Elbow flow analysis and optimal exhaust port profile design

In this study, the exhaust port profile of a diesel engine was numerically analyzed and optimized. First, the elbow profile results show that the separation loss of lower profile plays the main role in overall separation loss, it decreases sharply and then slowly with an increase of r_lower/d. Within the range of 0 ≤ r_lower/d ≤ 5, the total secondary flow loss increases sharply and then slowly with an increase of r_lower/d. Under the same condition of relative pressure difference and lower profile, the elbow discharge coefficient increases with an increase of d_mid/r_upper and remains almost constant when d_mid/r_upper > 1. The maximum discharge coefficient under a certain r_lower condition increases with an increase of r_lower. Afterwards, the applicability of elbow profile results to exhaust port were verified and an exhaust port profile design method was established based on a circular arc profile. Finally the feasibility of exhaust port profile design method was verified experimentally.