Browsing by Author "Mahmood, Tashfeen"

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    CFD investigation of a core-mounted-target-type thrust reverser, Part 1: reverser stowed configuration
    (ASME, 2017-12-25) Mahmood, Tashfeen; Jackson, Anthony J. B.; Sethi, Vishal; Khanal, Bidur; Ali, Fakhre
    During the second half of the 90's, NASA performed experimental investigations on six novel Thrust Reverser designs; Core Mounted Target Type Thrust Reverser (CMTTTR) design is one of them. To assess the CMTTTR efficiency and performance, NASA conducted several wind tunnel tests at Sea Level Static conditions. The results from these experiments are used in this paper series to validate the CFD results. This paper is part one of the three-part series; Part 1 and 2 discusses the CMTTTR in stowed and deployed configurations, all analysis in the first two papers are performed at SLS conditions. Part3 discusses the CMTTTR in the forward flight condition. The key objectives of this paper are: first, to perform the 3D CFD analysis of the reverser in stowed configuration; all analyses are performed at SLS condition. The second objective is to validate the acquired CFD results against the experimental data provided by NASA[1]. The third objective is to verify the fan and overall engine net thrust values acquired from the aforementioned CFD analyses against those derived based on 1-D engine performance simulations. The fourth and final objective is to examine and discuss the overall flow physics associated with the CMTTTR under stowed configuration. To support the successful implementation of the overall investigation, full-scale 3DCAD models are created, representing a fully integrated GE90 engine, B777 wing, and pylon configuration. Overall a good agreement is found between the CFD and test results; the difference between the two was less than 5%.
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    CFD investigation of a core-mounted-target-type thrust reverser, Part 2: reverser deployed configuration
    (ASME, 2017-12-25) Mahmood, Tashfeen; Jackson, Anthony J. B.; Sethi, Vishal; Khanal, Bidur; Fakhre, Ali
    CMTTTR design was proposed by NASA in the second half of the 90's. NASA carried out several experiments at static conditions, and their acquired results suggested that the performance characteristics of the CMTTTR design falls short to comply with the mandatory TR performance criteria, and were therefore regarded as an infeasible design. However, the authors of this paper believe that the results presented by NASA for CMTTTR design require further exploration to facilitate the complete understanding of its true performance potential. This Part2 paper is a continuation from Part1and presents a comprehensive three-dimensional (CFD) analyses of the CMTTTR in deployed configuration; the analyses at forward flight conditions will be covered in Part 3. The key objectives of this paper are: first, to validate the acquired CFD results with the experimental data provided by NASA: this is achieved by measuring the static pressure values on various surfaces of the deployed CMTTTR model. The second objective is to estimate the performance characteristics of the CMTTTR design and corroborate the results with experimental data. The third objective is to estimate the Pressure Thrust (i.e. axial thrust generated due to the pressure difference across various reverser surfaces) and discuss its significance for formulating the performance of any thrust reverser design. The fourth objective is to investigate the influence of kicker plate installation on overall TR performance. The fifth and final objective is to examine and discuss the overall flow physics associated with the thrust reverser under deployed configuration.
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    Performance and CFD analyses for a novel and existing thrust reverser designs.
    (2014-04) Mahmood, Tashfeen; Sethi, Vishal
    The landing phase of any flight is the most important one with respect to safety. For a high bypass ratio turbofan engine, aircraft deceleration can be achieved by the use of thrust reversers, lift spoilers and brakes. The use of thrust reversers naturally contributes to a reduction in engine life while the use of brakes has operational limitations with respect to aircraft “turn-around times”. With a drive towards improved engine efficiency and lower overall weight, research into novel thrust reverser concepts is imperative to identify designs which offer improved reverser effectiveness and lower weight as well as ease of installation and storage. The main contributions to knowledge of this PhD research are related to feasibility assessments of the following two thrust reverser concepts: A novel vane target type hybrid reverser (VTTHR) design concept has been conceived and evaluated (at a preliminary level) by the author. The design incorporates a target type thrust reverser with cascade vanes. This idea may be patentable. NASA has developed and tested a core mounted target type thrust reverser (CMTTTR) for which experimental data is available in the public domain. The second contribution to knowledge of this PhD research is extensive studies of this design. These studies comprise 2D and 3D CFD analyses to assess design feasibility and provide an understanding of performance and flow physics of this thrust reverser for both static and landing conditions (not available in public domain). In addition to these studies, comprehensive studies of the impact of thrust reverser deployment on overall engine and component performance (for both a mixed and a separate exhaust high bypass ratio turbofan engine) were performed. The preliminary feasibility studies of the VTTHR, which were performed using 2D CFD, suggest that this new design may offer benefits in terms of greater reverser efficiency, weight and ease of storage, relative to conventional designs. Additionally, it was deduced from a large number of CFD investigations that this may be the only feasible “core mounted” thrust reverser design concept for future high bypass ratio engines. There are of course several additional studies (aerodynamic and structural) that need to be performed to mature this technology but the preliminary studies performed provide a good foundation for these. The use of a VTTHR reverser concept relocates reverser hardware to the core cowl, offering potential reductions in reverser and nacelle weight while allowing the nacelle lines to be optimized. Also, installation of VTTHR would benefit aircraft cruise performance, as during cruise flight there will be no losses due to flow leakage and pressure drops that normally occur across the stowed reverser hardware for conventional cascade type thrust reversers, thus, an improvement in specific fuel consumption and therefore mission fuel burn is expected. The CMTTTR models developed were successfully validated using experimental data. However it was concluded that this design may not be feasible because of issues related to reverser effectiveness, mass flow compatibility and runway clearance.