3,482 research outputs found
Analysis of swirling flow in hydrocyclones operating under dense regime
There are many circumstances where hydrocyclone performance and dense flow are intertwined, such as for example when feed solids flow exceeds hydrocyclone capacity during continuous operations. The work reported here, which is part of an ongoing research effort to develop a robust CFD model for prediction of hydrocyclone performance, focuses on hydrocyclone operation under high solids concentration. The paper presents the basic physics framework that accounts for solidâliquid and solidâsolid interactions under hydrocycloneâs swirling flow. Operating conditions that are past the transition from spray to rope regime are deliberately chosen for this purpose. Model predictions are validated by comparison with solids split and separation curves measured on a 100 mm diameter hydrocyclone. CFD model predictions permit taking an insightful look at the inside of a hydrocyclone under extreme operating conditions, which would be difficult to achieve experimentally. Velocity profiles, G-force distribution and distribution of solids predicted by CFD are bound to lead to a better understanding of the separation that takes place inside a hydrocyclone, which may eventually help improve hydrocyclone design and performance
Mechanistic modelling of water partitioning behaviour in hydrocyclone
A new mechanistic model on water split behaviour in a hydrocyclone has been developed based on the convoluted hydrodynamics of swirling flows in a confined environment. A comprehensive study has been accomplished on the genesis and subsequent distribution of G force based on the characterization of internal flow features of a 2 in hydrocyclone through computational fluid dynamics (CFD) approach. The difference between the magnitude of G force in cylindrical and spigot regions is taken into account as a new hydrodynamic parameter to compute the water split behaviour. Specifically, our analysis reveals a semi-empirical relationship between the water split with G force difference (ÎG), the vortex finder diameter (Dvf) and the spigot diameter (Dsp). The developed model is validated against experimental data and show good prediction accuracy. Unique aspect of the developed empirical model is that the underlying mechanism of incipient flow peculiarity is implicitly accounted to rummage the separation characteristics in a quantifiable manner. In addition to rationalize the flow split behaviour of hydrocyclones, this new hydrodynamic indicator seems promising to be used as a scale-up parameter in envisaging the separation performance for a given application
Performance monitoring of a hydrocyclone based on underflow discharge angle
The performance of a hydrocyclone as a separation device is never perfect and rigorous research efforts are still continuing along various directions towards achieving optimum solutions. The modus operandi of performance optimization is important for quick and non-invasive monitoring of hydrocyclone performance. Therefore, in the present study, an application potential of spray angle as a performance monitoring tool has been explored to investigate the operation state of a hydrocyclone. In this context, phenomenological features of spray discharge over a wide range of injection pressure and feed solid concentration have been investigated. The emphasis of the present study is to verse the amendment of the hydrocyclone operational state with the corresponding change in underflow discharge pattern. The pattern of the underflowdischarge profilewas captured using a digital camera and analyzed based on an image processing algorithm to detect the discharge angle under different operating and design conditions. Stability and reproducibility of the spray angle at fixed operating condition have also been confirmed. Subsequent analysis shows that the spray angle is sensitive to variations of operating and design variables. More specifically the effect of feed slurry concentration has been characterized and is of major importance for the transition to roping. On this basis, an attempt has also been made to develop an empirical correlation based on experimental data. The developed correlation shows that the discharge angle could possibly be used as a reliable tool to monitor hydrocyclone performance
The CMS Outer Hadron Calorimeter
The CMS hadron calorimeter is a sampling calorimeter with brass absorber and plastic scintillator tiles with wavelength shifting fibres for carrying the light to the readout device. The barrel hadron calorimeter is complemented with a outer calorimeter to ensure high energy shower containment in CMS and thus working as a tail catcher. Fabrication, testing and calibrations of the outer hadron calorimeter are carried out keeping in mind its importance in the energy measurement of jets in view of linearity and resolution. It will provide a net improvement in missing \et measurements at LHC energies. The outer hadron calorimeter has a very good signal to background ratio even for a minimum ionising particle and can hence be used in coincidence with the Resistive Plate Chambers of the CMS detector for the muon trigger
Measurements of branching fraction ratios and CP-asymmetries in suppressed B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^- decays
We report the first reconstruction in hadron collisions of the suppressed
decays B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^-, sensitive to the
CKM phase gamma, using data from 7 fb^-1 of integrated luminosity collected by
the CDF II detector at the Tevatron collider. We reconstruct a signal for the
B^- -> D(-> K^+ pi^-)K^- suppressed mode with a significance of 3.2 standard
deviations, and measure the ratios of the suppressed to favored branching
fractions R(K) = [22.0 \pm 8.6(stat)\pm 2.6(syst)]\times 10^-3, R^+(K) =
[42.6\pm 13.7(stat)\pm 2.8(syst)]\times 10^-3, R^-(K)= [3.8\pm 10.3(stat)\pm
2.7(syst]\times 10^-3, as well as the direct CP-violating asymmetry A(K) =
-0.82\pm 0.44(stat)\pm 0.09(syst) of this mode. Corresponding quantities for
B^- -> D(-> K^+ pi^-)pi^- decay are also reported.Comment: 8 pages, 1 figure, accepted by Phys.Rev.D Rapid Communications for
Publicatio
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
Constraints on the Ď_(c1) versus Ď_(c2) polarizations in proton-proton collisions at âs = 8 TeV
The polarizations of promptly produced Ď_(c1) and Ď_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at âs=8ââTeV. The Ď_c states are reconstructed via their radiative decays Ď_c â J/ĎÎł, with the photons being measured through conversions to eâşeâť, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the Ď_(c2) to Ď_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/Ď â ÎźâşÎźâť decay, in three bins of J/Ď transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
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