Abstract:
Implementation of Variable Geometry during the off-design operation of an aero gas
turbine engine may cause deviations for restricted engine parameters when
fight envelope requirements are met. A method to optimize the thermodynamic
cycle of a engine with respect to fuel burn, while meeting a variety of airframe
or
technological restrictions at the three major operating points of the fight
envelope, namely the Top of Climb, End of Runway and mid-cruise points is
developed. Purpose is the comparison of engines on a common basis. The method
is
implemented and performance benefits are identified in a variety of studies,
such as:
o the theoretically infinite Variable
Geometry in turbomachinery components
o reduction of the turbine coolant fraction
during cruise for long range civil
fights
o
optimal variable nozzle geometry implementation during steady state and
transient
operation
Core of the
optimization procedure is a zero-dimensional engine arithmetic
solver
developed by the author from scratch for a 3-spool and 2-spool engine
configuration. The solver utilizes real gas properties and an approximate dimensionless
enthalpy rise profile at the fan exit for the separate modeling of the fan
tip and hub region. Purpose for the development of the new code has been a
common arithmetic treatment for
steady-state and transient calculations within
the same
engine solver, which is thoroughly described.
