Experimental Study on the Distribution of Temperature and Deformation in the Water Walls of an Opposed Firing Boiler under Variable Load Conditions

To study the operational problems of an opposed firing boiler in continuously changing working conditions, the temperature, strain, and thermal stress of water walls were measured to analyze the distribution and relationship between temperature and deformation. The results showed that the asymmetrical arrangement of the burners in flexible operation can cause serious nonuniform distribution of the water wall temperature. The high temperature will induce extreme compressive stress, and the temperature difference between the high- and low-temperature areas will aggravate the tensile stress, which can induce bulge deformation and cracking of the water walls. We proposed replacing water wall plates with arc-shaped plates and adjusting the arrangement of burners to reduce the thermal stress. In addition, experimental equations were obtained between stress and temperature under steady and unsteady states by the least-squares method. These equations can be used to estimate the approximate range of high-stress areas based on the temperature of water walls. Finally, we found that the time hysteresis between temperature and thermal stress can be ignored. This study highlights the distribution and relationship of temperature and thermal stress on water walls under variable load conditions to guide their safe operation.