Theory Analysis On The Propagation Of Ultrasonic And Design Of Measurement System For Mass Level Check Of Ball Mill

The measurement and control of mass level is the key that ensure the economy and security of the ball mill operation. According to the local instance, two schemes (Lamb waves measurement and Ultrasonic reflection measurement) are brought forward. For demonstrating the measurement schemes, the objects are simplified. Through the wave theory and corresponding boundary conditions, the single-layer model and two-layer model about the propagation of Lamb waves in a plate are established. At the same time, the reflection model with the incidence of the longitudinal wave on the difference interface is established.Using MATLAB and FORTRAN, the simulation model is established. Solving these models get some conclusion:(1) When Lamb waves propagate in a plate, the variable trend of every mode about Lamb waves propagating in the coal particle load plate is the same as that of single-layer model. (2) Along with the increase of Lame coefficient (?), the difference of the phase velocity between single-layer model and two-layer model increase. (3) For every mode of Lamb waves, the magnitude of phase velocity between the two models has the turning point.Through the compare between single-layer model and two-layer model, the methods of identifying coal level can be get: (1) Measuring the phase velocity. The coal load can be identified according to the deference of the phase velocity. (2) Analyzing the receiving energy. The energy of coal load is lower than that of no coal load, and the coal load can be further identified.Through solving the reflection model, some conclusions can be get: When longitudinal wave vertical incidence, the energy attenuation of the reflection on solid-solid particles interface is larger than on solid-gas interface.At the same time, the proving experiment of the Lamb waves propagation in the coal load plate and no load plate is carried through. The experiment result tallies with the conclusion of theory analysis.For the characteristic of the object, the field measurement system is designed. Its hardware mostly consists of pulser card, receiver card and PC. Its software mostly consists of three modules: control module, communication module and signal analysis module.