Push-Out Spring Metering Pump for Uniform Reducing-Agent Flow
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Solution Overview
Problem
Existing reducing agent dosing systems for internal combustion engines face challenges in providing uniform and continuous flow rates and generating a finely dispersed aerosol for effective selective catalytic reduction, particularly with urea-based solutions.
Innovation Solution
A reciprocating piston pump with a spring-driven mechanism is used to simultaneously execute delivery and suction strokes, ensuring uniform pressure and smooth injection, combined with a pressure-resistant line and volume expansion elements to maintain consistent spray quality, and a control device for monitoring and adjusting the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a reciprocating piston pump is used for dosing reducing agent, then the dosing quantity can be controlled, but the flow rate becomes discontinuous and pressure varies
Solution Approach 1:
The patent combines a reciprocating piston pump with a check valve system to merge the dosing function with continuous flow maintenance. The check valve prevents backflow during the piston's reciprocating motion, allowing the pump to deliver reducing agent in a controlled manner while maintaining continuous forward flow and stable pressure, thus resolving the contradiction between dosing control and flow uniformity.
2Temperature
If reducing agent is injected as aerosol, then evaporation occurs due to high exhaust temperatures, but uniform aerosol generation is difficult to achieve
Solution Approach 1:
The patent employs a reciprocating piston pump that dynamically adjusts the injection characteristics of the reducing agent. The piston's reciprocating motion creates dynamic pressure variations that enhance aerosolization, while the associated check valve system maintains stable overall pressure. This dynamic injection process produces fine, uniform aerosol droplets that evaporate efficiently at high exhaust temperatures, resolving the contradiction between evaporation efficiency and aerosol uniformity.
3Productivity
If the pump piston is retracted electromagnetically, then the spring is tensioned for the next stroke, but energy is consumed during retraction
Solution Approach 1:
The patent utilizes periodic electromagnetic actuation of the pump piston, where the piston is retracted electromagnetically only when needed to reset the spring for the next dosing stroke. During the dosing phase, the spring provides the driving force without additional energy input. This periodic electromagnetic action combined with spring energy storage minimizes overall energy consumption while maintaining high pump stroke speed and productivity.
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 ensures consistent and frost-resistant delivery of reducing agents, maintaining optimal spray quality and preventing blockages, thereby enhancing the efficiency of selective catalytic reduction processes.
Implementation Method 1
the feed stroke and the suction stroke are carried out simultaneously by a stroke of the piston up to the top dead center by means of a spring
Implementation Method 2
the piston is retracted electromagnetically against the spring force of the spring up to the bottom dead center by means of a switchable coil
Implementation Method 3
the reducing agent is introduced into the exhaust stream of the combustion engine in the form of an aerosol, with the aerosol evaporating due to the high exhaust temperatures
Implementation Method 4
In the exhaust gas, the urea decomposes into gaseous ammonia and CO2 at temperatures above 150°C
Implementation Method 5
In the second step, hydrolysis occurs in the presence of water, in which the isocyanic acid is also converted into ammonia, forming carbon dioxide (CO2)
Data Source
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AI summary
The invention relates to a reducing agent metering system for injecting a reducing agent into the exhaust gas stream of an internal combustion engine for selective catalytic reduction, comprising at least one feed pump (2) by means of which reducing agent is drawn from a reducing agent tank (1) via a suction line (3) and conveyed via at least one pressure line (4) to at least one nozzle (5) for injection into the exhaust gas stream of the internal combustion engine. The feed pump (2) is a reciprocating piston pump, wherein the delivery stroke and the suction stroke are executed simultaneously by a stroke of the piston to top dead center by means of a spring. After completion of the stroke, the piston is electromagnetically retracted against the spring force to bottom dead center by means of a switchable coil, thereby tensioning the spring. The invention further relates to a method for operating such a reducing agent metering system.