Mitsubishi Heavy Industries, Ltd. (MHI) has developed “LP-End Blades Series” by employing the ISB ( I ntegral S hroud B lade) structure and has lead high efficiency and reliability of the steam turbine. The latest technology has been integrated into Ultra-Long-Blades design for the next generation’s steam turbine. This paper describes the design summary of 3600rpm-50inch/3000rpm-60inches and 1800/1500rpm-74/62inches Blades and results of the verification tests.

Adding damped structure can decrease dynamic stress of blade and avoid blade fatigue failure from forced vibration. Based on the structural feature of long blade with friction damper, the numerical model for dynamic analysis of damped blade in steam turbine has been developed. The blade was described by twisted beam element, the usual space beam element was adopted to analyze the frame of damper, and the slip motion between rubbing surface was modeled by a damping connector. The following matrices which are necessary for finite element analysis were obtained: the stiffness matrix, mass matrix and damping matrix of finite element for blade and damper, the stiffness matrix and damping matrix of damping connector. Then the gross finite element motion equation of the blade was got. Meanwhile, harmonic wave propagation method was adopted to improve calculation efficiency. The comparison of calculation results and experimental data of a 360mm blade shows good agreement. The dynamic characteristic of a last stage long blade in steam turbine with damper was analyzed in detail, its responses with different thickness shroud and gap between shrouds were investigated in detail too, then the optimal structure of damped shroud was obtained, the comparison for response between damped blade and freestanding blade shows the maximum response of blade with optimal damper is 42.4% of that of freestanding blade. At last, a tie wire was added to the damped blade, numerical result shows it can decrease blade response further.

In order to promote high efficiency combined with high power output, reliability, and availability, Siemens advanced gas turbines are equipped with state-of-the-art turbine blades and hot gas path parts. These parts embody the latest developments in base materials (single crystal and directionally solidified), as well as complex cooling arrangements (round and shaped holes) and coating systems. A modern gas turbine blade (or other hot gas path part) is a duplex component consisting of base material and coating system. Planned recoating and repair intervals are established as part of the blade design. Advanced repair technologies are essential to allow cost-effective refurbishing while maintaining high reliability. This paper gives an overview of the operating experience and key technologies used to repair these parts.

The reliability of blade is very important for steam turbine. Adding damping structure can decrease dynamic stress of blade. Firstly, the numerical model for dynamic analysis of damping blade has been developed. The following matrices which are necessary for Finite Element analysis have been obtained: the stiffness matrix, mass matrix and damping matrix of Finite Element for blade and damper, then the gross Finite Element motion equation of the blade can be obtained. Secondly, the response energy formula of blade has been obtained by analyzing the relation between exciting force and response of blade, the response energy can be taken as optimization goal, POWELL Penalty Function Method is adopted as optimization algorithm. At last, the dynamic characteristic of a real blade is analyzed, some numerical results such as response energy varied with normal press force have been obtained, the normal press force of rubbing surface has an apparent effect on the damp and response energy of blade, it can change the dynamic characteristic of blade, and there is an optimal normal press force, which can lead to the minimum response energy of blade, i.e. the optimal damper for blade.