Hydraulic Characteristics On Rotor Of Oscillating Mud Pulse

The oscillating mud pulser is one integral part of MWD/LWD. With limited downhole energy, the pulser generates pressure pulse with high frequency and enough amplitude by means of cutting off mud liquid continuously. It is not easy to study the distribution of flow field within the pulser due to the effect of the turbulent around the rotor, as a result, the structure optimization and motion control of the pulser is sustainable.Firstly, this paper focuses on the mechanism study of hydraulic torque acting on the rotor and the mud pulse above the stator. The theory of the steady-state hydraulic torque and transient hydraulic torque in hydraulic machinery was employed to analyze the hydraulic torque on the rotor in the present paper, and comparisons are also made between the CFD simulation, the theoretical analysis and the experimental results. By studying the relationship between the mud pulse and the rotor’s rotation angle, the researcher shows how to generate pre-set wave shape by controlling the motion of the rotor. Secondly, with the guidance of mechanism study above, the structure optimization is carried out by CFD software, aiming at decreasing energy consumption. Based on the optimized structure, design of rotor’s motion control is described. At the end, two different sets of testing apparatus is used to verify the conclusion above.The test results show that the theoretical analysis and numerical forecasting describe the hydraulic torque and pulse shape accurately. The motor’s power output is cut down by the means of structure optimization and adding torsional spring. With the help of redesigned mud pulser, the test on the MWD/LWD turns out a great success.