Segmented Injection Unit for Exhaust Reducing Agent Dosing
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Solution Overview
Problem
Existing injection arrangements for reducing agents in combustion engines face challenges with extreme temperatures and vibrations, often requiring a more protected position which reduces their effectiveness in nitrogen oxide reduction due to increased distance from the turbine.
Innovation Solution
A robust and simple injection unit design with a housing and piston system that allows for precise pressure control between chambers, enabling the injection unit to be placed close to the engine while sensitive components are kept at a distance, utilizing a solenoid valve for efficient urea solution dosing and temperature management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the injection unit is positioned immediately downstream of the turbine to maximize nitrogen oxide reduction effectiveness, then the reduction efficiency is improved, but the injection unit is exposed to very high exhaust temperatures and vibrations which worsen its reliability
Solution Approach 1:
The injection unit is segmented into a housing containing only the orifice and piston, while the valve member is separated and positioned in the return line away from the exhaust passage. This segmentation allows the housing to be placed close to the turbine for effective injection while the valve member remains in a protected position, resolving the contradiction between reduction efficiency and reliability.
2Reliability
If the injection unit is positioned at a distance from the combustion engine to avoid high temperatures and vibrations, then the reliability is improved, but the distance from the turbine reduces the nitrogen oxide reduction effectiveness
Solution Approach 1:
The injection unit is divided into a housing that can be positioned close to the turbine and a valve member that can be positioned away from the exhaust passage. This allows the housing to be optimally positioned for injection effectiveness while the valve member is protected from extreme conditions.
Solution Approach 2:
The return line acts as an intermediary pathway, allowing the valve member to be positioned in a protected location while still controlling the injection process. The return line connects the injection unit to the reducing agent reservoir, enabling remote valve placement without compromising injection functionality.
3Measurement precision
If a complex injection unit design with multiple components is used to achieve precise control, then the control precision is improved, but the device complexity increases making it difficult to withstand extreme temperatures and vibrations
Solution Approach 1:
The injection unit is segmented into minimal components (housing, piston, orifice) with the valve member separated. This segmentation simplifies the housing structure, making it more robust for high-temperature and high-vibration environments while maintaining precise control through the separate valve member.
Solution Approach 2:
The valve member is extracted from the housing and positioned in the return line. This extraction removes the complex valve mechanism from the high-stress environment of the exhaust passage, allowing the housing to be simple and robust while the valve provides precise control from a protected position.
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 allows for effective injection of reducing agents at high exhaust gas temperatures, enhancing nitrogen oxide reduction capabilities while protecting sensitive components from extreme conditions.
Implementation Method 1
The pressure drop in the flow channel between the first chamber and the second chamber results in different pressures in the first chamber and the second chamber. The pressure ratio between the first chamber and the second chamber and the movement of the piston member is controlled in a simple manner by a valve member in the return line.
Implementation Method 2
When the urea solution is sprayed into the exhaust passage, the resulting finely divided solution becomes evaporated in contact with the hot exhaust gases so that ammonia is formed.
Data Source
Figure 1
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AI summary
The invention relates to an injection arrangement (7) for injection of a reducing agent into an exhaust line (3) of a combustion engine (2).The injection arrangement (7) comprises an injection unit (10) in the form of a housing (18, 19) and a piston member (21) dividing an inner space of the housing in a first chamber (23) and a second chamber (24). The injection arrangement (7) comprises at least one flow channel (25a, 25b) allowing a reducing agent flow with a specific pressure drop between the first chamber (23) and the second chamber (24), and a valve member (13) arranged in a return line (14) which in an open position creates a first ratio between the pressures in the first chamber (23) and in the second chamber (24) at which the piston member (21) is moved to a first position in which injection of reducing agent via the orifice (20) is prevented and which in a closed position creates a second ratio between the pressures in the first chamber (23) and in the second chamber (24) at which the piston member (21) is moved to a second position in which the injection of reducing agent via the orifice (20) is allowed