Prof.  Xinyu  Zhang
The University of Nottingham Ningbo China,  China

Title: A study of Deposits and Flashing Effect on Spray Characteristics in Gasoline Direct Injection Engines

Abstract:

This work studied the effects of deposits and flashing on spray characteristics in Gasoline Direct Injection Engines. An optical-based experimental study was performed first and it is found that the injector deposits can significantly alter the spray and droplet behaviors, leading to loss of mass flow rate, longer spray penetration and larger droplet sizes. CFD simulations were then carried out in the Euler-Euler framework with cavitation taken into account by a homogeneous relaxation model (HRM). Results highlight that rough deposit surfaces lead to additional cavitation inception in the counterbore and restrict the flow area, causing mass flow rate losses. In-cylinder simulations were carried out to study the deposit effect on the air/fuel mixing process in an optical research GDI engine. Results have shown that injector deposits can lead to stronger fuel impingement on the piston and cylinder walls, as well as a lower mean equivalence ratio during late injection events. The flash boiling effect on near-nozzle spray characteristics is also investigated. The near-nozzle spray behaviors of hexane and isooctane were studied both experimentally and numerically under different temperatures and back pressures. Simulations were conducted with OpenFOAM and the HRM model was implanted to account for phase change. Results have shown that flashing could significantly change the near-nozzle spray behavior. Then the near-field spray patterns of 2-methylfuran (MF), ethanol (ETH) and isooctane (ISO) under different saturation ratios were investigated in an optically accessible constant volume chamber. Results have shown that, MF shows the most intense flash boiling behavior due to its highest vapor pressure.

Biography: