Impact of Shift in Frequency of Online Water Washes on Corrected Isentropic Efficiency of Compressor of Heavy-Duty Gas Turbine

Frequent online water wash of Gas turbine compressor is a critical activity to sustain the site-corrected compressor isentropic efficiency after each offline water wash in dusty environment of Middle East. Higher frequency of online water wash impacts the compressor efficiency, compressor pressure ratio, power output, heat rate, exhaust flow and exhaust temperature of Gas Turbine. At one of the CCPP sites of ACWA Power, HDGT OEM requested to change the online water wash frequency from three times a week to once a week. The reason behind this request was compressor blade erosion due to higher droplet sizes of online water wash spraying circuit. This investigation is an effort to estimate how the frequency of online water wash impacts the isentropic efficiency of the compressor for two different scenarios having different frequencies of online water wash. The first scenario was a one-time online water wash per week with a water rinsing cycle and once a month with detergent cycle. The second scenario was with three-times online water washes per week; two with a water rinsing cycle and one with detergent cycle. Various parameters related to compressor performance were compared e.g. ISO-corrected compressor isentropic efficiency, compressor discharge temperature, compressor pressure ratio, exhaust temperature, exhaust temperature, exhaust temperature, exhaust flow, corrected power output and corrected heat rate. The impact on bottoming cycle due to shift in improved exhaust flow due to better compressor performance was also captured. During the investigation, it was identified that the higher frequency of online water wash contributed to sustaining the compressor efficiency for longer periods. By shifting the frequency of online water washing from once a week to three times a week, the GT output was improved by 2MW at similar operating conditions.