Person:

Tai, Jimmy C. M.

Permanent Link

https://hdl.handle.net/1853/71759

Associated Organization(s)

Organizational Unit

Daniel Guggenheim School of Aerospace Engineering

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Publication Search Results

Now showing 1 - 10 of 11

CFD Study of an Over-Wing Nacelle Configuration

(Georgia Institute of Technology, 2018-10-05) Berguin, Steven H. ; Renganathan, Sudharshan Ashwin ; Ahuja, Jai ; Chen, Mengzhen ; Perron, Christian ; Tai, Jimmy C. M. ; Mavris, Dimitri N.

Engine bypass ratio (BPR) has grown significantly over the years, due to a desire for increased efficiency, and the large fan diameters that have resulted are forcing the engines so close to the wing that there is no room left for them to grow any larger due to ground clearance constraints. As BPR increases even further in the future, conventional Under-Wing Nacelle (UWN) installations will therefore no longer be possible without drastic modification of the wing and landing gear. Over-Wing nacelle concepts solve this problem by offering a convenient installation for high BPR turbofans and, additionally, offer the potential to mitigate community noise through engine noise shielding using the wing as a shield. However, OWN has historically warranted concern about unacceptably high drag levels at transonic speeds and the purpose of this research was to determine whether or not drag can be improved enough to take advantage of the aforementioned cross-disciplinary benefits. To do so, three studies were conducted: study 1 conducted a simple nacelle sweep in order to identify and visualize the physical mechanisms driving the configuration, study 2 then conducted a sensitivity analysis in order to understand important design variables and, finally, study 3 performed single point optimization for a trailing edge OWN concept. Overall, results suggests that OWN drag can be improved to levels commensurate with its Under-Wing Nacelle (UWN) counterpart. However, limitations of the analysis tools employed for this research (in the area of shape optimization) were insufficient to outperform the UWN baseline. Such limitations were successfully overcome by modern OWN concepts, such as the Honda Business Jet and the military Lockheed HWB for air mobility missions. Overall, it is therefore the authors' opinion that either leading-edge or trailing-edge mounted OWN configurations are concepts worth investigating further for civil transport applications.
Modeling Airlift Operations for Humanitarian Aid and Disaster Relief to Support Acquisition Decision-Making

(Georgia Institute of Technology, 2018-06) Weit, Colby J. ; Chetcuti, Steven ; Chan, Cherlyn ; Muehlberg, Marc ; Wei, Lansing ; Gilani, Hassan ; Schwartz, Katherine G. ; Sudol, Alicia M. ; Tai, Jimmy C. M. ; Mavris, Dimitri N.

In a fiscally constrained environment, it is crucial that both equipment manufacturers and defence invest in technology that shows marked operational improvement. A priori identification of cost-benefit at the early acquisition stage is often limited and incomplete, leading to poor value propositions. This conundrum motivates the need to develop a method to evaluate technologies such as levels of autonomy, stealth capability, improved engines, etc. and make tradeoffs against operational measures of performance and effectiveness (MOP/Es) rather than solely against vehicle performance characteristics. The objective of this study is to create an environment in which those trades against MOEs could be performed rapidly to inform technology investment and acquisition decision-making. This environment is built on top of representative models of a discrete event simulation of disaster relief airlift operations to compare technology modifications or vehicle acquisition options rapidly against operational measures of effectiveness.
Sensitivity Analysis of Aero-Propulsive Coupling for Over-Wing-Nacelle Concepts

(Georgia Institute of Technology, 2018) Berguin, Steven H. ; Renganathan, Sudharshan Ashwin ; Ahuja, Jai ; Chen, Mengzhen ; Tai, Jimmy C. M. ; Mavris, Dimitri N.

A sensitivity analysis is performed to quantify the relative impact of perturbing a set of design variables representing an airplane configuration with Over-Wing Nacelles (OWN), operating at transonic cruise. The goal is to study the impact of perturbing the engine's XYZ position and power setting on installation drag, engine inlet pressure recovery, and lift curve characteristics. High- fidelity Reynolds Averaged Navier-Stokes (RANS) simulations of the Common Research Model (CRM) modified with powered, over-wing nacelles are performed and dominant main effects and interactions are identified. The most dominant effect was by far the engine's X position, but it was also found that podded OWN configurations exhibit statistically significant, aero-propulsive coupling. Specifically, certain engine locations cause changes in the flow-field that deteriorate inlet pressure recovery and, vice versa, a change in engine boundary conditions can affect installation drag. It is therefore recommended to simulate OWN concepts using a coupled MDA or MDAO approach to capture interdependencies between aerodynamics and propulsion.
Boeing propulsion sub-systems: NPSS/WATE parametric model, stage-stack & mean-line, and transient analyses

(Georgia Institute of Technology, 2012-12-31) Mavris, Dimitri N. ; Tai, Jimmy C. M. ; Schutte, Jeff ; Denney, Russell ; Kestner, Brian
Elements of an Emerging Virtual Stochastic life Cycle Design Environment

(Georgia Institute of Technology, 1999-10) Mavris, Dimitri N. ; DeLaurentis, Daniel A. ; Hale, Mark A. ; Tai, Jimmy C. M.

The challenge of designing next-generation systems that meet goals for system effectiveness, environmental compatibility, and cost has grown to the point that traditional design methodologies are becoming ineffective. Increases in the analysis complexity required, the number of objectives and constraints to be evaluated, and the multitude of uncertainties in today? design problems are primary drivers of this situation. A new environment for design has been formulated to treat this situation. It is viewed as a testbed, in which new techniques in such areas as design-oriented/physics-based analysis, uncertainty modeling, technology forecasting, system synthesis, and decision-making can be posed as hypotheses. Several recent advances in elements of this multidisciplinary environment, termed the Virtual Stochastic Life Cycle Design Environment, are summarized in this paper.
Additional development and systems analyses of pneumatic technology for high speed civil transport aircraft

(Georgia Institute of Technology, 1999) Willie, F. Scott ; Lee, Warren J. ; Niebur, Curt S. ; Gregory, Scott D. ; Mavris, Dimitri N. ; Tai, Jimmy C. M. ; Kirby, Michelle Rene ; Roth, Bryce Alexander ; Engler, R. J. (Robert J.)
A multidisciplinary design approach to size stopped rotor/wing configurations using reaction drive and circulation control

(Georgia Institute of Technology, 1998-08) Tai, Jimmy C. M.
A 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.
An 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.
An 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.