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  • 1
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    Approximation of Engine Casing Temperature Constraints for Casing Mounted Electronics (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The performance of propulsion engine systems is sensitive to weight and volume considerations. This can severely constrain the configuration and complexity of the control system hardware. Distributed Engine Control technology is a response to these concerns by providing more flexibility in designing the control system, and by extension, more functionality leading to higher performing engine systems. Consequently, there can be a weight benefit to mounting modular electronic hardware on the engine core casing in a high temperature environment. This paper attempts to quantify the in-flight temperature constraints for engine casing mounted electronics. In addition, an attempt is made at studying heat soak back effects. The Commercial Modular Aero Propulsion System Simulation 40k (C-MAPSS40k) software is leveraged with real flight data as the inputs to the simulation. A two-dimensional (2-D) heat transfer model is integrated with the engine simulation to approximate the temperature along the length of the engine casing. This modification to the existing C-MAPSS40k software will provide tools and methodologies to develop a better understanding of the requirements for the embedded electronics hardware in future engine systems. Results of the simulations are presented and their implications on temperature constraints for engine casing mounted electronics is discussed.
    Keywords: Aircraft Propulsion and Power; Statistics and Probability; Metals and Metallic Materials
    Type: NASA/TM-2017-219477 , AIAA Paper 2016-4858 , E-19349 , GRC-E-DAA-TN39546
    Format: application/pdf
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  • 2
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    A Parametric Study of Actuator Requirements for Active Turbine Tip Clearance Control of a Modern High Bypass Turbofan Engine (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The efficiency of aircraft gas turbine engines is sensitive to the distance between the tips of its turbine blades and its shroud, which serves as its containment structure. Maintaining tighter clearance between these components has been shown to increase turbine efficiency, increase fuel efficiency, and reduce the turbine inlet temperature, and this correlates to a longer time-on-wing for the engine. Therefore, there is a desire to maintain a tight clearance in the turbine, which requires fast response active clearance control. Fast response active tip clearance control will require an actuator to modify the physical or effective tip clearance in the turbine. This paper evaluates the requirements of a generic active turbine tip clearance actuator for a modern commercial aircraft engine using the Commercial Modular Aero-Propulsion System Simulation 40k (C-MAPSS40k) software that has previously been integrated with a dynamic tip clearance model. A parametric study was performed in an attempt to evaluate requirements for control actuators in terms of bandwidth, rate limits, saturation limits, and deadband. Constraints on the weight of the actuation system and some considerations as to the force which the actuator must be capable of exerting and maintaining are also investigated. From the results, the relevant range of the evaluated actuator parameters can be extracted. Some additional discussion is provided on the challenges posed by the tip clearance control problem and the implications for future small core aircraft engines.
    Keywords: Aircraft Propulsion and Power
    Type: GT2017-63472 , GRC-E-DAA-TN39865 , ASME 2017 Turbo Expo; Jun 26, 2017 - Jun 30, 2017; Charlotte, NC; United States
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  • 3
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    Active Turbine Tip Clearance Control Trade Space Analysis of an Advanced Geared Turbofan Engine (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Tip clearance within the high pressure turbine of a gas turbine engine is a significant factor in engine performance and efficiency. In the pursuit of higher efficiency, aero-engine designs are migrating toward compact gas turbine (CGT) technology that seeks to increase the bypass ratio of the gas turbine engine without increasing the size of the fan, which is constrained by its underwing location. The reduced size of CGTs invoke concern over increased sensitivity of engine performance due to turbine tip clearance gap that makes an argument for advanced tip clearance mitigation and control techniques to be employed. This paper evaluates the tip clearance trade space for a conceptual geared turbofan engine with a CGT core. This is accomplished through a modeling and simulation approach that includes a sensitivity analysis of engine performance in response to high pressure turbine tip clearance as well as an evaluation of the sensitivity of tip clearance to various design parameters, including material properties and component cooling characteristics. Also included is a parametric study of actuators that provides preliminary requirements for implementation of active turbine tip clearance control actuation systems. The results produced from these studies are meant to be informative, with special emphasis on the demonstration of a systematic approach. The modeling approach appears to capture expected trends. The studies suggest that the tip clearance gap will have a greater impact on the new CGT engines and that a relatively slow, actively controlled actuation system may be sufficient as long as it has control authority to both open and close the tip clearance gap.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN58715 , AIAA Propulsion and Energy Forum; Jul 09, 2018 - Jul 11, 2018; Cincinnati, Ohio; United States
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  • 4
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    Design and Benchmarking of a Network-In-the-Loop Simulation for Use in a Hardware-In-the-Loop System (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Distributed engine control (DEC) systems alter aircraft engine design constraints be- cause of fundamental differences in the input and output communication between DEC and centralized control architectures. The change in the way communication is implemented may create new optimum engine-aircraft configurations. This paper continues the exploration of digital network communication by demonstrating a Network-In-the-Loop simulation at the NASA Glenn Research Center. This simulation incorporates a real-time network protocol, the Engine Area Distributed Interconnect Network Lite (EADIN Lite), with the Commercial Modular Aero-Propulsion System Simulation 40k (C-MAPSS40k) software. The objective of this study is to assess digital control network impact to the control system. Performance is evaluated relative to a truth model for large transient maneuvers and a typical flight profile for commercial aircraft. Results show that a decrease in network bandwidth from 250 Kbps (sampling all sensors every time step) to 40 Kbps, resulted in very small differences in control system performance.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN37930 , SciTech 2017; Jan 09, 2017 - Jan 13, 2017; Grapevine, TX; United States
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  • 5
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    A Control Strategy for Turbine Electrified Energy Management (2019)
    In:  CASI
    Details
    Publication Date: 2019-11-07
    Description: Hybrid electric propulsion architectures provide the infrastructure to enable additional benefits to the propulsion system that are otherwise unrealizable with the sole use of the current, state-of-the-art, gas-driven, turbine engines. The presence of electric machines (EMs) coupled to the shaft(s) of the turbine engine provide the ability to actively alter the operation of the engine to the benefit of the propulsion system and the aircraft it propels. This is the goal of the Turbine Electrified Energy Management (TEEM) concept, which at its broadest level addresses the management of energy across the electrified propulsion system. Prior work has demonstrated the use of this concept to alter steady-state operation and improve transient operability of a hybrid-electric propulsion system. The main benefits previously illustrated include the elimination of stability bleeds and expansion of the turbomachinery design space in order to enable more efficient designs. This paper focuses on the development of control strategies to implement the TEEM concept, and it explores several possible architecture variants for applying this concept. Comparison studies are conducted between a purely gas-driven turbofan (baseline engine configuration) and TEEM augmented variants of the baseline engine. The variants are distinguished by the shaft(s) that possess an EM. The configurations consider EMs on both shafts, an EM on the high pressure spool (HPS) only, and an EM on the low pressure spool (LPS) only. These configurations are referred to as the dual-spool configuration, the HPS configuration, and LPS configuration, respectively. The studies expose several options in configuring and controlling the system, including the use of a single EM coupled to a single shaft of a two-spool engine to positively impact the operability of both shafts. The studies also demonstrate the use of independently designed controllers for the electric machine(s) that allow for a decoupled control design process.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70128 , AIAA/IEEE Electric Aircraft Technology Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
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  • 6
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    Benchmarking Model Variants in Development of a Hardware-in-the-Loop Simulation System (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: Distributed engine control architecture presents a significant increase in complexity over traditional implementations when viewed from the perspective of system simulation and hardware design and test. Even if the overall function of the control scheme remains the same, the hardware implementation can have a significant effect on the overall system performance due to differences in the creation and flow of data between control elements. A Hardware-in-the-Loop (HIL) simulation system is under development at NASA Glenn Research Center that enables the exploration of these hardware dependent issues. The system is based on, but not limited to, the Commercial Modular Aero-Propulsion System Simulation 40k (C-MAPSS40k). This paper describes the step-by-step conversion from the self-contained baseline model to the hardware in the loop model, and the validation of each step. As the control model hardware fidelity was improved during HIL system development, benchmarking simulations were performed to verify that engine system performance characteristics remained the same. The results demonstrate the goal of the effort; the new HIL configurations have similar functionality and performance compared to the baseline C-MAPSS40k system.
    Keywords: Aircraft Stability and Control; Air Transportation and Safety
    Type: NASA/TM-2016-219089 , AIAA Paper 2016-1425 , GRC-E-DAA-TN29895
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  • 7
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    Turbine Electrified Energy Management (TEEM) For Enabling More Efficient Engine Designs (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA is investing in Electrified Aircraft Propulsion (EAP) research as part of an effort to assist industry in meeting the future needs of a global aviation market. The integration of electric machines into traditional turbine-based propulsion provides opportunities to change system architectures effecting radical improvements in propulsive efficiency. However, less consideration has been afforded to the utilization of these electrical machines to improve the thermal efficiency and performance of the gas turbine engine. Noting this deficit, a novel operability concept is proposed and is referred to as Turbine Electrified Energy Management (TEEM). The concept is a transient control technology that supplements the main fuel control for the suppression of the natural off-design dynamics associated with changes in engine operating state. Here the electric machines, used as engine actuators during the transient, add or extract torque from the engine shafts to maintain the speed-flow characteristics of steady-state design operation. This greatly reduces the need to maintain transient stall margin stack in the compressors, among other potential benefits. This paper demonstrates the feasibility of the concept in dynamic simulation using a Numerical Propulsion System Simulation (NPSS) engine model of a NASA hybrid electric propulsion concept known as the Parallel Hybrid Electric Turbofan (hFan).
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Propulsion and Energy Forum; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
    Format: application/pdf
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  • 8
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    Dynamic Analysis of the hFan, a Parallel Hybrid Electric Turbofan Engine (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA and a variety of aerospace industry stakeholders are investing in conceptual studies of electrified aircraft, including parallel hybrid electric aircraft such as the Subsonic Ultra Green Aircraft Research (SUGAR) Volt. At this point, little of the work published in the literature has examined the transient behavior of the turbomachinery in these systems. This paper describes a control system built around the hFan, the parallel hybrid electric turbofan engine designed for the SUGAR Volt concept aircraft. This control system is used to show that the hFan, running with its baseline concept of operations, is capable of transient operation throughout the envelope. The design parameters of this controller are varied to assess the amount of operability margin built into the engine design, and whether this margin can be reduced to enable more aggressive designs, that may feature better fuel economy. Further, studies are performed as parameters for the hFan electric motor are varied to determine how the motor impacts the engine's need for transient operability margin. The studies suggest that the engine may be redesigned with as much as a 3% reduction in high pressure compressor stall margin. It was also demonstrated that appropriate design and control of the electric motor may be able to buy an additional 0.5% stall margin reduction or a turbine inlet temperature reduction of 35 R, as tested at the sea-level static condition.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN58686 , AIAA/SAE/ASEE Joint Propulsion Conference; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States|AIAA Propulsion and Energy Forum 2018; Jul 09, 2018 - Jul 11, 2018; Cincinnati, OH; United States
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  • 9
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    Dynamic Analysis of the hFan, a Parallel Hybrid Electric Turbofan Engine (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: NASA and a variety of aerospace industry stakeholders are investing in conceptual studies of electrified aircraft, including parallel hybrid electric aircraft such as the Subsonic Ultra Green Aircraft Research (SUGAR) Volt. At this point, little of the work published in the literature has examined the transient behavior of the turbomachinery in these systems. This paper describes a control system built around the hFan, the parallel hybrid electric turbofan engine designed for the SUGAR Volt concept aircraft. This control system is used to show that the hFan, running with its baseline concept of operations, is capable of transient operation throughout the envelope. The design parameters of this controller are varied to assess the amount of operability margin built into the engine design, and whether this margin can be reduced to enable more aggressive designs, that may feature better fuel economy. Further, studies are performed as parameters for the hFan electric motor are varied to determine how the motor impacts the engine's need for transient operability margin. The studies suggest that the engine may be redesigned with as much as a 3% reduction in high pressure compressor stall margin. It was also demonstrated that appropriate design and control of the electric motor may be able to buy an additional 0.5% stall margin reduction or a turbine inlet temperature reduction of 35 degR, as tested at the sea-level static condition.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN57636 , AIAA/SAE/ASEE Joint Propulsion Conference; Jul 07, 2018 - Jul 13, 2018; Cincinnati, OH; United States
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  • 10
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    Evaluation of Electrical System Requirements for Implementing Turbine Electrified Energy Management (2019)
    In:  CASI
    Details
    Publication Date: 2019-09-05
    Description: Turbine Electrified Energy Management (TEEM) is a concept concerned with the management of energy in an electrified propulsion system. The management of energy in the hybrid-electric architecture has potential to benefit the turbomachinery and the aircraft it powers. The concept is particularly useful for improving operability during transient operation and could be leveraged to design a better performing engine. The concept utilizes electric machines coupled to the engine shafts and an electric power distribution system that includes energy storage. A controller is used to decide when and how energy is moved around the electrified propulsion system, particularly when considering energy conversion between mechanical and electrical forms. Prior work has shown that the electric machines can be used to supply/or extract supplemental power to/from the engine shafts to improve their operability and achieve or enable propulsion efficiency and performance benefits. However, the previous studies did not consider the practical constraints of the electrical machines and energy storage devices that are required for implementing the TEEM system architecture concept. This paper presents an integrated engine and electrical system model that is used to evaluate the electrical system requirements. The model captures the physics of the conceptual, Advanced Geared Turbofan 30,000lbf (AGTF30) engine, which features advanced technologies such as a compact gas turbine and a variable area fan nozzle. For this work, the engine is augmented with electrical system components that allow for the implementation of the TEEM concept. The evaluation presented suggests the potential of the TEEM concept to provide performance benefits for a turbofan engine.
    Keywords: Aircraft Propulsion and Power
    Type: GRC-E-DAA-TN70911 , AIAA/IEEE Electric Aircraft Technology Symposium (EATS); Aug 22, 2019 - Aug 24, 2019; Indianapolis, IN; United States
    Format: application/pdf
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