Numerical and experimental study of an axially induced swirling pipe flow (original) (raw)
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Numerical and experimental study of an axially induced swirling pipe
In-line flow segregators based on axial induction of swirling flow have important applications in chemical, process and petroleum production industries. In the later, the segregation of gas bubbles and/or water droplets dispersed into viscous oil by swirling pipe flow may be beneficial by either providing a pre-separation mechanism (bubble and/or drop coalescer) or, in the case of water-in-oil dispersions, by causing a water-lubricated flow pattern to establish in the pipe (friction reduction). Works addressing these applications are rare in the literature. In this paper, the features and capabilities of swirling pipe flow axially induced by a vane-type swirl generator were investigated both numerically and experimentally. The numerical analysis has been carried out using a commercial CFD package for axial Reynolds numbers less than 2000. Pressure drop, tangential and axial velocity components as well as swirl intensity along a 5 cm i.d. size and 3 m long pipe were computed. Single phase flow experiments have been performed using a water–glycerin solution of 54 mPa s viscosity and 1210 kg/m3 density as working fluid. The numerical predictions of the pressure drop were compared with the experimental data and agreement could be observed within the range of experimental conditions. The experiments confirmed that swirl flow leads to much higher friction factors compared with theoretical values for non-swirl (i.e. purely axial) flow. Furthermore, the addition of a conical trailing edge reduces vortex breakdown. Visualization of the two-phase swirling flow pattern was achieved by adding different amounts of air to the water–glycerin solution upstream the swirl generator.
International Communications in Heat and Mass Transfer, 2014
Heat transfer and pressure drop characteristics of a decaying swirl flow in a horizontal pipe are investigated experimentally. The decaying swirl flow is produced by the insertion of vortex generators with propeller-type geometry, a kind of passive heat enhancement tools. Two different cases are comparatively examined: onepropeller case and two-propeller case. In the one-propeller case, the first propeller is placed at the entrance of the flow. In the two-propeller case, the second is placed at a specific distance where the swirl effect generated by the first propeller is decayed. The focus of the study is concentrated on comparatively examining the usage of one or two propeller-type swirl generators on the friction factor and heat transfer. For both cases, the effects of the joint angle about the core of the insert device and the number of the joint vanes attached circumferentially to the device on heat transfer and pressure drop are also investigated. Experiments are conducted at Reynolds numbers ranging from 5000 to 30,000. For validation, experimental data obtained for the smooth pipe are compared with those available in the literature.
Effects of geometry and gas composition on swirling flow
2015
Lean premixed swirl stabilised combustion is regarded as one of the most successful technologies for flame control and NOx reduction in gas turbines. Important characteristics of these flows are good mixing, flame stability through the formation of a Central Recirculation Zone, and low emissions at lean conditions as a consequence of the low operating temperature. This project presents a series of experiments and numerical simulations using commercial software (ANSYS) to determine the behaviour and impact on the blowoff process at various swirl numbers, nozzle geometries and gas compositions at same power outputs using confined and open conditions. Experiments were performed using a generic premixed swirl burner. The Central Recirculation Zone and the associated turbulent structure contained within it were obtained through CFD analyses providing details of the structures and the Damkolher Number (Da) close to blowoff limits. The results show how the strength and size of the recircul...
Effect of inlet and outlet boundary conditions on swirling flows
Computers & Fluids, 1997
Numerical simulations are conducted for both three-dimensional, turbulent flow in a multichannel swirler and axisymmetric, isothermal, turbulent flow in combustion chambers using the standard K-L turbulence model. Calculations are first carried out for three-dimensional, isothermal and turbulent flow inside the swirler channels in order to derive the velocity profiles of both air and gas at the swirler outlets, which are used as inlet boundary conditions of the model combustor and can also be used in future studies for different combustors with the same type of swirler. In order to study the sensitivity of swirling flow inside the chamber to the inlet and outlet boundary conditions, different inlet velocity profiles and outlet boundary conditions are also employed. The results show that in the cases considered, the flow behaviour in the chamber is not very sensitive to the actual shape of the inlet velocity profiles provided the averages of the inlet axial, radial and azimuthal velocity components are separately preserved. Other conditions being equal, we find that the swirling flow performance in the combustor depends not only on the inlet swirl number, but also strongly on the relative magnitude of the radial velocity component at inlet and introduce a new dimensionless number N,, analogous to the swirl number, to measure the relative importance of this quantity. Outlet boundary conditions have some influence near the outlet, but nearly no effect further upstream for the cases investigated. 0 1998 Elsevier Science Ltd.
Experimental investigation of propeller type swirl generator for a circular pipe flow
International Communications in Heat and Mass Transfer, 1999
The objective of this paper is to introduce the subject of heat transfer augmentation by inserting a propeller type swirl generator in a circular pipe. The propeller type swirl generator creates a flow pattem which is like a decaying swirl flow. This flow pattem is observed for laminar flow. The main advantage of this type of swirl generator is that it is easy to install the device into a circular pipe. Average and local Nusselt numbers were calculated by the method explained in detail in the main text. Comparison of the local Nusselt numbers for swirl flow considered in this study and local Nusselt numbers for flow in a smooth pipe revealed that the local Nusselt number increases substantially when the swirl generator is used. The swirl related heat transfer enhancement becomes stronger as Reynolds number increases.
Numerical Study of Swirling Flow in a Liquid-Liquid Axial Hydrocyclone Separator
Cyclone separators use swirling flow to provide a sorting mechanism to segregate dispersed material from within a carrier fluid. Large centrifugal forcres can be created by the swirling motion depending upon the density difference, cyclone diameter and flow rate. Compact oil-water-gas separators are often required in process industry and are essential in offshore petroleum production. In this work oil-water hydrocyclones are studied. A compact design is provided by the axial hydrociclone, which takes advantage of the pipe geometry of the incoming oil-water mixture. A flow pattern of small water droplets dispersed into a continuous oil phase can be assumed for the incoming flow. The swirl motion is generated by a system of fixed axial vanes. If the oil is relatively viscous, the incoming flow can be assumed to be laminar for moderate flow rates. By means of CFD, velocity profiles and pressure distributions past the swirl generator are determined for several geometries and flow conditions. The numerical study is aimed at determining the length for which swirl motion decays as a function of the flow and geometry variables involved. The decay length is compared with an approximate expression for the length required to segregate water droplets, as a criterium to assess the viability of a particular design.
Effects of 4-lobe swirl-inducing pipe on pressure drop
2008
This thesis describes the effects of the 4-lobe swirl-inducing pipe on pressure drops for water, sand-water slurry and carboxymethyl cellulose fluids. The pressure drops were measured for two 4-lobe swirl-inducing pipe combined, one 4-lobe swirl-inducing pipe and without swirl-inducing pipe. The swirling pipe applications were installed before a bend on radius-to-diameter (R/D) ratio of 4. The pressure drops were measured on three different locations, before and after the 4-lobe swirl-inducing pipe, and after the bend. Swirling flow behaviours were observed for sand-water slurry at different concentrations. Reynolds number indicated water and sand-water slurries in turbulent regimes. The sand particles were evenly distributed when induced with swirling flow, which caused less wear effect on a pipe-cross section. Results indicated that the swirlinducing pipe increased the pressure drop for higher concentrations. The 4-lobe swirl-inducing pipe caused an increased in pressure drop over horizontal pipe and a reduction in pressure drop over the bend. Results showed that the overall pressure drops across pipe (after swirl and bend) were increased with swirl-inducing pipe. I particularly appreciate colleagues who spent considerable effort and time for responding to some difficult issues. I am also indebted to the support of my family and friends.
Swirl Tubes as an In-Line Gas-Liquid Separator
cfd.com.au
This work investigates the gas-liquid separation process in swirl tubes also known as in-line separators. They are compact with no moving parts and have low maintenance. These features fit the exigent conditions expected in hostile offshore production environments but so far these devices are not technologically developed to comply with the demands of gas production fields. The goal of this work is to use CFD to investigate the feasibility of these devices as gas-liquid separators. NOMENCLATURE D vortex finder diameter m mass flow rate X radial coordinate Y axial coordinate Z tangential coordinate U radial velocity V axial velocity W tangential velocity S Swirl number ρ gas density φ dimensionless mass flow rate
2014
Swirling jet is used as a means of controlling flames in combustion chamber. Swirl flow offer an interesting field of study for aerospace & mechanical engineers in general and for combustion engineers in particular since it involves complex interaction of recirculation & turbulent mixing, which aid flame stabilization in combustion system. Swirling flow in both reacting & non-reacting conditions occur in wide range of application such as gas turbines, marine combustor burner, chemical processing plants, rotary kilns & spray dryers. Stabilization of flame can be achieved by various techniques. The most common techniques used in modern gas turbine combustors is swirl stabilization in which swirl velocity is imparted to inlet air using vane Swirler. Swirl can reduce combustion length by producing higher rates of entrainment of ambient fluid and fast mixing close to exit nozzle & on boundaries of recirculation zone in strongly swirling zones. Experimental studies show that swirl has lar...