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Investigations of Super-Lifting Co-Flow Jet Airfoil and Distributed Electric Propulsion Aircraft
Başlık:
Investigations of Super-Lifting Co-Flow Jet Airfoil and Distributed Electric Propulsion Aircraft
Yazar:
Yang, Yunchao, author.
ISBN:
9780355990287
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (364 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Gecheng Zha Committee members: Weiyong Gu; Hongtan Liu; Wangda Zuo.
Özet:
The objective of this dissertation is to investigate the super-lifting performance of Co-Flow Jet (CFJ) flow control airfoil and its applications to electric aircraft. The CFJ airfoil is promising to transform future aircraft design with extremely short takeoff/landing (ESTOL) and ultra-high cruise efficiency due to its substantial lift enhancement and drag reduction with very low energy expenditure. To resolve turbulent vortical structures for super-lifting CFJ airfoil flows, the improved delayed detached eddy simulation (IDDES) with high order schemes is developed and implemented in the in-house CFD code, FASIP. The high order schemes used in this study include a fifth-order weighted essentially non-oscillatory (WENO) scheme for the inviscid fluxes reconstruction and a fourth order conservative central differencing scheme for the viscous fluxes. An efficient and low diffusion E-CUSP (LDE) scheme as a Riemann solver designed to minimize numerical dissipation is utilized. The comparative study of the S-A URANS, DES, DDES, and IDDES simulation is performed on the turbulent boundary layer flows over the flat plate and the stalled flows of the NACA0012 airfoil. The validation study indicates that IDDES method can predict the law of the wall accurately for different mesh sizes, Reynolds numbers, and Mach numbers whereas the DES and DDES obtain the velocity profile in the boundary layer with model stress depletion and log layer mismatched at certain conditions. The 2D RANS simulation of a CFJ-NACA6421 airfoil discovers for the first time that CFJ airfoil is able to achieve the super-lift coefficient (SLC), which is defined as a lift coefficient that exceeds the theoretical limit based on potential flows. For the CFJ-NACA6421 airfoil, a maximum lift coefficient of 12.6 is achieved at the angle of attack (AoA) of 70 deg and jet momentum coefficient of Cmu = 0.60. It is 66% higher than the theoretical limit of 7.6 for an airfoil of 21% thickness (t/c = 0.21). The circulation achieved around the CFJ airfoil is so large that the stagnation point is detached from the airfoil solid body and the Kutta condition does not apply anymore. For the superlift condition at AoA of 70 deg, the vortex structures on the CFJ airfoil suction surface appear to have four counter-rotating vortex layers next to each other from the airfoil wall surface to the far field freestream. The 2D simulation of CFJ airfoil indicates that the CLmax appears to have no limit. The CLmax limit from the potential flows is the result of imposing Kutta condition, which is necessary for potential flows, but not a true physical condition. In reality, CLmax depends on how much energy can be added to the flow to overcome the severe adverse pressure gradient. To further verify the super-lift coefficient and the vortical structures of the CFJ airfoil, a 3D unsteady IDDES investigation of the CFJ-NACA6421 airfoil is performed with a span length of 10% of the chord. The IDDES results verify that the CFJ airfoil is able to achieve the super-lift coefficient at ultra-high AoAs with attached flow. The 3D steady RANS simulation of a finite-span super-lift CFJ wing is carried out with different aspect ratios (AR) without using any flaps. The RANS simulation results indicate that the CFJ wing can achieve the maximum lift coefficient of 7.8 at a very high AoA of 70 deg with good aerodynamic efficiency. At high AoAs, the outer 25% wingspan is affected more by the wingtip vortex that contributes the lift reduction and drag increase. The ultra-high lift coefficient does not appear to increase the penalty of induced drag due to the negative drag at zero lift. The Oswald efficiency is increased with the AR decreased from 20 to 5 at the same AoA and Cmu. It achieves the value as high as 0.967 at AR of 5, Cmu of 0.25 and AoA of 25 deg, indicating that the penalty of induced drag for 3D CFJ wing is small even though ultra high lift coefficient is obtained. Furthermore, the super-lifting CFJ flow control concept is applied to a 2D circular cylinder as a general lifting system to study the fundamental physics of the superlifting phenomenon. The 2D RANS simulation indicates that the CFJ cylinder can achieve a maximum lift coefficient of 28 at Cmu=0.8, far exceeding the potential limit of 4° where the stagnation point is on the bottom of the cylinder. A trade study of injection and suction slot configurations is performed to obtain the optimum injection and suction slot locations. An experimental investigation of CFJ airfoil with embedded compressors was conducted at the Low Speed Wind Tunnel of Texas A&M University. The wind tunnel experiment for the first time proves that an airfoil can achieve a lift coefficient exceeding the theoretical limit by CFJ flow control. A high thrust coefficient of the CFJ airfoil was also observed.
Notlar:
School code: 0125
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(678720.1) | 678720-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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