Reversible Urea Metering Pump for Ice Prevention
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Solution Overview
Problem
Existing metering systems for urea solutions in internal combustion engines face issues with ice formation and excessive ice pressures at low temperatures, which can damage components and lead to impermissible pressures.
Innovation Solution
A metering system with a reversible feed pump and metering valve arrangement that allows for evacuation of the region between the pump and valve in the opposite direction of normal operation, preventing ice formation and using a peristaltic pump for precise liquid delivery and counter-pressure generation, along with a ventilation valve to prevent contamination and a thermal preparation unit for evaporation, ensuring safe operation and efficient urea solution distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the urea solution is metered into the exhaust manifold, then nitrogen oxide conversion is achieved, but ice formation and excessive pressures can damage components at low temperatures
Solution Approach 1:
The system applies preliminary anti-action by evacuating the urea solution from the metering valve and associated components before the engine is started or before temperature drops below freezing point. This preventive evacuation removes the harmful substance (urea solution) that would otherwise freeze and expand, causing damage to components. The control unit monitors temperature and activates the feed pump in reverse to evacuate the solution proactively, preventing the harmful effect before it occurs.
Solution Approach 2:
The feed pump is designed to operate in reverse direction to evacuate the urea solution from the metering valve and lines. Normally the pump feeds solution from the tank to the metering valve, but when evacuation is required, the pump direction is reversed to withdraw the solution back toward the tank or discharge it safely. This inversion of the normal feeding direction enables the system to remove the harmful substance that causes ice formation damage.
2Measurement precision
If a thermal preparation unit is used to prepare the liquid, then metering precision is improved, but re-evaporation or crystallization can occur at high temperatures
Solution Approach 1:
The system performs preliminary evacuation of the thermal preparation unit and associated lines before the engine is started or before temperatures rise to levels that would cause re-evaporation or crystallization. By removing the urea solution proactively when the engine is off or at low temperature, the system prevents the harmful effects of re-evaporation and crystallization that would occur if the solution remained in the heated components during operation.
Solution Approach 2:
The system dynamically adjusts its operation based on engine state and temperature conditions. The control unit monitors whether the engine is running, the temperature of components, and the presence of urea solution, then activates evacuation only when conditions indicate potential harm (low temperature, engine off, or high temperature risking crystallization). This dynamic control enables the system to maintain metering precision while avoiding harmful effects by adapting the evacuation operation to current conditions.
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
The system effectively prevents damage from ice formation and excessive pressures, ensures precise metering, reduces environmental pollution, and enhances operational safety by allowing for reversible operation and efficient urea solution preparation, improving nitrogen oxide conversion rates even at low exhaust gas temperatures.
Implementation Method 1
use of a peristaltic pump makes it possible to improve the capability for winter operation
Implementation Method 2
if a thermal preparation unit is present for the liquid, unwanted re-evaporation or crystallization out of one or more components of the liquid can be avoided
Implementation Method 3
the reducing agent, required for the catalytic conversion of the nitrogen oxides, is carried along instead of ammonia in the vehicle, in the form of an aqueous urea solution from which the ammonia can be released by hydrolysis of the urea solution
Implementation Method 4
the nitrogen oxides are converted together with ammonia into nitrogen and water in a selective catalytic converter
Data Source
AI summary
The invention relates to a dosing system comprising a dosing means for metering a liquid, especially an aqueous urea solution used for the after treatment of exhaust gases generated by combustion engines. The liquid can be conveyed from a reservoir into an exhaust manifold through the dosing means in a normally operating conveying device. According to the invention, at least one area that is located between a dosing point and the reservoir and is impinged upon by the liquid can be emptied counter to a normal transport direction of the liquid.