplifies material selection and reduces overall system complexity.
Solution Approach 2:
The patent replaces expensive stainless steel heat exchangers with more economical aluminum alloy coolers. The aluminum components are designed to be cost-effective while meeting the thermal management requirements, reducing overall system cost and complexity.
3Productivity
If the intake manifold temperature differential is reduced to maximize engine power density, then fuel economy improves, but the requirement for advanced cooling systems increases
Solution Approach 1:
The cooling system is divided into two independent cooling circuits: one for exhaust gas recirculation and one for charge air. This segmentation allows each circuit to be optimized independently, achieving the required low intake manifold temperature differential without excessive system complexity.
Solution Approach 2:
The cooled exhaust gas and cooled charge air are combined in the intake manifold to achieve the target temperature differential. This multi-functional approach uses two cooling systems working together to achieve both exhaust temperature control and charge air temperature control, maximizing engine power density.
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 achieves a mixed gas intake manifold temperature differential of 15 degrees Celsius or less, enhancing engine power density and fuel economy while avoiding the use of costly and heavy stainless steel materials.
Implementation Method 1
A charge air cooler 64 is arranged along the flow path 63 and allows for cooling of the compressed charge air by rejecting heat to a cooling flow 68
Implementation Method 2
An exhaust gas recirculation cooler 69 is arranged along the flow path 65 and allows for cooling of the exhaust gas by rejecting heat to a cooling flow 71
Implementation Method 3
A flow mixer 9 combines a flow of cooled charge air with a flow of recirculated exhaust gas to form a mixed gas flow 16
Implementation Method 4
A mixed gas heat exchanger 17 is arranged along the mixed gas flow path 16 to cool the mixed gas to a low temperature prior to delivery of the mixed gas to the intake manifold 3
Implementation Method 5
Combustion air is drawn in and compressed by the compressor 57
Implementation Method 6
A portion of the exhaust from the engine 52 is routed from the exhaust manifold 54 to an expansion turbine 56
Data Source
AI summary
An engine system with exhaust gas recirculation includes a combustion engine, a flow mixer, and a turbocharger. An exhaust flow path and a charge air flow path each extend to an inlet of the flow mixer, and a mixed gas flow path extends between the outlet of the flow mixer and an intake manifold of the engine. A charge air heat exchanger is arranged along the charge air flow path to cool the charge air, and a mixed gas heat exchanger is arranged along the mixed gas flow path to cool mixed charge air and recirculated exhaust gas. The exhaust gas recirculation flow path does not extend through any heat exchangers.