Experimental and Numerical Investigation of Flow in Hydraulic Elbows

Elbow fittings are common in hydraulic and pipeline systems. These components cause a significant pressure drop in the total pressure of a system. The banjo elbow is advantageous in areas low to the ground and where flexible connection angles are needed. However, this elbow yields a larger pressure drop than a standard elbow. Additionally, the position of the internal bolt in the banjo elbow cannot be determined prior to installation, which corresponds to a wide range of possible pressure drop. In this study, the pressure drop through a 3/8” banjo elbow is investigated for different positions of the internal bolt, experimentally and numerically. Experiments and simulations were carried out on hydraulic oil with four different Reynolds numbers ranging from 3111 to 6222 and at nine bolt connection angles ranging from 0° to 60°. Experiments were repeated with the standard elbow of the same size to compare the pressure drops to those of the banjo elbow. Pressure was measured at both the inlets and outlets of the elbows. The results suggest that the connection angle of the internal bolt is an important factor in the pressure drop and minor head loss through a banjo elbow. For Reynolds numbers of 3111 and 6222, an improvement in minor head loss by 33% and 58%, respectively, was achieved by adjusting the connection angle of the internal bolt in the banjo elbows.