CFD simulation improves droplet coverage during turbine wash

Introducing computerized fluid dynamics (CFD) has enabled Gas Turbine Efficiency (GTE) to improve the effectiveness of its online gas turbine washing technique. Liquid is atomized at high pressure, creating a spray of fine droplets directed at the compressor inlet. The droplets travel at essentially the same speed as the air stream, thereby penetrating deep into the compressor, ensuring efficient cleaning of the internals.

“As gas turbines run with velocities approaching the speed of sound, the conditions created inside during online washing are difficult to monitor and understand,” says Carl-Johan Hjerpe, manager, research and development. “The CFD tool provides us with simulations of the droplet trajectories revealing where the liquid goes. With this knowledge, we are able to optimize the washing process.”

Online washing has proved popular with turbine operators. It does not replace offline washing, Hjerpe points out. Sooner or later fouling builds up on the turbine blades to the point where an offline wash is needed. But it enables the operator to postpone the turbine shutdown to a convenient time such as a planned maintenance turnaround.

GTE's high-pressure gas turbine washing system in action on an LM2500 turbine.

Statoil, which has thoroughly tested the GTE system, recently signed an agreement to use it on all its North Sea installations, replacing current equipment. The system is also making inroads elsewhere in the North Sea, having been used on Total’s Alwyn North, BP’s ETAP, CNR’s Banff, and Amerada Hess’s South Arne platforms.

Through Siemens, GTE recently received its first order for a Russian customer. Another agreement with Rolls-Royce, which is incorporating the technology into its gas turbine production, has led to retrofit installations for the first time in India, Malaysia, and Brunei.

With Far East customers increasingly in mind, GTE has adapted the system for use on small offshore platforms with space limitations. By doing away with the detergent tank and delivering detergent directly from the container to the cleaning system via a dosing pump, it has found a solution that does not compromise washing efficiency, Hjerpe says.

GTE also offers a water purification system. “The water has to be fresh so that it doesn’t pick up ions,” Hjerpe says. “During online washing, the water evaporates, so any minerals it contains will be deposited on the turbine parts.”•

For more information, contact Carl-Johan Hjerpe, Gas Turbine Efficiency. Tel +46 8546 10 513, fax +46 8546 10 501, [email protected], www.gtefficiency.com.