Abstract:
This is a detailed
study into the internal aerodynamics of labyrinth seals, with pmic|
reference to the effects of abradable
honeycomb stators on labyrinth seal leakage.-
A extensive
experimental programme established tables of friction factor for three
different
grades of honeycomb used by industry, and examined the effect of both
Reynolds number and clearance on these friction factors. The friction factor associated
with a
aerodynamically smooth surface was also experimentally determined in order to
establish the
experimental method.
The
experimental data was used to model the different grades of honeycomb used as
stator material in numerical simulations of a number
labyrinth seals, and allowed for
comparison of the leakage associated with both smooth and abradable stator straight
through labyrinth seals. Step-up and step-down seal geometries were also considered,
and the effects of pressure ratio, clearance and rotation on labyrinth seal leakage was
examined on all modelled seal
types.
This
numerically generated leakage data was comprehensive enough to allow for the
creation of a
second-generation one-dimensional labyrinth seal leakage predictor tool of
the
type used by design engineers in network models. This tool accounts for stator
material, seal clearance, overall pressure ratio, rotation and seal geometry, and the
accuracy associated with this tool allows labyrinth seal leakage to b predicted to within
10%. Functions of discharge coefficient and carry-over factor obtained from the
numerical
predictions are used by this tool, and as such it is capable of dealing with a
large number of different operating conditions for all the seal types modelled.
