This paper describes the advanced cooling technology and materials (directionally solidified and single-crystal superalloys) which are considered key technological factors when developing the 1500°C class high temperature gas turbine. Adopting a 1500°C class gas turbine developed on the basis of the new technology, a combined cycle plant is likely to achieve a plant thermal efficiency of more than 55% (LHV).
This paper describes the summary of a three year development program for the 1st stage stationary vane and rotating blade for the next generation, 1500°C Class, high efficiency gas turbine. In such a high temperature gas turbine, the 1st turbine vane and blade are the most important hot parts. Full coverage film cooling (FCFC) is adopted for the cooling scheme, and directionally solidified (DS) nickel base super-alloy and thermal barrier coating (TBC) will be used to prolong the creep and thermal fatigue life. The concept of the cooling configuration, fundamental cascade test results and material test results will be presented.
This paper describes the summary of a three-year development program for the first-stage stationary vane and rotating blade for the next generation, 1500°C class, high-efficiency gas turbine. In such a high-temperature gas turbine, the first turbine vane and blade are the most important hot parts. Full-coverage film cooling (FCFC) is adopted for the cooling scheme, and directionally solidified (DS) nickel base superalloy and thermal barrier coating (TBC) will be used to prolong the creep and thermal fatigue life. The concept of the cooling configuration, fundamental cascade test results, and material test results will be presented.
Al2O3-SiO2 moulds have been adopted successfully as shell moulds for a single crystal casting for jet engine blades. Heavy-duty gas turbine blades also have large dimensions and complex features comparable to those of jet engines. Then shell moulds should be subjected to similar severe service conditions when casting heavy-duty gas turbine blades. Creep behavior of 90mol%Al2O3+10mol%SiO2, which was manufactured through the lost wax process by using fused Al2O3 powder (average particle size, 15 μ m), was studied at temperatures of 1450 to 1550 °C. in four-point bending creep tests. Creep deflection rates were linearly proportional to stresses. The proposed creep mechanism was Al grain boundary diffusion at the interfacial regions between Al2O3 stucco powder. No severe metal/mould reaction appeared for the region adjacent to the interface between moulds and Ni base superalloys.
This paper describes an improvement in creep strength and thermal fatigue and hot corrosion resistance of a cobalt base superalloy developed for the applications of heavy duty gas turbine nozzles. The developed alloy has superior resistance to creep, thermal fatigue and hot corrosion over that of conventional alloys. The optimization of alloying elements which improve the creep properties and restrain the coarsening of carbides is discussed. A reduction in the volume fraction of eutectic carbides promoted the prevention of fast thermal fatigue cracking and also increased the hot corrosion resistance of the developed alloy. The mechanical properties were evaluated by general method for gas turbine materials. Thermal fatigue property was examined by introducing cyclic thermal stress into test pieces. During the test, crack propagation of the test pieces was observed. Hot corrosion resistance was evaluated by molten salt corrosion tests. After tests, mass loss of specimens was measured and penetration depth of sulfidized scale was observed. The developed alloy showed good properties which can allow a wide temperature margin for high temperature gas turbine nozzle designing. The developed alloy can be applicable to other gas turbine hot sections. Application of the developed alloy could realize an increase in gas firing temperature or extension of lifetime for current conditions.
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