Physical lumping methods for developing linear reduced models for high speed propulsion systems
Abstract
In gasdynamic systems, information travels in one direction for supersonic flow and in both directions for subsonic flow. A shock occurs at the transition from supersonic to subsonic flow. Thus, to simulate these systems, any simulation method implemented for the quasionedimensional Euler equations must have the ability to capture the shock. In this paper, a technique combining both backward and central differencing is presented. The equations are subsequently linearized about an operating point and formulated into a linear state space model. After proper implementation of the boundary conditions, the model order is reduced from 123 to less than 10 using the Schur method of balancing. Simulations comparing frequency and step response of the reduced order model and the original system models are presented.
 Publication:

In its Improved Large Perturbation Propulsion Models for Control System Design (19881989) and Large Perturbation Models of High Velocity Propulsion Systems (19891990) and Reduced Order Propulsion Models for Control System Design (19901991) 12 p (SEE N9222491 1334
 Pub Date:
 December 1991
 Bibcode:
 1991ilpp.rept.....I
 Keywords:

 Approximation;
 Computational Fluid Dynamics;
 Computerized Simulation;
 Euler Equations Of Motion;
 Gas Dynamics;
 High Speed;
 Intake Systems;
 Lumped Parameter Systems;
 Lumping;
 Mathematical Models;
 Nonlinear Systems;
 Propulsion System Performance;
 Backward Differencing;
 Boundary Conditions;
 Eigenvalues;
 Frequencies;
 Linear Systems;
 Partial Differential Equations;
 Propulsion System Configurations;
 Shock Waves;
 Subsonic Flow;
 Supersonic Flow;
 Fluid Mechanics and Heat Transfer