Visual test and evolutionary analysis of flow fields in cylinder of helical intake port diesel engine

Abstract

The paper intends to overcome the difficulties associated with conventional PIV test techniques in measuring the flow fields near curved surfaces. So the paper combines the visual steady flow test and the CFD simulation method, to help observe the law of particle distribution near the cylinder wall directly, and reveal the law of steady/transient flow field movement and airflow evolution. The results show that the distribution of particle density and the gradient boundary lines of the tracer concentration correspond to those of the CFD simulation. Therefore, a visual test can display the characteristics of the movement of air in the cylinder near the wall. The swirl ratio of each radial section in the cylinder and the ω combustion chamber during the intake stroke is influenced by the intake airflow, while the swirl ratio during the compression stroke is determined by the piston movement. At the end of a compression stroke, the location of the highest swirl ratio directly influences the air-fuel mixture. As a result, analyzing the swirl ratio and evolutionary process of the flow fields near the wall of the cylinder and combustion chamber help improve the quality of the air-fuel mixture and the efficiency of combustion.