Disk windage increases the losses in most types of turbomachine. The Ekmann layers on the spinning disks cause a recirculation in the cavity which brings in fresh fluid rotating slower than the disk. Can anyone think how we might reduce the disk friction by slowing the recirculation?
Dear Abdul,
Thankyou for your answer. I was thinking about a surface treatment designed to apply a radially inward force on the boundary layer to reduce the strength of the recirculation. My hope would be that weaker recirculation would lead to weaker disk windage torque. I have a student building a simple rig just now and intend to try out the idea. Do you have any suggestions of what the best configuration might be?
cheers Martin
I think you are describing a pre-swirl system. This involves passing the blade coolant through a set of preswirl nozzles (effectively turbine nozzle guide vanes). The swirling coolant has a lower relative total temperature which lowers the coolant temperature and off course the required massflow to cool the blades. A spin off from the pre-swirl system is a reduction of disc windage I am sure. But the pre-swirl system is associated with the destruction of a considerable amount of availability: increasing SFC.
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