Exhaust Nozzle Counter-Flow Cooling for SCR Urea Mixing
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Solution Overview
Problem
Existing exhaust gas purification devices face challenges in small ships due to lack of installation space for pressurized air tanks, leading to thermal damage and reduced durability of injection nozzles, and improper mixing of reducing agents, which affects normal operation and purification efficiency.
Innovation Solution
An exhaust gas purification device that uses a support member to position the injection nozzle near the radial center of the exhaust pipe, injecting reducing agents along the exhaust direction and cooling media opposite to it, utilizing boosted air from the supercharging passage for cooling, with an adjusting mechanism to control the flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the injection nozzle is positioned near the wall of the exhaust pipe to avoid thermal damage, then the durability of the injection nozzle is improved, but the reducing agent and exhaust gas are not appropriately mixed
Solution Approach 1:
The injection nozzle is positioned at the radial center of the exhaust pipe (changing the spatial dimension from wall-near to center-positioned), and cooling medium is supplied in the axial direction opposite to exhaust flow. This dimensional change allows the nozzle to be centrally positioned for proper mixing while using the cooling medium flow path to protect against thermal damage.
Solution Approach 2:
A cooling medium (such as boosted air from the supercharging passage) is introduced as an intermediary substance that flows through the injection nozzle in the opposite direction to exhaust gas. This intermediary cooling medium protects the injection nozzle from thermal damage while allowing the reducing agent to be properly injected and mixed with exhaust gas.
2Ease of operation
If the injection nozzle is positioned near the center of the exhaust pipe for proper mixing, then the mixing efficiency is improved, but thermal damage occurs reducing durability
Solution Approach 1:
A cooling medium (such as boosted air from the supercharging passage) is introduced as an intermediary substance that flows through the injection nozzle in the opposite direction to exhaust gas. This intermediary cooling medium protects the injection nozzle from thermal damage while allowing the reducing agent to be properly injected and mixed with exhaust gas.
Solution Approach 2:
The invention uses pneumatic flow of cooling medium (boosted air) through the injection nozzle to achieve cooling. The cooling medium is supplied from the supercharging passage and flows through the nozzle body, using gas flow dynamics to remove heat from the injection nozzle without mechanical moving parts.
3Reliability
If air-assisted urea injection system is adopted to cool the injection nozzle, then thermal damage is reduced, but installation space is required for pressurized air tank
Solution Approach 1:
The invention makes the exhaust gas purification system universally applicable to both large ships (with air tanks) and small ships (without air tanks) by using the supercharging passage, which is common to both configurations. The cooling medium supply mechanism can utilize existing boosted air from the supercharger, eliminating the need for separate pressurized air tanks and making the system universally installable.
Solution Approach 2:
The system uses its own supercharging passage and boosted air as the cooling medium source, rather than requiring an external pressurized air tank. The injection nozzle cools itself by having cooling medium flow through it, and the cooling medium is provided by the engine's own supercharging system, making the system self-sufficient.
4Reliability
If cooling medium is supplied to injection nozzle to prevent thermal damage, then durability is improved, but flow rate control is needed to maintain exhaust gas purification efficiency
Solution Approach 1:
The flow rate of cooling medium supplied to the injection nozzle is controlled based on the exhaust gas flow rate. When exhaust gas flow rate is high (indicating high engine load and high exhaust temperature), the cooling medium flow rate is increased to provide sufficient cooling. This feedback control maintains both nozzle durability and purification efficiency under varying operating 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 device reduces thermal damage and adhesion of reducing agents to the injection nozzle, ensuring normal operation and efficient purification of exhaust gases without the need for additional air tanks, enhancing durability and versatility.
Implementation Method 1
a discharge hole for discharging a cooling medium at least in a direction opposite to the exhaust direction
Implementation Method 2
a catalyst that is provided in an exhaust passage that allows the exhaust gas discharged from an engine to flow in a predetermined exhaust direction and promotes reduction of the exhaust gas
Implementation Method 3
a so-called air-assisted urea injection system that supplies pressurized air in an air tank to an injection nozzle by using a pressurized air supply pump and promotes atomization of urea by using the pressurized air
Data Source
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AI summary
[Problem] To provide: an exhaust gas purification device for restraining thermal damage to an injection nozzle without being bound by an air assist function of reducing agent injection; and an engine including the exhaust gas purification device. [Solution] An exhaust gas purification device 1 for purifying exhaust gas of nitrogen oxides includes: a catalyst 14 that is provided in an exhaust pipe 4 (exhaust passage) for transporting exhaust gas, discharged from an engine 2, in a predetermined exhaust direction, and promotes the reduction of the exhaust gas; and an injection nozzle 11 that is provided in the exhaust pipe 4 so as to be upstream of the catalyst 14 in the exhaust direction, and injects a reducing agent for reducing the exhaust gas. The injection nozzle 11 includes an injection hole 16 for injecting the reducing agent toward the catalyst 14, and a discharge hole 18 for discharging a cooling medium in at least the direction opposite the exhaust direction.