Pressure Swirl Injector Pintle Control for Urea Solidification
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Solution Overview
Problem
Aqueous urea solutions used in SCR systems for reducing NOx emissions from diesel engines are corrosive, prone to solidification, and inefficiently atomized, leading to clogging, fouling, and reduced injector lifespan due to heat transfer issues and poor lubrication, which affects the injector's performance and longevity.
Innovation Solution
The design includes a reagent injector system with a pole piece passage, collar passage, and distribution passages that direct the reagent through a series of slots and orifices, utilizing a magnetic coil for precise atomization and continuous reagent circulation to maintain low temperatures and prevent solidification, along with a heat shield and insulator to manage heat transfer and prevent fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high injection pressures are used to minimize insufficient atomization of urea mixture, then atomization quality is improved, but over-penetration of spray plume into exhaust stream occurs causing impingement on exhaust pipe inner surface
Solution Approach 1:
The injector divides the urea mixture flow into multiple separate spray streams through multiple orifices arranged in a circular pattern. This segmentation allows each individual spray plume to be smaller and less prone to over-penetration, while collectively providing sufficient atomization coverage. The segmented approach enables better control over spray trajectory and distribution.
Solution Approach 2:
The injector employs different orifice sizes and configurations at different locations around the circular arrangement. Each orifice is optimized for its specific position and local flow conditions, allowing precise control over atomization quality in different zones while preventing over-penetration in sensitive areas near the exhaust pipe surface.
2Productivity
If aqueous urea solution is used as reagent for SCR system, then NOx reduction effectiveness is improved, but corrosion of mechanical components and solidification in narrow passageways occurs
Solution Approach 1:
The patent introduces a heating element as an intermediary component between the urea solution storage and injection system. This heating element maintains the urea solution temperature above its freezing point, preventing solidification in narrow passageways and pump components. The intermediary heating system enables reliable operation of aqueous urea without the harmful effects of solidification.
Solution Approach 2:
The system actively controls the temperature parameter of the urea solution throughout circulation and injection. By maintaining temperature within a specific range (above freezing but not excessively high to cause degradation), the system preserves the reliability of narrow passageways and moving parts while retaining the NOx reduction effectiveness of aqueous urea.
3Reliability
If tight fits and clearances are employed between moving parts to compensate for poor lubrication by aqueous urea, then injector sealing is improved, but leakage and fouling of moving parts increases
Solution Approach 1:
The patent implements a continuous circulation system where urea solution constantly flows through the injector, carrying away deposits and preventing fouling of moving parts. This continuous action prevents the accumulation of solidified urea and other contaminants that would otherwise build up in tight clearances and cause leakage or seizure of moving components.
Solution Approach 2:
The circulating urea solution serves a dual function: it acts as the chemical reagent for NOx reduction and simultaneously serves as a cleaning agent for the injector internal passages and moving parts. The continuous flow self-cleans the system, removing fouling tendencies and maintaining the integrity of tight fits and clearances without additional lubrication systems.
4Productivity
If injector operates in hot exhaust environment, then SCR system effectiveness is maintained, but heat transfer causes urea solidification and deposit formation on injector components
Solution Approach 1:
The system pre-heats the urea solution in the storage tank and circulation lines before it reaches the injector. By controlling the temperature in advance, the solution arrives at the injector already above its freezing point, preventing solidification during injection despite the hot exhaust environment. This preliminary temperature management prevents deposit formation on injector components.
Solution Approach 2:
The patent introduces a thermal management system with heating elements and temperature sensors as intermediary components between the urea storage and injection points. These intermediaries actively monitor and control the temperature of the urea solution, creating a thermal buffer that protects against the hot exhaust environment and prevents both solidification and excessive heat-induced fouling.
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 reliable injection of aqueous urea, improves heat management, reduces fouling, and prolongs injector life by maintaining the reagent in a liquid state, ensuring efficient NOx reduction and minimizing the need for frequent reagent replenishment.
Implementation Method 1
an electromagnetic coil can be provided that surrounds an outside diameter of the pole piece
Implementation Method 2
The circulating aqueous urea can help cool the injector and/or components adjacent to the exhaust stream thereby preventing solidification of the aqueous urea
Implementation Method 3
injecting an atomized reagent into the exhaust stream of the engine
Data Source
AI summary
A reagent injector with a cartridge design has a body with a reagent inlet, outlet, and a swirl chamber, which has an exit orifice that may be covered and uncovered by a solid, movable pintle. Reagent flows through the injector when the exit orifice is covered and uncovered to cool the injector. An insulator may be disposed between the injector body and a mounting flange connectable to an exhaust system. A flow path ensures cooling of an electromagnetic actuator. Reagent may bypass an orifice swirl chamber when the pintle blocks the exit orifice. Fluid may flow between an outside diameter of a pole piece and an inside diameter of an electromagnetic actuator, through an orifice chamber and return through a central bore housing a solid pintle, around which fluid may flow. Different inner injector body passages may direct fluid into an orifice distribution chamber and out to the solid pintle.