Design and performance analysis of a magnetorheological fluid damper for drillstring

To mitigate the severe drillstring vibration during oil and gas drilling, this paper presents a design of mixed mode magnetorheological (MR) fluid damper based on the electromagnetic finite element analysis and Bingham plastic model. The 2D axisymmetric finite element model has been established, and a structural optimization method on the base of magnetic circuit design has also been put forward. The effects of structural parameters such as the radius of bobbin, the thickness of cylinder and the active bobbin length on the flux density inside the fluid gap have been analyzed, which consequently obtain the appropriate design with a higher and more even magnetic intensity. Besides, this analysis has found the relations between damping force, amplifying factor and vibration velocity under different field currents by a typical Bingham plastic model and test data when considering the negative effects of temperature on MR fluid, finally, made prediction on the performance of the MR fluid damper. The main research of the paper lays an important foundation to develop control strategy of the MR fluid damper for drillstring.