Algorithmic Aero Engine Life Usage Monitoring Based on Reference Analysis of Design Mission

Algorithmic Aero Engine Life Usage Monitoring
Based on Reference Analysis of Design Mission
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MANFRED KOEHL
1 ABSTRACT
Fracture critical areas in an aero engine are usually located in fast rotating com-
ponents which   are   exposed   to   high   temperatures. Therefore,   a   direct   local meas-
urement of damage related parameters   like strains and   temperatures   is not   feasible.
Instead,   only   a   few   remotely   measured   quantities,   e.g.   engine   intake   conditions,
rotational speeds, and, possibly, gas path temperatures and pressures, are accessible
as   input   for an on-board   life usage monitoring   system. This   shortcoming has been
compensated by sophisticated mathematical models which calculate the   local physi-
cal parameters needed for assessing the life consumption of each critical area.
The models   for   temperature   and   stress   calculation   consist   of   algorithms   con-
taining parameters which have   to be   adjusted   individually   for   each   considered   en-
gine area. This   is achieved by an optimization with   respect   to a   reference analysis
performed   for   the purpose of   structural   life prediction which   is part   of   the   engine
development process. The   reference analysis   is usually a   finite   element   calculation
applied to a representative flight profile (the design mission). The parameters of the
algorithm   are   determined   in   such   a way   that   the maximum   deviation   between   the
results   of   the   algorithm   and   those   of   the   reference   analysis   is minimized   over   the
whole design mission. The algorithms are suitable   for use   in   real   time. They allow
for fast   transition of   the   input signals, measured under   real aircraft and engine ma-
noeuvring, to the calculated temperatures and stresses.
From   the   temperature and   stress histories of a   flight,   the cyclic damage   is de-
termined by application of   the crack   initiation or crack propagation data. Life con-...