Influence of key structure of diesel engine helical intake port on intake stratification

Abstract

In order to control gas stratification in diesel engine cylinders and achieve stratified combustion, an experimental and computational fluid dynamics (CFD) coupled approach was employed. The intake section of the helical intake port was divided into four independent intake zones with equal areas by clockwise division: the upper right zone A, upper left zone B, lower left zone C, and lower right zone D. Each zone was supplied with a tracer gas to study the influence of key structural elements of the helical port on gas stratification characteristics within the cylinder. The results indicate that zone D had the highest intake mass, accounting for 27.3% of the total intake, while zone B had the lowest intake mass at 22.4%. In the combustion chamber, intake from zones A and B formed an upper-rich, lower-lean distribution pattern, while intake from zone C formed an upper-lean, lower-rich distribution pattern. The stratification concentration gradient might be quantitatively described thanks to the application of “density ratio.” Lift increased by 5.6% at a 15° intake port deflection angle because the combustion chamber’s maximum axial density ratio was 0.186 and its maximum swirl ratio was 3.57. Soot generation fell by 12.9% under axial stratification, although NOX generation increased by 4.9%.