Branched Exhaust Assembly for Catalyst Light-off and Turbo Lag
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Solution Overview
Problem
Existing engine systems face challenges in efficiently delivering exhaust heat to exhaust aftertreatment components, leading to delayed catalyst light-off, incomplete regeneration of particulate filters, and turbo lag due to the placement of turbines in exhaust systems, which affects emissions and performance.
Innovation Solution
A branched exhaust assembly with adjustable valves that reroutes exhaust flow through distinct sub-branches to optimize heat delivery to each component based on operating conditions, allowing for flexible routing to expedite catalyst light-off, assist regeneration, and reduce turbo lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the turbine is placed in the exhaust system to drive the intake compressor, then the turbocharger can provide boosted aircharge, but the turbine acts as a heat sink that absorbs exhaust heat during cold-start, delaying catalyst light-off temperature attainment
Solution Approach 1:
The exhaust system is segmented into multiple parallel passages with selective routing capabilities. During cold-start, exhaust is routed through a bypass passage that avoids the turbine, delivering heat directly to the catalyst. During normal operation, exhaust is routed through the turbine for compression. This segmentation allows independent optimization of thermal delivery and mechanical power generation.
Solution Approach 2:
The system performs preliminary heating of the catalyst by routing exhaust through a bypass passage before the turbine during cold-start conditions. This preliminary action ensures the catalyst reaches light-off temperature before the turbine is engaged for normal exhaust flow, eliminating the heat sink effect that would otherwise delay catalyst activation.
2Temperature
If the turbine is placed downstream of the exhaust aftertreatment devices, then exhaust heat can be delivered to the catalyst, but turbo lag occurs during vehicle acceleration
Solution Approach 1:
The exhaust system is divided into separate parallel passages: one routing exhaust through aftertreatment devices before the turbine, and another providing a bypass route. This segmentation enables selective routing where exhaust can be directed through the bypass passage during acceleration to reduce turbo lag, while still allowing heat delivery paths during other operating conditions.
Solution Approach 2:
The system dynamically adjusts exhaust routing based on operating conditions. During vehicle acceleration, exhaust is routed through the bypass passage to minimize turbo lag and improve response time. During steady-state or deceleration, exhaust is routed through the aftertreatment devices for optimal thermal management and emissions control.
3Temperature
If a passive thermally-operated valve is used to route exhaust bypassing the turbine during cold-start, then exhaust heat can be directly delivered to the exhaust catalyst, but the temperature of exhaust reaching each exhaust system component cannot be regulated
Solution Approach 1:
The system incorporates temperature sensors and active control that monitor exhaust temperatures at various points in the system. Based on feedback from these sensors, the control system adjusts valve positions and routing to maintain optimal temperatures for different components. This feedback mechanism enables precise temperature regulation for the catalyst, turbine, and aftertreatment devices under varying operating conditions.
Solution Approach 2:
The system actively changes operating parameters such as valve positions, exhaust flow rates, and routing configurations based on real-time temperature measurements. This allows dynamic adjustment of exhaust temperature delivery to each component, enabling the system to adapt to different operating conditions and maintain optimal temperatures for catalyst light-off, turbine operation, and aftertreatment efficiency.
4Loss of time
If exhaust is routed through a bypass passage during cold-start, then catalyst light-off temperature can be attained faster, but the temperature of exhaust reaching the DOC after light-off may be higher than desired, reducing catalyst functionality
Solution Approach 1:
The system dynamically transitions between different exhaust routing modes. During cold-start, exhaust is routed through the bypass passage to rapidly heat the catalyst. Once light-off temperature is attained, the system dynamically switches to routing exhaust through the turbine and aftertreatment devices, which provides thermal management to maintain optimal operating temperatures for catalyst functionality.
Solution Approach 2:
The exhaust routing operates in periodic phases: an initial heating phase where bypass routing delivers maximum heat to achieve light-off, followed by a maintenance phase where turbine routing provides thermal management. This periodic switching between routing modes ensures both rapid light-off and sustained optimal catalyst performance.
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 enhances engine efficiency, emissions quality, and fuel efficiency by ensuring optimal heat distribution to exhaust components, reducing reliance on wastegates, and maintaining boosted performance.
Implementation Method 1
the turbine acting as a heat sink. In particular, engine exhaust heat during the engine cold-start may be absorbed at the turbine
Data Source
AI summary
Methods and systems are provided for reducing engine emissions using a branched exhaust system. In one example, a branched exhaust system may include a plurality of sub-branches each housing a distinct exhaust component, and an order of exhaust flow through each of the exhaust components may be adjusted based on engine operating conditions and temperature demand of the distinct components.