Forced Air Exhaust Diffuser for Temperature Control
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Solution Overview
Problem
Existing exhaust gas cooling systems, such as mechanical diffusers and those using intake air or air injection upstream of aftertreatment systems, face limitations in reliably reducing exhaust outlet temperatures below certain thresholds, leading to increased backpressure and negative impacts on fuel economy, especially during aftertreatment maintenance when elevated exhaust temperatures are required.
Innovation Solution
An exhaust system with an external air source, an air blower connected downstream of the engine and aftertreatment system, and a conduit to the tailpipe, which forces ambient air into the exhaust gas flow independently of intake air, allowing for controlled mixing and cooling of exhaust gases, managed by an electronic controller to maintain or reduce exhaust outlet temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If mechanical diffusers are used to mix fresh ambient air with exhaust air to reduce exhaust temperature, then exhaust temperature is reduced, but back pressure on the engine increases and fuel economy deteriorates
Solution Approach 1:
The invention extracts the air cooling function from the exhaust system by using a separate air blower to introduce ambient air downstream of the aftertreatment system. This separates the cooling function from the exhaust flow path, avoiding the creation of backpressure that would occur if air mixing were done within the exhaust system itself.
Solution Approach 2:
The invention introduces an intermediary device (air blower) that brings in ambient air from the environment and delivers it to the exhaust outlet. This intermediary approach allows cooling without directly modifying the exhaust flow path, thereby avoiding backpressure issues while still achieving the desired temperature reduction.
2Stress or pressure
If larger diffusers are used to mitigate back pressure problems, then back pressure is reduced, but device footprint and packaging difficulty increase
Solution Approach 1:
The invention removes the large diffuser component entirely by extracting the air mixing function to a separate location downstream. The air blower system requires minimal space compared to large diffusers, thus reducing the device footprint while maintaining the ability to cool exhaust gases effectively.
3Temperature
If air injection is performed upstream of aftertreatment systems or using intake air, then exhaust temperature control is attempted, but control reliability is limited by engine operations and aftertreatment temperature requirements
Solution Approach 1:
The invention extracts the temperature control function from the engine operation-dependent systems by using an independent air blower located downstream of the aftertreatment system. This allows temperature control to be achieved independently of engine speed and aftertreatment temperature requirements, significantly improving control reliability.
Solution Approach 2:
The invention changes the operating parameters by introducing ambient air at a location downstream of the aftertreatment system, where it can be mixed with exhaust gases without being constrained by upstream temperature requirements or engine operational parameters. This enables reliable temperature control across a broader range of operating conditions.
Data Source
AI summary
Systems, methods and apparatus are disclosed that include an exhaust system and an air source external to the exhaust system that is configured to force additional air into the exhaust stream downstream of the engine and aftertreatment system to help mix cool air with the exhaust. The amount and timing of the mixing of the forced air with the exhaust can be determined by an electronic controller so that mixing air is provided in response to one or more predetermined operating conditions and/or anticipated operating conditions.