In a real gas turbine the fluid dynamics and the thermal conditions that prevail in the hot gas path and near hot parts walls are rather complex. This type of machine features indeed a very specific set of operating conditions, including: high gas temperatures and velocities, complex gas streamlines combined with a wide range and fast variability of operation load. The artifacts caused by internal cooling devices and thermal barriers or anti-corrosion coatings add to this complexity. For these reasons, predicting the fate of ash particles approaching or impinging a hot part represents a real challenge.

In addition the particular conditions that prevail in the combustors, especially: the pressurized and very oxidizing flames, the high temperature but short residence time, make the chemistry of ash formation fairly complex as well.

A work recently undertaken by GE Energy and LERMPS shows that HVOF (High Velocity Oxy-Fuel) facilities represent interesting tools to simulate the “in-flame generation” of ash particles and their fate when impinging on a part wall, provided the test conditions, especially the thermal and velocity fields, are properly adjusted and controlled.

The paper summarizes the development of HVOF experiments specifically devised to study the formation of ash particles with controlled chemistry and their deposition onto hot parts.

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