High Fogging Tests and Performance Model for High Fogging

High fogging refers to water injection upstream of a compressor intake beyond saturation. This leads to water droplet evaporation within the compressor and as a result to a reduction in compressor outlet temperature. This form of compressor intercooling leads to enhancement of the overall gas turbine power output. High Fogging systems were developed by Alstom and have been commissioned and tested in the Alstom Test Center on the GT8C2 and the GT26 in 2001. In this paper, the main principles of inlet cooling systems and High Fogging are described. Initial concerns during commissioning and testing are presented. Operation concept and special supervisions during the tests are discussed. The main effects of the High Fogging operation on the gas turbine are presented. Especially the transient effects and impact of the High Fogging on the cooling air system of the gas turbine are shown. To analyze and simulate the influence of High Fogging on the gas turbine, an analytical model using empirical corrections is presented. The model used is based on an existing conventional performance model with a compressor map for a dry compressor. It includes an algorithm for simulation of the evaporative cooling. The interest is to know how the dry compressor map is changed with High Fogging water injection. Correction factors are derived from measurements. NOMENCLATURE