Research On Parameter Matching And Structure Optimization Of The Guide Wheel And Turbine Of Downhole Generator

At present,the lithium batteries are the main power supply for the MWD,LWD and rotary steering tool in domestic.But the batteries are susceptible to the influence of the high temperature and pressure in the downhole environment,which will directly affect the drilling efficiency.At the same time,the continuous use of the batteries will also have adverse effects on the ecological environment.By using drilling fluid to make electricity,turbine generator have much more long-term and persistent power supply.It can adapt to the downhole environment of high temperature and pressure,so it is important to study the downhole turbine generator with high power and efficiency.In this paper,the interaction between the stator and rotor has been studied,and the blade structure design has been improved.The parameters matching and optimization design have been carried on by using the Computational Fluid Dynamics(CFD)simulation technology,the orthogonal experiment,the response surface method and the matlab numerical calculation method.The main researches are as follows:(1)According to the theoretical analysis and initial design requirement of the traditional spiral turbine,the values of blade structure parameters were decided.Then the three-dimensional models and related calculation models of the stator and rotor were established by the 3D software SolidWorks.(2)The flow field numerical simulation of the spiral stator and rotor was analyzed by using the CFX simulation system.The effects of different structural parameters on the performance of the turbine performance have been obtained.(3)Based on the analysis of flow field,the first and second significant parameters which affect the turbine performance were selected out.It is concluded that the first significant factors are as follows:the spiral angle ?1 of the stator,the spiral angle ?2 of the rotor,the stator's blade number Z1 and the rotor's blade number Z2.And the second significant factors are as follows:the stator's blade thickness m1,the rotor's blade thickness m2,the stator's rotation angle ?1 and the rotor's rotation angle ?2.(4)The highest efficiency of turbine was defined as the objective function.Based on the Box-Behnken design method,the effects of the first significant parameters on the turbine performance were analyzed.And the interaction among the first significant parameters was obtained.For the second significant parameters,their effects on the the turbine performance were analyzed by the orthogonal design method to optimize the structure parameters further.The eight parameters have their optimal values after the first matching analysis,which are?1=46°,?2=29.2°,Z1=15,Z2=5,m1=2mm,m2=5mm and ?1=?2=60°,respectively.(5)On the basis of the first matching analysis,the blade structures of the stator and rotor were improved.After the second matching analysis,the efficiency,torque and pressure drop of the turbine were obtained when the stator and rotor were different structures.Through the contrast analysis,the stator is the twisted blade,whose structure line is the combination of the linear,arc and linear.While the rotor blade structure is the airfoil twisted blade,whose airfoil data is the NACA66(mod).(6)On the basis of the second matching analysis,one group of the improved blade structure of the stator and rotor was selected for the parameters matching analysis,within the range of parameters selection.The sample data of BP neural network was obtained by using the multiparameter orthogonal experimental design.By the method of the BP neural network,genetic algorithm,Fmincon function and the for loop function,the optimal combination of the third matching analysis in the range of parameter selection was constructed.(7)After the third optimization,turbine efficiency has been improved by about 24.1%than before.The corresponding work speed in the highest efficiency has risen from the original 1250 r/min to 2250 r/min,therefore,the optimized turbine is more adaptable to the high speed working environment.After optimization,the torque increases 2.1 N·m than the original design under the maximum efficiency,but the ideal output power has increased 1449.3w than before.The output power of the turbine has been effectively improved,and the whole machine output power of downhole turbine generator will also increase,Therefore,the turbine has a good performance and practical application value after three-time optimization.Finally,the turbine performance after optimizing was analyzed under different flow rate.The relationship between power and speed,efficiency and speed were studied,which would have a certain guiding significance in engineering application.