1114 A study on a vibration behavior of cruciform circular cylinders in a uniform flow : Analysis for flow field of downstream of cylinder

The present paper deals with oil droplet now phenomena in aero engine bearing chambers. An experimental investigation of droplet sizes and velocities utilizing a Phase Doppler Particle Analyzer (PDPA) has been performed for the first time in bearing chamber atmospheres under real engine conditions. Influences of high rotational speeds are discussed for individual droplet size classes. Although this is an important contribution to a better understanding of the droplet flow impact on secondary air/oil system performance, an analysis of the droplet flow behaviour requires an incorporation of numerical methods because detailed measurements as performed here suffer from both strong spatial limitations with respect to the optical accessibility in real engine applications and constraints due to the extremely time consuming nature of an experimental flow field analysis. Therefore, further analysis is based on numerical methods. Droplets characterized within the experiments are exposed to the flow field of the gaseous phase predicted by use of our well-known CFD code EPOS. The droplet trajectories and velocities are calculated within a Lagrangian frame of reference by forward numerical integration of the particle momentum equation. This paper has been initiated rather to show a successful method of bearing chamber droplet flow analysis by a combination of droplet sizing techniques and numerical approaches than to present field values as a function of all operating parameters. However, a first insight into the complex droplet flow phenomena is given and specific problems in bearing chamber heat transfer are related to the droplet flow.

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Influence of a Cylindrical Exhaust Hood Installation on the Last Stage Rotor Blades of a Low Pressure Model Steam Turbine

Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines ◽

10.1115/gt2017-63280 ◽

2017 ◽

Author(s):

Fabian F. Müller ◽

Markus Schatz ◽

Damian M. Vogt ◽

Jens Aschenbruck

Keyword(s):

Flow Field ◽

Steam Turbine ◽

Operating Conditions ◽

Rotor Blades ◽

Pressure Measurements ◽

Exhaust Hood ◽

Blade Vibration ◽

Time Resolved ◽

Vibration Behavior ◽

Last Stage

The influence of a cylindrical strut shortly downstream of the bladerow on the vibration behavior of the last stage rotor blades of a single stage LP model steam turbine was investigated in the present study. Steam turbine retrofits often result in an increase of turbine size, aiming for more power and higher efficiency. As the existing LP steam turbine exhaust hoods are generally not modified, the last stage rotor blades frequently move closer to installations within the exhaust hood. To capture the influence of such an installation on the flow field characteristics, extensive flow field measurements using pneumatic probes were conducted at the turbine outlet plane. In addition, time-resolved pressure measurements along the casing contour of the diffuser and on the surface of the cylinder were made, aiming for the identification of pressure fluctuations induced by the flow around the installation. Blade vibration behavior was measured at three different operating conditions by means of a tip timing system. Despite the considerable changes in the flow field and its frequency content, no significant impact on blade vibration amplitudes were observed for the investigated case and considered operating conditions. Nevertheless, time-resolved pressure measurements suggest that notable pressure oscillations induced by the vortex shedding can reach the upstream bladerow.

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Unsteady Flow Analysis and Vibratory Stress Predictions for a High Work Single Stage Turbine Blade

Volume 7: Structures and Dynamics, Parts A and B ◽

10.1115/gt2012-69085 ◽

2012 ◽

Author(s):

Kurt Weber ◽

Girish Modgil ◽

Steve Gegg ◽

Shyam Neerarambam ◽

Moujin Zhang

Keyword(s):

Flow Field ◽

Strain Gauge ◽

Flow Analysis ◽

Forced Response ◽

Single Stage ◽

Turbine Stage ◽

Rotating Blade ◽

Gauge Data ◽

Unsteady Flow Analysis ◽

High Work

The flow field in High-Work Single-Stage (HWSS) turbines differs from traditional turbine flow fields. Operating at increased pressure ratios, wakes and trailing edge shocks at the exit of the vane are more likely to cause a vibratory response in the rotating blade. This flow field can produce increased excitation at harmonics that correspond to the vane passing frequency and harmonics higher than the vane passing frequency. In this paper, blade vibratory stresses in a HWSS gas turbine stage are predicted using unsteady pressures from two Rolls-Royce in-house flow codes that employ different phase lagged unsteady approaches. Hydra uses a harmonic storage approach, and the Vane/Blade Interaction (VBI) code uses a direct storage approach. Harmonic storage reduces memory requirements considerably. The predicted stress for four modes at two engine speeds are presented and are compared with rig test strain gauge data to assess and validate the predictive capability of the codes for forced response. Strain gauge data showed the need to consider harmonics higher than the fundamental vane passing frequency for the max power shaft speed and operating at the conditions. Because of this, it was a good case for validation and for comparing the two codes. Overall, it was found that, stress predictions using the Hydra flow code compare better with data. To the best of the authors’ knowledge, this paper is a first in comparing two different phase lagged unsteady approaches, in the context of forced response, to engine rig data for a High-Work Single Stage turbine.

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Experimental and CFD Studies of the Hydrodynamics in Wet Agglomeration Process

ChemEngineering ◽

10.3390/chemengineering2030032 ◽

2018 ◽

Vol 2 (3) ◽

pp. 32 ◽

Cited By ~ 1

Author(s):

Benjamin Oyegbile ◽

Guven Akdogan ◽

Mohsen Karimi

Keyword(s):

Numerical Simulation ◽

Flow Field ◽

Flow Analysis ◽

Outer Region ◽

Tangential Velocity ◽

Numerical Code ◽

Cfd Model ◽

Rotating Disc ◽

Batch Mode ◽

Agglomeration Process

In this study, an experimentally validated computational model was developed to investigate the hydrodynamics in a rotor-stator vortex agglomeration reactor RVR having a rotating disc at the centre with two shrouded outer plates. A numerical simulation was performed using a simplified form of the reactor geometry to compute the 3-D flow field in batch mode operations. Thereafter, the model was validated using data from a 2-D Particle Image Velocimetry (PIV) flow analysis performed during the design of the reactor. Using different operating speeds, namely 70, 90, 110, and 130 rpm, the flow fields were computed numerically, followed by a comprehensive data analysis. The simulation results showed separated boundary layers on the rotating disc and the stator. The flow field within the reactor was characterized by a rotational plane circular forced vortex flow, in which the streamlines are concentric circles with a rotational vortex. Overall, the results of the numerical simulation demonstrated a fairly good agreement between the Computational Fluid Dynamics (CFD) model and the experimental data, as well as the available theoretical predictions. The swirl ratio β was found to be approximately 0.4044, 0.4038, 0.4044, and 0.4043 for the operating speeds of N = 70, 90, 110, and 130 rpm, respectively. In terms of the spatial distribution, the turbulence intensity and kinetic energy were concentrated on the outer region of the reactor, while the circumferential velocity showed a decreasing intensity towards the shroud. However, a comparison of the CFD and experimental predictions of the tangential velocity and the vorticity amplitude profiles showed that these parameters were under-predicted by the experimental analysis, which could be attributed to some of the experimental limitations rather than the robustness of the CFD model or numerical code.

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Magnetohydrodynamic effects on flow structures and heat transfer over two cylinders wrapped with a porous layer in side

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-03-2015-0112 ◽

2016 ◽

Vol 26 (5) ◽

pp. 1416-1432 ◽

Cited By ~ 8

Author(s):

Saman Rashidi ◽

Javad Abolfazli Esfahani ◽

Mohammad Sadegh Valipour ◽

Masoud Bovand ◽

Ioan Pop

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Flow Field ◽

Porous Layer ◽

Numerical Study ◽

Convection Heat Transfer ◽

Circular Cylinders ◽

Flow Structures ◽

Content Type ◽

The Magnetic Field

Purpose – The analysis of the flow field and heat transfer around a tube row or tube banks wrapped with porous layer have many related engineering applications. Examples include the reactor safety analysis, combustion, compact heat exchangers, solar power collectors, high-performance insulation for buildings and many another applications. The purpose of this paper is to perform a numerical study on flows passing through two circular cylinders in side-by-side arrangement wrapped with a porous layer under the influence of a magnetic field. The authors focus the attention to the effects of magnetic field, Darcy number and pitch ratio on the mechanism of convection heat transfer and flow structures. Design/methodology/approach – The Darcy-Brinkman-Forchheimer model for simulating the flow in porous medium along with the Maxwell equations for providing the coupling between the flow field and the magnetic field have been used. Equations with the relevant boundary conditions are numerically solved using a finite volume approach. In this study, Stuart and Darcy numbers are varied within the range of 0 < N < 3 and 1e-6 < Da < 1e-2, respectively, and Reynolds and Prandtl numbers are equal to Re=100 and Pr=0.71, respectively. Findings – The results show that the drag coefficient decreases for N < 0.6 and increases for N > 0.6. Also, the effect of magnetic field is negligible in the gap between two cylinders because the magnetic field for two cylinders counteracts each other in these regions. Originality/value – To the authors knowledge, in the open literature, flow passing over two circular cylinders in side-by-side arrangement wrapped with a porous layer has been rarely investigated especially under the influence of a magnetic field.

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Experimental and Numerical Flow Analysis around Circular Cylinders Using POD and DMD

44th AIAA Fluid Dynamics Conference ◽

10.2514/6.2014-3325 ◽

2014 ◽

Author(s):

Masayuki Sakai ◽

Yasuto Sunada ◽

Taro Imamura ◽

Kenichi Rinoie

Keyword(s):

Flow Analysis ◽

Circular Cylinders ◽

Numerical Flow Analysis

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Non-premixed swirl-type tubular flames burning liquid fuels

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.248 ◽

2018 ◽

Vol 846 ◽

pp. 210-239

Author(s):

Vinicius M. Sauer ◽

Fernando F. Fachini ◽

Derek Dunn-Rankin

Keyword(s):

Flow Field ◽

Swirling Flow ◽

Flame Structure ◽

Flow Analysis ◽

Liquid Fuels ◽

Reacting Flow ◽

Surface Mass ◽

Surface Mass Transfer ◽

Incompressible Viscous Flow ◽

Porous Walls

Tubular flames represent a canonical combustion configuration that can simplify reacting flow analysis and also be employed in practical power generation systems. In this paper, a theoretical model for non-premixed tubular flames, with delivery of liquid fuel through porous walls into a swirling flow field, is presented. Perturbation theory is used to analyse this new tubular flame configuration, which is the non-premixed equivalent to a premixed swirl-type tubular burner – following the original classification of premixed tubular systems into swirl and counterflow types. The incompressible viscous flow field is modelled with an axisymmetric similarity solution. Axial decay of the initial swirl velocity and surface mass transfer from the porous walls are considered through the superposition of laminar swirling flow on a Berman flow with uniform mass injection in a straight pipe. The flame structure is obtained assuming infinitely fast conversion of reactants into products and unity Lewis numbers, allowing the application of the Shvab–Zel’dovich coupling function approach.

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