Exhaust Reductant Injector Shielding Flow Guide

Solution Overview

Problem

The existing methods for injecting reductants into exhaust systems, such as diesel exhaust systems, face inefficiencies due to droplet deposition on the exhaust pipe walls, which reduces the effectiveness of NOx conversion, especially at low temperatures and in air-assisted injection systems where droplets follow the main exhaust flow and impinge on the pipe walls.

Innovation Solution

A flow guide assembly with a shield member and vane is used to divert a portion of the exhaust flow and create a shielding effect, preventing reductant droplets from contacting the pipe walls by guiding them along the centerline of the exhaust pipe, ensuring uniform distribution and reducing the risk of deposits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If reductant is injected into exhaust gas upstream of SCR module, then NOx conversion efficiency is improved, but droplet deposition on exhaust pipe walls increases

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSLoss of substance

Solution Approach 1:

A gas barrier (intermediary fluid layer) is introduced between the injected reductant droplets and the exhaust pipe wall. This gas barrier prevents direct contact between droplets and the wall surface, eliminating deposition while allowing droplets to remain in the exhaust gas stream for effective NOx conversion at the SCR catalyst.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The solution moves the problem from a two-dimensional wall surface deposition issue to a three-dimensional gas flow control problem. By manipulating gas flow patterns in the third dimension (creating recirculation zones and gas barriers), the system prevents droplet-wall interaction while maintaining droplet-catalyst interaction.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If air-assisted dosing system is used, then droplet size is reduced and mixing is improved, but wall impingement increases due to droplet following exhaust flow

Engineering Contradiction:

Core Design Contradiction:

Manufacturing precisionVSEase of operation

Solution Approach 1:

The system creates a replica of the favorable centerline injection conditions throughout the exhaust pipe cross-section. By inducing gas recirculation, exhaust gas from the center (where uniform droplet distribution is achieved) is redirected to the wall regions, copying the effective droplet pattern to areas that would otherwise experience direct wall impingement.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The solution uses pneumatic principles by utilizing exhaust gas flow itself as the transporting medium. The recirculation of exhaust gas creates aerodynamic forces that carry droplets away from the wall and distribute them uniformly, replacing the need for complex mechanical control systems.

Inventive Principle:

Principle #29Pneumatics and hydraulics

3Adaptability or versatility

If injector is placed on exhaust pipe bend, then packaging flexibility is improved and injector temperature issues are reduced, but droplet wall impingement increases

Engineering Contradiction:

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The system introduces dynamic gas recirculation patterns that adapt to the geometric constraints of the exhaust pipe bend. By creating moving recirculation zones and transient gas barriers, the system dynamically compensates for the unfavorable injector positioning, ensuring continuous effective droplet transport to the catalyst despite the bend geometry.

Inventive Principle:

Principle #15Dynamics

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 solution enhances the delivery of reductant droplets to the SCR catalyst, improving NOx conversion efficiency by minimizing wall impingement and deposit formation, thus maintaining system performance and flexibility.

Implementation Method 1

A flow guide assembly with a shield member and vane is used to divert a portion of the exhaust flow and create a shielding effect

Methodology Applied

Scientific EffectGas flow:

Implementation Method 2

The reductant converts NOx to nitrogen gas and water in the presence of the SCR

Methodology Applied

Scientific EffectChemical reaction:

Implementation Method 3

Urea is converted to ammonia through thermal decomposition

Methodology Applied

Scientific EffectThermal decomposition: Thermolysis

Data Source

PatentEP2983809B1Reductant injection in an exhaust system

Publication Date: 2018.05.02

Figure 1~2
Figure 3~4
Figure 5

AI summary

An engine exhaust system comprises: an exhaust pipe (18) having a bend routing an exhaust flow in a curved path, the exhaust pipe having an interior surface and being in fluid communication with a catalyst (22) downstream of the bend. An injector (12) mounted to the exterior of the exhaust pipe (18) and having an injector tip (28) which is disposed within the interior of the exhaust pipe at the bend, for injecting liquid reductant into the exhaust pipe. A shield member (4) mounted in the exhaust pipe and spaced apart from the interior surface of the exhaust pipe, the shield member comprising a generally tubular or frustoconical structure having an open proximal end (14) and an open distal end (16), the proximal end (14) being disposed such that the injector tip (28) is inside the shield member (4), the distal end (16) being disposed at or towards a centre line (26) of the exhaust pipe. A vane (6) mounted in relation to the shield member (4), the vane being arranged and adapted to direct a proportion (24) of exhaust flow from upstream of the bend (30) in a substantially arcuate path into the proximal end (14) of the shield member (4).