Propulsion Control for the Electrified Turbine Engine Exergy

Propulsion Control for the Electrified Turbine Engine Exergy Analysis & Design for 21 st Century Aerospace Systems, Control, & Optimization AFRL – NASA – MIT Workshop April 18, 2019 Dennis Culley NASA Glenn Research Center 1

Outline 1. Electrified Propulsion 2. Performance, Operability & Stability 3. The TEEM Concept 4. Conclusion 2

Electrification of Aero-Propulsion Systems Comb Electric Machine Low Spool LPC HPC LPT HPT Electric Machine High Spool Electronics Energy Storage EM_P Turbomachinery Electric Machines and Power Distribution Thermal Management Vehicle Control Propulsion Control used to be synonymous with turbine engine control. 3

Microgrid Electrified Propulsion Systems are about the establishment of a flying Microgrid where the most efficient source of power is the fuel-fed turbine engine. It is desirable to minimize the weight of electrical energy storage elements, however, that also decreases their energy capacity thereby increasing the dynamic coupling between the power system and the turbine engine. Turbine engines must be protected from sudden changes in loading that can induce catastrophic instability. 4

NASA’s STARC-ABL Advanced Concept STARC-ABL: Single-aisle Turboelectric Ai. RCraft with Aft Boundary Layer propulsion

NASA’s N 3 -X Turbo-electric Distributed Propulsion

Outline 1. Electrified Propulsion 2. Performance, Operability & Stability 3. The TEEM Concept 4. Conclusion 7

Compressor Performance High Pressure Compressor Map Operating Line Pressure Ratio Thermal Efficiency Aerodynamic Loss (Compressor Efficiency) Corrected Mass Flow 8

Compressor Operability & Stability High Pressure Compressor Map Stall Margin is an unmeasurable parameter that estimates how close the compressor operation is to stall. Operating Line Pressure Ratio Uncertainty Stack Transient Stack Stall Margin is an abstraction representing the quality of the flow condition in the compressor gas path Corrected Mass Flow 9

Turbine Engine Dynamics 10

Turbine Engine Dynamics 11

Turbine Engine Dynamics 12

TEEM Transient Impact Accel: Power Augmentation to LP Shaft = 0 hp ~0. 6 k. W-hr consumed during flight (on order of energy present in a car battery) Each spike represents the occurrence and magnitude of compressor transient suppression during a typical transport flight profile Decel: Power Augmentation to HP Shaft = 0 hp 10/18/2018 13

Outline 1. Electrified Propulsion 2. Performance, Operability & Stability 3. The TEEM Concept 4. Conclusion 14

Using the Hybrid Propulsion Architecture Comb Electric Machine Low Spool LPC HPC LPT HPT Electric Machine High Spool Electronics Energy Storage EM_P Can Electric Machines improve the operation of turbomachinery during transient conditions by maintaining the steady state design condition across its components, specifically the rotational speed relative to the flow condition? 15

TEEM Operability Concept • Any electric machine can be used as a motor or a generator regardless of its original design intent. . • The electric machine can be used as an actuator to apply or extract torque from the connected shaft. • Adjusting torque enables speed control independent of the main fuel control. 16

TEEM Operability Concept Electric speed control can compensate for the natural response of the rotating parts, which lag due to inertia, during changes in state. In the compressor … it’s all about the incidence angle. 17

The TEEM Steady-State Operability Concept Electric Machines Potentially Simpler, More Efficient Variable Vanes & Blades Bleeds 10/18/2018 Inefficient Complex 18

Objectives versus Goals Objective: What specific new capability do we provide? TEEM actively alters the dynamic response of the engine for the purpose of eliminating the need for transient operability margin. Why do we care? Because system performance is set by the steady-state engine design, which must carry margin to accommodate wear and operability. Goal: What is the ultimate purpose of what we are doing? Improving the performance and efficiency of turbomachinery (propulsion). 19

Outline 1. Electrified Propulsion 2. Performance, Operability & Stability 3. The TEEM Concept 4. Conclusion 20

Conclusions • Hybrid Propulsion concepts involving Gas Turbine Engines provide new opportunities to benefit: • air vehicles • turbine-based propulsion • The Turbine Electrified Energy Management (TEEM) operability concept leverages the hybrid propulsion architecture to improve the performance of the turbine engine. • Electric machines coupled to the shafts of the turbine engine can be used to alter the engine natural dynamic response to approximate the engine steady-state design conditions. • The concept demonstrates the ability to reduce the need for transient stability margin in the compressors, thus expanding the engine design space and enabling new performance and efficiency benefits for propulsion systems. 21

Acknowledgements Thanks to Jonathan Kratz and George Thomas who are coinnovators on TEEM. Thanks to Joe Connolly and Dr. Sanjay Garg for sharing their insight. We would like to thank the Convergent Aeronautics Solutions (CAS) project for initial funding of this work and the Transformational Tools and Technologies (TTT) project for its continued development. 22

Questions? Culley, D. , Kratz, J. , Thomas, G. , “Turbine Electrified Energy Management (TEEM) For Enabling More Efficient Engine Designs, ” 2018 AIAA Propulsion and Energy Forum, AIAA-2018 -4798 23