Internal Cone Reductant Injection for SCR Evaporation

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Solution Overview

Problem

In diesel engine exhaust systems, the evaporation and decomposition of urea reductant in SCR systems are inefficient due to high exhaust gas velocity, leading to incomplete evaporation before reaching the catalyst, which reduces SCR performance and causes solid deposits on the exhaust pipe.

Innovation Solution

An internal cone is installed within the exhaust pipe to direct exhaust gases around the injected urea, creating a drag force that increases the reductant's travel time and maintains elevated temperatures for complete evaporation and decomposition, preventing contact with the cooler pipe surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If the injector is placed far upstream of the SCR catalyst to facilitate evaporation and decomposition, then the reductant has more time to evaporate and decompose, but the residual time of evaporation is still larger than the travel time to the catalyst due to high exhaust gas flow velocity

Engineering Contradiction:

Improvetravel time of reductantVSAvoidevaporation and decomposition efficiency

Core Design Contradiction:

Duration of action of moving objectVSProductivity

Solution Approach 1:

An internal cone structure is introduced as an intermediary component within the exhaust pipe. This cone creates a drag force on the exhaust gas flow, reducing the gas velocity and increasing the residence time of the reductant in the hot exhaust zone, thereby improving evaporation and decomposition efficiency without requiring the injector to be placed far upstream

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the exhaust gas velocity is high to maintain system flow, then the system operates efficiently, but the exhaust gas stream carries large droplets at high velocity to the catalyst, resulting in insufficient availability of reductant

Engineering Contradiction:

Improveexhaust gas velocityVSAvoidSCR catalyst performance

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The internal cone acts as a flow conditioning intermediary that reduces exhaust gas velocity in the region where reductant evaporation and decomposition occur. This localized velocity reduction allows complete evaporation and decomposition while maintaining overall system flow efficiency

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The internal cone changes the flow parameters (velocity, residence time) in the critical evaporation zone. By creating a drag force, the cone reduces gas velocity and increases residence time, enabling complete reductant decomposition before reaching the catalyst

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the urea solution is injected into the cooler exhaust pipe surface, then the injection process is simple, but the urea solution will remain liquid and form solid deposits on the inner surface

Engineering Contradiction:

Improveinjection system simplicityVSAvoidsolid deposits on exhaust pipe

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The exhaust pipe interior is segmented into two zones: a central cone region where hot exhaust gas flows and an outer annular region where the cooler pipe wall is located. The reductant is injected into the central hot zone, ensuring evaporation and decomposition occur away from the cooler pipe surface, preventing solid deposit formation

Inventive Principle:

Principle #1Segmentation

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 method enhances urea evaporation and decomposition efficiency, reduces solid deposits, and allows for a closer injector placement, improving SCR system performance and reducing corrosion.

Implementation Method 1

creating a drag force on the injected liquid reductant to increase the travel time of the injected liquid reductant from the injector to the catalyst

Methodology Applied

Scientific EffectDrag force: Drag

Implementation Method 2

The heat required for evaporating most reductants is high. For example, a urea solution is injected into the system at an ambient temperature and typically needs to be heated above 150° C. or 200° C. to evaporate the water and decompose the remaining urea into ammonia and isocyanic acid

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

heated above 150° C. or 200° C. to evaporate the water and decompose the remaining urea into ammonia and isocyanic acid

Methodology Applied

Scientific EffectDecomposition: Decomposition (biological)

Data Source

PatentUS8173088B2Method, system and apparatus for liquid injection into a gas system

Publication Date: 2012.05.08 INT ENGINE INTPROP CO LLC

AI summary

A method for injection reductant into an exhaust gas and for evaporating and decomposing the reductant at an elevated temperature includes providing an exhaust pipe having an interior surface and disposing the pipe in fluid communication with and upstream of a catalyst. The method includes the steps of disposing an internal cone within the pipe generally parallel to the pipe, mounting an injector to the exterior of the pipe in fluid communication with the cone, injecting the reductant into the cone, and directing the exhaust gas in a passage between the interior surface of the pipe and the cone. The exhaust gas is directed within the cone. The flow of exhaust gas has an elevated temperature compared to an ambient. A further step includes creating a drag force on the injected reductant to increase travel time of the injected reductant from the injector to the catalyst.