Exhaust Reactant Shielding Bypass Flow
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Solution Overview
Problem
The introduction of reducing agents like urea into exhaust gas streams in internal combustion engines can lead to deposit formation on exhaust gas ducts, disrupting reactant release and flow direction, and creating recirculation zones that increase the risk of deposit precipitation near the reactant release area.
Innovation Solution
An exhaust system with a bypass flow generation arrangement that surrounds the reactant stream to shield and guide it, reducing the risk of deposits by creating a protective flow that corresponds to the main direction of the reactant stream and using either compressed air or partial exhaust gas as the bypass flow to enhance evaporation and miscibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If reactant is introduced opposite to the exhaust gas stream direction to achieve efficient mixing, then mixing efficiency is improved, but recirculation zones develop causing reactant to precipitate near the injector
Solution Approach 1:
A bypass flow is introduced as an intermediary fluid stream that flows alongside the reactant stream from the injection point. This bypass flow acts as a protective mediator, preventing the reactant from contacting the exhaust gas duct wall and forming deposits, while also preventing recirculation zones that would cause precipitation near the injector.
Solution Approach 2:
The solution uses fluid dynamic principles by introducing a bypass flow stream that follows the reactant stream. The bypass flow creates a protective boundary layer through pneumatic/hydraulic action, utilizing flow patterns and pressure distributions to shield the reactant from the exhaust gas duct environment and maintain reliable injection.
2Productivity
If reactant is released in a droplet or spray configuration to enhance mixing, then mixing is improved, but deposits form on the exhaust gas duct wall
Solution Approach 1:
The bypass flow serves as an intermediary protective layer between the reactant droplets/spray and the exhaust gas duct wall. This intermediary flow prevents direct contact between the reactant and the wall surface, eliminating the harmful deposit formation while preserving the beneficial spray configuration for mixing.
3Manufacturing precision
If the reactant release arrangement is positioned to optimize injection, then injection precision is improved, but the area becomes susceptible to recirculation and deposit formation
Solution Approach 1:
The bypass flow acts as a protective intermediary that shields the reactant release arrangement area from recirculation effects. By flowing alongside the reactant stream, the bypass flow creates a protective boundary that prevents recirculation zones from forming near the injector, thereby protecting the precisely positioned injection system.
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 bypass flow effectively prevents reactant droplets from precipitating on the exhaust gas duct and reduces recirculation, ensuring efficient reactant release and mixing while minimizing deposit formation, thus maintaining the integrity of the reactant release process.
Implementation Method 1
a bypass flow surrounding or enveloping the reactant stream is associated with the reactant stream in the exhaust system configured according to the present invention, the risk that reactant droplets will precipitate on the exhaust gas duct or in the area of the reactant release arrangement is reduced
Implementation Method 2
The bypass flow has an effect shielding the reactant release arrangement as well as an effect moving the reactant stream during introduction into the exhaust gas stream
Implementation Method 3
The reactant stream is efficiently protected by the bypass flow from an effect of flow separations of the exhaust gas stream
Implementation Method 4
The development of a secondary flow in the area in which the reactant is released is prevented, and the development of secondary droplets separating from the reactant stream is prevented or at least made difficult by the bypass flow surrounding or guiding and shielding the reactant stream
Implementation Method 5
using either compressed air or partial exhaust gas as the bypass flow to enhance evaporation and miscibility
Implementation Method 6
using either compressed air or partial exhaust gas as the bypass flow to enhance evaporation and miscibility
Data Source
AI summary
An exhaust system for an internal combustion engine, especially for the internal combustion engine of a vehicle, includes an exhaust gas duct (12) carrying an exhaust gas stream (A) and a reactant release arrangement (18) for releasing a reactant ® into the exhaust gas stream (A). A bypass flow generation arrangement (25) generates a bypass flow (M) surrounding the reactant stream ® that is released from the reactant release arrangement (18).