Development and validation of the new ALSTOM GT24/GT26 upgrade compressor

Since 1996 more than 75 ALSTOM GT24/GT26 heavy-duty gas turbines have been installed worldwide for the 50 Hz and 60 Hz market. The GT24/GT26 features a unique advanced sequential combustion system, a one stage high-pressure turbine and a 4-stage low-pressure turbine. The 22-stage compressor delivers a pressure ratio of 32:1. Typical power output is up to 281MW (GT24: 188MW) in single-cycle (with quench cooler) and more than 400MW in combined cycle operation (CCPP). In 2001, ALSTOM launched a performance improvement and upgrade program for these heavy-duty gas turbines after experiencing some problems with the advanced technology. Several upgrade packages were rolled out into the field after extensive testing at the Birr Test Center; Switzerland. A new GT24/GT26B-compressor is part of the upgrade and retrofit packages that were developed. These were extensively tested and validated during several test campaigns at the Test Centre in 2002. The GT24 compressor is a scaled version of the GT26 compressor. The compressor tests were completed in 2002 and since then fifteen engines have received the compressor upgrade and further installations are planned. This paper gives an overview of the compressor development, validation and the impact on the gas turbine performance of the GT24/GT26 upgrade compressor.