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41.
Aerodynamic performance of an annular cascade of film cooled nozzle guide vanes under engine representative conditions 总被引:1,自引:0,他引:1
This paper addresses two important issues relevant to efficiency measurements in film-cooled annular cascades: the definition
of the ideal flow to be used in loss calculation, and the measurements that are necessary for such loss calculation. The paper
also addresses the question of the correct parameterisation of coolant density effects, showing that the momentum flux ratio,
rather than the blowing rate, is the most appropriate parameter.
Experiments examining the effect of extensive aerofoil surface film cooling on the aerodynamic efficiency of an annular cascade
of transonic nozzle guide vanes are reported. A dense foreign gas (SF6/Ar mixture) is used to simulate engine representative coolant-to-mainstream density ratios, momentum ratios and blowing rates
under ambient temperature conditions. Experiments are also conducted with air coolant to study the effect of density ratio
on efficiency. The flowfield measurements have been obtained using a four-hole pyramid probe in a short duration blowdown
facility which correctly models engine Reynolds and Mach numbers.
This work compares the measured aerodynamic efficiencies of uncooled vanes with those which employ an extensive amount of
cooling. The engine-representative cooling geometry investigated features 14 rows of cylindrical cooling holes, and a second
geometry where 8 of these rows are replaced by holes having a fan-shaped exit. The effects of adding trailing edge slot ejection
are also presented. By selectively blocking rows of holes, the cumulative effect on the mid-span efficiency of adding rows
of cooling holes has also been determined.
Experimental results are presented as area traverse maps (total pressure, isentropic Mach number and flow angles), from which
the relative changes in efficiency due to film cooling have been calculated. These calculations reveal that the presence of
foreign-gas coolant from the cylindrical-hole geometry increases the aerodynamic loss (relative to the uncooled baseline)
by 6.7%; and coolant from the fan-shaped holes increases the loss by 15%. The effects of different assumptions for the coolant
total pressure are shown to significantly change the measured loss; if the loss measurements are based on the mainstream total
pressure, rather than the total pressure in the coolant cavity, the respective increase in loss (relative to the uncooled
baseline) of cylindrical and fan-shaped holes is 4.5% and 12.5%. Experimental data is compared with loss predictions using
a Hartsel model.
Received: 4 December 1998/Accepted: 1 September 1999 相似文献
42.
43.
44.
Inside Cover: Interfacial Nanoprecipitation toward Stable and Responsive Microbubbles and Their Use as a Resuscitative Fluid (Angew. Chem. Int. Ed. 5/2018) 下载免费PDF全文
45.
46.
Silveira PC da Silva LA Tromm PT Scheffer Dda L de Souza CT Pinho RA 《Ultrasonics》2012,52(5):650-654
Introduction
The aim of the study was to evaluate the effects of TPU together with DMSO on oxidative stress parameters after eccentric exercise.Methods
Thirty and six animals were divided in control; eccentric exercise (EE); EE + saline gel 0.9%; EE + TPU 0.8 W/cm2; EE + DMSO gel; EE + TPU + DMSO gel and submitted to one 90-min downhill run (1.0 km h−1). TPU was used 2, 12, 24, 46 h after exercise session and 48 h after the animals were killed and the gastrocnemius muscles were surgically removed. Production of superoxide anion, creatine kinase (CK) levels, lipoperoxidation, carbonylation, and antioxidants enzymes were analyzed.Results
Showed that TPU and gel-DMSO improved muscle healing. Moreover, superoxide anion production, TBARS level and protein carbonyls levels, superoxide dismutase and catalase activity were all decreased in the group TPU plus gel-DMSO.Discussion
Our results show that DMSO is effective in the reduction of the muscular lesion and in the oxidative stress after eccentric exercise only when used with TPU. 相似文献47.
Ohne Zusammenfassung 相似文献
48.
Christensen M Lock N Overgaard J Iversen BB 《Journal of the American Chemical Society》2006,128(49):15657-15665
Comprehensive single-crystal structural investigations of n- and p-type Ba8Ga16Ge30 have been carried out using multitemperature neutron and conventional X-ray diffraction as well as resonant synchrotron X-ray diffraction. The data show that the guest atom positions and dynamics are very similar in the two structures, although the barium atoms are slightly more displaced from the cage centers in the p-type structure than in the n-type structure (Deltad = 0.025 A). For both structures Fourier difference maps calculated from very high-resolution neutron diffraction data (sin theta/lambda > 2 A-1) show that the Ba nuclear density at lowest temperatures (15 K) is distributed in a torus around the crystallographic 6d site with maxima in the 24j positions. At room temperature the maxima have shifted to the 24k position. Analysis of atomic displacement parameters give Einstein temperatures of approximately 60(1) K for both structures. Thus, the fundamental difference in the low temperature thermal conductivity observed for p- and n-type Ba8Ga16Ge30 appear not to be directly related to the guest atom behavior as is commonly assumed in thermoelectric research. The neutron data and the resonant synchrotron X-ray data facilitate refinement of Ga/Ge framework occupancies. The Ga atoms have a clear preference for the 6c site with the preference being somewhat stronger for the n-type structure. 相似文献
49.
Spiral morphology-dependent resonances have been observed in a tilted optical fiber. The polarization-preserving and the cross-polarized elastic-scattering spectra for plane-wave illumination show that the wavelengths of the resonances are blueshifted quadratically as the fiber tilt angle increases. When a focused Gaussian beam illuminates the fiber at its edge, the resonances are blueshifted and broadened as the detector is offset from the scattering plane with the maximum scattering intensity. The blueshift with focused beam illumination is also a consequence of the spiral resonances. 相似文献
50.
The title compound (1) was prepared from chlorodimesitylsilyl-2,4,6-tri-tert-butyl-phenylphosphine (4) with n-butyllithium and characterized by its spectral data and by its chemical conversion with methanol to the adduct 6. 相似文献