The large design area of the first stage static blade in steam turbine is considered as the major reason for poor actual operation economy of the unit.According to the engineering thermal dynamics theory

the steam thermal process in turbine was analyzed.Furthermore

the retrofit schemes for the first stage static blade area were presented

namely(1)partially blocking the steam passage for the first stage static blade;(2)closing the last opened control valve oil circuit immediately or through thermal control;(3)reasonably decreasing the blade height or shortening the throat diameter of the steam passage to decrease the first stage static blade area.After the scheme(3)was performed on a sub-critical unit steam turbine

the original design area of the nozzle at the first stage dropped from 245.3cm2 to 190cm2;compared to the 300MW unit load condition

the coal consumption rate for power generation under 240MW unit load condition relatively decreased by 6.4g/(kW·h).