The current steady-state performance-based system studies are not adequate to evaluate certain advanced technologies for the challenges associated with meeting the transient performance requirements without better definition and control of component operating margins. Additional dynamic analyses would require more detailed, physics-based, component-level models and controllers in order to better identify dynamic issues that may arise during operation of the engine. The additional complexity in these models increases the effort necessary throughout the design processes, including the system-analysis step. The solution would be a physics-based engine model with full envelope controller. C-MAPSS and C-MAPSS40k are examples of engine models with full envelope controllers, but because they are designed to model a specific engine, they are not good candidates for systems analysis.

The engine should be capable of safely transitioning from one steady-state operating point to another while maintaining adequate stall and temperature margins with consideration for off-nominal operation (e.g., engine degradation, atmospheric disturbances, vehicle maneuver/angle-of-attack, etc).

The Tool for Turbine Engine Closed-loop Transient Analysis (TTECTrA) is a tool, developed in the MathWorks MATLAB/Simulink environment, intended to extend systems analysis by providing an estimate of the transient performance/capability of a conceptual engine design. The TTECTrA tool is capable of designing a basic turbofan engine controller, with transient protection, based on the user’s engine model and constraints. TTECTrA relies on the MATLAB Control Systems Toolbox to provide additional functionality and streamline the control design process.

Advantages to this tool include design of transient limiters to meet surge margin requirements, and the ability to interface with any engine model design in MATLAB/Simulink, provided the appropriate connections can be made between the model and the TTECTrA block. This software can design a controller and simulate the response of the closed-loop system (controller and engine) at a single operating point to estimate the performance of the system without designing a full envelope nonlinear controller.

TTECTrA provides verification of the controller through two simulations executed after designing the controller. One simulation uses small throttle transients to test the ability of the controller to provide actuation to track the set point changes necessary to meet the desired thrust output. The second simulation uses large throttle transients to demonstrate the functionality of the transient limiters. TTECTrA will plot the typical data required for systems analysis, and the user can easily add additional signals to be plotted.

This work was done by Jeffrey Csank of Glenn Research Center and Alicia Zinnecker of N&R Engineering & Management Services. Contact NASA Glenn Research Center’s Technology Transfer Program at This email address is being protected from spambots. You need JavaScript enabled to view it. or visit us on the Web at . Please reference LEW-19177-1.

NASA Tech Briefs Magazine

This article first appeared in the June, 2015 issue of NASA Tech Briefs Magazine.

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