Research On Liquid Level Detection Method Based On Ultrasonic Guided Waves

The liquid level of the bolier drum and drain tank is very important to the safe and economic running of power plant,on the basis of nondestructive to the power plant equipment.Currently,the existing several kinds of methods for the liquid level measuring all need to layout components on the power plant equipment,so we need to reprocess the power plant equipments.We use the ultrasonic guided waves testing technologies to detect the liquid level without damage to the power plant equipment.Based on the propagation and transformation rules of the quasi-Scholte in the plate loaded water,the main content is as follows :(1)On the basis of the research at domestic and overseas,we calculate and compare the propagation modes difference between the free plate and the plate with one side in the water;we find a new wave mode in the plate with one side in water,the quasi-Scholte.This mode is similar to A0 mode’s structure under low frequency.Finally,we verify the transformational relation between the quasi-Scholte mode and A0 mode in the hydroatmospheric interface,and clarify the basic principle of the liquid level measurement.(2)Based on the finite element method,we studied the excitation frequency and the thickness of the plate about the quasi-Scholte mode which appears in the water loaded plate,and we get the optimal frequency of the quasi-Scholte mode in the liquid level measurement.(3)For the quasi-Scholte mode in the plate with one side in the water,we embarks from the excitation by using the PZT way and EMAT way.Basing on the problems of the PZT way,we design and optimize the EMAT sensor,and finally we verify the feasibility of the two kinds of excitation ways through the water level measurement.