Effect of asymmetric structural characteristics of multi-hole marine diesel injectors on internal cavitation patterns and flow characteristics: A numerical study

Abstract

Cavitating flow potentially emerging in diesel injector nozzles plays a prominent role influencing the subsequent process of spray atomization and combustion reaction. A computational study is conducted to investigate influences of asymmetric structural characteristics on interior nozzle flow in a multi-hole marine low-speed diesel injector. The simulation results illustrate that both mass flow rates and flow discharge coefficients of two holes on both sides are larger than those of two holes in the middle with increasing hole entrance corner radius (R), hole diameter (D) and hole length. The concave sphere shapes connecting the injector body and the holes are beneficial to reduce the negative effect of eccentric holes and bring about different flow patterns. R/D has a significant effect on the flow discharge coefficient but little influence on the mass flow rate. Besides, the hole entrance corner radius of 0.10 mm is an appropriate option to ensure the consistency of injections. The increasing hole length is conducive to the development of geometry-induced cavitation and vortex-induced cavitation. The development trends of flow phenomena in all holes are different with various hole taper degrees. It suggests that multi-hole marine diesel injectors with Kfactor of 1 ~ 2.5 can be considered in the actual manufacture.