Parametric studies of the acoustic behavior of lined ducts and duct lining materials for turbofan engine applications

Flow-duct test facility data on acoustic behavior of lined ducts and duct-lining materials for turbojet engine application

Development of acoustically lined ejector technology for multitube jet noise suppressor nozzles by model and engine tests over a wide range of jet pressure ratios and temperatures

An experimental program comprising model nozzle and full-scale engine tests was undertaken to acquire parametric data for acoustically lined ejectors applied to primary jet noise suppression. Ejector lining design technology and acoustical scaling of lined ejector configurations were the major objectives. Ground static tests were run with a J-75 turbojet engine fitted with a 37-tube, area ratio 3.3 suppressor nozzle and two lengths of ejector shroud (L/D = 1 and 2). Seven ejector lining configurations were tested over the engine pressure ratio range of 1.40 to 2.40 with corresponding jet velocities between 305 and 610 M/sec. One-fourth scale model nozzles were tested over a pressure ratio range of 1.40 to 4.0 with jet total temperatures between ambient and 1088 K. Scaling of multielement nozzle ejector configurations was also studied using a single element of the nozzle array with identical ejector lengths and lining materials. Acoustic far field and near field data together with nozzle thrust performance and jet aerodynamic flow profiles are presented

Refraction of sound by jet flow or jet temperature

Refraction of sound by jet flow or jet temperatur

Improving the electroluminescence of [Zn(salophen)(OH2)] in polyfluorene-based light-emitting diode: the role of energy transfer and charge recombination

Combining two or more different compounds with advantageous properties has been a useful and straightforward strategy in achieving a new class of materials with improved physical properties. This has been especially true for electronic polymers, whose optoelectronic properties can be completely tuned, and even improved, when mixed with other polymeric materials, dye molecules and guest coordination compounds. Here, a light-emitting diode prepared with the conjugated polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(9,9-di-{5'-pentanyl}-fluorenyl-2,7-diyl)] (PFOFPen) as the host material and aquo[N,N'-bis(salicylidene)-o-phenylenediamine]zinc(II) ([Zn(salophen)(OH2)]) as the guest molecule was studied in terms of its photo and electroluminescence properties. The role of the ZnII coordination compound as a guest in the electroluminescence is discussed as a strategy for the improvement of the electroluminescence performance of coordination compounds using conjugated polymers as matrices. An additional advantage of these composites is that they are solution processable, a low-cost and time efficient alternative to vacuum vapor deposition. Additionally, the photophysical processes involved in both electroluminescence and photoluminescence emissions are discussed because they are markedly different.Combining two or more different compounds with advantageous properties has been a useful and straightforward strategy in achieving a new class of materials with improved physical properties. This has been especially true for electronic polymers, whose opt272295302FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO2013/16245-2470529/2012-1The authors acknowledge FAPESP (2013/16245-2), CNPq (470529/2012-1), National Institute of Organic Electronics (INEO) (MCT/CNPq/FAPESP) and UNICAMP/FAEPEX for financial support and fellowship

Experimental and Computational Investigation of an “Open” Transonic Cavity Flow

This paper presents an investigation of a transonic flow (M∞ = 0.85) over a rectangular cavity having a length-to-depth ratio of 5. Velocities were measured inside the cavity on the central plane and two off-centre planes using a two-component particle image velocimetry system. These measurements were supported by surface flow visualisation, and mean and time-varying surface pressure measurements. The flow was also simulated using an unsteady Reynolds-averaged Navier Stokes code, with a realizable κ− ε turbulence model. It is shown that this CFD model does not capture all the characteristics of the flow field correctly. However, by using this integrated experimental and computational approach we have been able to identify three-dimensional flow field structures within the cavity. The influence of the thickness of the approaching boundary layer is discussed

Host/guest simulation of fluorescent probes adsorbed into low-density polyethylene, 1 - Excimer formation of 1,3-Di(1-pyrenyl)propane

Molecular dynamics and Rotational Isomer State/Monte Carlo techniques with a Dreiding 1.01 Force Field are employed to study the excimer formation of isolated 1,3-di(1-pyrenyl)propane and the probe adsorbed into a low-density polyethylene (LDPE) matrix model. The probability of formation of each molecular conformer at several temperatures was calculated using these theoretical techniques. Conformational statistical analysis of the four torsion angles (phi (1), phi (2), theta (1), theta (2)) of Py3MPy showed that the angles -C-C-ar- (phi (1), phi (2)) present two states c(+/-) = +/- 90 degrees; and the angles -C-C- (theta (1), theta (2)), the three trans states = 180 degrees, g(+/-) = +/- 60 degrees. The correlation of theta (1)-theta (2) torsion angles showed that the most probable pairs were g(+)g(-) and g(-)g(+) for the excimer-like specimens, although these angles are distorted because of interactions with the polymer matrix. The temperature dependence of the excimer-formation probability revealed that this process was thermodynamically controlled in the isolated case. When the probe was adsorbed into the LDPE matrix, the excimer formation process was reversed at T = 375 K. At T > 375 K, the behavior was similar to the isolated case but, at T < 375 K, excimer formation probability increased with temperature as found experimentally by steady-state fluorescence spectroscopy. This temperature was coincident with the onset of the LDPE melting process, determined experimentally by thermal analysis. [GRAPHICS] Initial structures of Py3MPy (top) and of LDPE (bottom).10980881

A Luminescence Study Of Microstructure Development And Melting/crystallization Processes In Low Density Polyethylene (ldpe)

Pyrene, a fluorescent probe, was inserted in low density polyethylene and the emission spectrum was recorded during a cooling cycle from 150°C to -100°C and during isothermal crystallization at 105°C. Analysis of the temperature dependence of the fluorescence band at 365.5 nm reveals that, during dynamic crystallization, excited pyrene couples with vibrations which may correspond to crystalline defects. It was also found that pyrene emission increases about 10-fold during the final steps of the crystallization process, indicating that the interfacial cavity in which pyrene becomes lodged restricts its mobility. © 1998 Elsevier Science B.V. All rights reserved.235-237554558Vigil, M.R., Bravo, J., Atvars, T.D.Z., Baselga, J., (1997) Macromolecules, 30, p. 4871Mandelkern, L., Physical properties of polymers (1993) ACS Prof. Ref. Book, , Washington, DC, ch. 4Bershtein, V.A., Egorov, V.M., (1994) Differential Scanning Calorimetry of Polymers, p. 65. , Ellis Horwood, Chichester, UKKoenig, J.L., Spectroscopy of polymers (1991) ACS Prof. Ref. Book, p. 37Painter, P., Coleman, M., Koenig, J.L., (1982) Theory of Vibrational Spectroscopy and Its Applications to Polymeric Materials, , Wiley, New YorkSerrano, B., Levenfeld, B., Bravo, J., Baselga, J., (1996) Polym. Eng. Sci., 36, p. 175Becker, R.S., (1968) Theory and Interpretation of Fluorescence and Phosphorescence, , Wiley, New YorkCanpolat, M., Pekcan, Ö., (1996) J. Polym. Sci., Polym. Phys. Ed., 34, p. 69

Photochemical sensing of semicrystalline morphology in polymers: Pyrene in polyethylene

Pyrene was inserted into a low-density polyethylene matrix. Fluorescence spectra as a function of temperature and the differential scanning calorimetry (DSC) trace were recorded simultaneously. Along with the usual vibronic bands, a low-intensity band at 365 nm appears at higher energies with respect to the 0-0 transition in the pyrene fluorescence spectra. The fluorescence intensity of this small band increased with temperature, and an isoemissive point was observed to occur at 368 nm. This emission was interpreted as arising from pyrene molecules located in the outer rigid interfacial region of polymer crystallites. Its temperature-dependent fluorescence was interpreted in terms of electron-phonon coupling; two phonons which coincide with fundamental vibrations of polyethylene were necessary to fit experimental data. Coupling with a high-energy phonon was possible at low temperature, whereas, above the beta relaxation temperature, phonon coupling occurs with a lower-energy phonon. The a relaxation was detected as a maximum in fluorescence intensity since above its characteristic temperature, nonradiative processes begin to operate.30174871487