In recirculation

Volvo Construction Equipment, Asheville, N.C., developed and patented its own internal exhaust-gas recirculation (I-EGR) technique to lower NOx emissions on its new generation of diesel engines for off-road applications. The Volvo Advanced Combustion Technology (V-ACT) engines (Circle 929) feature an improved fuel-injection system, a more effective air-management system and enhanced engine management. The V-ACT engines meet the Tier 3/Stage IIIA emission limits without needing any major changes to the base engine and while keeping machine performance high and fuel consumption low, according to Volvo. In the heavy-duty off-road D12D engine, for example, the exhaust rocker arm is fitted with a patented, switchable double-rocker device that allows for a small second opening of the exhaust valve, whereby a controlled amount of exhaust gas is fed back into the cylinder during the inlet stroke. The process lowers the peak combustion temperature and reduces the formation of NOx.