Optimization of the Compressor Water Wash System

GTEGas Turbine Efficiency

Hugh SalesVP – Americas

Gas Turbine EfficiencyHouston, TX

1-713-425-4950www.GTEfficiency.com

Email: GTEHugh@aol.com

Improved ON- and OFF- line cleaning, preferably with pure water.

No detrimental wear on coatings.

Complete gas path penetration in less than 15 seconds.

No strain on rotating or other components.

Resource saving (water - detergent).

SOME REQUIREMENTS OF THE CLEANING UPGRADE PROGRAM :

Keyword: OPTIMIZATION

• Design Goal: maximize the safe efficiency of gas turbines by developing a water wash system that optimizes the variable components of the water wash.

– Benefits:• Reduce complexity• Reduce environmental issues (turbine emissions and waste wash

water effluents)• Increase MW production revenue and decrease operation costs

(chemicals, fuel, time, off-line wash frequency, etc.)

A wash system that gives you this . . .

. . . So you don’t end up like this !

Optimization Variables

• Water Temperature

• Water Pressure

• Water Droplet Size

• Water Volume

• Nozzle Placement and Dispersion Fields

Optimized Water Temperature

• Water Too Cold: – Blade temperature variation – Loss of cleaning efficacy– Increases need for expensive chemicals

• Water Too Hot: – Increased early vaporization, loss of penetration into core– Higher safety risk to operators– Loss of droplet size stability

• OPTIMIZED: About 140 deg. F

Optimized Water Pressure

• Too Low Water Pressure (< 30 bar / 450 psi):– Cannot penetrate airflow boundary layer

• Wastes wash water• Streaking on bellmouth• “Puddling” at 6 o’clock position• Very Important: Leads to increased droplet size, a contributing factor

in blade erosion and vibration

• Too High Water Pressure (>140 bar / 2000 psi):– Too-high pressure velocity over airflow acceleration leads to

greater impact force on blades, another contributing factor leading to blade erosion

– Cannot control proper atomization of the droplets

Streaking, a common problem of low pressure systems due to the air mass pressing the droplets against the surfaces.

Streaking on IGV’s and Bellmouth

Very limited cleaning effect on the blades !

Copyright GTE

Optimized Water Pressure (cont)

• OPTIMIZED:– Between 50 and 90 bar (roughly 750 – 1400 p.s.i.)

• Penetration of airflow boundary layer• Negates airflow turbulence spray disruption• Best control of proper water droplet size atomization• Maximum dispersion across IGV’s and R0• Maximum penetration into core of compressor• Allows for minimal waste of water / chemicals • Water spray velocity is roughly equivalent to airflow velocity leading

to no increased net force impact on blades (“erosion resistance”)

Exact, consistent droplet velocity with laser-based Particle Dynamic Analysis

Optimized Water Droplet Size

– Most critical variable in terms of cleaning penetration and erosion !!!

• Too Small (< 40 microns):– Does not impact blade at all – follows air flow resulting in no cleaning

effect

• Too Large (> 160 microns)– The “Newton’s Laws of Motion” Effect:

• Some droplets follow Newton’s First Law• Some droplets follow Newton’s Second Law

FYI: A Drop of a Gentle Spring Rain is about 1000 Microns

Optimized Water Droplet Size (cont)• Newton’s First Law: Inertia

– If the droplets are too large, many are just flung to the side /deflected by centrifugal force

• Resulting in root and tip damage potential to blade• Resulting in waste of water since these droplets do not penetrate

beyond IGV’s or R0

• Newton’s Second Law: Impact Force = Mass x Acc– If the large droplets do strike the blade, they can cause

erosion / damage due to the too-high impact force• With water, it’s an exponential increase: Doubling the size of the

droplet approximately cubes the mass and impact force; tripling the droplet size increases mass / impact force over 25 times; etc.

Optimized Water Droplet Size (cont)

• OPTIMIZED:– Droplets between 60 and 160 microns (only)

• Large enough to wet the blade allowing DI water to dissolve contaminants, but not with so much force that the blade is damaged.

• Tight dispersal of droplets within this size range decreases waste and erosion potential

• IMPORTANT!!! - The main key to an efficient wash system with little vibration or blade erosion potential is optimized droplets delivered at optimal pressure!

OptimizedTechnology

EFFECTIVE PRESSURE andWATER DROPLET SIZE

- Low total water volume

- Optimal cleaning effect

- Maximizes gas path penetration

- Vibration / Blade Erosion resistance

- Less disposal mess (environmental concerns)

Exact, consistent droplet size measured with laser diffraction

Optimized Water Volume

• Too Large Water Volume:

– Increased vibration / blade erosion / damage risk– Longer water heating time– Larger water tanks / skid required– More complex manifold and piping required– More cleaning chemical / demin water required– Much greater waste of water / cleaning fluids– More effluent to dispose of (environmental issues)

Optimized Water Volume (cont)

• OPTIMIZED:– Research and field experience have determined that

for many turbines only 20% to 40% of the water typically used in an OEM system is really required for an optimal compressor wash assuming that all other variables are optimized.

Aero-derivative original wash system, note that most of the liquid is flowing out from the inlet .

Even under load: Too

much water – just flows back out the

bellmouth

OPTIMIZED NOZZLES

• OPTIMIZED NOZZLES:– Spray Pattern:

• Engineered according to the other variables being optimized

• Maximum coverage across blades

– Number of nozzles:• Optimized variables allow for single set of nozzles for on-

line and off-line washing• Optimized variables allow for greatly reduced number of

nozzles (about 1/3 of typical OEM)

Here is a typical OEM

complex nozzle

installation

Compared withthis optimized nozzle installation

RESULTS ACHIEVED BY OPTIMIZATION• No erosion or blade damage ever reported (over 1000 turbines,

over 10 years)– Safe and effective off- and on-line washing allowing for revenue

enhancement and cost reductions

• Fewer pollutants in compressor and waste water– Reduced need for costly and polluting chemicals

• Many times, only demin water is necessary– Greatly reduced volume of water (fresh in and waste out)

• Reduced complexity in wash system– Easier implementation of wash system with lower operational costs– Smaller, more compact, potentially portable wash skids– On-line wash at full turbine power because of reduced water volume

Spray pattern at cranking speed Spray pattern at base load speed

Optimized Technology

DIRECT INJECTION SYSTEM

- Excellent gas path penetration

- Practically no wasted liquid

“A Clean Turbine is a Happy Turbine”

Optimized Technology

SIMPLIFIED INSTALLATION

- Minimum number of nozzles- Takes away ”hidden” costs- Reduced cost & complexity- Re-use existing OEM nozzle

placement

CONCLUSION

• OPTIMIZATION of the water wash system variables allows for maximum cleaning efficiency using minimum water, cleaning fluids, nozzles, time and expense.

• OPTIMIZATION leads to . . .

. . . a spray with perfectly sized droplets - not too small to be carried with the air stream- not too large to cause erosion damage

traveling at the ideal velocity with the ideal spray pattern

R4 before cleaning

Same R4 after optimized cleaning

On Line Washing

Time - 3 Months.

Output Comparison - Off Line versus On Line Washing

Small reduction in output

Large reductionin output

Off Line Washing

1 month 2 months 3 monthsTime

Operational experiences of Optimizedwashing system at Frame 6B site

30

32

34

36

38

40

15.2.2002 2.3.2002 17.3.2002 1.4.2002 16.4.2002 1.5.2002 16.5.2002 31.5.2002 15.6.2002

Gas

Tur

bine

cor

rect

ed o

utpu

t (M

W)

Installation of new GTE system

GT output deterioration without on-line washing system

Off-line washes

Since Optimized Wash System installation, off-line cleaning frequency has moved from once per month to once per four months. Average daily performance gain: 2.1 MW

Operational experiences of optimizedwashing system at Frame 6B site