Gas Turbine Inlet Fogging System Tuning: Operator Point of View

Abstract

High-pressure water fogging is a relatively new technique for gas turbine inlet air cooling. Nevertheless, up to now, several hundreds of fogging systems have been installed around the world and this figure is rapidly growing. A large number of the fogging installations provided sufficient experience to establish a general approach to design, operation and maintenance of such systems. However, a fogging system could require some tuning to a specific gas turbine configuration and site conditions. Israel Electric Corporation (IEC) has implemented fourteen fogging systems on 120–150 MW gas turbines, and each system was tuned to provide higher effectiveness. Several systems were basically modified in order to reduce the risk of compressor blade erosion. Subsequent field tests had shown that the goals of the system modification and tuning were successfully achieved. This allowed extending operational hours of the fogging systems and provided noticeable fuel savings. Moreover, during the summer 2005 the fogging systems helped to achieve the all-time high peak of electricity demand. Extended use of the fogging systems features a prolonged operation at partial cooling capacity and at varying ambient temperature, pressure and humidity. This required a thorough evaluation of the fogging systems performance, in order to provide the systems settings that would allow the most effective operation with minimal risk of damage to gas turbine components, mainly the compressor blades. The paper describes an approach and results of the fogging system performance evaluation at the different operational conditions. The method allows for the rate of compressor airflow as a function of the injected water flow rate as well as of ambient pressure, temperature and humidity. Actual operational limitations are also considered. The results are illustrated with the examples that correspond to real fogging systems operating under Israeli weather conditions. The method is general and, therefore, is applicable to other weather conditions and for different fogging systems.