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Mingjun Zhang - One of the best experts on this subject based on the ideXlab platform.
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Energy-Efficient Surface Propulsion Inspired by Whirligig Beetles
IEEE Transactions on Robotics, 2015Co-Authors: Zongyao Chen, Andrew Riedel, Ting Si, William R. Hamel, Mingjun ZhangAbstract:The whirligig beetle, claimed to be one of the most energy-efficient swimmers in the animal kingdom, has evolved a series of propulsion strategies that may serve as a source of inspiration for the design of propulsion mechanisms for energy-efficient surface swimming. In this paper, we introduce a robot platform that was developed to test an energy-efficient propulsion mechanism inspired by the whirligig beetle. A Propulsor-body-fluid interaction dynamics model is proposed, and based on this model, the Propulsor flexural rigidity and beating patterns are optimized in order to achieve energy-efficient linear swimming and turning. The optimization results indicate that a Propulsor with decreasing flexural rigidity enhances vortex shedding and improves thrust generation. It has also been found that an alternating asymmetrical beating sequence and optimal beating frequency of 0.71 Hz improves propulsion efficiency for linear swimming of the robot. The alternating beating of the outboard Propulsors and the unfolded inboard Propulsors working as brakes results in efficient turning with a smaller turning radius. Both simulation and experimental studies were conducted, and the results illustrate that decreasing flexural rigidity along the Propulsor length, an oscillating body motion, and an S-shaped trajectory are critical for energy-efficient propulsion of the robot.
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Energy-efficient propulsion inspired by whirligig beetles
2014 IEEE International Conference on Robotics and Automation (ICRA), 2014Co-Authors: Zongyao Chen, Andrew Riedel, William R. Hamel, Mingjun ZhangAbstract:Whirligig beetle, claimed in the literature to be one of the highest measured for a thrust-generating apparatus within the animal kingdom, has evolved a series of propulsion strategies that may serve as a source of inspiration for designing highly efficient propulsive systems. First, a robotic platform was developed to test an energy-efficient propulsion mechanism inspired by the whirligig beetle. Second, a mathematical model for the robot was proposed to account for the fluid dynamics generated by the robotic swimming. Third, an optimal problem was formulated and solved for the Propulsor and beating pattern design. The results indicated that soft middle, stiff end Propulsor, and alternating, asymmetrical beating pattern will improve the propulsion efficiency for a swimming robot with four Propulsors. Finally, simulation and experiments were conducted to further analyze the effect of beating pattern to the robotic propulsion efficiency. It was found that the oscillated body movement and S-shaped trajectory introduced by the optimal beating pattern would improve the propulsion efficiency for the designed robot.
Christopher Niezrecki - One of the best experts on this subject based on the ideXlab platform.
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Investigation of THUNDER (TM) Actuators as Underwater Propulsors
Journal of Intelligent Materials Systems and Structures, 2002Co-Authors: Sivakumar Balakrishnan, Christopher NiezreckiAbstract:Piezoelectric actuators have been used for active vibration control, noise suppression, health monitoring, etc. The large appeal in using smart material actuators stems from their high mechanical energy density. A relatively new actuator Thin Layer Composite Unimorph Ferroelectric Driver and Sensor (THUNDER) has overcome the displacement hurdles that have plagued traditional piezoelectric based actuators. It is capable of providing a displacement of the order of 0.5 cm. This allows the actuator to be used in some underwater applications, such as propulsion. To date the electrical power consumption and electro-mechanical efficiency of these actuators has not been quantified; specifically, applied as underwater Propulsors. Some of the challenges in obtaining this information stems from the actuator's nontraditional actuating architecture, high voltage requirements, and its electrical nonlinearity. This work experimentally determines the mechanical displacement and the electrical power consumption of the THUNDER actuators used as underwater Propulsors. An estimate of a lower bound of the thrust that can be generated by the clamshell actuator is obtained. It is found that the actuator has a peak flow rate of approximately 1500 cm3/s and can generate a peak thrust greater than approximately 4.5 N. This preliminary analysis neglected the pressure forces acting on the actuator and therefore, the actual thrust is not computed. It is found that the average electrical power consumed by two THUNDER actuators placed in a clamshell configuration operating at 14 Hz is approximately 8 W, which is significantly less than that consumed by other autonomous underwater vehicles. The displacement response and the current draw of the actuators are determined to be nonlinear. The result of this work indicates that the use of THUNDER actuators has great potential to create an underwater Propulsor that has low power consumption, can operate at great depths, and eliminates the need for seals, bearings and a propeller.
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Investigation of THUNDER[sup TM] Actuators as Underwater Propulsors.
Journal of Intelligent Material Systems & Structures, 2002Co-Authors: Sivakumar Balakrishnan, Christopher NiezreckiAbstract:Piezoelectric actuators have been used for active vibration control, noise suppression, health monitoring, etc. The large appeal in using smart material actuators stems from their high mechanical energy density. A relatively new actuator Thin Layer Composite Unimorph Ferroelectric Driver and Sensor (THUNDER) has overcome the displacement hurdles that have plagued traditional piezoelectric based actuators. It is capable of providing a displacement of the order of 0.5 cm. This allows the actuator to be used in some underwater applications, such as propulsion. To date the electrical power consumption and electromechanical efficiency of these actuators has not been quantified; specifically, applied as underwater Propulsors. Some of the challenges in obtaining this information stems from the actuator's nontraditional actuating architecture, high voltage requirements, and its electrical nonlinearity. This work experimentally determines the mechanical displacement and the electrical power consumption of the THUNDER actuators used as underwater Propulsors. An estimate of a lower bound of the thrust that can be generated by the clamshell actuator is obtained. It is found that the actuator has a peak flow rate of approximately 1500cm³/s and can generate a peak thrust greater than approximately 4.5N. This preliminary analysis neglected the pressure forces acting on the actuator and therefore, the actual thrust is not computed. It is found that the average electrical power consumed by two THUNDER actuators placed in a clamshell configuration operating at ∼14Hz is approximately 8 W, which is significantly less than that consumed by other autonomous underwater vehicles. The displacement response and the current draw of the actuators are determined to be nonlinear. The result of this work indicates that the use of THUNDER actuators has great potential to create an underwater Propulsor that has low power consumption, can operate at great depths, and eliminates the... [ABSTRACT FROM AUTHOR]
Zongyao Chen - One of the best experts on this subject based on the ideXlab platform.
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Energy-Efficient Surface Propulsion Inspired by Whirligig Beetles
IEEE Transactions on Robotics, 2015Co-Authors: Zongyao Chen, Andrew Riedel, Ting Si, William R. Hamel, Mingjun ZhangAbstract:The whirligig beetle, claimed to be one of the most energy-efficient swimmers in the animal kingdom, has evolved a series of propulsion strategies that may serve as a source of inspiration for the design of propulsion mechanisms for energy-efficient surface swimming. In this paper, we introduce a robot platform that was developed to test an energy-efficient propulsion mechanism inspired by the whirligig beetle. A Propulsor-body-fluid interaction dynamics model is proposed, and based on this model, the Propulsor flexural rigidity and beating patterns are optimized in order to achieve energy-efficient linear swimming and turning. The optimization results indicate that a Propulsor with decreasing flexural rigidity enhances vortex shedding and improves thrust generation. It has also been found that an alternating asymmetrical beating sequence and optimal beating frequency of 0.71 Hz improves propulsion efficiency for linear swimming of the robot. The alternating beating of the outboard Propulsors and the unfolded inboard Propulsors working as brakes results in efficient turning with a smaller turning radius. Both simulation and experimental studies were conducted, and the results illustrate that decreasing flexural rigidity along the Propulsor length, an oscillating body motion, and an S-shaped trajectory are critical for energy-efficient propulsion of the robot.
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Energy-efficient propulsion inspired by whirligig beetles
2014 IEEE International Conference on Robotics and Automation (ICRA), 2014Co-Authors: Zongyao Chen, Andrew Riedel, William R. Hamel, Mingjun ZhangAbstract:Whirligig beetle, claimed in the literature to be one of the highest measured for a thrust-generating apparatus within the animal kingdom, has evolved a series of propulsion strategies that may serve as a source of inspiration for designing highly efficient propulsive systems. First, a robotic platform was developed to test an energy-efficient propulsion mechanism inspired by the whirligig beetle. Second, a mathematical model for the robot was proposed to account for the fluid dynamics generated by the robotic swimming. Third, an optimal problem was formulated and solved for the Propulsor and beating pattern design. The results indicated that soft middle, stiff end Propulsor, and alternating, asymmetrical beating pattern will improve the propulsion efficiency for a swimming robot with four Propulsors. Finally, simulation and experiments were conducted to further analyze the effect of beating pattern to the robotic propulsion efficiency. It was found that the oscillated body movement and S-shaped trajectory introduced by the optimal beating pattern would improve the propulsion efficiency for the designed robot.
Riti Singh - One of the best experts on this subject based on the ideXlab platform.
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Performance Assessment of a Boundary Layer Ingesting Distributed Propulsion System at Off-Design
53rd AIAA SAE ASEE Joint Propulsion Conference, 2017Co-Authors: Chana Goldberg, Devaiah Nalianda, Pericles Pilidis, Riti SinghAbstract:Boundary layer ingesting systems have been proposed as a concept with great po-tential for reducing the fuel consumption of conventional propulsion systems and the overall drag of an aircraft. These studies have indicated that if the aerodynamic and efficiency losses were minimised, the propulsion system demonstrated substantial power consumption benefits in comparison to equivalent propulsion systems operating in free-stream flow. Previously assessed analytical methods for BLI simulation have been from an uninstalled perspective. This research will present the formulation of an rapid ana-lytical method for preliminary design studies which evaluates the installed performance of a boundary layer ingesting system. The method uses boundary layer theory and one dimensional gas dynamics to assess the performance of an integrated system. The method was applied to a case study of the distributed Propulsor array of a blended wing body aircraft. There was particular focus on assessment how local flow characteristics influence the performance of individual Propulsors and the propulsion system as a whole. The application of the model show that the spanwise flow variation has a significant impact on the performance of the array as a whole. A clear optimum design point is identified which minimises the power consumption for an array with a fixed configuration and net propulsive force requirement. In addition, the sensitivity of the system to distortion related losses is determined and a point is identified where a conventional free-stream Propulsor is the lower power option. Power saving coefficient for the configurations considered is estimated to lie in the region of 15%. Nomenclature Acronyms AR = Aspect ratio BL = Boundary layer BLC = Boundary layer control BLI = Boundary layer ingestion BWB = Blended wing Body FPR = Fan pressure ratio MAG = Mass flow non-dimensional group MFR = Mass flow ratio MOG = Momentum non-dimensional group mom = Momentum NPF = Net propulsive force PSC = Power saving coefficient Re = Reynolds Number Symbols δ = Boundary layer thickness δ * = Displacement thickness ρ = Density τ w = Skin friction θ = Momentum thickness θ * = Energy thickness φ nacelle = Nacelle force A = Area c = Aircraft chord length D = Drag F G = Gross thrust F N = Net thrust h = Stream Height L Array = Array total length ˙ m = Mass flow rate N fan = Number of fans/Propulsors P = Total pressure p = Static pressure P BLI = BLI propulsion system power P ref = Reference propulsion system power Re = Reynolds number S wet = Wetted surface area u = Axial velocity w = Stream width y = Vertical distance above surface x = Reference length x 0 = Reference length at aircraft centreline Subscripts ∞ = Wake 0 = Free-stream 0i = Local free-stream 1 = Inlet (Highlight) 2 = Fan face 3 = Fan exit 9 = Nozzle exhaust i = Interface plane j = Exhaust jet
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Methodology for the assessment of distributed propulsion configurations with boundary layer ingestion using the discretized miller approach
International Review of Aerospace Engineering, 2017Co-Authors: Esteban A. Valencia, Panagiotis Laskaridis, Nalianda Devaiah, Iain Gray, Chengyuan Liu, Riti SinghAbstract:The growing global environmental awareness has motivated the search for more fuel- efficient aircraft propulsion systems. In this context, a configuration based on distributed propulsion with Boundary Layer Ingestion (BLI) has been found to present potential performance benefits. The concept has been documented and explored extensively during the last few years and various aerodynamic integration issues, such as: high levels of distortion and low intake pressure recovery; have been identified as factors that may be detrimental in realizing the technology full potential. Parametric and parallel compressor (PC) approaches have been used to assess the effect of these aerodynamic issues on Propulsors fan performance. However, in the context of BLI, these tools are unable to assess the effects of combined radial and circumferential distortion that are present. In order to assess the combined distortion patterns and the effects of distortion at component and system levels, this study uses a novel method based on semi-empirical correlations denominated the Discretized Miller (DM) approach. This method was developed for BLI systems previously by the author, and it is now incorporated into the Propulsor performance method to assess the effects of the combined radial and circumferential distortion patterns. The performance analysis, undertaken at a component and system level, aims to assess several propulsion architectures, using Thrust Specific Fuel Consumption (TSFC) as figure of merit. To define the suitability of the distributed Propulsor array in this study, an airframe layout based on the N3-X aircraft concept and High Temperature Superconducting (HTS) electric motor capabilities were assumed. The key contribution of this study is to enable the introduction of the concept of thrust split between energy source and propulsion system in the system analysis, and thereby, allows the assessment of its effects on different propulsion system layouts, while considering the BLI induced distortion. The results obtained with this alternative performance method showed that BLI reduces the fan efficiency of a conventional fan by approximately 2%, whilst corroborating the TSFC trends observed in previous studies. The study also indicates that when sizing effects of Propulsors and core-engines were neglected, a propulsion system configuration with 75% thrust split was found optimum.
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Methodology to assess the performance of an aircraft concept with distributed propulsion and boundary layer ingestion using a parametric approach
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering, 2015Co-Authors: Esteban A. Valencia, Panagiotis Laskaridis, Devaiah Nalianda, Riti SinghAbstract:The performance benefits of boundary layer ingestion in aircraft with distributed propulsion have been extensively studied in the past. These studies have indicated that propulsion system integration issues such as distortion and intake pressure losses could mitigate the expected benefits. This paper introduces and develops a methodology that enables the assessment of different propulsion system designs, which are optimized to be less sensitive to the effects of the aforementioned issues. The study models the Propulsor array and main engine performance at design point using a parametric approach, and further at component level, the study focuses on identifying optimum Propulsor configurations, in terms of Propulsor pressure ratio and BL capture sheet height. At a system level, the study assesses the effects of splitting the thrust between the Propulsor array and main engines. The figure of merit used in the optimization is the TSFC. The suitability of the concepts is further assessed using performance predictions for HTS electrical motors. For the purpose of this study, the NASA N3-X aircraft concept is selected as baseline configuration, where the different propulsion designs are tested. As the study focuses on performance assessment of the propulsion system, sizing impli- cation issues and aircraft performance installations effects have not been included in the analysis. The results from the parametric analysis corroborated previous studies regarding the high sensitivity of the propulsion system performance to intake losses and BL inlet conditions. As the study found low-power consumption configurations at these operating conditions, this may be considered as a major issue. The system analysis from the study indicated that splitting the thrust between Propulsors and main engines results in improved system efficiency with beneficial effects in fuel savings. When a 2% increase in intake pressure losses and a similar reduction in fan efficiency were assumed due to boundary layer ingestion, the study found an optimum configuration with 65% of thrust delivered by the Propulsor array. To summarize, the present work built on past research further contributes to the field through the inclusion of the thrust split as a key variable in the propulsion system design. The thrust split, when introduced, enabled reduction of the detrimental effects of intake losses on the overall system performance. Additionally, as it reduces the power required for the Propulsor array, it is expected to reduce the operating power of HTS and cooling systems and therefore improve the effectiveness of the concept.
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Design Point Analysis of an Hybrid Fuel Cell Gas Turbine Cycle for Advanced Distributed Propulsion Systems
51st AIAA SAE ASEE Joint Propulsion Conference, 2015Co-Authors: Esteban A. Valencia, Laskaridis Panagiotis, Victor Hidalgo, Riti Singh, Devaiah Nalianda, Chengyuan LiuAbstract:The performance benefits of boundary layer ingestion in the case of air vehicles powered by distributed Propulsors have been documented and explored extensively in numerous studies. Therefore, it is well known that increased inlet flow distortion and associated pressure losses due to boundary layer ingestion (BLI) can dramatically reduce these benefits. Additionally the high power required by the distributed Propulsors implies large electrical components for generation and transmission which compromise the possible configurations for TeDP systems with BLI. In order to reduce the aforementioned aerodynamic integration aspects and the high power demands of TeDP systems alternative configurations which split he thrust between the Propulsor unit and the turbofans have been investigated. In this work the potential benefits and challenges that an alternative thermodynamic cycle based on an hybrid gas turbine with SOFC’s implemented in an optimum TeDP system with BLI using thrust split is assessed. For this preliminary analysis simplified parametric models for fuel cells, gas turbines and weight have been used to capture important trends in the implementation of this cycle. The results obtained at design point conditions has shown that the implementation of this cycle and the use of liquid hydrogen for fuel and coolant could contribute to reduce by 70 % the TSFC before iterating and resizing. However, as main challenges for the implementation of this system arise hydrogen storage issues and the weight increment of the propulsion system due to the use of fuel cells. This latter parameter was observed to increase by 40 % before iterating and resizing. Furthermore, it was found that the use of thrust split could be beneficial to find an optimum configuration which presents a trade-off between the TSFC reduction and weight increment. Finally, it has been found that the synergistic advantages of the hybrid Brayton cycle and fuel cells with the TeDP system may offer opportunities for the performance improvement of the whole propulsion system. © 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.
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Turboelectric Distributed Propulsion System Modelling for Hybrid-Wing-Body Aircraft
48th AIAA ASME SAE ASEE Joint Propulsion Conference & Exhibit, 2012Co-Authors: Chengyuan Liu, Georgios Doulgeris, Panagiotis Laskaridis, Riti SinghAbstract:In 2005, NASA released plans of next generation commercial airplane for 2030, with a cross-disciplinary effort on: reduced fuel consumption, aviation reliability, fundamental noise reduction and shorter take-off length. Meeting these requirements will need a fundamental shift in aircraft and engine design. Turboelectric distributed propulsion system was chosen to achieve these targets. Different from traditional turbofan, distributed propulsion system employs a large number of fans embedded on upper surface of the airframe and two turbogenerators at wing tip. This novel configuration benefits from boundary layer ingestion and distributed fans to achieve higher bypass ratio but lower fuel burn. The N3-X hybrid-wing-body is used as a baseline aircraft for the study. This paper gives basic simulation methods, as well as computational models for turboelectric distributed propulsion system. Initially, a boundary layer ingesting model has been built from computational results for embedded Propulsor at different inlet conditions. In a further step, a weight estimation model of Propulsors was concluded to estimate Propulsors' weight and size. Then, thermal cycle model was built to calculate engine's performance at both design point and off design conditions. Finally, effects of boundary layer ingestion on the propulsion system were examined. The boundary layer ingesting model showed mass-average inlet pressure and Mach number are function of flight Mach number and fan inlet mass flow, on the N3-X airframe. The weight estimation model shows the overall system weight decreased with increased number of Propulsors, which also caused total inlet width of Propulsors increasing. So for a given total inlet width, the Propulsor should be used as many as possible to reduce weight. Thermal cycle results show that fan shaft speed should be chosen as high as possible before reaching the fan tip speed limitation, and fan pressure ratio (FPR) between 1.3 and 1.35 yields minimum thrust specific fuel consumption (TSFC) at the aerodynamic design point. A fan pressure ratio of 1.3 is chosen for its potential effects on noise control. In the end, a turboelectric distributed engine was simulated to satisfy NASA N+3 subsonic commercial airplane goals. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Stephen A. Huyer - One of the best experts on this subject based on the ideXlab platform.
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A Post-Swirl Maneuvering Propulsor Application to Undersea Vehicles
IEEE Journal of Oceanic Engineering, 2017Co-Authors: Stephen A. HuyerAbstract:A method to generate vehicle maneuvering forces from a Propulsor alone has been applied to a generic undersea vehicle. Open and ducted post-swirl Propulsors were configured with an upstream rotor and downstream stator row. During normal operation, the downstream stator blades are all situated at the same pitch angle and generate a roll moment to counter the torque produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to generate a mean stator side force that can be used to maneuver the vehicle. In addition, the side force can be increased with increasing thrust producing side forces at very low vehicle velocities enabling low-speed maneuvering capability. The viscous, 3-D Reynolds-averaged Navier–Stokes (RANS) commercial code Fluent was used to predict the vehicle and Propulsor component forces as well as the velocity field. Open and ducted geometric configurations were studied and force coefficients computed and compared with currently used control surface forces. Computations predicted that the maneuvering Propulsor generated side forces equivalent to those produced by conventional control surfaces with side force coefficients on the order of 0.25 for the open Propulsor at the self-propulsion point. This translates to 50% larger forces than can be generated by conventional control surfaces on 21 $^{\prime \prime}$ unmanned undersea vehicles. The ducted configuration produces maximum side force coefficients on the order of 0.15, which is still sufficient for vehicle control. Both configurations produced side forces for the Bollard pull condition indicating low-speed maneuvering capability.
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A Post-Swirl Maneuvering Propulsor Application to Undersea Vehicles
IEEE Journal of Oceanic Engineering, 2017Co-Authors: Stephen A. HuyerAbstract:A method to generate vehicle maneuvering forces from a Propulsor alone has been applied to a generic undersea vehicle. Open and ducted post-swirl Propulsors were configured with an upstream rotor and downstream stator row. During normal operation, the downstream stator blades are all situated at the same pitch angle and generate a roll moment to counter the torque produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to generate a mean stator side force that can be used to maneuver the vehicle. In addition, the side force can be increased with increasing thrust producing side forces at very low vehicle velocities enabling low-speed maneuvering capability. The viscous, 3-D Reynolds-averaged Navier-Stokes (RANS) commercial code Fluent was used to predict the vehicle and Propulsor component forces as well as the velocity field. Open and ducted geometric configurations were studied and force coefficients computed and compared with currently used control surface forces. Computations predicted that the maneuvering Propulsor generated side forces equivalent to those produced by conventional control surfaces with side force coefficients on the order of 0.25 for the open Propulsor at the self-propulsion point. This translates to 50% larger forces than can be generated by conventional control surfaces on 21" unmanned undersea vehicles. The ducted configuration produces maximum side force coefficients on the order of 0.15, which is still sufficient for vehicle control. Both configurations produced side forces for the Bollard pull condition indicating low-speed maneuvering capability.
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Postswirl Maneuvering Propulsor
Journal of Fluids Engineering-transactions of The Asme, 2015Co-Authors: Stephen A. HuyerAbstract:This research examines the novel use of a postswirl Propulsor to generate side forces sufficient for undersea vehicle control. Numerical simulations using the commercial computational fluid dynamics (CFD) code Fluent® were used to predict the side forces for open and ducted, post-swirl Propulsors configured with an upstream rotor and movable downstream stator row. By varying the pitch angles of the stator blade about the circumference, it is possible to generate a mean stator side force that can be used to maneuver the vehicle while generating sufficient roll to counter the torque produced by the rotor. A simple geometric configuration was used to minimize body geometry effects to better understand the flow physics with simulations conducted in a water tunnel environment. Flow computations highlighted the component forces and were used to characterize the velocity fields between the rotor and stator blade rows as well as the velocity field in the stator wake. There was significant coupling between the rotor and stator blade rows as demonstrated by the rotor wake velocity profiles. While the flow fields were coupled, there was not a significant difference in rotor axial or side forces except for the largest pitch amplitudes. Predictions showed that the maneuvering Propulsor generated side forces predominantly by the stator and body that significantly exceeded those produced by conventional undersea vehicle control surfaces with side force coefficients on the order of 0.5. These forces are approximately three times larger than those generated by conventional control surfaces on 21 in. unmanned undersea vehicles (UUV's). Even for zero flow velocities, side forces were produced due to the induced flow produced by the rotor over the stator, further demonstrating the potential for this technology to be used for undersea vehicle maneuvering.
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Application of a Maneuvering Propulsor Technology to Undersea Vehicles
Journal of Fluids Engineering-transactions of The Asme, 2013Co-Authors: Stephen A. HuyerAbstract:Previous computational and experimental studies that have demonstrated a method to generate vehicle maneuvering forces from a Propulsor alone have been applied to a generic undersea vehicle. An open, preswirl Propulsor was configured with an upstream stator row and downstream rotor. During normal operation, the upstream stator blades are all situated at the same pitch angle and preswirl the flow into the Propulsor while generating a roll moment to counter the torque produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to generate a mean stator side force that can be used to maneuver the vehicle. The stator wake axial velocity and swirl that is ingested into the rotor produces a counter-force by the rotor. Optimal design of the rotor minimizes the unsteady force and redirects the rotor force vector in an orthogonal direction to minimize the counter force. The viscous, 3D Reynolds-averaged Navier–Stokes (RANS) commercial code FLUENT® was used to predict the stator forces, velocity fields, and rotor response. Radiated noise was computed for the rotor separately and the entire geometry utilizing the Ffowcs Williams–Hawkings module available in FLUENT. Two separate geometries were studied—the first with a maximum stator blade row diameter contained within the body diameter and a second that was allowed to exceed the body diameter. Side force coefficients were computed for the two maneuvering Propulsor configurations and compared with currently used control surface forces. Computations predicted that the maneuvering Propulsor generated side forces equivalent to those produced by conventional control surfaces with side force coefficients on the order of 0.3. This translates to 50% larger forces than can be generated by conventional control surfaces on 21 in. unmanned undersea vehicles. Radiated noise calculations in air demonstrated that the total sound pressure levels produced by the maneuvering Propulsor were on the order of 5 dB lower than the control fin test cases.
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Preswirl Maneuvering Propulsor
IEEE Journal of Oceanic Engineering, 2012Co-Authors: Stephen A. Huyer, Amanda Dropkin, David N. Beal, John Farnsworth, Michael AmitayAbstract:Recent concept studies have demonstrated the potential to utilize a preswirl Propulsor configuration with adjustable upstream stator blades to generate Propulsor side forces. These studies led to a set of experiments and corresponding computations to validate this concept. Ducted and open preswirl Propulsors were configured with an upstream stator row and downstream rotor. During normal operation, the upstream stator blades are all situated at the same pitch angle and preswirl the flow into the Propulsor while generating a roll moment to counter the moment produced by the rotor. By varying the pitch angles of the stator blade about the circumference, it is possible to both generate a mean stator side force and subsequently vary the axial velocity and swirl that is ingested into the rotor. The rotor then generates side forces in response to the modified inflow. Wind tunnel experiments were conducted to measure the steady, spatially varying stator wake flows for various stator geometric configurations using stereoscopic particle image velocimetry. Water tunnel experiments were conducted to measure the forces produced. Experimental data were used to validate computations, which utilized fully viscous 3-D [Reynolds averaged Navier-Stokes (RANS)] computations to predict the stator forces, velocity field, and rotor response. Both methods provided insight into the underlying mechanisms of side force generation. Optimized rotor designs were specifically investigated to isolate the blade forces as well as the induced body forces. In this way, RANS provided high fidelity performance predictions of the final Propulsor design. Experimental and computational data demonstrated that total side force coefficients on the order of 0.26 could be generated by the open Propulsor. This amount of control authority exceeds current control surface capabilities for Navy 21" (0.5334 m) unmanned undersea vehicles and is comparable to novel thrust-vectored designs.
