Vaporized Reducing Agent Metering for Lean Burn Engines

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Solution Overview

Problem

Current SCR systems for reducing NOx emissions in lean burn internal combustion engines face challenges in delivering and controlling the reducing agent effectively, especially during transient conditions, leading to inefficiencies and ammonia slip, which is hazardous and detrimental to fuel economy.

Innovation Solution

A reducing agent metering system that transitions between vaporized and atomized forms, utilizing capillary flow passages heated by a resistance heating element to deliver a stream of vaporized reducing agent upstream of a deNOx catalyst, with a computer-controlled system to optimize injection based on engine conditions and exhaust temperature.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If urea is converted from solid or aqueous form to gaseous species for SCR applications, then NOx reduction efficiency is improved, but the complexity of the conversion process increases

Engineering Contradiction:

ImproveNOx reduction efficiencyVSAvoidconversion process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the physical state parameter of the reducing agent from liquid to vapor phase by heating it to temperatures above its boiling point. This phase change enables the reducing agent to be effectively delivered to the combustion zone where it can reduce NOx emissions without requiring complex conversion systems.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces complex mechanical conversion systems with a thermal field approach. By using heating elements and thermal energy to vaporize the reducing agent, the system eliminates the need for mechanical pumps, valves, and complex delivery mechanisms required for liquid or solid reducing agents.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If ammonia is used for SCR systems to reduce NOx, then NOx conversion percentage is improved, but safety problems in storage and transport worsen

Engineering Contradiction:

ImproveNOx conversion percentageVSAvoidsafety problems

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses urea as a stable, safe-to-store reducing agent that is converted to ammonia in-situ at the point of use. This approach replaces the need for storing and transporting hazardous gaseous ammonia with a stable solid or liquid urea formulation that can be safely handled and then thermally decomposed to generate the required ammonia.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent introduces urea as an intermediary substance that serves as a safe storage form of the reducing agent. Urea is stored and transported in stable form, then thermally decomposed to ammonia which immediately reacts with NOx in the combustion exhaust, eliminating the need for direct ammonia storage and transport.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If the reducing agent is injected as liquid to achieve rapid vaporization, then response time is improved, but droplet size and fuel economy penalty worsen

Engineering Contradiction:

Improveresponse timeVSAvoidfuel economy penalty

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent utilizes the phase transition of the reducing agent from liquid to vapor by injecting it into the high-temperature combustion zone. The thermal energy from the combustion gases rapidly vaporizes the liquid reducing agent, achieving quick response times without requiring additional energy input or creating large droplet sizes that would penalize fuel economy.

Inventive Principle:

Principle #36Phase transitions

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 system achieves rapid warm-up, high efficiency, and reduced ammonia slip, enabling effective NOx reduction while minimizing power consumption and droplet size, thus improving NOx reduction efficiency and reducing cold-start emissions.

Implementation Method 1

a heat source arranged along the plurality of capillary flow passages. The heat source is operable to heat liquid reducing agent in the plurality of capillary flow passages sufficiently to deliver a stream of vaporized reducing agent

Methodology Applied

Scientific EffectJoule Heating: Joule Heating

Implementation Method 2

heat liquid reducing agent in the plurality of capillary flow passages sufficiently to deliver a stream of vaporized reducing agent

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS7644577B2Reducing agent metering system for reducing NO.sub.x in lean burn internal combustion engines

Publication Date: 2010.01.12 PHILIP MORRIS USA INC

AI summary

A reducing agent metering system for delivering reducing agent to a lean burn internal combustion engine. The reducing agent metering system includes a metering system housing, a system for metering vaporized reducing agent to the internal combustion engine, the system positioned within the metering system housing and a system for delivering an atomized stream of liquid reducing agent to the lean burn internal combustion engine, the system positioned within the metering system housing, wherein the reducing agent metering system is operable to transition from metering vaporized reducing agent to delivering an atomized stream of liquid reducing agent to the lean burn internal combustion engine.