Reduced NOx Emissions Exhaust Gas Recirculation Coolers For Two-Stroke Engines

Reduced NOx Emissions Exhaust Gas Recirculation Coolers for Two-Stroke Engines

Working Principle
Heat Exchange Process: The EGR cooler operates on the liquid - to - gas heat exchange principle. Hot exhaust gas from the engine, with a temperature typically ranging from 350°C to 600°C for diesel engines and 250°C to 450°C for gasoline engines, enters the EGR cooler through the exhaust gas inlet. At the same time, engine coolant, with a temperature of around 80°C to 100°C, circulates around the exhaust gas passages in the cooler. The heat - resistant materials of the exhaust gas passages, such as stainless steel or aluminum - silicon alloys, enable efficient heat transfer from the hot exhaust gas to the coolant. As a result, the exhaust gas is cooled to a lower temperature, usually between 150°C and 250°C for diesel engines and 120°C to 200°C for gasoline engines, before being recirculated.
Cooling Medium Flow: In most cases, the cooling medium used in EGR coolers is the engine's own coolant. The coolant is pumped into the EGR cooler's coolant inlet and flows around the exterior of the exhaust gas passages in the cooler's shell or jacket. To ensure uniform cooling and prevent "hot spots", internal baffles are often used to direct the coolant flow evenly. In some heavy - duty applications, a dedicated cooling loop may be used instead of the engine coolant.

Special Considerations for Two - Stroke Engines
Higher Exhaust Gas Temperatures and Pressures: Two - stroke engines generally have higher exhaust gas temperatures and pressures compared to four - stroke engines. Therefore, EGR coolers for two - stroke engines need to be designed to withstand these harsher conditions. They often use thicker - walled heat - resistant materials and more robust structural designs to ensure durability and reliability under high - temperature and high - pressure environments.
Integration with the EGR System: In two - stroke engines, the EGR cooler is an important part of the entire EGR system. For example, in the iCER system of marine two - stroke main engines, the recirculated exhaust gas needs to be cooled, cleaned, and desulfurized (when using high - sulfur - content fuel) before entering the cylinder. The EGR cooler first cools the exhaust gas to a suitable temperature, and then the cooled exhaust gas is mixed with fresh air and enters the supercharger inlet, and finally enters the cylinder.
Control of EGR Rate: Controlling the EGR rate is crucial for two - stroke engines. An appropriate EGR rate can effectively reduce NOₓ emissions while maintaining engine performance. The EGR cooler works in conjunction with other components of the EGR system, such as the EGR valve and flow control valve, to precisely control the amount of recirculated exhaust gas. By adjusting the opening degree of the EGR valve and the flow rate of the coolant in the EGR cooler, the temperature and flow rate of the recirculated exhaust gas can be adjusted, thereby optimizing the EGR rate.