The steam input flow of low pressure cylinder under zero-output heating conditions is decreased sharply

which causes the last stage blade to seriously deviate from the design value and then affects its safety. Based on the finite element method

the vibration equation of the low pressure last stage blade of a 300 MW steam turbine under steam flow excitation force is established. The dynamic stresses of the blade under the design condition and zerooutput heating conditions of low pressure cylinder are calculated separately by direct integration method. The calculation results show that the maximum dynamic stress under the design condition is 5.973 MPa

which is located in the tip region of the blade. On the other hand

the maximum dynamic stress under zero-output heating conditions of low pressure cylinder is 1.119 MPa

which is located in the shoulder region. The dynamic stress under zerooutput heating conditions of low pressure cylinder is less than that under the design condition

indicating that the dynamic strength of the blade under zero-output heating conditions of low pressure cylinder meets the design requirements of the manufacturer.