387 / 2018-12-20 13:18:37

Experimental study on the temperature, heat flux, strain and stress distributions on the membrane wall of the W-shaped flame boiler

W-shaped flame boiler; Membrane wall; Temperature distribution; Strain and stress distribution; Heat flux distribution

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The W-shaped flame boiler has been widely used in the combustion of the anthracite at present. There are some problems on the boiler’s heating surface during the operation, such as slagging, corrosion, deformation, fracture (longitudinal and circumferential). In order to ensure the safe operation of the W-shaped flame boiler, it is necessary to have more understanding of the temperature, heat flux, strain and stress distributions on the membrane wall. Due to the principle of similarity, it is feasible to replace the phenomena in a real boiler with the phenomena in a scaled-down model. Through the thermal experiment, the temperature and strain were measured on the membrane wall, and the corresponding temperature, heat flux, stress and strain distributions on the membrane wall are obtained by calculation. By comparing these distributions, the influence of them towards the heat transfer and deformation of the membrane wall are understood. Some conclusions are as follow: The temperature distribution in the horizontal direction is symmetrical, and the overall temperature of the front wall is higher than that of the rear wall. The high temperature zone appears on the front wall, in the connection area between the furnace and the ash hopper. It is formed because the flame impinges the membrane wall which is caused by the deflection of the flow field in the furnace chamber. The heat flux distribution is mainly affected by the radiation heat transfer of the flame and the funnel gas. The high heat flux zone appears near the burner and is determined by the flame temperature. The middle and low heat flux zone reflects the path of the funnel gas, which is determined by the funnel gas temperature. The strain and stress distributions are not directly related to the heat flux distribution, but it can be basically matched the temperature distribution, especially in the high strain-stress region. The magnitude of the stress depends on the temperature difference, but the direction depends on both the temperature difference and external constraints. The front wall is prone to deformation and facture, especially in the joint area between the furnace and the ash hopper. Because this area is a coupling zone of high temperature and high stress, and it has initial mechanical stress which is generated by an angle formed during processing. The asymmetric conditions under the same heat load or the special conditions that occur during combustion can cause the situation to deteriorate. These conclusions have reference significance for the safe operation of the boiler and the structural optimization of the furnace chamber.