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Recent developments in high-performance and high-reliability gas turbine engines necessitate enforced cooling to maintain the blade temperature at reasonably low levels associated with increased turbine inlet temperature and compressor pressure ratio. However, the gas turbine performance is strongly penalized by the consumption of cooling flow, resulting in temperature dilution of hot mainstream, aerodynamic mixing loss, and pumping power loss. In this paper, a new practical blade cooling system using state-of-the-art engineering, which aims at minimizing the dilution effect, is presented. Trade-off studies between performance and reliability in terms of blade metal temperature are performed to evaluate cooling systems. Analytical comparison of different cooling systems demonstrates that the proposed cooling system provides significant improvements in performance gain and growth potential over conventional air cooling systems.

The effects of three types of cooling systems on the calculated operating performances of a hydrogen-fueled thermal power plant with a 1,700°C-class gas turbine were studied with the goal of attaining a thermal efficiency of greater than 60 percent. The combination of a closed-circuit water cooling system for the nozzle blades and a steam cooling system for the rotor blades was found to be the most efficient, since it eliminated the penalties of a conventional open-circuit cooling system which ejects coolant into the main hot gas stream. Based on the results, the water cooled, first-stage nozzle blade and the steam cooled first-stage rotor blade were designed. The former features array of circular cooling holes close to the surface and uses a copper alloy taking advantage of recent coating technologies such as thermal barrier coatings (TBCs) and metal coatings to decrease the temperature and protect the blade core material. The later has cooling by serpentine cooling passages with V-shaped staggered turbulence promoter ribs which intensify the internal cooling.

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Laser printers, which feature quiet, fast, high-quality printing, are evolving towards digital copiers with even faster and higher quality printing performance. This trend requires faster and more precise rotation of the polygon mirror motor of the laser beam scanning mechanism. Thus, bearings are becoming a key technology for the advancement of laser printers. This report proposes an integrated bearing unit that employs ferro-fluid for the bearing lubrication and seals in a new concept of leakage-free high-speed bearings. The intention is to take advantage of hydrodynamic oil-film bearings with high stiffness and damping characteristics to solve the oil leakage problem, and use them in place of ball-bearings or air bearings to get highly precise rotation. Leakage is completely prevented by using a compound seal of a ferro-magnetic seal and a viscous seal. The structural features of these bearings and experimental results concerning their lubrication and sealing performance and rotation accuracy when applied to a polygon mirror motor operating from 10000 to 30000 r/min are presented. The ferro-fluid bearings provide satisfactory friction torque and stiffness characteristics and the proposed bearing unit can be utilized with the polygon mirror motor.