Estimation of Steam Turbine Shafts Fatigue Damage Caused by Torsional Vibrations

В Україні 74 енергоблоки потужністю 150-800 МВт теплових електростанцій із 102 перебувають на межі перевищення паркового ресурсу (220 тис. Годин). З них 17 енергоблоків наближаються до кінця ресурсу парку, а 11 енергоблоків досягли передбачуваного ресурсу (100 тис. Годин). Статистика аварій на електростанціях у різних країнах показує, що більшість з них спричинені тривалим накопиченням збитків від втоми. Серед основних причин пошкодження втоми - пульсація високотемпературних потоків пари в циліндрах турбіни, поперечні та крутильні коливання валів при тривалій експлуатації тощо. Це обумовлює розробку обчислювальних та експериментальних методів визначення втомних пошкоджень вали турбінних установок при динамічних навантаженнях. Оцінка втомних пошкоджень вала парової турбіни К-200-130 базується на 3D-моделі кінцевих елементів. Розрахунки враховують експериментально визначені втомні властивості роторної сталі. Розраховано втомну пошкодження в результаті крутильних коливань валу турбіни, спричинених аномальною роботою турбінного генератора. Зони концентрації напружень в обертових елементах парової турбіни типу К-200-130 встановлені для різних режимів роботи. Запропоновано процедуру прогнозування впливу втоми від пошкоджень на розрахунковий ресурс турбінного агрегату.In Ukraine, 74 power units with a capacity of 150-800 MW of thermal power plants out of 102 are on the verge of exceeding the park resource (220 thousand hours). Of these, 17 power units are close to the end the park resource, and 11 units have reached their estimated resource (100 thousand hours). Statistics of power plants accidents in different countries indicates that most of them are caused by the long term accumulation of fatigue damage. Among the main causes of fatigue damage are the pulsating of high-temperature steam flows in the turbine cylinders, transverse and torsional vibrations of shafts during long-term operation etc. This causes the development of computational and experimental methods for the determination of fatigue damage of turbine units’ shafts under dynamic loads. The evaluation of fatigue damage of steam turbine K-200-130 shaft is based on the 3D finite element model. The calculations take into account experimentally determined fatigue properties of rotor steel. The fatigue damage as a result of torsional vibrations of turbine shaft caused by the abnormal operation of turbine generator is calculated. Zones of stress concentration in the rotating elements of the steam turbine type K-200-130 are established for various operating modes. The procedure to predict the effect of fatigue damage on the estimated resource of turbine unit is proposed.В Украине 74 энергоблока мощностью 150-800 МВт тепловых электростанций из 102 находятся на грани превышения ресурса парка (220 тыс. Часов). Из них 17 энергоблоков близки к исчерпанию ресурса парка, а 11 энергоблоков вышли на расчетный ресурс (100 тыс. Часов). Статистика аварий на электростанциях в разных странах показывает, что большинство из них вызвано длительным накоплением усталостных повреждений. Среди основных причин усталостных повреждений - пульсации высокотемпературных потоков пара в цилиндрах турбины, поперечные и крутильные колебания валов при длительной эксплуатации и т. Д. Это вызывает развитие расчетных и экспериментальных методов определения усталостных повреждений. валы турбоагрегатов при динамических нагрузках. Оценка усталостных повреждений вала паровой турбины К-200-130 проводится на основе трехмерной конечно-элементной модели. В расчетах учтены экспериментально определенные усталостные свойства роторной стали. Рассчитано усталостное повреждение в результате крутильных колебаний вала турбины, вызванных ненормальной работой турбогенератора. Установлены зоны концентрации напряжений во вращающихся элементах паровой турбины типа К-200-130 для различных режимов работы. Предложена методика прогнозирования влияния усталостных повреждений на расчетный ресурс турбоагрегата

Long term time variability of cosmic rays and possible relevance to the development of life on Earth

An analysis is made of the manner in which the cosmic ray intensity at Earth has varied over its existence and its possible relevance to both the origin and the evolution of life. Much of the analysis relates to the 'high energy' cosmic rays ($E>10^{14}eV;=0.1PeV$) and their variability due to the changing proximity of the solar system to supernova remnants which are generally believed to be responsible for most cosmic rays up to PeV energies. It is pointed out that, on a statistical basis, there will have been considerable variations in the likely 100 My between the Earth's biosphere reaching reasonable stability and the onset of very elementary life. Interestingly, there is the increasingly strong possibility that PeV cosmic rays are responsible for the initiation of terrestrial lightning strokes and the possibility arises of considerable increases in the frequency of lightnings and thereby the formation of some of the complex molecules which are the 'building blocks of life'. Attention is also given to the well known generation of the oxides of nitrogen by lightning strokes which are poisonous to animal life but helpful to plant growth; here, too, the violent swings of cosmic ray intensities may have had relevance to evolutionary changes. A particular variant of the cosmic ray acceleration model, put forward by us, predicts an increase in lightning rate in the past and this has been sought in Korean historical records. Finally, the time dependence of the overall cosmic ray intensity, which manifests itself mainly at sub-10 GeV energies, has been examined. The relevance of cosmic rays to the 'global electrical circuit' points to the importance of this concept.Comment: 18 pages, 5 figures, accepted by 'Surveys in Geophysics

Search for CP violation in D+→ϕπ+ and D+s→K0Sπ+ decays

A search for CP violation in D + → ϕπ + decays is performed using data collected in 2011 by the LHCb experiment corresponding to an integrated luminosity of 1.0 fb−1 at a centre of mass energy of 7 TeV. The CP -violating asymmetry is measured to be (−0.04 ± 0.14 ± 0.14)% for candidates with K − K + mass within 20 MeV/c 2 of the ϕ meson mass. A search for a CP -violating asymmetry that varies across the ϕ mass region of the D + → K − K + π + Dalitz plot is also performed, and no evidence for CP violation is found. In addition, the CP asymmetry in the D+s→K0Sπ+ decay is measured to be (0.61 ± 0.83 ± 0.14)%

Study of Bc+B_c^+ decays to the K+K−π+K^+K^-\pi^+ final state and evidence for the decay Bc+→χc0π+B_c^+\to\chi_{c0}\pi^+

A study of $B_c^+\to K^+K^-\pi^+$ decays is performed for the first time using data corresponding to an integrated luminosity of 3.0 $\mathrm{fb}^{-1}$ collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of $7$ and $8$ TeV. Evidence for the decay $B_c^+\to\chi_{c0}(\to K^+K^-)\pi^+$ is reported with a significance of 4.0 standard deviations, resulting in the measurement of $\frac{\sigma(B_c^+)}{\sigma(B^+)}\times\mathcal{B}(B_c^+\to\chi_{c0}\pi^+)$ to be $(9.8^{+3.4}_{-3.0}(\mathrm{stat})\pm 0.8(\mathrm{syst}))\times 10^{-6}$. Here $\mathcal{B}$ denotes a branching fraction while $\sigma(B_c^+)$ and $\sigma(B^+)$ are the production cross-sections for $B_c^+$ and $B^+$ mesons. An indication of $\bar b c$ weak annihilation is found for the region $m(K^-\pi^+)<1.834\mathrm{\,Ge\kern -0.1em V\!/}c^2$, with a significance of 2.4 standard deviations.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-022.html, link to supplemental material inserted in the reference

Updated measurements of exclusive J/ψ and ψ(2S) production cross-sections in pp collisions at √s = 7 TeV

The differential cross-section as a function of rapidity has been measured for the exclusive production of J/ψ and ψ(2S) mesons in proton–proton collisions at √s = 7 TeV, using data collected by the LHCb experiment, corresponding to an integrated luminosity of 930 pb−1. The cross-sections times branching fractions to two muons having pseudorapidities between 2.0 and 4.5 are measured to be where the first uncertainty is statistical and the second is systematic. The measurements agree with next-to-leading order QCD predictions as well as with models that include saturation effects

Measurement of the Λb0, Ξb-, and Ωb- Baryon Masses

Bottom baryons decaying to a J/ψ meson and a hyperon are reconstructed using 1.0  fb-1 of data collected in 2011 with the LHCb detector. Significant Λb0→J/ψΛ, Ξb-→J/ψΞ- and Ωb-→J/ψΩ- signals are observed and the corresponding masses are measured to be M(Λb0)=5619.53±0.13(stat.)±0.45(syst.)  MeV/c2, M(Ξb-)=5795.8±0.9(stat.)±0.4(syst.)  MeV/c2, M(Ωb-)=6046.0±2.2(stat.)±0.5(syst.)  MeV/c2, while the differences with respect to the Λb0 mass are M(Ξb-)-M(Λb0)=176.2±0.9(stat.)±0.1(syst.)  MeV/c2, M(Ωb-)-M(Λb0)=426.4±2.2(stat.)±0.4(syst.)  MeV/c2. These are the most precise mass measurements of the Λb0, Ξb- and Ωb- baryons to date. Averaging the above Λb0 mass measurement with that published by LHCb using 35  pb-1 of data collected in 2010 yields M(Λb0)=5619.44±0.13(stat.)±0.38(syst.)  MeV/c2

First Measurement of the Charge Asymmetry in Beauty-Quark Pair Production

The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in b (b) over bar pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0 fb(-1) collected at 7 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the b (b) over bar system. The results obtained are A(C)(b (b) over bar) (40 10(5) GeV/c(2)) = 1.6 +/- 1.7 +/- 0.6%,where A(C)(b (b) over bar) is defined as the asymmetry in the difference in rapidity between jets formed from the beauty quark and antiquark, where in each case the first uncertainty is statistical and the second systematic. The beauty jets are required to satisfy 2 20 GeV, and have an opening angle in the transverse plane Delta phi > 2.6 rad. These measurements are consistent with the predictions of the standard model

Observation of B(s)0→J/ψpp¯ decays and precision measurements of the B(s)0 masses

The first observation of the decays B 0 ( s ) → J / ψ p ¯ p is reported, using proton-proton collision data corresponding to an integrated luminosity of 5.2     fb − 1 , collected with the LHCb detector. These decays are suppressed due to limited available phase space, as well as due to Okubo-Zweig-Iizuka or Cabibbo suppression. The measured branching fractions are B ( B 0 → J / ψ p ¯ p ) = [ 4.51 ± 0.40 ( stat ) ± 0.44 ( syst ) ] × 10 − 7 , B ( B 0 s → J / ψ p ¯ p ) = [ 3.58 ± 0.19 ( stat ) ± 0.39 ( syst ) ] × 10 − 6 . For the B 0 s meson, the result is much higher than the expected value of O ( 10 − 9 ) . The small available phase space in these decays also allows for the most precise single measurement of both the B 0 mass as 5279.74 ± 0.30 ( stat ) ± 0.10 ( syst )     MeV and the B 0 s mass as 5366.85 ± 0.19 ( stat ) ± 0.13 ( syst )     MeV

Measurement of the B0s →J/ψη lifetime

Using a data set corresponding to an integrated luminosity of 3 fb−1, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the Bs0→J/ψη decay mode, τeff, is measured to be τeff=1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τeff corresponds to the lifetime of the light Bs0 mass eigenstate. This is the first measurement of the effective lifetime in this decay mode

Observation of B+c → D0K+ decays

Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb−1, recorded by the LHCb detector at center-of-mass energies of 7 and 8 TeV, the B+ c → D0K+ decay is observed with a statistical significance of 5.1 standard deviations. By normalizing to B+ → D¯ 0π+ decays, a measurement of the branching fraction multiplied by the production rates for B+ c relative to B+ mesons in the LHCb acceptance is obtained, R D 0 K = ( f c / f u ) × B ( B + c → D 0 K + ) = ( 9. 3 + 2.8 − 2.5 ± 0.6 ) × 10 − 7, where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first B+ c decay of this nature to be observed