Ye Peng’s research while affiliated with Harbin Engineering University and other places

The spray/wall interaction plays a significant role on the mixture formation, combustion, and exhaust emissions. In the present study, the numerical code General Transport Equation Analysis (GTEA) is used to investigate the effect of fuel primary spray on the spray/wall interaction process. Taylor Analogy Breakup (TAB) model, Kelvin-Helmholtz-Rayleigh-Taylor (KH-RT) model, and Hybrid breakup (Hybrid) model are used to simulate the fuel spray process. By comparing the radius and height of the impinged spray, the performance of these breakup models is evaluated. Then, Bai and Gosman (BG) and Zhang and Jia (ZJ) spray/wall interaction models are implemented into GTEA code to describe the complicated spray/wall interaction process, and these interaction models are validated by the radius and height of the impinged spray and the size and velocity of the secondary droplets. The results indicate that the better levels of agreement between the experimental data and Hybrid breakup model are achieved than those of TAB and KH-RT breakup models under various conditions. The Hybrid breakup model incorporates the turbulence inside the nozzle in addition to aerodynamic breakup; the influence of inner nozzle flow on spray development can be captured. In addition, the inclusion of turbulence inside the nozzle enhances the fuel primary spray, leads to smaller momentum and size of incident droplets, decreases in radius and height of impinged spray, and then affects the tangential velocity and the sizes of the secondary droplet about 6-9% and 8-11%, respectively. This means that the flow inside the nozzle has an indirect effect on spray/wall interaction process. The results also indicate that the numerical predictions from the ZJ interaction model illustrate better agreements with experimental data than that of the BG interaction model, especially for cases with high injection pressure. Thus the ZJ spray/wall interaction model is more suitable for predicting the outcomes of the impinged spray.

Injection flow dynamics plays a significant role in fuel spray; this process controls the fuel-air mixing, which in turn is critical for the combustion and emissions process in diesel engine. In the current study, an integrated spray, combustion, and emission numerical model is developed for diesel engine computations based on the general transport equation analysis (GTEA) code. The model is first applied to predict the effect of turbulence inside the nozzle, which is considered by the submodel of hybrid breakup model on diesel spray process. The results indicate that turbulence term enhances the rate of breakup, resulting in more new droplets and smaller droplet sizes, leading to high evaporation rate with more evaporated mass. The model is also applied to simulate combustion and soot formation process of diesel. The effects of ambient density, ambient temperature, oxygen concentration and reaction mechanism on ignition delay, flame lift-off length, and soot formation are analyzed and discussed. The results show that although higher ambient density and temperature reduce the ignition delay and cause the flame stabilization location to move upstream, this is not helpful for fuel-air mixing because it increases the soot level in the fuel jet. While higher oxygen concentration has negative effects on soot formation. In addition, the model is employed to simulate the combustion and emission characteristics of a low-temperature combustion engine. The overall agreement between the measurements and predictions of in-cylinder pressure, heat release, and emission characteristics are satisfactory.