Experimental and numerical modal analysis of wall tubes in the coal‐fired boiler or radiant syngas cooler

Abstract

AbstractThe slag deposited on the wall tubes in the coal‐fired boiler or radiant syngas cooler (RSC) of the entrained flow gasifier could reduce the heat transfer efficiency and degrade the tubes by corrosion. During the operation of the boiler or RSC, the rapping‐off‐ash method is an effective method to remove slag deposits, especially in a high‐pressure environment. The operating parameters of the rapping‐off‐ash method are related to the modal parameters of wall tubes, including the natural frequency, damping ratio, and mode shapes. In this study, modal parameters of wall tubes composed of three single tubes and fins were experimentally determined through the modal test analysis under both empty and water‐filled conditions. The dynamic characteristics of wall tubes were extracted by using the roving hammer‐impact test and the frequency response function (FRF). A numerical simulation based on the finite element method in ABAQUS was conducted to compare with the experimental modal analysis. The first five natural modes ranged from 14 to 154 Hz, and the maximum vibration or torsion locations of wall tubes under the corresponding mode frequencies were investigated. The water inside the wall tubes could reduce the stiffness of the structure and decrease the values of natural frequency.