Hydraulic ram analysis: a new look at an old problem

The discretized method of characteristics was used to develop a new numeric al model for the analysis of the wave processes in the hydraulic ram. The m odel encompasses all parts of the device including, for the first time, the air chamber and the delivery pipe. This in turn allows a comprehensive stu dy of the unsteady flows in the unit as the air chamber extensively interac ts with the supply side of the ram. The program accounts for all possible f low states of the ram, i.e. with impulse and discharge valves closed, with both valves open and with either of the valves closed or open. The state of the partially or fully open discharge valve requires extensive and careful treatment of all physical phenomena involved, namely the transient boundar y conditions, relevant to the air chamber and its connection to the drive p ipe. The treatment is for the special case of constant sonic velocity in ea ch of the ram pipes. The numerical model was validated against experimental data obtained from various test set-ups. Comparing the velocity and pressu re head variations from numerical and experimental tests at selected points along the ram supply pipe performed the most stringent test. Excellent agr eement was shown to exist, validating the analytical approach.