Transient flow and cavitation within the injector-like geometry 2019-01-0284
Cavitation plays a significant role in the the spray and the subsequent mixing and combustion process. Cavitation has beneficial effects to the development of the fuel sprays through improving the injection velocity and promoting the primary break-up. On the other hand, pressure peaks induced by the vapor collapse may lead to erosion damage and serious degradation of the injector performance. The reliable reproduction of the cavitation characteristics, especially for the transient characteristics is the prerequisite for the accurate simulation of the spray process. In the present paper, the transient cavitating flow in the injector-like geometry was investigated using the modified turbulence model and cavitation criterion. A local density correction was used in the RANS turbulence model to reduce the turbulent viscosity, which facilitates the cavitation development. The turbulent stress was also considered in the cavitation inception stage. The modified model is capable of reproducing the cavitating flow with an affordable computational cost. For a better understanding of the cavitating transient characteristics, an integrated one-dimensional/two-dimensional method is used to study the cavitation excited pressure oscillations on the solid surface. The results show that the pressure oscillations are related to the second derivative of the cavity volume and thus demonstrate that the cavity volume acceleration is mainly responsible for the cavitation induced pressure fluctuations. The vortex structure was also investigated since it is closely correlated with the cavitation flow. In addition, the condensation term in the cavitation model was extracted to evaluate the cavitation erosion. The dynamic parameters at the nozzle exit were analyzed to illuminate the cavitation effects on the spray process. This study may provide useful information for the development of injector design.
Wenchuan Liu, Yong Kang, Wayne Chang, Qi Liu, Chia-Fon Lee
Wuhan University, Univ of Illinois at Urbana-Champaign, China Ship Development and Design Center