Re: Airfoil surface finish

Date:         17 Oct 99 23:30:00 
From:         <mark.johnston@mindspring.com>
Organization: MindSpring Enterprises
References:   1
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davidwells wrote in message ...
>I am having difficulty finding information on the benefits of improved
>surface finish on airfoils in gas turbine engines (ie. fan blades and
>compressor blades and vanes).
>snip

Most production engine components I am familiar with have surface finishes
in the 16 to 32 mircoinch range.  32 is not to difficult to achieve with
normal production methods, 16 usual requires an abrasive flow operation
(like Extrude hone) or hand finishing/polishing and is more expensive to
achieve than a 32 finish.  I have seen some fluidized bed arrangements which
use a powered abrasive media which could offer a lower cost method of
improving the finish.

There is a point of diminishing returns with regards to surface finish.
There is a definite improvement going from 32 to 16 which is why a lot of
components are polished to a 16 finish.  However, after a period of service,
parts tend to get rougher due to ingestion of sand and dust.  Going for a
surface finish much below 16 provides only a very short term improvement -
great for passing a test cell performance calibration but not much else.

Mark Johnston
Sr Development Engineer
LT101 engine project
AlliedSignal Engines
Phx, AZ
LT101