Analysis on possibility of expanding low-load operation area for homogeneous charge compression ignition in CI engine with variable exhaust valve actuation

Various technologies are being studied for the advancement of diesel passenger cars and associated environmental regulations. Effective compression ignition combustion in diesel engines is highly dependent on the cylinder charging temperature, composition, and cylinder pressure during valve train operation. The application of variable valve control in diesel engines has several potential advantages. In this study, we applied the variable valve actuation system to a single-cylinder engine model using a GT-POWER simulation and analyzed the effects of the recompression and rebreathing valve profiles, and fuel-injection pressure on the combustion characteristics of a compression ignition engine. As a result, NOx emissions were reduced by more than 90 %, while those of indicated mean effective pressure were reduced by up to 35 %. The benefits of recompression strategies in terms of NOx emissions reduction were confirmed.