tailieunhanh - Gas Turbine Engineering Handbook 2 Episode 9

Tham khảo tài liệu 'gas turbine engineering handbook 2 episode 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Combustors 385 Advantages of the TBCs are the reduction of metal temperatures of cooled components by about 8-14 F 4-9 C per mil microns of coating the microstructure and a coated liner. The primary benefit of the TBCs is to provide an insulating layer that reduces the underlying base material temperature and mitigates the effects of hot streaking or uneven gas temperature distributions. These coatings are now standard on most high-performance gas turbines and have demonstrated excellent performance in production machines. The third major change was the introduction of steam cooling of the liners. This concept especially in combined cycle application has great potential. Transition Pieces. Although technically not part of the combustor they are an important part of the combustion system. Less complicated than the liners the transition pieces have probably been more challenging from a materials processes standpoint. Therefore new materials have tended to be first introduced on the transition piece. From a design standpoint significant improvements have been made on advanced models through the use of heavier walls single-piece aft ends ribs floating seal arrangements and selective cooling. These design changes have been matched by material improvements. Early transition pieces were made from AISI 309 stainless steel. In the early 1960s nickel base alloys Hastelloy-X and RA-333 were used in the more limiting parts. These alloys became standard for transition pieces by 1970. In the early 1980s a new material Nimonic 263 was introduced into service for transition pieces. This material is a precipitation-strengthened nickel-base alloy with higher strength capability than Hastelloy-X. Since the early 1980s Thermal Barrier Coatings TBCs have been applied to the transition pieces of the higher firing temperature gas turbine models and to uprated machines. Field experience over thousands of hours of service has demonstrated good durability for this coating on transition