Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16895
M. Sharifi, I. Brown, D. Jordan, G. Tandon
Structural adhesives with silicone-tolerant characteristics (surface tolerant adhesives) were developed, aiming to find solutions to overcome silicone contaminations present at bonding surfaces. This study overviews mechanical performance aspects of the surface tolerant adhesives with composite-to-composite and composite-to-titanium joints, where contaminated adherends were spray-coated with predetermined amounts of silicone (mold release) solutions. Shear strength values, in single lap shear mode, revealed a shear strength retention of up to nearly 80% in contaminated bonded joints with surface tolerant adhesives, when compared to nearly 20% strength retention with a control (standard aerospace-qualified) adhesive. In Mode I fracture, a substantially large resistance to fracture (cohesive-type failure) was observed with the surface tolerant adhesives, whereas a pure adhesive-type failure was observed in the control adhesive. Mechanical performance and relevant surface analyses of surface tolerant adhesives are detailed in this study.
{"title":"Surface Tolerant Adhesives for Bonded Airframe Structures","authors":"M. Sharifi, I. Brown, D. Jordan, G. Tandon","doi":"10.4050/f-0077-2021-16895","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16895","url":null,"abstract":"\u0000 Structural adhesives with silicone-tolerant characteristics (surface tolerant adhesives) were developed, aiming to find solutions to overcome silicone contaminations present at bonding surfaces. This study overviews mechanical performance aspects of the surface tolerant adhesives with composite-to-composite and composite-to-titanium joints, where contaminated adherends were spray-coated with predetermined amounts of silicone (mold release) solutions. Shear strength values, in single lap shear mode, revealed a shear strength retention of up to nearly 80% in contaminated bonded joints with surface tolerant adhesives, when compared to nearly 20% strength retention with a control (standard aerospace-qualified) adhesive. In Mode I fracture, a substantially large resistance to fracture (cohesive-type failure) was observed with the surface tolerant adhesives, whereas a pure adhesive-type failure was observed in the control adhesive. Mechanical performance and relevant surface analyses of surface tolerant adhesives are detailed in this study.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"135 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117344404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16728
J. Tritschler, O. Juhasz, John Holder, J. McCue, John O'Connor
Energy-maneuverability diagrams are an important tool that operational pilots use to understand helicopter maneuver performance across a wide range of conditions, however these representations are based upon a number of assumptions that have not been rigorously investigated. The present work reports the results of an investigation into the theory and application of helicopter maneuverability through simulation and flight test. The computational portion of the work focused on a systematic investigation into some of the key simplifying assumptions that are commonly applied in the creation of energy-maneuverability representations. This investigation included aerodynamic simulations of steady maneuvers using a dynamic inflow model as well as a free vortex method. The flight test portion of the work provided important operational context for understanding the practical application of the simulation results. The study illustrated that the fundamental assumption employed in estimating maneuver power requirements for energy-maneuverability representations appears to be reasonable in conditions of the greatest practical relevance, however another key assumption that is invoked to convert excess power into climb performance would likely lead to overestimating the vehicle capability in important operational conditions. Additionally, the flight test data demonstrated that energy-maneuverability results for high angles of bank should be considered for trending information rather than for detailed climb performance values.
{"title":"Reconsidering the Theory and Application of Helicopter Maneuverability","authors":"J. Tritschler, O. Juhasz, John Holder, J. McCue, John O'Connor","doi":"10.4050/f-0077-2021-16728","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16728","url":null,"abstract":"\u0000 Energy-maneuverability diagrams are an important tool that operational pilots use to understand helicopter maneuver performance across a wide range of conditions, however these representations are based upon a number of assumptions that have not been rigorously investigated. The present work reports the results of an investigation into the theory and application of helicopter maneuverability through simulation and flight test. The computational portion of the work focused on a systematic investigation into some of the key simplifying assumptions that are commonly applied in the creation of energy-maneuverability representations. This investigation included aerodynamic simulations of steady maneuvers using a dynamic inflow model as well as a free vortex method. The flight test portion of the work provided important operational context for understanding the practical application of the simulation results. The study illustrated that the fundamental assumption employed in estimating maneuver power requirements for energy-maneuverability representations appears to be reasonable in conditions of the greatest practical relevance, however another key assumption that is invoked to convert excess power into climb performance would likely lead to overestimating the vehicle capability in important operational conditions. Additionally, the flight test data demonstrated that energy-maneuverability results for high angles of bank should be considered for trending information rather than for detailed climb performance values.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116093028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16866
K. Tennakoon, Awantha Jayasiri, Oscar Silva, R. Gosine, George Maan
Current Vertical Take-Off and Landing (VTOL) systems rely mainly on Global Positioning System (GPS) for autonomous navigation. Due to the unreliability of GPS, the need for alternative methods has become significant. Among the alternative approaches, Visual Place Recognition (VPR) systems have taken prominence. The latest advancements of these VPR systems involve using deep neural networks, such as Convolutional Neural Nets (CNNs), to overcome the limitations of conventional feature-based systems. These VPR methods have been tested and validated primarily for ground-based datasets. However, to properly assess the suitability of those approaches in VTOL navigation, they need to be evaluated for aerial image data sets. This study evaluates the performance of a CNN-based VPR system against a conventional feature-based method for an aerial image dataset, focusing mainly on the systems' front-end. Furthermore, experimental validation of the CNN-based VPR system is conducted. The results suggest that it is a better addition to the navigation stack of a VTOL vehicle under GPS-denied situations.
{"title":"Evaluation of a CNN-based Visual Place Recognition system for GPS-denied Navigation of VTOL Vehicles","authors":"K. Tennakoon, Awantha Jayasiri, Oscar Silva, R. Gosine, George Maan","doi":"10.4050/f-0077-2021-16866","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16866","url":null,"abstract":"\u0000 Current Vertical Take-Off and Landing (VTOL) systems rely mainly on Global Positioning System (GPS) for autonomous navigation. Due to the unreliability of GPS, the need for alternative methods has become significant. Among the alternative approaches, Visual Place Recognition (VPR) systems have taken prominence. The latest advancements of these VPR systems involve using deep neural networks, such as Convolutional Neural Nets (CNNs), to overcome the limitations of conventional feature-based systems. These VPR methods have been tested and validated primarily for ground-based datasets. However, to properly assess the suitability of those approaches in VTOL navigation, they need to be evaluated for aerial image data sets. This study evaluates the performance of a CNN-based VPR system against a conventional feature-based method for an aerial image dataset, focusing mainly on the systems' front-end. Furthermore, experimental validation of the CNN-based VPR system is conducted. The results suggest that it is a better addition to the navigation stack of a VTOL vehicle under GPS-denied situations.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114607396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16819
L. Thomassey, Lionel Arlen
Since several years the UAVs (Unmanned Aerial Vehicle) win more and more market. For specific short missions, UAVs perform surveillance or infrastructure checking. However, due to the UAV limitation in terms of endurance and autonomy, for many missions the cooperation between manned and unmanned aircraft is needed. The UAV will play the role of deported arms and eyes of the helicopter. With such innovation, the helicopter performs what the UAV cannot do and on the operation theatre the UAV performs what the helicopter cannot do anymore. In order to ensure the multipurpose platform functionality of the helicopter, the cooperation system will be considered as an optional and will demand only simple and quick plug and play actions. The main constraints are to relatively locate the UAV and Helicopter with a centimetric accuracy and in addition to ensure safety in flight (collision avoidance) with functionality such as geo and helicopter fencing. With an efficient MUM-T architecture system, we will be capable to perform missions with an increased level of safety, to increase the availability of the H/C, to enlarge the H/C mission perimeter, to reduce the pilot workload and to avoid human operation in the so called 3D (Dull, Dirty, Dangerous) zones.
{"title":"TEAMX or Manned and Unmanned Cooperation","authors":"L. Thomassey, Lionel Arlen","doi":"10.4050/f-0077-2021-16819","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16819","url":null,"abstract":"\u0000 Since several years the UAVs (Unmanned Aerial Vehicle) win more and more market. For specific short missions, UAVs perform surveillance or infrastructure checking. However, due to the UAV limitation in terms of endurance and autonomy, for many missions the cooperation between manned and unmanned aircraft is needed. The UAV will play the role of deported arms and eyes of the helicopter. With such innovation, the helicopter performs what the UAV cannot do and on the operation theatre the UAV performs what the helicopter cannot do anymore. \u0000\u0000In order to ensure the multipurpose platform functionality of the helicopter, the cooperation system will be considered as an optional and will demand only simple and quick plug and play actions. The main constraints are to relatively locate the UAV and Helicopter with a centimetric accuracy and in addition to ensure safety in flight (collision avoidance) with functionality such as geo and helicopter fencing. With an efficient MUM-T architecture system, we will be capable to perform missions with an increased level of safety, to increase the availability of the H/C, to enlarge the H/C mission perimeter, to reduce the pilot workload and to avoid human operation in the so called 3D (Dull, Dirty, Dangerous) zones. \u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126659657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16727
P. Lorber, P. Bowles, H. Xin, Jing-gen Zhao
A combination of experimental and analytical methods has been applied to study the aerodynamic interaction of the S97 RAIDER® coaxial main rotor and its wake on an empennage. The primary goal was to characterize the periodic aerodynamic forcing from the rotor on the horizontal stabilizer over a wide range of flight conditions, and use those data to develop and validate computational fluid dynamics (CFD) methods that can then be applied to optimize future designs. The flight test aircraft was instrumented with 29 unsteady pressure sensors and flown for speed sweeps from 20 to 180 kts as well as a range of maneuvers. The data were processed to provide both unsteady and time-averaged aerodynamic forces and moments. Two CFD codes were then applied: HELIOS/RCAS using discrete main rotor and propulsor blades and STARCCM+ using a recently developed unsteady virtual blade model. Both codes captured the trends of the flight test data and agreed that the vibratory aerodynamic forcing on the empennage was not particularly large. The flight data were also compared with previously acquired powered wind tunnel model data, and showed good agreement. Finally, the Sikorsky GenHel flight dynamics model was applied to level flight and maneuver conditions, and the match was also acceptable. This study has that current state-of-the-art methodology, carefully applied, can capture complex aerodynamic interactions with sufficient accuracy for aircraft design, and that this implementation of X2 Technology(TM) does not result in unacceptable rotor on empennage interactions.
{"title":"S-97 RAIDER® Wake-Empennage Interaction Fight Data and Correlation","authors":"P. Lorber, P. Bowles, H. Xin, Jing-gen Zhao","doi":"10.4050/f-0077-2021-16727","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16727","url":null,"abstract":"\u0000 A combination of experimental and analytical methods has been applied to study the aerodynamic interaction of the S97 RAIDER® coaxial main rotor and its wake on an empennage. The primary goal was to characterize the periodic aerodynamic forcing from the rotor on the horizontal stabilizer over a wide range of flight conditions, and use those data to develop and validate computational fluid dynamics (CFD) methods that can then be applied to optimize future designs. The flight test aircraft was instrumented with 29 unsteady pressure sensors and flown for speed sweeps from 20 to 180 kts as well as a range of maneuvers. The data were processed to provide both unsteady and time-averaged aerodynamic forces and moments. Two CFD codes were then applied: HELIOS/RCAS using discrete main rotor and propulsor blades and STARCCM+ using a recently developed unsteady virtual blade model. Both codes captured the trends of the flight test data and agreed that the vibratory aerodynamic forcing on the empennage was not particularly large. The flight data were also compared with previously acquired powered wind tunnel model data, and showed good agreement. Finally, the Sikorsky GenHel flight dynamics model was applied to level flight and maneuver conditions, and the match was also acceptable. This study has that current state-of-the-art methodology, carefully applied, can capture complex aerodynamic interactions with sufficient accuracy for aircraft design, and that this implementation of X2 Technology(TM) does not result in unacceptable rotor on empennage interactions.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127067271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16752
Kathryn A. Feltman, A. Kelley, Colby Mathews, Lance Randles
Advanced technology being introduced into Army aviation platforms may place aviators at an increased risk for performance decrements due to the increased need to maintain vigilance. One method of offsetting potential performance decrements is the introduction of biomedical interventions, in this case, transcranial direct current stimulation (tDCS). To assess the utility of tDCS in maintaining performance, two groups of aviators performed two separate long-duration flights requiring sustained attention. One group received tDCS prior to the flight, while the other group received tDCS during the flight. Flight performance and secondary task performance measures were collected throughout the duration of both flights. A total of 8 Army aviators participated in the study to-date. No significant differences between groups were identified, although some trends in the data were noted. It is likely that the study was underpowered and thus unable to detect any differences between groups.
{"title":"Do We Need Biomedical Interventions to Maintain Crew Performance under Sustained Attention? ","authors":"Kathryn A. Feltman, A. Kelley, Colby Mathews, Lance Randles","doi":"10.4050/f-0077-2021-16752","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16752","url":null,"abstract":"\u0000 Advanced technology being introduced into Army aviation platforms may place aviators at an increased risk for performance decrements due to the increased need to maintain vigilance. One method of offsetting potential performance decrements is the introduction of biomedical interventions, in this case, transcranial direct current stimulation (tDCS). To assess the utility of tDCS in maintaining performance, two groups of aviators performed two separate long-duration flights requiring sustained attention. One group received tDCS prior to the flight, while the other group received tDCS during the flight. Flight performance and secondary task performance measures were collected throughout the duration of both flights. A total of 8 Army aviators participated in the study to-date. No significant differences between groups were identified, although some trends in the data were noted. It is likely that the study was underpowered and thus unable to detect any differences between groups.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126088378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16740
Orazio Pinti, F. Gandhi, A. Oberai, R. Healy, R. Niemiec
The growing interest in large electric multicopters (eVTOL aircraft) has prompted the search for methods that can accurately and efficiently predict their aerodynamic performance under different designs and operating conditions. The challenge is modeling the complex interactional effects of rotors operating in close proximity. This can be tackled with high-fidelity computational fluid dynamics (CFD) models, which capture the physics of rotor interaction from first principles. However, they are computationally demanding for performing studies over a range of parameters. On the other hand, lower-fidelity models are computationally inexpensive, but approximate the underlying physics and can be imprecise in predicting the fields of interest. In this study we present a multi-fidelity approach that inherits the accuracy of a high-fidelity model, while retaining most of the computational efficiency of a low-fidelity model. In this approach, the low-fidelity model is used to investigate the entire space of parameters and identify key parameter values to perform high-fidelity simulations. Thereafter, these high-fidelity simulations are used in a lifting procedure to determine multi-fidelity solutions at desired parameter values. We apply this strategy to determine the rotors' lift and drag distributions of a 2-rotor assembly in forward flight. The parameters considered are design variables, namely the longitudinal and vertical rotor-to-rotor separation, and operating conditions variables: forward speed and disk loading (DL). We conclude that over a large of parameters this approach yields results that retain the accuracy of the high-fidelity predictions at the computational cost of the low-fidelity model.
{"title":"Multi-Fidelity Surrogate Model for Interactional Aerodynamics of a Multicopter ","authors":"Orazio Pinti, F. Gandhi, A. Oberai, R. Healy, R. Niemiec","doi":"10.4050/f-0077-2021-16740","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16740","url":null,"abstract":"\u0000 The growing interest in large electric multicopters (eVTOL aircraft) has prompted the search for methods that can accurately and efficiently predict their aerodynamic performance under different designs and operating conditions. The challenge is modeling the complex interactional effects of rotors operating in close proximity. This can be tackled with high-fidelity computational fluid dynamics (CFD) models, which capture the physics of rotor interaction from first principles. However, they are computationally demanding for performing studies over a range of parameters. On the other hand, lower-fidelity models are computationally inexpensive, but approximate the underlying physics and can be imprecise in predicting the fields of interest. In this study we present a multi-fidelity approach that inherits the accuracy of a high-fidelity model, while retaining most of the computational efficiency of a low-fidelity model. In this approach, the low-fidelity model is used to investigate the entire space of parameters and identify key parameter values to perform high-fidelity simulations. Thereafter, these high-fidelity simulations are used in a lifting procedure to determine multi-fidelity solutions at desired parameter values. We apply this strategy to determine the rotors' lift and drag distributions of a 2-rotor assembly in forward flight. The parameters considered are design variables, namely the longitudinal and vertical rotor-to-rotor separation, and operating conditions variables: forward speed and disk loading (DL). We conclude that over a large of parameters this approach yields results that retain the accuracy of the high-fidelity predictions at the computational cost of the low-fidelity model.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128075423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16877
Charles Tierney, Nicholas A. Jaffa, D. Reich, S. Schmitz
Rotor hub parasite drag remains a primary obstacle to improving the forward-flight capabilities of helicopters. As part of a rotor hub flow physics project at the Vertical Lift Research Center of Excellence (VLRCOE) at Penn State, this investigation was designed to improve the understanding of the interactional aerodynamics and wake flow physics of counter-rotating coaxial rotor hubs and explore designs for reducing the rotor hub drag factor, Kfe. These experiments measured the time-averaged and time-varying drag on four rotor hub designs, each with unique blade stubs. The four shapes tested were the DBLN 526 airfoil, 3.25:1 Rectangle, 4:1 Ellipse, and the novel profile named the Optimized Cambered Shape (OCS). Load data was collected at four Reynolds numbers ranging from 3.77×105 to 1.51×106 and advance ratios ranging from .25 to .6. Additionally, stereoscopic particle-image velocimetry (SPIV) measured the three velocity components at two downstream locations in the wake of the DBLN 526 rotor hub at Re=1.13×106 and advance ratios of .25 and .6, providing insight into and visualizing the development of the wake. Presented here is the compiled load data and calculated Kfe from these experiments, as well as the flow fields at the near- and midwake locations, with discussion of new knowledge gained of the coaxial rotor hub wakes.
{"title":"Scaled Model Testing of Coaxial Rotor Hub Flows","authors":"Charles Tierney, Nicholas A. Jaffa, D. Reich, S. Schmitz","doi":"10.4050/f-0077-2021-16877","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16877","url":null,"abstract":"\u0000 Rotor hub parasite drag remains a primary obstacle to improving the forward-flight capabilities of helicopters. As part of a rotor hub flow physics project at the Vertical Lift Research Center of Excellence (VLRCOE) at Penn State, this investigation was designed to improve the understanding of the interactional aerodynamics and wake flow physics of counter-rotating coaxial rotor hubs and explore designs for reducing the rotor hub drag factor, Kfe. These experiments measured the time-averaged and time-varying drag on four rotor hub designs, each with unique blade stubs. The four shapes tested were the DBLN 526 airfoil, 3.25:1 Rectangle, 4:1 Ellipse, and the novel profile named the Optimized Cambered Shape (OCS). Load data was collected at four Reynolds numbers ranging from 3.77×105 to 1.51×106 and advance ratios ranging from .25 to .6. Additionally, stereoscopic particle-image velocimetry (SPIV) measured the three velocity components at two downstream locations in the wake of the DBLN 526 rotor hub at Re=1.13×106 and advance ratios of .25 and .6, providing insight into and visualizing the development of the wake. Presented here is the compiled load data and calculated Kfe from these experiments, as well as the flow fields at the near- and midwake locations, with discussion of new knowledge gained of the coaxial rotor hub wakes.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123524719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16892
C. Heathco
Advancements in distributed electric propulsion have given rise to a wide array of new eVTOL designs featuring tilt rotors, tilt wings and ducted fans. All of these systems pose a common challenge, meeting the electrical power demands of the propulsors. Hybrid-electric drives which combine an engine driven generator with batteries are being pursued to address the range and payload limitations of all electric drives using only batteries. The hybrid systems currently being considered rely on traditional gasoline, diesel, and turbine engines. Gas turbines offer exceptional energy density but are less fuel efficient than piston engines. Two technologies, heat recovery and power transfer, can be incorporated into the gas turbine to significantly improve fuel efficiency. New Centerline Design has conducted parametric trade studies on eVTOL aircraft with turbine based hybrid-electric systems to quantify the benefits that heat recovery and power transfer will have on eVTOL payload and range. The results of this study show that heat recovered gas turbines with power transfer are excellent candidates for next generation eVTOL hybrid-electric propulsion systems.
{"title":"Optimizing Turbogenerators for Hybrid-Electric Applications","authors":"C. Heathco","doi":"10.4050/f-0077-2021-16892","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16892","url":null,"abstract":"\u0000 Advancements in distributed electric propulsion have given rise to a wide array of new eVTOL designs featuring tilt rotors, tilt wings and ducted fans. All of these systems pose a common challenge, meeting the electrical power demands of the propulsors. Hybrid-electric drives which combine an engine driven generator with batteries are being pursued to address the range and payload limitations of all electric drives using only batteries. The hybrid systems currently being considered rely on traditional gasoline, diesel, and turbine engines. Gas turbines offer exceptional energy density but are less fuel efficient than piston engines. Two technologies, heat recovery and power transfer, can be incorporated into the gas turbine to significantly improve fuel efficiency. New Centerline Design has conducted parametric trade studies on eVTOL aircraft with turbine based hybrid-electric systems to quantify the benefits that heat recovery and power transfer will have on eVTOL payload and range. The results of this study show that heat recovered gas turbines with power transfer are excellent candidates for next generation eVTOL hybrid-electric propulsion systems.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131491207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16865
Anthony Gong, R. Hess, M. Tischler
Multirotor UAS are prime candidates for autonomous package delivery due to their VTOL capability and payload carrying capacity. The effect of payloads on flight control system performance is investigated for three different inner-loop flight control system architectures, namely, explicit model following, nonlinear dynamic inversion, and incremental nonlinear dynamic inversion. Outer-loop flight control systems are wrapped around the various inner-loop architectures for waypoint tracking control. The flight control systems are designed and optimized using CONDUIT R to meet a common, comprehensive set of stability and performance specifications. Deterministic reconfiguration was designed for each inner-loop control architecture to account for the change in vehicle dynamics when a payload is added or removed. Robustness analyses are conducted considering both deterministic payload variations and modeling uncertainty. A notional package delivery mission scenario is simulated using a full-flight envelope stitched model with measurement noise and turbulence models identified from flight test data. The mission scenario is simulated for three different cases to evaluate the baseline performance, the degraded performance when a payload is added, and the recovery of performance with deterministic reconfiguration of the flight control systems.
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