What is Gas Turbine Inlet Fogging?

Fog Cooling Theory

Inlet air can be cooled using a variety of systems, including cooling coils, evaporative cooling, and fog cooling. Air Process Systems designs fog cooling systems. These systems require low capital outlay, are easy to install and maintain, offer low-pressure drop, and approach 100 % evaporative efficiency.

Cooler air is denser than warm air. Dense air provides higher mass flow rates and pressure ratios, increasing gas turbine power output. Inlet air-cooling is the most cost-effective way to improve gas turbine efficiency.

The Fog Cooling System

A series of stainless steel tubing lances distribute demineralized water under pressure to Air Process Systems designed nozzles. The nozzles, in turn, atomize the water into droplets. This atomization is accomplished using duel fluid nozzles. Compressed air is required as well as lower pressure water. Droplet size is dependent upon the air pressure; the higher the pressure, the smaller the droplet. Smaller droplets, in turn, evaporate more quickly. Compressor air is bled off a turbine stage with no effect on turbine efficiency. Hence no compressor is required. The shorter the residence time of the water droplets the smaller the droplet needs to be so as to assure complete evaporation. Air Process Systems designs its own nozzles. For this application the micron droplet sizing would range from 5-15 microns.

Water droplets less than 40 microns in diameter are considered fog. There are some concerns about compressor blade erosion if the water droplets are not fully evaporated. It is generally agreed that compressor blades do not suffer damage if the average droplet size remains below 30 microns.