Cooled nozzle design of gas turbine often uses inserts to intentionally distribute cooling air through impingement holes to hot spots, especially at leading edge areas of stage-1 nozzles. Owing to the variations of engine operation environment, inlet air filtration system, surface coatings, and oil/air sealing material and technology employed, solid particles could be brought into engine from outside or generated inside from rotor rubbing, seal debris, peeled off coating layers or rusty surfaces, etc.  These particles and their agglomerates can be carried by airflow to enter into nozzle inserts and clog impingement holes, thus may reduce a significant amount of cooling air of cooled nozzles and result in severe engine failures. To reduce the risk of insert clogging, particle separation devices and filtration mesh screens have been often implemented in front of nozzle inlets to prevent large particles from entering inside. On the other hand, appropriate hole sizes of nozzle insert in design become very critical to allow small particles to pass through and exhaust from the engine exit. This experimental study focuses on finding a correlation between the impingement hole sizes of a nozzle insert and their clogged areas caused by seeded fine and medium size particles. A nozzle insert was chosen, and a single row of impingement holes was machined at the leading edge of the inert. The results indicated that the insert clogging is a strong function of the hole size, particle size, and pressure ratio. For a specific nozzle insert design, optimized hole sizes are important and beneficial to reduce the risk of insert clogging.


Turbine Nozzle Insert Clogging With Seeded Medium Size Particles

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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