Dennis Culley NASA Glenn Research Center Exergy Analysis amp Design for 21st Century Aerospace Systems Control amp Optimization AFRL NASA MIT Workshop April 18 2019 1 2 Outline ID: 1010505
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1. Propulsion Control for the Electrified Turbine EngineDennis Culley NASA Glenn Research CenterExergy Analysis & Design for 21st Century Aerospace Systems, Control, & OptimizationAFRL – NASA – MIT WorkshopApril 18, 20191
2. 2OutlineElectrified PropulsionPerformance, Operability & StabilityThe TEEM ConceptConclusion
3. Electrification of Aero-Propulsion Systems3ElectricMachineHighSpoolHPCHPTElectricMachineLowSpoolEnergy StorageElectronicsEM_PCombLPTLPCTurbomachineryThermal ManagementElectric Machines and Power DistributionPropulsion Control used to be synonymous with turbine engine control.Vehicle Control
4. Microgrid4Electrified 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.
5. STARC-ABL: Single-aisle Turboelectric AiRCraft with Aft Boundary Layer propulsionNASA’s STARC-ABL Advanced Concept
6. NASA’s N3-XTurbo-electric Distributed Propulsion
7. 7OutlineElectrified PropulsionPerformance, Operability & StabilityThe TEEM ConceptConclusion
8. High Pressure Compressor MapPressure RatioCorrected Mass Flow8Operating LineCompressor PerformanceAerodynamic Loss(Compressor Efficiency) Thermal Efficiency
9. High Pressure Compressor MapPressure RatioCorrected Mass Flow9Uncertainty StackTransient StackCompressor Operability & StabilityOperating LineStall Margin is an unmeasurable parameter that estimates how close the compressor operation is to stall.Stall Margin is an abstraction representing the quality of the flow condition in the compressor gas path
10. 10Turbine Engine DynamicsThe turbine engine stores energy as a pressure vessel.From the compressor map we know that mismatches in pressure relative to the flow through the hot gas path define off-nominal conditions that threaten engine stability.The transient pressure-flow characteristic defines the stall margin.Gas Dynamics where R is gas constant, T is temperature, V is volume , is mass flow rateJaw, L.C., Mattingly, J.D., Aircraft Engine Controls, ISBN:978-1-60086-705-7
11. 11Turbine Engine DynamicsThe turbine engine stores energy as a fly wheel.The high moment of inertia causes the spool speeds to lag behind the flow in the hot gas path.Shaft Dynamics where N is shaft speed, Wf is fuel flow, I is mass moment of inertiaJaw, L.C., Mattingly, J.D., Aircraft Engine Controls, ISBN:978-1-60086-705-7
12. 12Turbine Engine DynamicsThe turbine engine stores thermal energy in its material.Mismatches in coefficient of expansion affect clearances, which impact the hot gas flow path.Temperature Dynamics where is time constant, T41 is turbine inlet temperature, is mass flow rateJaw, L.C., Mattingly, J.D., Aircraft Engine Controls, ISBN:978-1-60086-705-7
13. 10/18/201813Accel: Power Augmentation to LP Shaft = 0hpDecel: Power Augmentation to HP Shaft = 0hp~0.6 kW-hr consumed during flight (on order of energy present in a car battery)TEEM Transient ImpactEach spike represents the occurrence and magnitude of compressor transient suppression during a typical transport flight profile
14. 14OutlineElectrified PropulsionPerformance, Operability & StabilityThe TEEM ConceptConclusion
15. Using the Hybrid Propulsion ArchitectureCan 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?15ElectricMachineHighSpoolHPCHPTElectricMachineLowSpoolEnergy StorageElectronicsEM_PCombLPTLPC
16. TEEM Operability Concept16Any 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.
17. TEEM Operability Concept17Electric 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.
18. The TEEM Steady-State Operability Concept10/18/201818Potentially Simpler, More EfficientElectric MachinesComplexVariable Vanes & BladesInefficientBleeds
19. 19Objectives versus GoalsObjective: 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).
20. 20OutlineElectrified PropulsionPerformance, Operability & StabilityThe TEEM ConceptConclusion
21. 21ConclusionsHybrid Propulsion concepts involving Gas Turbine Engines provide new opportunities to benefit:air vehiclesturbine-based propulsionThe 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.
22. 22AcknowledgementsThanks to Jonathan Kratz and George Thomas who are co-innovators 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.
23. 23Questions?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