Fog System

Inlet Fogging System

What it offers

In hot ambient temperature, gas turbine (GT) operators are confronted by a significant problem as turbine generation capacity usually drops. It has been estimated that every 1°F rise of ambient air temperature reduces the gas turbine output by approximately 0.3 to 0.5%. As a result, a number of cooling techniques have evolved over the years to maximize turbine output.

 Among various cooling schemes, fog cooling (a direct evaporative cooling) has gained increasing popularity due to its simplicity and low installation costs. Fogging basically occurs in gas turbine power augmentation by means of injecting water into fine fog droplets and evaporation inside the gas turbine intake duct. The evaporation process cools the air, increases the mass flow rate and thus boosts the power of the gas turbine.

A glimpse into the design

The basic theory of inlet air cooling for gas turbines is quite simple. Combustion turbines are constant volume machines meaning at a given shaft speed they always move the same volume of air. However, the power output of a turbine depends on the mass flow. That’s why in hot days, when air is less dense, power output drops. By feeding cooler air into the CT, mass flow increases which results in higher output. Another factor is the power consumed by the CT’s compressor. As the work required for compressing the air is directly proportional to the temperature of the air, reducing the inlet air temperature decreases the work of compression and there is more work available at the turbine output shaft.

High pressure fogging is a more recent technology employed for inlet air cooling. Fogging systems perform the cooling process by evaporating water which is atomized into billions of super-small fog droplets. Fog systems use high pressure water pumps to pressurize demineralized water to reach 1000 to 3000 psi. The water then flows through a network of stainless steel tubes to fog nozzle manifolds that are installed in the air stream. These nozzles atomize the water into micro-fine fog droplets which quickly evaporate.


Customer benefits include:

  • Increasing the output up to 20%
  • Improving the heat rate up to 6%
  • NOx reduction
  • Longer compressor wash intervals
  • Easy to install
  • Simple to service and maintain
  • Field tested, proven technology
  • Short duration of execution
  • Excellent return on investment
  • Increasing process production


  • Pump skid comprising the pumps, motors, filters and controls
  • Nozzle manifolds located in the inlet duct
  • Interconnecting stainless steel tubing between the pump skid and nozzle lines
  • Compression Fittings, Pipe supports, and hardware for installing the above