Abstract:  The cooling effect of needle valve was investigated to improve the durability and reliability of an engine injector under micro pilot ignition condition. The temperature fields of an injector needle valve were simulated in a dual fuel mode of heavy oil and natural gas by using a multiphase flow model and a k-ε standard turbulence model in a CFD (computational fluid dynamics). The cooling effects of different inlet temperature of cooling lube were simulated numerically and verified experimentally. The results show that the needle valve head has the highest temperature point at the needle valve bottom. The cooling effect of needle valve enhances at beginning and decreases at following when the inlet temperature of cooling lube increases continuously. The needle valve head reaches its lowest temperature of 256.8 ℃ for heavy oil mode and of 361.1 ℃ for natural gas mode, when the inlet temperature is 80 ℃ , so that having the best cooling effect. Therefore, it is feasible to investigate the cooling performance of the needle valve of dual fuel engine with CFD numerical simulation method. 

Key words: dual fuel engine, micro pilot ignition, injector needle valve, cooling lube, computer fluent dynamic (CFD), numerical simulation