Experimental and theoretical investigation of the influence of liquid droplet size on effectiveness of online compressor cleaning for industrial gas turbines

The effectiveness of online compressor washing is site specific and it is determined by several factors, amongst which is liquid injection droplet size that relates to the nozzle orifice diameter and injection pressure. To investigate the influence of liquid injection droplet size on the effectiveness of online compressor washing, three elliptical flat fan nozzles with different orifice diameters were selected, followed by ascertaining the mean droplet sizes for each of the nozzles with the Malvern Spraytec Particle Analyzer. Two of the three nozzles that generated droplet sizes of 55 and 80 μm were employed to investigate the influence liquid injection droplet on the online compressor washing effectiveness. Prior to the washing effectiveness investigations, the three middle blades of the cascade were fouled in a uniform and repeatable manner, after which washing was conducted with different injection droplet sizes. When the washing effectiveness for droplet sizes of 55.1 and 80.24 μm were compared on the aerodynamic performance plots of exit flow angle, total pressure loss, and non-dimensional velocity; a slight difference was observed for the two droplet sizes. The washing effectiveness of using liquid injection droplet size of 80.24 μm produced a lower exit flow angle and total pressure loss coefficient than the droplet size of 55.1 μm. This implies that the droplet size of 80.24 μm has a higher momentum, thereby dislodging the particles more easily than the 55.1 μm droplet size. The reduction in isentropic efficiency and flow capacity obtained from the experimental data for the fouled and washed cases were used as input into Turbomatch to simulate the effects of washing with different fluid injection droplet sizes. Blades washed with a droplet size of 80.24 μm produced a higher recovery of power output and efficiency from the fouled case than the ones washed with a droplet size of 55.1 μm.