Diagnostic Analysis Method of Direct Air Cooling Unit Limited Output Based on Pressure Ratio

Abstract

Given the limited output of a 600MW direct air cooling steam turbine unit, through the thermal performance test, historical operation data extraction, and comparative analysis combined with the data after the latest overhaul, it is found that the extraction pressure of the first section of the high-pressure cylinder began to appear over-pressure in recent two years. After further calculating the pressure ratio of the HP cylinder flow passage stage group, it is found that the pressure ratio of HP cylinder exhaust steam to Section I extraction steam has increased by nearly 4% in the last two years, indicating that the area of flow passage part of this stage group has become smaller and serious salt deposition has occurred, resulting in the reduction of HP cylinder flow passage capacity and the ultimate limitation of the output of the whole unit. The cylinder uncovering inspection results verify the correctness of the diagnosis. The diagnosis method is simple and suitable for the fault diagnosis of the actual flow passage.