Design And Implementation Of Ultrasonic Generator Used For Coalbed Methane Extraction Experiment

Coalbed methane is a kind of mixed gas which formatted in the process of coal formation, stored in the coalbed, and its major component is methane. As China's coal field's geological conditions are complex, so that the coal bed methane extraction rate is low, and total output is less, we still have not formed commercial exploiture. We can increase the extraction rate of coalbed methane by changing the pressure, permeability and saturation degree of coalbed, and the coalbed methane extraction experiment's aim is to finding out the best ultrasonic field by study the characters of the coalbed methane's desorption, diffusion and percolation under sound field. Ultrasonic generator is the important component of the coalbed methane extraction experiment's equipment, and its main function is to supply the ultrasonic field which is needed by the experiment.This paper's emphasis is to study and design the ultrasonic generator which is the key part of the coalbed methane extraction experiment's equipment, according to actual needs of the coalbed methane extraction experiment. The main research works including: Firstly, the function's requirements and structure of ultrasonic generator used for coalbed methane extraction experiment is put out, the ultrasonic generator is composed of signal generating, power magnify-Impedance matching, signal receiver module, and so on. And then broad band signal generating module is designed by using AD9835, this module has 0-10MHz bandwidth and 0.0058 Hz frequency resolution, so it can satisfy the need of experiment to 20-100 KHz signal, and the signal's frequency can be set by input device. The power magnifier and impedance matching module is designed in the next step, the power magnifier which is designed by using IRF540N can magnify the signals to 30w successfully. Finally, the signal receiver module is designed in this paper, the bandpass filter designed by using MAX262 can change its center frequency by program, its can satisfy the filter requirement by filtering the 1Hz-140 KHz signals. So that the signal receiver module can supply ways to adjust the input signal frequency and detect the energy attenuation of ultrasonic.The ultrasonic generator designed by this paper meets the function requirements, and it is used in the coalbed methane extraction experiment successfully.