Heat Shielded Reducing Agent Injection Nozzle
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Solution Overview
Problem
Existing injection nozzles for internal combustion engines face thermal stress and heat transfer issues due to high exhaust gas temperatures, which can lead to damage and inefficiency in reducing agent injection for selective catalytic reduction, particularly with urea solutions.
Innovation Solution
An external-mixing injection nozzle design featuring a heat shield integrated into the nozzle body to reduce thermal expansion and stress, combined with a curved reducing agent line and compressed air cooling, allows for efficient atomization of the reducing agent outside the nozzle head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the nozzle body and reducing agent line are exposed to high exhaust gas temperatures, then the reducing agent can be injected into the exhaust stream, but thermal stress and heat transfer cause damage and reduce service life
Solution Approach 1:
A heat shield made of heat-resistant material is introduced as an intermediary component between the exhaust gas environment and the reducing agent line. The heat shield has a first end connected to the exhaust pipe and a second end connected to the nozzle body, creating a thermal barrier that protects the reducing agent line from direct heat exposure while still allowing the system to function at high temperatures
2Productivity
If the nozzle protrudes deeper into the exhaust gas stream to improve mixing, then atomization efficiency improves, but thermal stress and heat exposure increase
Solution Approach 1:
The heat shield serves as a protective intermediary that enables the nozzle to protrude deeper into the hot exhaust stream by bearing the thermal load. This allows the nozzle head to be positioned closer to the optimal injection zone for better atomization and mixing while the heat shield absorbs the thermal stress
3Object-affected harmful factors
If additional insulation components are added to protect the nozzle body, then thermal protection improves, but device complexity and assembly effort increase
Solution Approach 1:
The heat shield is integrated with the existing nozzle structure by connecting its ends to the exhaust pipe and nozzle body respectively. This merging approach provides thermal protection without requiring completely separate insulation assemblies, reducing overall system complexity while maintaining protective function
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 enhances the nozzle's tolerance to high exhaust gas temperatures, increases service life, and improves mixing efficiency of the reducing agent with exhaust gases, reducing thermal stress and potential decomposition of the urea solution.
Implementation Method 1
the nozzle body has at least one heat shield which thermally insulates the reducing agent line at least partially
Implementation Method 2
for atomizing the reducing agent by means of compressed air or propellant gas
Implementation Method 3
In the exhaust gas, the urea decomposes into gaseous ammonia and CO2 at temperatures above 150° Celsius
Implementation Method 4
Through thermal radiation or heat transfer by contact or convection, heat can also be transferred to the reducing agent-carrying elements
Implementation Method 5
Through thermal radiation or heat transfer by contact or convection, heat can also be transferred to the reducing agent-carrying elements
Implementation Method 6
stresses can occur at the connection, especially a welded joint, between the reducing agent line and the nozzle head if the thermal expansion of the nozzle body differs from that of the reducing agent line
Data Source
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AI summary
The invention relates to an external mixing injection nozzle (60) for injecting a reducing agent into the exhaust gas stream of an internal combustion engine for selective catalytic reduction, in particular for atomizing the reducing agent by means of compressed air or propellant gas, wherein the injection nozzle (60) comprises a nozzle body (61) and a nozzle head (62), wherein a reducing agent line (68) is arranged in the nozzle body (61) and connected to the nozzle head (62), characterized in that the nozzle body (62) has at least one heat shield (70) which thermally insulates the reducing agent line (68) at least partially. Furthermore, 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 using such an injection nozzle.