Design Of Drilling Fluid Continuous Wave Generator And Experiment Research Of Signal Transmission Characteristic

The dissertation is aimed at improving the data transmission rate of MWD drilling fluid continuous-wave information transmission system and some key issues are investigated centered on the design of continuous-wave generator and signal transmission characteristic. The main research achievements include the design and optimization of rotary valve orifice, the load characteristics analysis of continuous-wave generator, the erosion prediction and weakening of rotary valve, the design of continuous-wave generator, the conception and design of continuous-wave generator control system, the reflection and superposition of continuous-wave signal. Finally, the water flow loop and wind tunnel is used to do the surface simulation experiment studies of the signal waveform, hydraulic torque, reflection and superposition of signal. The main works are summarized as follows:1 Design and optimization of rotary valve orificeSeveral characteristic parameters related to the design of rotary valve are determined according to the basic theory of signal and system. The design criterion of maximum correlation coefficient is proposed based on the minimum and maximum opening criterion. The parametric calculation model of rotary valve flow area with different orifice shape is established, after that, the optimization model of the shape of rotary valve orifice is built up according to the criterion mentioned above. The design method of curve orifice which can be used to get the ideal sinusoidal pressure is inspired by the parametric calculation model. The affecting factors of the signal quality are analyzed, and the phenomenon that the pressure amplitude decreases with the signal frequency increase in experiment is interpreted by the unsteady Bernoulli equation.2 Load characteristics analysis of continuous-wave generatorThe calculation mechod for the jet angle of dual side orifice with wide opening is proposed which is the basic of the theory calculation for the hydraulic torque acted on the rotary valve. The theory calculation of the hydraulic torque is done based the angular momentum theorem and jet theory. The effect laws of several factors on the hydraulic torque is studied by the CFD simulation, the results show that the torque increases with the increase of signal frequency, the decrease of the number of valve lobe, and the gap between stator and rotor. The occurred position and value of the reverse axial force is analyzed.3 Erosion prediction and weakening of rotary valveThe prediction of 3D erosion deformation is made by the UDF in Fluent. The result shows that the prediction with deformation is similar with the prediction without deformation in the starting stage of erosion, and then, the maximum erosion occurred position is transferred with the erosion deformation of the orifice increase. The drag force of particle in the Non-Newtonian fluid is used to calculate the trajectory, and get the different results from that in the Newtonian fluid. The erosion model of the particles whose size are smaller than 40μm is established, the prediction result is added to the discrete phase result to get the finally erosion prediction. The series orifice rotary valve is proposed to solve the jam and erosion problems.4 Structure and control system design of continuous-wave generatorcontinuous-wave generator is designed based on the studies of orifice shape and hydraulic torque. The communication protocol of the continuous-wave information transmission system is conceived according to the positive pulse information transmission system, and the control flow of continuous-wave generator is conceived, too. The hardware and software of motor control system is designed, and the dynamic simulation model of continuous-wave generator is built up to analyse the dynamic performance under different control pattern, the results show that the precise phase shift key signal and lower dynamic torque can be attained by using the position closed-loop control pattern including the velocity characteristic.5 Analysis of continuous-wave signal transmission characteristicThe transmission characteristic of continuous-wave signal is the key step in the continuous-wave transmission. The attenuation of the signal is the inherent and inevitable problem, however, the reflection and superposition is a double-edged sword, if it is used properly, the data transmission rate may be increased, otherwise, no signal will be got in the surface. The multilayer coupled waveguide model of the drilling fluid tunnel is built up, and the influence of the coupling effect on the transmission speed of the pressure is analyzed. The influence of the reflection on the upstream signal of the generator is analyzed by establishing the reflection model of the drill bit. The transfer function of complex system is built up and is used to select the carrier frequency for the Continuous-wave information transmission.6 Simulation experiment of continous-wave information transmission systemThe experiment equipments for continous-wave information transmission is designed and rebuilt based on Multiphase Flow Loop. The similar design of the wind tunnel and the software design of the data acquisition system are performed. The signal waveform experiment is performed, the results show that the curve orifice can get good pressure wave and the results of CFD conform to the experiment results. The experiment of hydraulic torque on the rotary valve is performed, and the influence factors on the hydraulic torque are analyzed. The experiment of reflection at the drill bit is done, and the influence of the start stage of the rotary valve on the pressure signal is analyzed. The reflection characteristics of the main reflection source, drill bit, is analyzed, and results show that the boundary condition of the drill bit can be seen as the closed-end boundary.