  This paper presents a novel, more efficient proper orthogonal decomposition
(POD) based reduced-order model (ROM) for compressible flows. In this POD model
the governing equations, i.e., the conservation of mass, momentum, and energy
equations were written using specific volume instead of density. This
substitution allowed for the pre-computation of the coefficients of the system
of ODEs that make up the reduced-order model. Several methods were employed to
enhance the stability of the ODE solver: the penalty method to enforce boundary
conditions, artificial dissipation, and a method that modifies the number of
modes used in the POD approximation. This new POD-based reduced-order model was
validated for four cases at both on- and off-reference conditions: a
quasi-one-dimensional nozzle, a two-dimensional channel, a three-dimensional
axisymmetric nozzle, and a transonic fan. The speedup obtained by using the
POD-based ROM vs. the full-order model exceeded four orders of magnitude in all
cases tested.
