Phenomenon of Flow Pumping Through Counterbore Cavities

CFD analysis of flow through high pressure packaging seal passage of a typical land based gas turbine was performed which contained a rotating bolted joint region. Analysis reveals that the annular space between the nut and the counterbore surface acts as a fluid pump, sucking and pumping out fluid with significant temperature rise as high as 40 F. Factorial DoEs were carried out to filter out vital few parameters among geometric, flow and operational parameters that impacts counterbore flow. A detailed space filling DoE with more than 100 CFD models were developed and studied to estimate the influence of parameters impacting counterbore mass flow. A mathematical model (transfer function) developed using PEZ was created to calculate counterbore mass flow as a function of vital few geometric and flow variables. Finally, 2D Axi symmetric thermal analysis with counterbore mass flow modelling better matched the field temperature compared to that of one without counterbore model.