THE NEW LM2500 CHENG CYCLE FOR POWER-GENERATION AND COGENERATION

The advanced general electric (GE) LM2500 Cheng cycle is a recent deve lopment to improve the performance of the LM2500 STIG cycle. The therm al efficiency increases by 7%, and the complexity of the plant is redu ced appreciably due to the fully automated configuration. The system i ncludes a self-regulated pressure HRSG, steam-air cooling of the turbi ne blades and a fully automated computerized process control to implem ent fast start-up and shut-down. The system's fast response allows ful l steam injection within 30 min. The operation is integrated by severa l layers of microprocessor architectural structure to allow the choice of the most economic operation that follows a fluctuating electric pr ice of local utilities. This results in a reduction of the operating m anpower and maintenance costs. The system capital cost is comparable t o the simple cycle of the LM2500 GEN SET COGEN systems. Performance of the advanced Cheng cycle using the general electric LM2500 gas turbin e indicates that the power output (about 27 MW) and efficiency (betwee n 44 and 45%) remain fairly constant regardless of a high ambient temp erature. Existing gas turbine plants can be retrofitted to operate on the Cheng cycle resulting in a true parallel steam and gas turbine com bined cycle. Equipment diagrams showing typical one-unit arrangements for the 27.5 MW GE LM2500/CHENG are presented. In addition to power ge neration, the advanced Cheng cycle is particularly attractive for coge neration due to its flexible use of excess steam in the combustion cha mber. (C) 1997 Elsevier Science Ltd.