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ROCHEM Fyrewash Ltd
5-6 Sun Valley Business Park
Winnall Close, Winchester
Hampshire
SO23 0LB
ROCHEM Fyrewash Inc
23707 West Hardy Road
Spring
Texas
77373
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02 Oct 2026
Many gas turbine operators have no idea that their compressor is fouled; after all, it’s easy to disregard dirt you can’t see. However, today we’re looking at the impact of low-level contamination, what can be done about it, and whether it’s worth taking action.
Gas turbine compressors intentionally create an internal environment which is extremely hot and under extremely high pressure. This has an amplifying effect when it comes to contaminants: low levels of fouling can have a significant effect on airflow and aerodynamic performance.
Even fouling which is difficult to see with the naked eye can be significant, so it’s important to remember that fouling should not be measured simply by how much dirt you can see.
Compressor blades are precisely engineered aerodynamic surfaces. They are tuned to accurately control how gas moves through each compressor stage for peak performance. This performance relies on unimpeded surface condition, allowing gas to smoothly flow where directed.
Any deposits that adhere to or damage the blade surfaces increase roughness, introducing resistance and altering the aerodynamic behaviour of the blade. The flow of gas is altered and efficiency is compromised. The effect is magnified by the high-pressure environment.
Let’s dig into the details a little and find out exactly how surface roughness affects airflow.
A boundary layer is the thin layer of air next to the blade where airflow is drastically slowed. The air molecules actually touching the surface stop completely and velocity of molecules gradually increases the further you get from the blade.
Boundary layers begin at the leading edge of the blade and get thicker as the airflow moves downstream.
It’s important to understand this because the flow through the gas turbine compressor reacts with the boundary layer, not simply the solid surface of the blade.
When the gas turbine compressor blades are made even slightly rough with fouling, friction increases, micro separation bubbles appear (where the boundary layer detaches from the surface and forms a recirculating pocket of reversed flow), wake disturbances arise behind each foulant, and the boundary layer is altered.
This all in turn leads to:
Even at a level which cannot be seen with the naked eye, you can understand how surface roughness can have a big effect on gas turbine performance.
When honing in on tiny levels of fouling, it’s easy to focus on the detail instead of the big picture. However, many gas turbine compressors contain multiple stages of rotating and stationary aerofoils.
A relatively small deterioration in performance at any individual stage can seem insignificant but actually have considerable impact on overall compressor performance.
Every stage depends on the gas flow it receives from the previous one. Even if just one stage suffers fouling, the distorted/compromised flow is inherited by the next stage and so on, with a cascading effect on overall performance.
We must remember that the gas turbine compressor is part of a bigger gas turbine. Its purpose is to compress gas to optimum pressure before injecting it into the combustor to be burned. Anything that reduces the compressor’s ability to function at peak performance has an impact on the whole turbine: it reduces the available power and/or accrues additional fuel requirements and costs to achieve the same end result.
Fouling usually ‘sneaks up’ on operators, developing progressively. Gradual deterioration in performance, especially if the foulants can’t be physically seen, therefore goes unnoticed unless performance data is compared over time.
As foulants build up and blade surfaces are increasingly corroded/eroded, that boundary layer is progressively disturbed, airflow is compromised and there is a ‘slippery slope’ in terms of performance: a meaningful cumulative effect.
While it can be easy to miss, there are a few warning signs to look out for when it comes to gas turbine compressor fouling. This article explores them in more detail.
Despite the routine use of air filters, there are a number of different contaminants that can be found on gas turbine compressor blades. Many of these contaminants are introduced via the air, and the high-pressure environment exacerbates their impact.
The geographical location of the gas turbine has a big impact on the type of contaminants you’ll encounter. For example, salts will feature heavily at offshore oil rigs, hydrocarbons in highly industrial areas, and tree sap in/near forests.
Other factors include:
Foulants can be solid, such as dust, pollen, and salt, or liquid. Different foulants will have different impacts (e.g., some may corrode the compressor blade surface as well as impacting airflow), and it’s helpful to have an idea of the foulant type in order to effectively remove it.
Some performance loss can be recovered through gas turbine compressor cleaning: washing away foulants removes resistance and restores airflow. However, cleaning cannot repair damage caused by corrosion or erosion. I.e. if the blade itself is physically compromised, cleaning will do little to help.
This article explores the topic of achievable performance recovery.
Removing foulants before they can build up and/or in some cases seriously corrode delicate surfaces is a good way to dodge avoidable performance loss. Regular on-line washing and occasional off-line washing will keep foulants to a minimum. Improve results by choosing a detergent designed for your environment/fouling issues.
As we’ve explored, operators should be mindful of small amounts of compressor fouling as the impact can be bigger than they realise. If you’d like to discuss this topic in relation to your own gas turbine site or need help choosing a relevant cleaning chemical, please get in touch to find out more.
Sources:
Post written by Martin Howarth
An extensive knowledge of mechanical and electrical engineering together with hands on experience with gas turbines provides a bedrock for his work at Rochem.
