AIRCRAFT ENGINE COMMITTEE BEST 1993 PAPER AWARD - CONTROL-ORIENTED HIGH-FREQUENCY TURBOMACHINERY MODELING - GENERAL ONE-DIMENSIONAL MODEL DEVELOPMENT

In this paper, an approach for control-oriented high-frequency turboma chinery modeling previously developed by the authors is applied to dev elop one-dimensional unsteady compressible viscous flow models for a g eneric turbojet engine and a generic compression system, We begin by d eveloping models for various components commonly found in turbomachine ry systems. These components include: ducting without combustion, blad ing, ducting with combustion, heat soak, blading with heat soak, inlet , nozzle, abrupt area change with incurred total pressure losses, flow splitting, bleed mixing, and the spool. Once the component models hav e been developed, they are combined to form system models for a generi c turbojet engine and a generic compression system. These models are d eveloped so that they can be easily modified and used with appropriate maps to form a model for a specific rig. It is shown that these syste m models are explicit (i.e., can be solved with any standard ODE solve r without iteration) due to the approach used in their development. Fu rthermore, since the nonlinear models are explicit explicit analytical linear models can be derived from the nonlinear models. The procedure for developing these analytical linear models is discussed. An intere sting feature of the models developed here is the use of effective len gths within the models, as functions of axial Mach number and nondimen sional rotational speed, for rotating components. These effective leng ths account for the helical path of the flow as it moves through a rot ating component. Use of these effective lengths in the unsteady conser vation equations introduces a nonlinear dynamic lag consistent with ex perimentally observed compressor lag and replaces less accurate linear first-order empirical lags proposed to account for this phenomenon. M odels of the type developed here are expected to prove useful in the d esign and simulation of (integrated) surge control and rotating stall avoidance schemes.