Study on the influence of oil jet angle on oscillatory flow and heat transfer non-uniformity in piston dual cooling galleries

Oscillatory cooling is an effective technology for enhancing piston heat transfer. However, traditional designs often overlook the non-uniformity of piston surface temperature caused by intake air cooling. A computational fluid dynamics (CFD) model was developed for a diesel piston with a dual cooling gallery, incorporating various cooling oil jet angles, to investigate how variations in jet angle influence internal flow and heat transfer non-uniformity. The results show that the right gallery exhibits less variation in heat transfer than the left. As the distance between the galleries increased, the amplitude of the instantaneous heat transfer coefficient gradually decreased, with a minimal variation of only 11.91 % observed under the R-d10(−2°) condition. When d = 10 mm, the sample standard deviation of the steady-state heat transfer coefficient on the right oil gallery reaches its minimum value of 56, while the overall variation of the coefficient is 156 W/(m 2 ·K), indicating a more uniform heat transfer distribution. Based on the simulation data, a correlation was established to describe the relationship among jet angle, engine speed, distance, and fluid charge ratio. The fitting errors were 4.0 % for the left gallery and 11.1 % for the right gallery. The predictive model developed in this study supports the optimization of injection strategies and structural parameters, providing a theoretical basis for the heat transfer enhancement design of internal oil galleries in high efficiency diesel engine pistons.