Abstract

Compressor fouling due to the deposition of airborne particulates on the compressor blades is a major cause of the degradation of compressor performance and the decline of overall gas turbine efficiency. The online water washing technology refers to an effective method to clean the compressor blades during engine operation. In such systems, typically a series of flat-fan injectors are peripherally located at the entry section of the gas turbine which injects water sprays into the intake air flow. The injected water spray droplets are transported towards the compressor and impinge on the compressor blades, thus removing the foulant. However, such injector arrangement usually leads to the interaction of adjacent sprays which may modify the resulting spray characteristics such as droplet size, velocity, and momentum. Hence, the study of spray interaction in the flat-fan injectors and its effect on the blade cleaning effectiveness is important for the design and development of water washing units. The objective of the present work is to study the spray interaction in two adjacent flat-fan injectors under open atmospheric condition as well as in an experimental test facility that essentially consists of a suction type wind-tunnel that mimics the gas turbine compressor inlet conditions in an optically transparent test section. Different optical diagnostic tools are used to visualize the spray interaction process as well as measure droplet size and velocity. To study the effect of spray interaction on blade cleaning, foulant-coated coupons (SS flat plates) are placed inside the test section of the wind tunnel and are exposed to the sprays for a fixed interval of time. The foulant cleaning efficiency is measured by weighing the coupon before and after the cleaning tests. A parametric investigation is carried out to investigate the cleaning efficiency for different air flow velocities, angle of attack, and injector separation distance. The current experimental results not only further elucidate the understanding of the blade cleaning process in online water wash systems but also provide valuable data for the validation of numerical spray simulations.

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