Advanced Control Considerations for Turbofan Engine Design

Abstract

This paper covers the application of a model-based engine control (MBEC) methodology featuring a self tuning on-board model for an aircraft turbofan engine simulation. The nonlinear engine model is capable of modeling realistic engine performance, allowing for a verification of the advanced control methodology over a wide range of operating points and life cycle conditions. The on-board model is a piece-wise linear model derived from the nonlinear engine model and updated using an optimal tuner Kalman Filter estimation routine, which enables the on-board model to self-tune to account for engine performance variations. MBEC is used here to show how advanced control architectures can improve efficiency during the design phase of a turbofan engine by reducing conservative operability margins. The operability margins that can be reduced, such as stall margin, can expand the engine design space and offer potential for efficiency improvements. Application of MBEC architecture to a nonlinear engine simulation is shown to reduce the thrust specific fuel consumption by approximately 1% over the baseline design, while maintaining safe operation of the engine across the flight envelope.

Gas turbine aero-engines real time on-board modelling: A review, research challenges, and exploring the future

“…So, engines could be designed to avoid excessive safety margin. Experiments adopted by NASA on a high-fidelity aero-thermal model of a large turbofan engine with 178 kN ( 40,000 pounds) thrust, Commercial Modular Aero-Propulsion System Simulation (C-MAPSS40k), showed that a 13% reduction in surge margin threshold contributes to the benefit of a 1% reduction in fuel consumption [79]. This is accomplished by re-designing the engine with a lower surge margin limit so that the compressor operating line runs within a much higher efficiency zone.…”

An Improved Onboard Adaptive Aero-Engine Model Based on an Enhanced Neural Network and Linear Parameter Variance for Parameter Prediction

“…Compared with traditional control methods that directly utilize sensor measurements as feedback, an onboard model is introduced into the control structure in the model-based control system. Then, the unmeasurable parameters estimated with the onboard model are used as feedback in engine control [4][5][6].…”

Propulsion Controls Modeling for a Small Turbofan Engine

“…This baseline nonlinear dynamic model will enable comparison testing of advanced controls in the DART facility to improve upon the technology readiness level of previous simulation studies. [10][11][12] The DGEN family of engines are small, dual spool, high-bypass, geared turbofan engines used in several system level technology studies. [13][14][15][16] A cut out side view of the DGEN 380 engine is shown in Fig.…”