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Dimitri Papamoschou - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic and acoustic optimization for fan Flow Deflection
49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, 2011Co-Authors: Andrew Johnson, Juntao Xiong, Sara Rostamimonjezi, Feng Liu, Dimitri PapamoschouAbstract:This investigation seeks to optimize the implementation of fan Flow Deflection for jet noise suppression from a supersonic turbofan nozzle with bypass ratio 2.7. The design objective is to maximize reduction of noise perceived by the community while minimizing aerodynamic losses. An adjoint method for shape optimization is used to obtain deflector vane designs with sufficient Flow Deflection and minimum thrust penalty. A NACA0012 airfoil is used as the initial shape for the vane airfoil. Optimization leads to reduction in specific-thrust loss and a thicker airfoil which is beneficial for structural reasons. The optimal vane airfoil is used in a parametric acoustic study of 50 deflector configurations with variable vane chord length, angle of attack and azimuth angle. The best configuration leads to reductions in effective perceived noise level (EPNL) of 2.8 dB in the downward direction and 2.5 dB in the sideline direction. Addition of a porous wedge-shaped fan Flow deflector increases the EPNL reductions to 5.0 dB and 3.9 dB in the downward and sideline directions, respectively.
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Computation of High-Speed Coaxial Jets with Fan Flow Deflection
2010Co-Authors: Juntao Xiong, Feng Liu, Preben Nielsen, Dimitri PapamoschouAbstract:We present a computational study, validated by mean-Flow experiments, of a dual-stream nozzle simulating the exit conditions of a supersonic turbofan engine with noise-suppressing fan Flow deflectors. The study is conducted for eight nozzle configurations and two operating conditions: a cold condition at which mean velocity surveys were conducted and against which the computational code was validated and a hot condition that corresponds to the takeoff engine cycle and at which acoustic data were collected. The code predictions successfully replicate the mean velocity fields and the inflectional layers of the experimental Flows. The code is then extended to the conditions of the actual engine cycle. The computations reveal a similar velocity profile for the hot and cold conditions when the axial distance is normalized by the potential core length. For both conditions, the vane deflectors reduce the turbulent kinetic energy k on the underside of the jet. An overall noise source strength is modeled as the axial integral of k7=2.A significant correlation is found between the reduction in the noise source strength and the reduction in the peak level of the overall sound pressure level. Nomenclature A = area a = speed of sound c = vane chord lengt
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computation of high speed coaxial jets with fan Flow Deflection
AIAA Journal, 2010Co-Authors: Juntao Xiong, Feng Liu, Preben E Nielsen, Dimitri PapamoschouAbstract:We present a computational study, validated by mean-Flow experiments, of a dual-stream nozzle simulating the exit conditions of a supersonic turbofan engine with noise-suppressing fan Flow deflectors. The study is conducted for eight nozzle configurations and two operating conditions: a cold condition at which mean velocity surveys were conducted and against which the computational code was validated and a hot condition that corresponds to the takeoff engine cycle and at which acoustic data were collected. The code predictions successfully replicate the mean velocity fields and the inflectional layers of the experimental Flows. The code is then extended to the conditions of the actual engine cycle. The computations reveal a similar velocity profile for the hot and cold conditions when the axial distance is normalized by the potential core length. For both conditions, the vane deflectors reduce the turbulent kinetic energy k on the underside of the jet. An overall noise source strength is modeled as the axial integral of k 7/2 . A significant correlation is found between the reduction in the noise source strength and the reduction in the peak level of the overall sound pressure level.
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optimization of fan Flow Deflection for supersonic turbofan engines
AIAA CEAS Aeroacoustics Conference, 2008Co-Authors: Preben E Nielsen, Dimitri PapamoschouAbstract:*† This study involves the application of fan Flow deflectors for suppression of jet noise from low-bypass turbofan engines for next-generation supersonic aircraft. Experiments using canonical vane deflectors seek to establish correlations between aerodynamics, distortion of the mean velocity field in the jet plume, and noise reduction. The maximum radial velocity gradient, as a function of axial distance and azimuth angle, is used to quantify distortions of the plume. Vanes mounted at low azimuth angles (with respect to the downward vertical) reduce gradients in the downward direction, while vanes mounted at high azimuth angles reduce gradients in the sideline reduction. There is a significant correlation between gradient reduction and noise suppression in the azimuthal direction of the gradient. In addition, it is found that vanes with cambered airfoils perform better than vanes with symmetric airfoils. The trends obtained were used in the successful design of deflector configurations consisting of two pairs of vanes which resulted in cumulative peak overall sound pressure level (OASPL) and effective perceived noise level (EPNL) reductions of 8.8 dB and 6.7 dB respectively.
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fan Flow Deflection for supersonic turbofan engines
46th AIAA Aerospace Sciences Meeting and Exhibit, 2008Co-Authors: Dimitri Papamoschou, Preben E NielsenAbstract:We present an initial parametric investigation of fan Flow deflectors for suppressing noise from supersonic turbofan engines. Realistic exhaust geometry and Flow conditions for bypass ratio 2.7 were simulated in a subscale experiment. The study encompassed acoustic measurement and mean velocity surveys. The deflectors comprised internal vanes with both symmetric and cambered airfoil sections and deployable external flaps. Superior acoustic results were achieved using a combination of cambered vanes and perforated flaps, yielding cumulative (downward plus sideline) EPNL and OASPL reductions of 7.7 dB and 9.2 dB respectively. A fair correlation is established between the suppression of peak OASPL and the reduction of the radial velocity gradient on the underside of the jet.
Zhongqian Ling - One of the best experts on this subject based on the ideXlab platform.
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alleviating gas particle Flow Deflection and asymmetric combustion in a 600 mwe supercritical down fired boiler by expanding its furnace throat space
Applied Thermal Engineering, 2017Co-Authors: Yanhui Wei, Min Kuang, Qunyi Zhu, Zhongqian LingAbstract:Abstract Cold-modeling gas/particle Flow experiments and numerical simulations on coal combustion were performed for evaluating the furnace throat effect on the Flow-field Deflection and asymmetric combustion in a 600 MWe supercritical down-fired boiler. At the furnace design setting (CW = 0.529), a severely deflected gas/particle Flow field appears, corresponding to a badly asymmetric combustion pattern with poor burnout and high NOx emissions. Shrinking the furnace throat from CW = 0.529 to CW = 0.500 apparently aggravates both the experimental and simulated Flow-field Deflection and meanwhile deteriorates asymmetric combustion. In contrast, expanding the furnace throat space to CW = 0.558 improves greatly the above problems and the Flow-field symmetries are generally acceptable, accompanied by improved burnout rate and lowered NOx emissions. Findings in this work suggest that new down-fired boiler designs should be equipped with a larger furnace throat space under the circumstances with a short upper furnace aggravating the asymmetric upper furnace configuration effect.
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improving gas particle Flow Deflection and asymmetric combustion of a 600 mwe supercritical down fired boiler by increasing its upper furnace height
Energy, 2017Co-Authors: Min Kuang, Qunyi Zhu, Zhongqian LingAbstract:A solution characterized by lengthening its short upper furnace was put forward for improving the gas/particle Flow Deflection and asymmetric combustion within a 600 MWe supercritical down-fired boiler. Based on the present design dimensionless upper furnace height CH2 = 0.864, upper furnace was lengthened in turn to CH2 = 1.00, 1.125, and 1.263 so as to form four comparable settings. Accordingly, cold-modeling gas/particle Flow experiments and numerical simulations on coal combustion were performed at these settings for confirming the solution and meanwhile recommending a reasonable CH2 setup. Moreover, real-furnace measurements, used to confirm the numerical simulation validity, were carried out under normal full load. Results at the design setting (CH2 = 0.864) show shat a severely deflected gas/particle Flow field appears, with (i) the downward gas/particle Flow penetrating much deeper in the front-half side than in the rear-half side and (ii) the upward Flow fully deflecting towards the front-half side. Consequently, a bad asymmetric combustion pattern with gas temperatures being much higher in the rear-half side than in the front-half side (temperature gap reaching about 300–600 °C) develops, generating poor burnout and high NOx emissions. Additionally, the simulated results are consistent well with the acquired real-furnace data. In comparison with cold-modeling gas/particle Flow experiments, the simulated downward gas/particle Flow penetrates clearly shallower in a hot environment. Lengthening upper furnace apparently weakens both the experimental and simulated Flow-field Deflection and meanwhile improves the asymmetric gas velocity distribution in the upper furnace. As CH2 increases to 1.125 and 1.263, both the experimental and simulated Flow-field symmetries are acceptable, accompanied by symmetrical gas velocity distribution in the upper furnace, improved burnout rate, and lowered NOx emissions. A comprehensive consideration of symmetrical combustion, high burnout rate, relatively low NOx emissions, and controlled cost for lengthening upper furnace suggests that a reasonable CH2 should be set at 1.125.
Yanhui Wei - One of the best experts on this subject based on the ideXlab platform.
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alleviating gas particle Flow Deflection and asymmetric combustion in a 600 mwe supercritical down fired boiler by expanding its furnace throat space
Applied Thermal Engineering, 2017Co-Authors: Yanhui Wei, Min Kuang, Qunyi Zhu, Zhongqian LingAbstract:Abstract Cold-modeling gas/particle Flow experiments and numerical simulations on coal combustion were performed for evaluating the furnace throat effect on the Flow-field Deflection and asymmetric combustion in a 600 MWe supercritical down-fired boiler. At the furnace design setting (CW = 0.529), a severely deflected gas/particle Flow field appears, corresponding to a badly asymmetric combustion pattern with poor burnout and high NOx emissions. Shrinking the furnace throat from CW = 0.529 to CW = 0.500 apparently aggravates both the experimental and simulated Flow-field Deflection and meanwhile deteriorates asymmetric combustion. In contrast, expanding the furnace throat space to CW = 0.558 improves greatly the above problems and the Flow-field symmetries are generally acceptable, accompanied by improved burnout rate and lowered NOx emissions. Findings in this work suggest that new down-fired boiler designs should be equipped with a larger furnace throat space under the circumstances with a short upper furnace aggravating the asymmetric upper furnace configuration effect.
Min Kuang - One of the best experts on this subject based on the ideXlab platform.
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alleviating gas particle Flow Deflection and asymmetric combustion in a 600 mwe supercritical down fired boiler by expanding its furnace throat space
Applied Thermal Engineering, 2017Co-Authors: Yanhui Wei, Min Kuang, Qunyi Zhu, Zhongqian LingAbstract:Abstract Cold-modeling gas/particle Flow experiments and numerical simulations on coal combustion were performed for evaluating the furnace throat effect on the Flow-field Deflection and asymmetric combustion in a 600 MWe supercritical down-fired boiler. At the furnace design setting (CW = 0.529), a severely deflected gas/particle Flow field appears, corresponding to a badly asymmetric combustion pattern with poor burnout and high NOx emissions. Shrinking the furnace throat from CW = 0.529 to CW = 0.500 apparently aggravates both the experimental and simulated Flow-field Deflection and meanwhile deteriorates asymmetric combustion. In contrast, expanding the furnace throat space to CW = 0.558 improves greatly the above problems and the Flow-field symmetries are generally acceptable, accompanied by improved burnout rate and lowered NOx emissions. Findings in this work suggest that new down-fired boiler designs should be equipped with a larger furnace throat space under the circumstances with a short upper furnace aggravating the asymmetric upper furnace configuration effect.
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improving gas particle Flow Deflection and asymmetric combustion of a 600 mwe supercritical down fired boiler by increasing its upper furnace height
Energy, 2017Co-Authors: Min Kuang, Qunyi Zhu, Zhongqian LingAbstract:A solution characterized by lengthening its short upper furnace was put forward for improving the gas/particle Flow Deflection and asymmetric combustion within a 600 MWe supercritical down-fired boiler. Based on the present design dimensionless upper furnace height CH2 = 0.864, upper furnace was lengthened in turn to CH2 = 1.00, 1.125, and 1.263 so as to form four comparable settings. Accordingly, cold-modeling gas/particle Flow experiments and numerical simulations on coal combustion were performed at these settings for confirming the solution and meanwhile recommending a reasonable CH2 setup. Moreover, real-furnace measurements, used to confirm the numerical simulation validity, were carried out under normal full load. Results at the design setting (CH2 = 0.864) show shat a severely deflected gas/particle Flow field appears, with (i) the downward gas/particle Flow penetrating much deeper in the front-half side than in the rear-half side and (ii) the upward Flow fully deflecting towards the front-half side. Consequently, a bad asymmetric combustion pattern with gas temperatures being much higher in the rear-half side than in the front-half side (temperature gap reaching about 300–600 °C) develops, generating poor burnout and high NOx emissions. Additionally, the simulated results are consistent well with the acquired real-furnace data. In comparison with cold-modeling gas/particle Flow experiments, the simulated downward gas/particle Flow penetrates clearly shallower in a hot environment. Lengthening upper furnace apparently weakens both the experimental and simulated Flow-field Deflection and meanwhile improves the asymmetric gas velocity distribution in the upper furnace. As CH2 increases to 1.125 and 1.263, both the experimental and simulated Flow-field symmetries are acceptable, accompanied by symmetrical gas velocity distribution in the upper furnace, improved burnout rate, and lowered NOx emissions. A comprehensive consideration of symmetrical combustion, high burnout rate, relatively low NOx emissions, and controlled cost for lengthening upper furnace suggests that a reasonable CH2 should be set at 1.125.
Paul J K Bruce - One of the best experts on this subject based on the ideXlab platform.
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confinement effects on regular irregular transition in shock wave boundary layer interactions
Journal of Fluid Mechanics, 2018Co-Authors: Ilan J Grossman, Paul J K BruceAbstract:An oblique shock wave is generated in a Mach 2 Flow at a Flow Deflection angle of $12^{\circ }$ . The resulting shock-wave–boundary-layer interaction (SWBLI) at the tunnel wall is observed. A novel traversable shock generator allows the position of the SWBLI to be varied relative to a downstream expansion fan. The relationship between the SWBLI, the expansion fan and the wind tunnel arrangement is studied. Schlieren photography, surface oil Flow visualisation, particle image velocimetry and high-spatial-resolution wall pressure measurements are used to investigate the Flow. It is observed that stream-normal movement of the shock generator downwards (towards the floor and hence the point of shock reflection) is accompanied by (1) growth in the streamwise extent of the shock-induced boundary layer separation, (2) upstream movement of the shock-induced separation point while the reattachment point remains nearly fixed, (3) an increase in separation shock strength and (4) transition between regular and irregular (Mach) reflection without an increase in incident shock strength. The role of free interaction theory in defining the separation shock angle is considered and shown to be consistent with the present measurements over a short streamwise extent. An SWBLI representation is proposed and reasoned which explains the apparent increase in separation shock strength that occurs without an increase in incident shock strength.