Ammonia Injector Anti-Backflow Layout for Cold-Start Clog Prevention
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Solution Overview
Problem
Existing injectors for gaseous ammonia in internal combustion engines are prone to clogging by ammonia salts at cold temperatures, leading to operational failures and prolonged unavailability when the engine starts.
Innovation Solution
The injector design includes an anti-backflow device with a constriction, chicane, or check valve, and a heater to prevent clogging, allowing fluid flow from the upstream to the downstream pipe, and the upstream pipe is heated during engine operation to maintain functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gaseous ammonia is injected directly into the exhaust line, then the effectiveness of NOx reduction is improved, but the injection nozzle becomes clogged by ammonia salts at cold temperatures
Solution Approach 1:
The harmful backflow of ammonia salts from the downstream pipe to the upstream pipe is extracted and prevented by the anti-backflow device. This device isolates the clogging issue to the downstream side while protecting the upstream dosing system and injection nozzle from salt accumulation, thereby maintaining injection effectiveness without suffering from clogging problems.
Solution Approach 2:
The anti-backflow device acts as an intermediary element between the upstream and downstream pipes. It allows forward flow of ammonia for effective NOx reduction while blocking the reverse flow of ammonia salts that would otherwise cause clogging. This mediator resolves the contradiction by selectively permitting beneficial flow while preventing harmful backflow.
2Ease of operation
If the injection nozzle is clogged at cold temperatures, then the injector becomes non-operational, but clearing the clog takes several hours
Solution Approach 1:
The anti-backflow device performs a preliminary protective action by preventing ammonia salts from reaching and clogging the injection nozzle in the first place. By blocking the backflow path before salts can accumulate, the device eliminates the need for lengthy unclogging operations and maintains continuous operational availability.
Solution Approach 2:
The anti-backflow device provides beforehand cushioning against the harmful effect of ammonia salt backflow. It creates a protective barrier that cushions the upstream system from the damaging impact of salt accumulation, preventing operational disruptions before they can occur.
3Reliability
If the anti-backflow device includes a constriction with reduced flow-section, then the anti-backflow effect is improved, but the pressure loss increases
Solution Approach 1:
The anti-backflow device applies local quality by creating a restricted flow section only at the specific location where backflow prevention is needed, rather than restricting the entire flow path. This localized constriction provides effective anti-backflow action while minimizing overall pressure loss in the system.
Solution Approach 2:
The anti-backflow device addresses the flow control problem in another dimension by using a check valve mechanism that controls flow direction rather than simply restricting flow magnitude. This dimensional approach to flow control provides backflow prevention without the continuous pressure penalty associated with fixed constrictions.
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 design significantly reduces the risk of clogging and minimizes unavailability time, ensuring the injector is operational quickly after engine start-up, effectively maintaining exhaust gas depollution.
Implementation Method 1
the injector further comprises a heater configured to heat the anti-backflow device during a starting phase of the internal combustion engine
Implementation Method 2
the upstream pipe is configured to be heated during working phases of the internal combustion engine
Data Source
AI summary
An injector comprises at least one injection nozzle, a dosing system to provide a dosed flow of reducing agent to the at least one or each injection nozzle, and an injection line fluidically connecting the dosing system to the at least one or each injection nozzle. The injection line comprises an upstream pipe fluidically connected to the dosing system, at least one downstream pipe fluidically connected to a respective injection nozzle, and at least one anti-backflow device to avoid or minimize fluidic flow from the at least one or each downstream pipe toward the upstream pipe.