Different approaches to compressor design exist in industrial practice. This paper describes two design philosophies that can be followed with compressor development (re-staggering and new airfoil design), and reports on field experience gained with an advanced compressor design using CDA (Controlled Diffusion Airfoils) profiles. The first philosophy described is based on incremental changes of compressor design, consisting of keeping the same blade profiles and re-staggering a number of rotor blades and/or stator vanes. The second philosophy described is to utilize advanced CDA profiles in compressor design, optimized for increased mass-flow and backpressure. The second philosophy was followed in the development of a compressor upgrade for ALSTOM's GT11NM gas turbines, where a significant increase in GT power output (exceeding 10%) and improved overall engine efficiency (+0.4 % additive) at unchanged surge margin were achieved. Power output and improved efficiency resulted solely from the advanced blade design, requiring no additional power augmentation techniques. These figures were measured on a natural gas-fired GT operating in an open-cycle power plant.
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