Abstract
The new NOx reduction method, "Expansive Vertical Vortex Combustion (EVVC)" was suggested as follows. A combustion expansive flow developed along the piston bowl can form a strong vertical vortex. This vortex can mix hot burned gas into the cold excess air existing in the center of the piston bowl, which gets burned gas cool rapidly. Therefore, it is possible to reduce NOx which would be produced if burned gas remained hot. In this paper the EVVC effect was verified by CFD analyses and experiments on a 4-cilinder 2.0-liter direct injection diesel engine. As a result, it was found that the EVVC was an effective method, because the stronger vertex could reduce NOx by over 20% without worsening smoke and thermal efficiency.
