Research On Magnetostrictive Stress Sensing Device For Turbine Testing

The safety of the turbine is the basic guarantee for the efficient operation of the hydrogenerator unit.However,during the operation of the turbine,the runner is subjected to the hydraulic excitation force for a long time.In order to accurately judge the operating life of the turbine runner under the action of the exciting force,the dynamic stress testing technique is needed to measure the stress magnitude and distribution of the runner.The excellent stress sensor performance is an important guarantee for the dynamic stress testing accuracy.At present,the common stress sensors on the market have their own advantages,but they cannot meet the requirements of simple wiring,small size,long service life and high sensitivity.Therefore,based on the magnetostrictive inverse effect and the magnetostrictive material as the sensitive component,the magnetostrictive stress sensor has the characteristics of small volume,high sensitivity,long service life and simple wiring.The designed sensor can be well applied to the dynamic stress test of the turbine.The main contents of the paper are as follows:1.The properties of magnetostrictive materials were expounded,and the properties of different magnetostrictive materials were tested and compared.Galfenol was selected as the sensor sensitive component material.Based on the principle of minimum volume design,combined with the principle of magnetic circuit design,the sensor core with circular arc variable cross-section structure with smooth magnetic circuit is designed.Taking the dynamic stress fluctuation range of the turbine as a reference,the WSH202 meeting the design requirements was selected as the sensor conversion structure.And according to the mechanics principle and magnetic conduction theory,a sensitive gate structure with high sensitivity is designed for Galfenol.Based on the design structure,the force-magnetic coupling constitutive model of magnetostrictive material is expounded.Combined with Hooke’s law and Hopkinson’s law,the mathematical model of sensor output characteristics is established.2.Based on the finite element method,the structural size of Galfenol was optimized with the highest sensitivity as the optimization goal.And based on the optimized magnetostrictive stress sensor,the finite element simulation software was used to analyze the stress and magnetic field distribution of the core component Galfenol under different external excitation currents and different external forces.The simulation results show that the stress and magnetic field are evenly distributed,and the measurement range and sensitivity meet the design requirements.3.According to the optimized magnetostrictive stress sensor structure,the experimental prototype was fabricated,and the static stress test performance and dynamic stress response performance of the static and dynamic experimental platform were tested.The experimental results show that under the excitation of 0.1A,0.2A and 0.3A coils,the static sensitivity of tensile stress can reach up to 6.062mV/MPa,the static sensitivity of compressive stress can reach 5.743mV/MPa,and the dynamic response of the sensor is good.In this thesis,the magnetostrictive stress sensor with sensitive gate structure is designed and tested,which provides a new application reference for hydrodynamic stress testing.It provides theoretical and experimental basis for further research of this type of sensor,and makes magnetostrictive stress sensor have application prospects.