810 research outputs found
ВЛИЯНИЕ РАЗЛИЧНЫХ ВАРИАНТОВ ЛОПАСТЕЙ НЕСУЩЕГО ВИНТА НА Х-ОБРАЗНЫЙ РУЛЕВОЙ ВИНТ ВЕРТОЛЕТА
This paper describes the effect of different rotor blades on the X-shaped tail rotor of the Mi-171 LL, observed conducting flight tests. The tests were carried out on the same helicopter in the similar atmospheric conditions.The objective of the tests was the comparison of flight performance of two sets of rotor blades of the helicopter Mi-171 LL. However, materials test revealed a difference in the angles of the tail rotor at different MRs with the same takeoff weight.The authors are grateful to I.G. Peskov, S.R. Zamula and A.I. Orlov for assistance in carrying out this work and the preparation of this article.Noted that the helicopter takeoff weight when hovering out of ground effect in ISA with blades from polymer composite materials (PCM) exceeds the takeoff weight of the helicopter with the serial blades in the nominal mode of the engine operation at ~ 750kg, in the takeoff mode at ~ 700kg.Knowing the altitude and climatic characteristics of the engine, the obtained dependence allows to determine the balancing value of jрв on hovering at different combinations of pressure altitude and outside air temperature for a given speed of the main rotor (MR).It follows from the work that when the same value Nпр(95/nнвпр)3 or Nfact the balancing values of jрв for the helicopter with the main rotor blades from the PCM is less than for the helicopters with serial blades by 0.5…0.9°. The difference in the angles of the tail rotor increases with growing of Nепр(95/nнвпр)3 (Nfact). Perhaps this is caused by different induction effect of the main rotor on the tail rotor to the MR from PCM and the serial ones.As follows from the materials, the thrust of the main rotor with blades from PCM with the same engine power is more in comparison with the serial blades. Consequently inductive speeds of the main rotor are more and the angles of the tail rotor are less. It can be assumed that a large induced velocity of the main rotor increases the thrust of X-shaped tail rotor.В настоящей работе описывается влияние различных лопастей несущего винта на Х-образный рулевой винт вертолета Ми-171 ЛЛ, замеченное при проведении летных испытаний. Испытания проводились на одном и том же вертолете в близких атмосферных условиях.Задачей испытаний ставилось сравнение летно-технических характеристик двух комплектов лопастей несущего винта вертолета Ми-171 ЛЛ. Однако при обработке материалов испытаний было выявлено отличие в углах установки рулевого винта при различных несущих винтах с одинаковыми взлетными массами.Отмечено, что взлетная масса вертолета при висении вне влияния земли в условиях международной стандартной атмосферы с лопастями из композиционных материалов превышает взлетную массу вертолета с серийными лопастями на номинальном режиме работы двигателей на ~ 750 кг, на взлетном – на ~ 700 кг.Полученная в работе зависимость позволяет, зная высотно-климатические характеристики двигателя, определить балансировочное значение jрв на режиме висения при различных сочетаниях барометрической высоты и температуры наружного воздуха для заданных оборотов несущего винта.Из материалов работы следует, что при одном и том же значении Nпр (95/nнвпр)3 или Nфакт балансировочные значения jрв для вертолета с лопастями несущего винта из композиционных материалов меньше, чем для вертолета с серийными лопастями несущего винта на 0,5…0,9°. При этом разница в углах установки рулевого винта увеличивается с увеличением величины Nепр (95/nнвпр)3 (Nфакт). Возможно, это вызвано различным влиянием индукции от несущего винта на рулевой винт для лопастей несущего винта из композиционных материалов и серийных.Как следует из материалов, тяга несущего винта с лопастями несущего винта из композиционных материалов при одинаковой мощности двигателей больше, по сравнению с серийным, следовательно, больше индуктивные скорости от несущего винта. При этом углы установки рулевого винта меньше. Можно предположить, что большая индуктивная скорость от несущего винта увеличивает тягу Х-образного рулевого винта
Observation of direct-photon collective flow in sqrt(s_NN)=200 GeV Au+Au collisions
The second Fourier component v_2 of the azimuthal anisotropy with respect to
the reaction plane was measured for direct photons at midrapidity and
transverse momentum (p_T) of 1--13 GeV/c in Au+Au collisions at sqr(s_NN)=200
GeV. Previous measurements of this quantity for hadrons with p_T < 6 GeV/c
indicate that the medium behaves like a nearly perfect fluid, while for p_T > 6
GeV/c a reduced anisotropy is interpreted in terms of a path-length dependence
for parton energy loss. In this measurement with the PHENIX detector at the
Relativistic Heavy Ion Collider we find that for p_T > 4 GeV/c the anisotropy
for direct photons is consistent with zero, as expected if the dominant source
of direct photons is initial hard scattering. However, in the p_T < 4 GeV/c
region dominated by thermal photons, we find a substantial direct photon v_2
comparable to that of hadrons, whereas model calculations for thermal photons
in this kinematic region significantly underpredict the observed v_2.Comment: 384 authors, 6 pages, 3 figures, and 1 table. Submitted to Phys. Rev.
Lett. v2 has minor changes to match the submission version. Plain text data
tables for the points plotted in the figures are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/info/data/ppg126_data.htm
Azimuthal anisotropy of neutral pion production in Au+Au collisions at sqrt(s_NN) = 200 GeV: Path-length dependence of jet quenching and the role of initial geometry
We have measured the azimuthal anisotropy of pi0's for 1 < pT < 18 GeV/c for
Au+Au collisions at sqrt s_NN = 200 GeV. The observed anisotropy shows a
gradual decrease in 3 < pT < 7 - 10 GeV/c, but remains positive beyond 10
GeV/c. The magnitude of this anisotropy is under-predicted, up to at least 10
GeV/c, by current perturbative QCD (pQCD) energy-loss model calculations. An
estimate of the increase in anisotropy expected from initial-geometry
modification due to gluon saturation effects and initial-geometry fluctuations
is insufficient to account for this discrepancy. Calculations which implement a
path length dependence steeper than what is implied by current pQCD energy-loss
models, show reasonable agreement with the data.Comment: 384 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Azimuthal anisotropy of pi^0 and eta mesons in Au+Au collisions at sqrt(s_NN)=200 GeV
The azimuthal anisotropy coefficients v_2 and v_4 of pi^0 and eta mesons are
measured in Au+Au collisions at sqrt(s_NN)=200 GeV, as a function of transverse
momentum p_T (1-14 GeV/c) and centrality. The extracted v_2 coefficients are
found to be consistent between the two meson species over the measured p_T
range. The ratio of v_4/v_2^2 for pi^0 mesons is found to be independent of p_T
for 1-9 GeV/c, implying a lack of sensitivity of the ratio to the change of
underlying physics with p_T. Furthermore, the ratio of v_4/v_2^2 is
systematically larger in central collisions, which may reflect the combined
effects of fluctuations in the initial collision geometry and finite viscosity
in the evolving medium.Comment: 384 authors, 71 institutions, 11 pages, 9 figures, and 2 tables.
Submitted to Physical Review C. Plain text data tables for the points plotted
in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Measurement of higher cumulants of net-charge multiplicity distributions in AuAu collisions at GeV
We report the measurement of cumulants () of the net-charge
distributions measured within pseudorapidity () in AuAu
collisions at GeV with the PHENIX experiment at the
Relativistic Heavy Ion Collider. The ratios of cumulants (e.g. ,
) of the net-charge distributions, which can be related to volume
independent susceptibility ratios, are studied as a function of centrality and
energy. These quantities are important to understand the quantum-chromodynamics
phase diagram and possible existence of a critical end point. The measured
values are very well described by expectation from negative binomial
distributions. We do not observe any nonmonotonic behavior in the ratios of the
cumulants as a function of collision energy. The measured values of and can be directly compared to lattice
quantum-chromodynamics calculations and thus allow extraction of both the
chemical freeze-out temperature and the baryon chemical potential at each
center-of-mass energy.Comment: 512 authors, 8 pages, 4 figures, 1 table. v2 is version accepted for
publication in Phys. Rev. C as a Rapid Communication. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Cross sections and double-helicity asymmetries of midrapidity inclusive charged hadrons in p+p collisions at sqrt(s)=62.4 GeV
Unpolarized cross sections and double-helicity asymmetries of
single-inclusive positive and negative charged hadrons at midrapidity from p+p
collisions at sqrt(s)=62.4 GeV are presented. The PHENIX measurements for 1.0 <
p_T < 4.5 GeV/c are consistent with perturbative QCD calculations at
next-to-leading order in the strong coupling constant, alpha_s. Resummed pQCD
calculations including terms with next-to-leading-log accuracy, yielding
reduced theoretical uncertainties, also agree with the data. The
double-helicity asymmetry, sensitive at leading order to the gluon polarization
in a momentum-fraction range of 0.05 ~< x_gluon ~< 0.2, is consistent with
recent global parameterizations disfavoring large gluon polarization.Comment: PHENIX Collaboration. 447 authors, 12 pages, 5 figures, 5 tables.
Submitted to Physical Review
Systematic study of charged-pion and kaon femtoscopy in AuAu collisions at =200 GeV
We present a systematic study of charged pion and kaon interferometry in
AuAu collisions at =200 GeV. The kaon mean source radii
are found to be larger than pion radii in the outward and longitudinal
directions for the same transverse mass; this difference increases for more
central collisions. The azimuthal-angle dependence of the radii was measured
with respect to the second-order event plane and similar oscillations of the
source radii were found for pions and kaons. Hydrodynamic models qualitatively
describe the similar oscillations of the mean source radii for pions and kaons,
but they do not fully describe the transverse-mass dependence of the
oscillations.Comment: 499 authors, 27 pages, 13 figures, and 11 tables. v2 is the version
accepted for publication in Phys. Rev. C. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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