Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
1999-08-31
2001-02-06
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
Reexamination Certificate
active
06182439
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to long blades for a high and low pressure sides-integrated steam turbine, using a noble heat resistant alloy, a high and low pressure integral steam turbine using the long blades, and a combined cycle power generation system.
At present, 12Cr—Mo—V—N steel is used for steam turbine blades. In recent years, it has been desired to raise the thermal efficiency of a fossil fuel power plant in view of energy-saving, and make apparatuses used therefore compact in view of space-saving.
Elongation of the turbine blades is an effective means for improving the thermal efficiency and making the apparatuses compact. Therefore, the length of blades of the final stage tends to be increased year by year. Thereby, under conditions in which the steam turbine blades are used also become severe, a conventional 12Cr—Mo—V—N steel can not provide turbine blades having sufficient strength. Therefore, a stronger material is necessary. Accordingly the strength of material for long blades, tensile strength, which is a base of mechanical property, is required.
Further, toughness also is required to securing safety against rupture.
As a structural material having a higher tensile strength than the conventional 12Cr—Mo—V—N steel (martensite steel), a Ni-base alloy and Co-base alloy are well known. However, the are not sufficient in hot workability, machine-cutting property and vibration-attenuating properties, so that they are not desirable.
Material for gas turbine discs is disclosed in JP A 63-171856. Such material however, does not have a high tensile strength.
Further, an integral turbine, which has a high pressure side which and a low pressure side are integrated into one unit in view of space-saving in turbines of a small capacity less than 100,000 kW and a middle capacity of from 100,000 to 300,000 kW, has been put into practice. The length of final stage blades of this integral turbine is 33.5 inches at most because the strength of material for the rotor and blade is limited. The blade length, however, is desired to be further elongated in order to increase the turbine output.
JP A 3-130502 discloses blades for high and low pressure sides-integrated steam turbines, using 12% Cr steels. However, the steel is too low in tensile strength to provide long blades for recent low pressure steam turbines.
SUMMARY OF THE INVENTION
An object of the invention is to provide blades of a high and low pressure side-integrating steam turbine, using martensite steel having a high tensile strength, a high and low pressure side-integrating steam turbine using the blades, and a combined cycle power generation system.
The present invention resides in a high and low pressure side-integrating steam turbine for 50 Hz power generation, which has long blades, each made of martensite stainless steel comprising 8-13 wt % Cr, and having a blade length of not less than 40 inches, preferably not less than 43 inches.
The present invention also resides in a high and low pressure sides-integrating steam turbine for 60 Hz power generation, which has long blades, each made of the above-mentioned martensite stainless steel, and having blade length of not less than 33 inches, preferably, not less than 35 inches.
The above-mentioned martensite stainless steel, preferably, comprises, by weight percentage, 0.08-0.18% C, not more than 0.25% Si, not more than 1.00% Mn, 8.0-13.0% Cr, more than 2.1% and not more than 3% Ni, 1.5-3.0% Mo, 0.05-0.35% V, 0.02-0.20% in total of at least one kind of Nb and Ta, and 0.02-0.10% N.
Further, the invention resides in a high and low pressure sides-integrating steam turbine which has a rotor shaft made of martensite heat resistant steel comprising, by weight percentage, 0.18-0.28% C, not more than 0.1% Si, 0.1-0.3% Mn, 1.5-2.5% Cr, 1.5-2.5% Ni, 1-2% Mo, 0.1-0.35% V and not more than 0.003% O, and having a 538° C. 10
5
h flatness and notch creep rupture strength of not less than 13 kg/mm
2
at a high pressure side, a tensile strength of not less than 84 kg/mm
2
at a low pressure side and a 50% fracture appearance transition temperature (FATT) of not more than 35° C., and the above-mentioned long blades each planted or mounted on the rotor shaft and having tensile strength of not less than 128.5 kg/mm
2
.
The present invention resides in a steam turbine for 50 Hz power generation, which is provided with a rotor having blades planted on a mono-block rotor shaft in multi-stages from a high steam pressure side to a low steam pressure side, wherein an inlet temperature of steam to first stage blades is not less than 530° C., the mono-block rotor shaft is made of a Ni—Cr—Mo—V low alloy steel of bainitic structure having a higher strength at the high pressure side than at the low pressure side, or a higher toughness at the low pressure side than at the high pressure side, and the blades of at least a final stage each have a length of not less than 40 inches, preferably, not less than 43 inches and are made of martensite stainless steel including 8-13 wt % Cr, or a steam turbine for 60 Hz power generation, which has the blades of at least a final stage each having a length of not less than 33 inches, preferably, not less than 35 inches and made of martensite stainless steel including 8-13 wt % Cr.
The present invention resides in a combined cycle power generation system in which a generator is driven by a steam turbine and gas turbine, wherein the steam turbine comprises a rotor having blades planted on a mono-block rotor shaft in multi-stages from a high steam pressure side to a low steam pressure side and a casing covering the rotor, an inlet temperature of steam to first stage blades being not less than 530° C., and wherein the rotor shaft is made of a Ni—Cr—Mo—V low alloy steel of bainitic structure having a higher strength at the high steam pressure side than at the low steam pressure side or a higher toughness at the low steam pressure side than at the high steam pressure side, a 538° C. 10
5
h creep rupture strength of not less than 12 kg/mm at a central portion planting or mounting thereon first stage blades at the high steam pressure side or FATT of not more than 20° C. at a central portion, planting or mounting final stage blades at the low steam pressure side having a room temperature V-notch impact value of not less than 4 kg-m, and blades of at least a final stage among the above-mentioned blades have a value of (blade length (inches)×revolution number (rpm)) of not less than 120,000 and are made of martensite stainless steel including 8-13 wt % Cr.
The present invention resides in a combined cycle power generation system in which a generator is driven by a steam turbine and gas turbine, wherein the steam turbine comprises a rotor having blades planted on a mono-block rotor shaft in multi-stages from a high steam pressure side to a low steam pressure side and a casing covering said rotor, an inlet temperature of steam to first stage blades is not less than 530° C., the blades of least a final stage have a value of (blade length (inches)×revolution number (rpm)) of not less than 120,000 and is made of martensite steel including 8-13 wt % Cr, and the mono-block rotor shaft has a higher creep rupture strength at the high pressure side than at the low pressure side or a higher toughness at the low pressure side than at the high pressure side, and a combustion gas temperature at a first stage blade of the gas turbine is not less than 1200° C., preferably, not less than 1300° C. and, more preferably, not less than 1400° C.
Further, the present invention resides in a combined cycle power generation system comprising a gas turbine driven by a combustion gas flowing at a high speed, an exhaust heat recovery boiler generating steam with energy of exhaust gas of the gas turbine, a steam turbine driven by the steam from the boiler and a generator driven by the gas turbine and the steam turbine, wherein the gas turbine has blades of at least three stages, a temperature of the combustion gas at a turbine inlet is not less than 1200° C., a temp
Hiraga Ryo
Nakamura Shigeyoshi
Onoda Takeshi
Siga Masao
Hitachi , Ltd.
Kim Ted
Mattingly, Stanger & Malur
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