Gas Turbine Inlet Air Fogging & Evaporative Cooling Calculator
Psychrometric wet-bulb cooling, mass flow recovery, power augmentation (MW), and demineralized fog injection sizing.
1. Ambient Weather Conditions
2. Gas Turbine Specifications
3. Cooling Technology & Architecture
Power Augmentation & Thermodynamic Output
Turbomachinery & Pumping Balance
Gas Turbine Inlet Filter House & High-Pressure Fogging Simulator
Interactive schematic: Ambient air entering weather louvers, high-pressure 10-micron fog nozzle array, rapid evaporative flash cooling zone, compressor bellmouth, and turbine power train.
5 Fatal Traps & Industrial Engineering Pitfalls
1. Compressor Bellmouth Icing & Catastrophic Blade Ingestion
As air accelerates through the inlet bellmouth into the first-stage compressor blades, Mach number increases, causing static air temperature to drop by 4 to 8 deg C due to aerodynamic static pressure expansion. If fogging or evaporative cooling is activated when ambient dry-bulb temperatures drop below 10 deg C to 12 deg C, static temperatures inside the inlet plunge below 0 deg C. Supercooled moisture freezes instantly into thick ice sheets on inlet guide vanes (IGVs), breaking loose as massive ice chunks that destroy rotating titanium compressor blades.
2. Sub-Micron Mineral Deposition & High-Temperature Blade Pitting
Using municipal potable water or improperly polished demineralized water (TDS > 5 ppm) introduces calcium, sodium, and silica. In a 500 kg/s turbine running 25 m3/h of fog water, 10 ppm TDS injects 250 grams of abrasive salts per hour. Salt crumbles into crystalline sandpaper on compressor blades, eroding aerodynamic foils. Downstream in the 1300 deg C hot gas path, sodium and potassium react with sulfur to form molten alkali sulfates that strip thermal barrier coatings (TBC), destroying turbine blades within hundreds of operating hours.
3. Duct Water Puddling & Uncontrolled Liquid Slug Ingestion
Fogging systems spray thousands of liters of water into high-velocity intake ducts. If spray manifolds lack automated multi-stage drain troughs or if drain traps become clogged with dust, unevaporated water coalesces on duct floors into standing pools. During rapid gas turbine load ramps, surging airflow scoops up water puddles as sudden multi-gallon liquid slugs. Water striking rotating compressor blades running at 3,600 RPM causes severe hydrodynamic impact damage and trips the unit on high vibration.
4. Droplet Coalescence & Wet Compression Leading-Edge Erosion
While 10 to 15 micron droplets evaporate benignly or pass through blades without damage, droplets larger than 30 to 40 microns possess sufficient inertia to penetrate the aerodynamic boundary layer and collide with blade leading edges. If fog nozzles wear or lose high pressure (falling below 1000 psi / 70 bar), atomization deteriorates into coarse droplets. In wet compression overspray service, coarse water droplets act as ball bearings traveling at 400 m/s, scalloping and thinning the leading edges of stage 1 and 2 compressor blades.
5. Compressor Surge Margin Degradation on Fast Trip
Inlet cooling shifts the compressor operating line toward the surge limit by densifying air and increasing pressure ratio across intermediate stages. If the fogging high-pressure pumps are suddenly tripped offline instantly without modulating IGVs and fuel gas flow simultaneously, the compressor experiences an abrupt thermal and density shock. Axial airflow stalls instantaneously, plunging the machine into violent rotating stall or destructive full-body surge cycles.
Psychrometric & Gas Turbine Power Augmentation Equations
The ambient wet-bulb temperature ($T_{wb}$) is accurately calculated from dry-bulb temperature ($T$) and relative humidity ($RH$) using the Stull psychrometric empirical formula:
The effective cooled compressor inlet temperature ($T_{cooled}$) achieved by evaporative saturation efficiency ($eta_{evap}$) is:
Where $eta_{evap} approx 1.00$ for high-pressure fogging and $approx 0.88$ for evaporative media pads.
The Net Gas Turbine Power Augmentation ($Delta P$) and required demineralized water flow ($dot{m}_w$) are: