Diesel Exhaust Fluid Injector Cleaning via Engine Idle Control
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Solution Overview
Problem
Diesel engine DEF injectors clog due to urea crystallization, leading to reduced NOx emission reduction and increased repair times and costs, as existing remediation methods are limited by duration and effectiveness in melting urea crystals.
Innovation Solution
Operating the engine in a DEF injector cleaning mode by increasing idle speed and decreasing air intake flow and exhaust backpressure to warm the engine and exhaust system, allowing for quick and cost-effective cleaning of the injector without removing it from the vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DEF injector is removed from the vehicle for cleaning, then the clogged DEF injector can be thoroughly cleaned, but the repair time and cost increase
Solution Approach 1:
The DEF injector cleaning system allows the injector to be cleaned in-place within the vehicle without removal. The system uses the vehicle's own exhaust heat and DEF dosing system to melt and flush out urea crystals, enabling self-service cleaning that reduces repair time and costs while restoring injector flow
Solution Approach 2:
A controller acts as an intermediary to coordinate the cleaning process by activating the DEF pump to deliver DEF through the injector while simultaneously controlling engine operation to generate sufficient exhaust heat. This intermediary control system orchestrates the interaction between thermal and fluid systems to achieve effective in-place cleaning
2Reliability
If the exhaust gas temperature is raised to melt urea crystals, then the DEF injector can be cleaned, but urea crystals not in close proximity to the exhaust gas flow may not be melted
Solution Approach 1:
The system uses high-pressure DEF fluid delivery through the pump and injector to physically flush out melted urea crystals from the injector. The hydraulic action of the DEF flow works in conjunction with thermal heating to ensure complete clearing of the injector, addressing crystals that may not be directly exposed to exhaust heat
Solution Approach 2:
The cleaning process maintains continuous operation of the DEF pump and engine to sustain both thermal heating and fluid flow through the injector. This continuous action ensures that urea crystals are progressively melted and flushed out over time, achieving complete cleaning effectiveness
3Reliability
If a finite duration remediation mode is used, then the cleaning process can be initiated, but the cleaning may not be completed if the vehicle operating status does not allow sufficient time
Solution Approach 1:
The cleaning mode duration is made dynamic rather than fixed. The controller continuously monitors whether the pump duty cycle has returned to normal levels and adjusts the cleaning duration accordingly. This dynamic adaptation allows the cleaning process to extend beyond predetermined time limits when vehicle operating conditions prevent completion, ensuring thorough cleaning while accommodating real-time operational constraints
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 effectively clears clogged DEF injectors while in-service, reducing repair costs and vehicle downtime by ensuring the engine and SCR system operate within normal temperature ranges, thus maintaining efficient NOx emission reduction.
Implementation Method 1
raising the exhaust gas temperature may melt urea crystals within the DEF injector
Implementation Method 2
Hot exhaust gases may heat the DEF, causing water to evaporate and leave behind solid urea in the form of urea crystals
Implementation Method 3
delivering diesel exhaust fluid (DEF) from a DEF dosing system to an exhaust passage of an engine via a DEF injector
Data Source
AI summary
Methods and systems are provided for cleaning a urea-clogged diesel exhaust fluid (DEF) injector included in a selective catalytic reduction (SCR) engine exhaust after-treatment system. In one example, a method may include, responsive to a diagnostic code indicating a clogged DEF injector, operating an engine in a DEF injector cleaning mode comprising operating the engine at a high idle speed, activating a DEF pump to deliver a desired amount of DEF at a desired flowrate, and measuring a duty cycle of DEF pump activation during DEF delivery. Responsive to the duty cycle being greater than a threshold duty cycle for a duration, DEF flow restoration is indicated.