Effect of Thermal Cyclic Loads on the Efficiency of Steam Turbines under Hydrogen Overheating of Steam

Explaining the use of the hydrogen energy complex will solve the problem with increasing the share of NPPs in the unified energy system of Russia by ensuring their operation in the variable part of the electrical load graph. An increase in the power of the NPP unit can be achieved by improving the steam parameters at the inlet of the steam-turbine installation in the process of hydrogen overheating. In this paper, the authors evaluated effect of hydrogen overheating of steam on the efficiency of steam turbine installations in terms of the power increase and life-time reduction caused by the operation in the variable part of the electrical load graph. For this purpose a non-stationary heating of the blades first stage of the high-pressure cylinder with account for the change in the main steam parameters has been simulated, and the temperature gradients have been determined. As a result, the generalized dependences of thermomechanical stresses in the blade metal on the rate and level of main steam temperature increase have been developed. Based on the method of equivalent operating hours, it was shown that an increase in the temperature of fresh steam by 25°C leads to an insignificant decrease of specific life-time of steam turbine unit by 0.09-1.27 h/MW, depending on the rate of the temperature increase. When the steam temperature rises by 100°C, the largest specific life-time falls by 0.64-3.3 h/MW, depending on the rate of the temperature increase.