Flow Hood Baffle and Deflector for SCR Injector
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Solution Overview
Problem
Engine aftertreatment systems face challenges in reducing NOx emissions due to deposits forming on injector nozzles from reducing agents, which can interfere with the performance of selective catalytic reduction (SCR) devices, especially when the injector orientation is not vertical, and existing flow hood designs may not effectively manage gas flow velocities for NOx sensors.
Innovation Solution
A flow hood assembly with an outer case, a baffle, and a deflector member is used to direct exhaust gases from a particulate filter to an SCR device, incorporating a NOx sensor and an injector nozzle, where the baffle reduces the cross-sectional area and the deflector directs gases towards the nozzle to enhance gas velocity and reduce deposits, and the injector nozzle can be oriented to minimize buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the injector nozzle is oriented vertically to reduce deposits, then deposit buildup is reduced, but not all engine configurations permit this orientation
Solution Approach 1:
Instead of requiring the engine configuration to adapt to a vertical nozzle orientation, the invention inverts the approach by designing a flow hood with a deflector member that actively directs exhaust gas flow onto the nozzle surface. This allows the nozzle to maintain its optimal vertical orientation relative to the gas flow regardless of the engine's installation configuration, resolving the contradiction between reliability and adaptability.
2Measurement precision
If the NOx sensor is placed in the flow hood cavity, then NOx detection is enabled, but the sensor may not receive adequate gas flow velocity for accurate measurement
Solution Approach 1:
The flow hood cavity acts as an intermediary chamber that conditions the exhaust gas flow before it reaches the NOx sensor. By providing a confined space with controlled geometry, the flow hood ensures that exhaust gases maintain adequate velocity and turbulence as they pass over the sensor, enabling accurate measurements without requiring direct high-velocity flow from the exhaust pipe.
3Reliability
If the flow hood directs exhaust gases across the injector nozzle, then reducing agent deposits are reduced, but the system complexity increases with additional components
Solution Approach 1:
The flow hood assembly is designed as a multi-functional component that simultaneously conditions exhaust gas flow for sensor measurement, directs flow onto the injector nozzle to prevent deposits, and provides structural support for mounting the sensor and injector. By combining multiple functions into a single integrated structure, the invention reduces overall system complexity while achieving the desired protective effect.
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
The solution effectively reduces the buildup of reducing agents on injector nozzles and ensures adequate gas flow velocity for NOx sensors, improving the performance of the SCR device and maintaining system efficiency across various engine configurations.
Implementation Method 1
the deflector member being inclined towards the socket to direct a portion of the exhaust gases towards the socket and across the nozzle
Implementation Method 2
A baffle is provided in the cavity, the baffle reducing a cross-sectional area of the cavity at the neck section
Data Source
AI summary
A flow hood assembly for an engine aftertreatment system having a particulate filter and a selective catalytic reduction device is disclosed. An outer case defines a cavity, the outer case having an inlet and an outlet formed therein, and a neck section formed between the inlet and the outlet. A socket in the outer case is in an opposed relationship to the outlet and is shaped to receive an injector that introduces a reducing agent into the flow of exhaust gases. A baffle reduces a cross-sectional area of the cavity at the neck section to increase exhaust gas velocity at a sensor positioned at the neck section. A deflector member in the cavity between the baffle and the socket directs a portion of the exhaust gases towards the socket and across the injector nozzle.