Overview

The ^[*] inlet to a gas turbine is designed to promote optimum air swallowing capability. Smooth geometry is essential, so its surface contour generally is kept as simple as possible. Its smooth surface may conceal pressure probes and heating boots that are part of an anti-icing system (depending on where the turbine is located geographically).

Land- and marine-based engines frequently are equipped with inlet air filtration systems to protect the gas turbine against ingestion of contaminants potentially including, but not limited to, salt sea spray, insects, sand, and oil stack fumes. These contaminants could coat themselves on the airfoils in the compressor or further downstream and cause erosive or corrosive damage to gas turbine components. They also may just adhere temporarily to the compressor blade surfaces and cause incremental performance loss.

However, the filter system must cause as small a pressure (power loss) drop as possible. The compromise of these two requirements results in a filter system that allows some dirt through, which eventually clogs enough of the compressor air passages that a compressor wash is required to restore performance.

Most gas turbines, therefore, are fitted with wash systems (See Chapter 8, Accessory Systems, for details on wash systems). In summary, these systems include nozzles through which cleaning fluid may be conducted into the gas turbine compressor. The wash is conducted at a variety of speeds, from slow roll to "while online." Wash parameters depend on the...