|A conventional EGR Cooling System.|
Nikkei. Tokyo Radiator Mfg. Co., an established maker of cooling systems, has developed a new exhaust gas recirculation (EGR) cooler with a bypass channel to reduce incomplete combustion and the resulting emissions of hydrocarbons and soot.
NOx forms primarily due to the presence of oxygen and high temperatures. By recirculating exhaust gas back into the cylinders, EGR lowers the heat of combustion and thereby reduces NOx. EGR coolers further lower the temperature of the exhaust gas before recirculation, thereby achieving an even greater reduction in NOx.
However, the constant use of cooled exhaust gas results in the engine taking longer to reach optimal combustion temperatures. Incomplete combustion—and the associated emissions—can result during that period.
Tokyo Radiator’s new EGR cooler has a built-in bypass channel to send exhaust gases directly back to the combustion chambers when the engine temperature is low. Sensors calculate the engine temperature from the temperature of the radiator coolant, and a pressure valve opens the bypass channel whenever the temperature is below a set value. This helps the engine warm faster, reducing the time for incomplete combustion.
The company plans to mass-produce the new EGR cooler starting this fall. GM reportedly plans to use the device in passenger cars for Europe next year.
|Schematic of advanced EGR system for the Ricardo-GM ADEC engine. Click to enlarge.|
GM and Ricardo have been developing an advanced diesel engine control (ADEC) system designed to enable consistent achievement of very low emissions levels through closed loop control of the combustion process. An EGR Cooler with bypass is part of that development, which the partners will demonstrate on a 1.9-liter engine.
The ADEC coordinator uses a range of sensors to measure combustion states and then establishes the optimal balance of fuel quantity and timing and air path control (the latter being where the EGR cooler with bypass system comes in).