Numerical simulation on casing of a 300 MW steam turbine was conducted via ANSYS software

and the divariant device rapid cooling technique

namely using high temperature air produced by a new kind of gas generator with function of mass flow and outlet temperature adjusting to cool the turbine

was compared with the traditional cooling method.Results show that

under the same working condition

the upper-lower and inner-outer cylinder temperature difference through variable temperature cooling method is lower than that by traditional ways

about 30 ℃ on the same position.With the increasing cooling air flow rate

the cooling time was shortened

but the upper-lower and inner-outer cylinder temperature difference grows

thus the rapid cooling safety decreases.So

the divariant device rapid cooling technique with short optimal cooling time

small temperature difference

and by which the maximum thermal stress of turbine casing is lower than ultimate stress of the material was proposed as the optimum cooling method

and the safety and economy during the casing's cooling was improved.