Mathematical modeling and experimental investigation of a rotary valve generating sinusoidal pressure signals based on fan-arc-straight orifice

Abstract

The continuous-wave mud pulse telemetry is currently one of the most advantageous methods for wireless downhole transmission. The rotary valve orifice of a continuous-wave mud pulser must be optimized to generate highly similar sinusoidal pressure waves for high-speed and reliable transmission. In this study, an improved fan-arc-straight-based valve orifice is designed based on a general fan-based valve orifice by analyzing the relationship between throttle area and relative rotation angle of the rotor/stator on the basis of thin-walled cutting edge differential pressure generation mechanism. Then, CFD simulation studies are investigated. It is indicated that the peak-to-peak value of the differential pressure is proportional to the square of the inlet flow; and with the increase of axial clearances between the stator and rotor, the peak-to-peak values of the differential pressure signals show a negative exponential decrease trend, while the correlation coefficients also decrease monotonously. Furthermore, surface hydraulic system experiments have also been implemented; and the actual 8 Hz and 12 Hz pressure waves with correlation coefficients greater than 0.99 are obtained compared with the corresponding sinusoidal signals. It is believed that the optimized valve can achieve highly similar sinusoidal pressure waves with acceptable amplitudes during practical operation to meet the field operation requirements. • An improved fan-arc-straight-based valve orifice is designed based on a general fan valve orifice. • CFD simulations investigate features of the differential pressure signals. • Actual 8 Hz and 12 Hz pressure waves with correlation coefficients greater than 0.99 are obtained.