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Tai,
Jimmy C. M.
Tai,
Jimmy C. M.
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ItemA Comparative Assessment of Highspeed Rotorcraft Concepts (HSRC) : Reaction Driven Stopped Rotor/Wing and Variable Diameter Tiltrotor(Georgia Institute of Technology, 1997-10) Tai, Jimmy C. M. ; Mavris, Dimitri N. ; Schrage, Daniel P.The objective of this paper is to illustrate the methods and tools developed to size and synthesize a stopped rotor/wing vehicle using a reaction drive system, including how this design capability is incorporated into a sizing and synthesis tool, VASCOMP II. This new capability is used to design a vehicle capable of performing a V-22 escort mission, and a sized vehicle description with performance characteristics is presented. The resulting vehicle is then compared side-by-side to a variable diameter tiltrotor designed for the same mission. Results of this analysis indicate that the reaction-driven rotor concept holds promise relative to alternative concepts, but that the variable diameter tiltrotor has several inherent performance advantages. Additionally, the stopped rotor/wing needs considerably more development to reach maturity.
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ItemAn Assessment of Reaction Driven Stopped Rotor/Wing Using Circulation Control in Forward Flight(Georgia Institute of Technology, 1996-10) Tai, Jimmy C. M. ; Mavris, Dimitri N. ; Schrage, Daniel P.The desire of achieving faster cruise speed for rotorcraft vehicles has been around since the inception of the helicopter. Many unconventional concepts have been considered and researched such as the advanced tilt rotor with canards, the tilt-wing, the folding tiltrotor, the coaxial propfan/folding tiltrotor, the variable diameter tiltrotor, and the stopped rotor/wing concept, in order to fulfill this goal. The most notable program which addressed the technology challenges of accomplishing a high speed civil transport mission is the High Speed Rotorcraft Concept (HSRC) program. Among the long list of potential configurations to fulfill the HSRC intended mission, the stopped rotor/wing is the least investigated due to the fact that the existing rotorcraft synthesis codes cannot handle this type of vehicle. In order to develop such a tool, a designer must understand the physics behind this unique concept. The uniqueness of stopped rotor/wing vehicles that use reaction drive can be found in the tight coupling that is present between the rotor and the engine which in turn requires these subsystems to be sized concurrently rather than in isolation. A methodology and simulation tool capable of handling this coupling is under development at the Aerospace Systems Design Laboratory (ASDL) at Georgia Institute of Technology. The development of a new design tool (TJCC) and the use of a statistical technique called Response Surface Methodology linked into the V/STOL Aircraft Sizing and Performance Computer Program (VASCOMP II) has provided the capability of sizing stopped rotor/wings. The potential success of a stopped rotor/wing configuration can only be determined through direct performance comparisons with other high speed rotorcraft concepts using analytical methods of comparable sophistication. The authors have previously presented limited results from this study detailing the rotor/wing performance during hover. In this paper the forward flight regime for both the helicopter and fixed wing modes are discussed. Representative results presented include performance characteristics such as the horsepower required curves versus forward flight for both the rotorcraft and fixed wing modes of operation. Furthermore, the mass flow requirements, and transition performance associated with this aircraft are also examined in this paper.
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ItemAn Application of Response Surface Methodology to the Design of Tipjet Driven Stopped Rotor/Wing Concepts(Georgia Institute of Technology, 1995-09) Tai, Jimmy C. M. ; Mavris, Dimitri N. ; Schrage, Daniel P.The possibility of a new aircraft that is capable of solving the increasing demand of inter-city transportation has attracted the attention of the aerospace industry for quite some time. Under the High Speed Rotorcraft Concept (HSRC) program, both NASA and the U.S. helicopter industry have studied a series of candidate rotorcraft configurations capable of cruising at high speeds and capable of taking off and landing vertically at vertiports located at downtown. Among these candidates, the stopped rotor/wing configuration has been the least studied due to lack of appropriate analytical tools to assist in its design and due to a general lack of understanding of the physics behind this unconventional concept. Even though the HSRC program has since been canceled, Georgia Tech's Aerospace Systems Design Laboratory (ASDL) recognized the need for a design methodology capable of handling the synthesis and sizing of such vehicles and has continued its pursuit. Therefore, such a computer simulation code has been developed to size reaction driven stopped rotor/wing vehicles which may or may not enable Circulation Control. The difficulty in sizing such a concept is primarily due to the unique coupling of rotor and engine which need to be sized concurrently since they are directly linked to each other and cannot be studied in isolation. This coupling, in fact, is not seen in any other concept. The methodology and computer simulation tool presented in this paper show how this coupling is accomplished. Furthermore, the results from this rotor/engine coupling are presented in the form of Response Surface Equations that is derived through the application of Response Surface Methodology. These RSE's also provide the designer with a unique ability to predict what the response will be, based on the settings of the design variables that he/she chooses. The robustness advantages of using these RSE's are also presented in the vehicle sizing portion of the overall design methodology for the stopped rotor/wing configurations.
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ItemA Multidisciplinary Design Optimization Approach to Sizing Stopped Rotor Configurations Utilizing Reaction Drive and Circulation Control(Georgia Institute of Technology, 1994-09) Mavris, Dimitri N. ; Tai, Jimmy C. M. ; Schrage, Daniel P.Over the years, the U. S. rotorcraft industry and NASA have conducted numerous studies to determine possible candidates for a potential High Speed Rotorcraft Concept (HSRC) and to identify and provide suggestions and solutions to technology issues that might hinder the development of such concept. Many feasible concepts have been proposed and studied including the tilt rotor, the tilt wing, the folding tilt rotor, the variable diameter tilt rotor, the advanced canard tilt rotor, the coaxial propfan/folding tilt rotor, and the stopped rotor/wing configuration. Among these concepts, the rotor/wing still remains the least studied compared with the other candidates. This can be attributed primarily to lack of suitable analytical tools to assist the design process and to unfamiliarity with this unconventional concept. The potential success of a stopped rotor/wing configuration can only be determined through direct performance comparisons with the concepts mentioned above using analytical methods of comparable sophistication. The intention of this paper is to address the issues associated with sizing and optimizing a stopped rotor/wing configuration which incorporates a tip jet drive system and Circulation Control devices. In addition, a methodology has been formulated and is presented which forms a foundation upon which a new sizing code capable of handling this unique concept can be developed. Since the subject of this paper deals with a concept that enables relatively uncommon technologies, a review of the physics associated with these concepts is also presented.