To investigate the influence of shaft arrangements and shaft speed on efficiency and economy of the 1 350 MW ultra-supercritical double reheat unit

schemes of four different steam turbine types were built to carry out simulation and calculations.The effects of exhausting outlet number

single-and doubleshaft arrangement(cross-compound or tandem-compound)and shaft speed selection on the unit's efficiency and economy were analyzed.The results show that

for the 1 350 MW ultra-supercritical double-reheat condensing unit

a tandem-compound 4-flow steam turbine with a primary rotor portion running at 3 000 rpm and a secondary rotor portion running at 1 500 rpm is the best scheme

the plant net efficiency can reach up to 46.01%.Then the second choice is the scheme of a cross-compound 6-flow steam turbine with rotor portion running at full-speed.Due to the technical limitation and investment economic weakness

it is better not adopt the scheme of a cross-compound 4-flow steam turbine with rotor portion running at full speed and the scheme of a tandem-compound 6-flow steam turbine with a primary rotor portion running at3000 rpm and a secondary rotor portion running at 1 500 rpm.