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  • 1
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    A Study on the Requirements for Fast Active Turbine Tip Clearance Control Systems (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper addresses the requirements of a control system for active turbine tip clearance control in a generic commercial turbofan engine through design and analysis. The control objective is to articulate the shroud in the high pressure turbine section in order to maintain a certain clearance set point given several possible engine transient events. The system must also exhibit reasonable robustness to modeling uncertainties and reasonable noise rejection properties. Two actuators were chosen to fulfill such a requirement, both of which possess different levels of technological readiness: electrohydraulic servovalves and piezoelectric stacks. Identification of design constraints, desired actuator parameters, and actuator limitations are addressed in depth; all of which are intimately tied with the hardware and controller design process. Analytical demonstrations of the performance and robustness characteristics of the two axisymmetric LQG clearance control systems are presented. Takeoff simulation results show that both actuators are capable of maintaining the clearance within acceptable bounds and demonstrate robustness to parameter uncertainty. The present model-based control strategy was employed to demonstrate the tradeoff between performance, control effort, and robustness and to implement optimal state estimation in a noisy engine environment with intent to eliminate ad hoc methods for designing reliable control systems.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2004-213121 , E-14615 , AIAA Paper 2004-4176 , 40th Joint Propulsion Conference and Exhibit; Jul 11, 2004 - Jul 14, 2004; Fort Lauderdale, FL; United States
    Format: application/pdf
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  • 2
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    User's Guide for the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS): Version 2 (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This report is a Users Guide for version 2 of the NASA-developed Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) software, which is a transient simulation of a large commercial turbofan engine (up to 90,000-lb thrust) with a realistic engine control system. The software supports easy access to health, control, and engine parameters through a graphical user interface (GUI). C-MAPSS v.2 has some enhancements over the original, including three actuators rather than one, the addition of actuator and sensor dynamics, and an improved controller, while retaining or improving on the convenience and user-friendliness of the original. C-MAPSS v.2 provides the user with a graphical turbofan engine simulation environment in which advanced algorithms can be implemented and tested. C-MAPSS can run user-specified transient simulations, and it can generate state-space linear models of the nonlinear engine model at an operating point. The code has a number of GUI screens that allow point-and-click operation, and have editable fields for user-specified input. The software includes an atmospheric model which allows simulation of engine operation at altitudes from sea level to 40,000 ft, Mach numbers from 0 to 0.90, and ambient temperatures from -60 to 103 F. The package also includes a power-management system that allows the engine to be operated over a wide range of thrust levels throughout the full range of flight conditions.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2012-217432 , E-18125
    Format: application/pdf
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  • 3
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    A Modular Aero-Propulsion System Simulation of a Large Commercial Aircraft Engine (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A simulation of a commercial engine has been developed in a graphical environment to meet the increasing need across the controls and health management community for a common research and development platform. This paper describes the Commercial Modular Aero Propulsion System Simulation (C-MAPSS), which is representative of a 90,000-lb thrust class two spool, high bypass ratio commercial turbofan engine. A control law resembling the state-of-the-art on board modern aircraft engines is included, consisting of a fan-speed control loop supplemented by relevant engine limit protection regulator loops. The objective of this paper is to provide a top-down overview of the complete engine simulation package.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA/TM-2008-215303 , AIAA Paper 2008-4579 , E-16573
    Format: application/pdf
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  • 4
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    A Sequential Shifting Algorithm for Variable Rotor Speed Control (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A proof of concept of a continuously variable rotor speed control methodology for rotorcraft is described. Variable rotor speed is desirable for several reasons including improved maneuverability, agility, and noise reduction. However, it has been difficult to implement because turboshaft engines are designed to operate within a narrow speed band, and a reliable drive train that can provide continuous power over a wide speed range does not exist. The new methodology proposed here is a sequential shifting control for twin-engine rotorcraft that coordinates the disengagement and engagement of the two turboshaft engines in such a way that the rotor speed may vary over a wide range, but the engines remain within their prescribed speed bands and provide continuous torque to the rotor; two multi-speed gearboxes facilitate the wide rotor speed variation. The shifting process begins when one engine slows down and disengages from the transmission by way of a standard freewheeling clutch mechanism; the other engine continues to apply torque to the rotor. Once one engine disengages, its gear shifts, the multi-speed gearbox output shaft speed resynchronizes and it re-engages. This process is then repeated with the other engine. By tailoring the sequential shifting, the rotor may perform large, rapid speed changes smoothly, as demonstrated in several examples. The emphasis of this effort is on the coordination and control aspects for proof of concept. The engines, rotor, and transmission are all simplified linear models, integrated to capture the basic dynamics of the problem.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA/TM-2007-214842 , ARL-TR-4086 , E-16058 , AHS 63rd Annual Forum and Technology Display; Apr 29, 2007 - May 03, 2007; Virginia Beach, VA; United States
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  • 5
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    Rate-Based Model Predictive Control of Turbofan Engine Clearance (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An innovative model predictive control strategy is developed for control of nonlinear aircraft propulsion systems and sub-systems. At the heart of the controller is a rate-based linear parameter-varying model that propagates the state derivatives across the prediction horizon, extending prediction fidelity to transient regimes where conventional models begin to lose validity. The new control law is applied to a demanding active clearance control application, where the objectives are to tightly regulate blade tip clearances and also anticipate and avoid detrimental blade-shroud rub occurrences by optimally maintaining a predefined minimum clearance. Simulation results verify that the rate-based controller is capable of satisfying the objectives during realistic flight scenarios where both a conventional Jacobian-based model predictive control law and an unconstrained linear-quadratic optimal controller are incapable of doing so. The controller is evaluated using a variety of different actuators, illustrating the efficacy and versatility of the control approach. It is concluded that the new strategy has promise for this and other nonlinear aerospace applications that place high importance on the attainment of control objectives during transient regimes.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2006-214419 , E-15692 , 42nd AIAA Joint Propulsion Conference and Exhibit; Jul 09, 2006 - Jul 12, 2006; Sacramento, CA; United States
    Format: application/pdf
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  • 6
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    Evaluation of an Active Clearance Control System Concept (2005)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Reducing blade tip clearances through active tip clearance control in the high pressure turbine can lead to significant reductions in emissions and specific fuel consumption as well as dramatic improvements in operating efficiency and increased service life. Current engines employ scheduled cooling of the outer case flanges to reduce high pressure turbine tip clearances during cruise conditions. These systems have relatively slow response and do not use clearance measurement, thereby forcing cold build clearances to set the minimum clearances at extreme operating conditions (e.g., takeoff, reburst) and not allowing cruise clearances to be minimized due to the possibility of throttle transients (e.g., step change in altitude). In an effort to improve upon current thermal methods, a first generation mechanically-actuated active clearance control (ACC) system has been designed and fabricated. The system utilizes independent actuators, a segmented shroud structure, and clearance measurement feedback to provide fast and precise active clearance control throughout engine operation. Ambient temperature performance tests of this first generation ACC system assessed individual seal component leakage rates and both static and dynamic overall system leakage rates. The ability of the nine electric stepper motors to control the position of the seal carriers in both open- and closed-loop control modes for single and multiple cycles was investigated. The ability of the system to follow simulated engine clearance transients in closed-loop mode showed the system was able to track clearances to within a tight tolerance ( 0.001 in. error).
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2005-213856 , AIAA Paper-2005-3989 , E-15226 , 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference; Jul 10, 2005 - Jul 13, 2005; Tucson, AZ; United States
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  • 7
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    User's Guide for the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) (2007)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This report is a Users Guide for the NASA-developed Commercial Modular Aero-Propulsion System Simulation (C-MAPSS) software, which is a transient simulation of a large commercial turbofan engine (up to 90,000-lb thrust) with a realistic engine control system. The software supports easy access to health, control, and engine parameters through a graphical user interface (GUI). C-MAPSS provides the user with a graphical turbofan engine simulation environment in which advanced algorithms can be implemented and tested. C-MAPSS can run user-specified transient simulations, and it can generate state-space linear models of the nonlinear engine model at an operating point. The code has a number of GUI screens that allow point-and-click operation, and have editable fields for user-specified input. The software includes an atmospheric model which allows simulation of engine operation at altitudes from sea level to 40,000 ft, Mach numbers from 0 to 0.90, and ambient temperatures from -60 to 103 F. The package also includes a power-management system that allows the engine to be operated over a wide range of thrust levels throughout the full range of flight conditions.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2007-215026 , E-16205
    Format: application/pdf
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  • 8
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    Onboard Nonlinear Engine Sensor and Component Fault Diagnosis and Isolation Scheme (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A method detects and isolates in-flight sensor, actuator, and component faults for advanced propulsion systems. In sharp contrast to many conventional methods, which deal with either sensor fault or component fault, but not both, this method considers sensor fault, actuator fault, and component fault under one systemic and unified framework. The proposed solution consists of two main components: a bank of real-time, nonlinear adaptive fault diagnostic estimators for residual generation, and a residual evaluation module that includes adaptive thresholds and a Transferable Belief Model (TBM)-based residual evaluation scheme. By employing a nonlinear adaptive learning architecture, the developed approach is capable of directly dealing with nonlinear engine models and nonlinear faults without the need of linearization. Software modules have been developed and evaluated with the NASA C-MAPSS engine model. Several typical engine-fault modes, including a subset of sensor/actuator/components faults, were tested with a mild transient operation scenario. The simulation results demonstrated that the algorithm was able to successfully detect and isolate all simulated faults as long as the fault magnitudes were larger than the minimum detectable/isolable sizes, and no misdiagnosis occurred
    Keywords: Man/System Technology and Life Support
    Type: LEW-18518-1/9-1 , NASA Tech Briefs, January 2011; 6
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  • 9
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    Development of a Numerical Model for High-Temperature Shape Memory Alloys (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-11
    Description: A thermomechanical hysteresis model for a high-temperature shape memory alloy (HTSMA) actuator material is presented. The model is capable of predicting strain output of a tensile-loaded HTSMA when excited by arbitrary temperature-stress inputs for the purpose of actuator and controls design. Common quasi-static generalized Preisach hysteresis models available in the literature require large sets of experimental data for model identification at a particular operating point, and substantially more data for multiple operating points. The novel algorithm introduced here proposes an alternate approach to Preisach methods that is better suited for research-stage alloys, such as recently-developed HTSMAs, for which a complete database is not yet available. A detailed description of the minor loop hysteresis model is presented in this paper, as well as a methodology for determination of model parameters. The model is then qualitatively evaluated with respect to well-established Preisach properties and against a set of low-temperature cycled loading data using a modified form of the one-dimensional Brinson constitutive equation. The computationally efficient algorithm demonstrates adherence to Preisach properties and excellent agreement to the validation data set.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2006-214356 , E-15631
    Format: application/pdf
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  • 10
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    Seal Investigations of an Active Clearance Control System Concept (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In an effort to improve upon current thermal active clearance control methods, a first generation, fast-acting mechanically actuated, active clearance control system has been designed and installed into a non-rotating test rig. In order to harvest the benefit of tighter blade tip clearances, low-leakage seals are required for the actuated carrier segments of the seal shroud to prevent excessive leakage of compressor discharge (P3) cooling air. The test rig was designed and fabricated to facilitate the evaluation of these types of seals, identify seal leakage sources, and test other active clearance control system concepts. The objective of this paper is to present both experimental and analytical investigations into the nature of the face-seal to seal-carrier interface. Finite element analyses were used to examine face seal contact pressures and edge-loading under multiple loading conditions, varied E-seal positions and two new face seal heights. The analyses indicated that moving the E-seal inward radially and reducing face seal height would lead to more uniform contact conditions between the face seal and the carriers. Lab testing confirmed that moving the balance diameter inward radially caused a decrease in overall system leakage.
    Keywords: Mechanical Engineering
    Type: NASA/TM-2006-214114 , E-15372-1 , 120-ISROMAC-11 , 11th International Symposium on Transport Phenomena and Dynamics of Rotating Machinery; Feb 26, 2006 - Mar 02, 2006; Honolulu, HI; United States
    Format: application/pdf
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