Two Phase Computational Study of Flow Behaviour in a Region Within an Aeroengine Gearbox

2014 ◽  
Author(s):  
A. Turner ◽  
H. P. Morvan ◽  
K. Simmons
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Complex Geometry ◽  
Computational Study ◽  
Flow Behaviour ◽  
Phase Flow ◽  
Two Phase ◽  
Validation Data ◽  
Air Jet ◽  
Vof Model

Within large civil aeroengines a significant contributor to parasitic power loss (manifest as increased heat-to-oil) is the internal gearbox (IGB). An IGB typically contains high speed shafts, a spiral bevel gear pair, bearings and seals as well as the complex geometry of the stationary components. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems (UTC) has conducted experimental and computational projects to enhance understanding of two phase flow behaviour. Validated single phase modelling capability for an unmeshed shrouded crown gear has been established [1–3] and discrete phase modelling [3] has been applied to investigate the oil path under the shroud. Experimental work on shroud configurations [5] and two-phase flow [6] has also been conducted at the UTC using a rig with representative but simplified geometry relative to an aeroengine. Recent modelling activity has focussed on the region behind the gear. In an aeroengine this region includes a large shaft location bearing that sheds oil into the rear chamber. This oil, combined with the high speed and complex airflows generated by proximity to the gear, makes this region particularly challenging to model. In the experimental test rig at the UTC this zone does not contain a bearing and so as yet no validation data exists. In this paper an axisymmetric sector model of the rig back chamber is presented. Two phase flow behaviour was modelled using the Volume of Fluid (VOF) and Eulerian models within the CFD software ANSYS-Fluent. A comparison between these two multiphase models is made and their suitability to model the oil behaviour in the back chamber is discussed. Oil flow behaviour in this region is also reported. The CFD results show that the VOF model is insufficient for predicting oil flows in this environment. Although there is a significant amount of liquid present as wall film, the liquid not on the walls appears important and is not adequately modelled by VOF, which is well-known as being most suitable where there is a definite interface between liquid and gaseous phases. The Eulerian model shows significantly more likely flow behaviour with results indicating a non-uniform distribution of oil across the axial length of the rear chamber with a bias towards the rear (bearing side). The air jet entering in the rear chamber from between the gear and shroud strongly influences flow behaviour in the rear chamber. The computed flow field is such that a full 360° model is recommended for future work of this nature.

Behavior of Bubbles Separated by a Cross-Shaped Obstacle Placed in a Circular Flow Channel

2017 ◽  
Author(s):  
Kazuyuki Takase ◽  
Hiep H. Nguyen ◽  
Gaku Takase ◽  
Yoshihisa Hiraki
Keyword(s):  
High Speed ◽  
Nuclear Reactor ◽  
Two Phase Flow ◽  
Flow Direction ◽  
Flow Behavior ◽  
Bubbly Flow ◽  
Wire Mesh ◽  
Phase Flow ◽  
Two Phase ◽  
Validation Data

Clarifying two-phase flow characteristics in a nuclear reactor core is important in particular to enhance the thermo-fluid safety of nuclear reactors. Moreover, bubbly flow data in subchannels with spacers are needed as validation data for current CFD codes like a direct two-phase flow analysis code. In order to investigate the spacer effect on the bubbly flow behavior in a subchannel of the nuclear reactor, bubble dynamics around the simply simulated spacer was visually observed by a high speed camera. Furthermore, the void fraction and interfacial velocity distributions just behind the simulated spacer were measured quantitatively by using a wire-mesh sensor system with three wire-layers in the flow direction. From the present study, bubble separation behavior dependence upon the spacer shape was clarified.

Entrainment Into High Speed Air Jet Blowing Out From a Hole to Stagnant Water

2013 ◽  
Author(s):  
Yasuo Koizumi ◽  
Kohei Nago ◽  
Akihiro Uchibori ◽  
Hideki Kamide ◽  
Hiroyuku Ohshima
Keyword(s):  
High Speed ◽  
Open Space ◽  
Two Phase Flow ◽  
Video Camera ◽  
Diameter Distribution ◽  
Phase Flow ◽  
Flow State ◽  
Two Phase ◽  
Air Jet ◽  
Test Vessel

Flow visualization experiments of an air jet in liquid were performed. The test vessel was 270 mm wide, 5 mm depth and 300 mm high. The air jet was blown vertically upward into stagnant liquid in the test vessel from a nozzle of 1 mm wide, 5 mm depth and 20 mm long which was located at the bottom of the test vessel. A flow state of the jet in the liquid was recorded with a high speed video camera at fastest 5×105 f/s. The test liquid was water and kerosene. Experiments were performed at atmospheric pressure and ambient temperature. Filament-like ears and wisps pulled out from the wavy interface were noticed on the interface between liquid and the air jet. The ears and wisps were broken off and entrained into the air jet. The droplets broke up to small entrainments. This process seemed quite similar to the entrainment process in the annular dispersed flow in a pipe. As the air jet velocity increased, the number of entrainments created by the air jet increased lineally and the smaller entrainments increased. The correlation for the entrainment diameter distribution which was developed for the annular dispersed two-phase flow in a pipe predicted well the present results. The correlations for the entrainment diameter developed for entrainments in the annular dispersed two-phase flow in a pipe and for droplets that were blown out into open space above a water pool by a nitrogen gas jet that blew into water vertically upwards considerably underpredicted the experimental results. Measured entrainment rates were considerably lower than the prediction of the correlation for the annular dispersed two-phase flow in a pipe.

Visualization of Entrainment and Surface Behavior of High Speed Air Jet Blowing Out From a Hole to Stagnant Water

2012 ◽  
Author(s):  
Kohei Nago ◽  
Yasuo Koizumi ◽  
Akihiro Uchibori ◽  
Hiroyuki Ohshima
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Droplet Diameter ◽  
Video Camera ◽  
Diameter Distribution ◽  
Phase Flow ◽  
Stagnant Water ◽  
Two Phase ◽  
Air Jet ◽  
Jet Blowing

A two dimensional air jet was blown out from a nozzle into water in a thin vessel. The behavior of the interface between water and the air jet and also the air jet were recorded with a high speed video camera. Filament-like ears and wisps pulled-out from the wavy water surface were noticed in the recorded photos. Droplets are formed from these. Droplet diameters were obtained from the recorded photos. As the air velocity increased, the number of droplets created by the air jet increased lineally and the smaller droplets increased. The correlation for the droplet diameter distribution developed for the annular dispersed two-phase flow in a pipe predicted well the present results. The correlations for the droplet diameter developed for the annular dispersed two-phase flow in a pipe and for the jet blowing out from the stagnant water pool considerably underpredict the experimental results.

High Speed Imaging and Two-Phase Flow Patterns During Flow Boiling in a Single Microchannel

2008 ◽  
Author(s):  
Jacqueline Barber ◽  
Khellil Sefiane ◽  
David Brutin ◽  
Lounes Tadrist
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Pressure Sensors ◽  
Flow Patterns ◽  
Bubble Nucleation ◽  
Phase Flow ◽  
Vapour Bubble ◽  
Two Phase ◽  
Over Time

Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two phase flow at a fundamental level. We induced boiling in a single microchannel geometry (hydraulic diameter 727 μm), using a refrigerant FC-72, to investigate several flow patterns. A transparent, metallic, conductive deposit has been developed on the exterior of rectangular microchannels, allowing simultaneous uniform heating and visualisation to be conducted. The data presented in this paper is for a particular case with a uniform heat flux of 4.26 kW/m2 applied to the microchannel and inlet liquid mass flowrate, held constant at 1.33×10−5 kg/s. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop profiles across the microchannel over time. Bubble nucleation, growth and coalescence, as well as periodic slug flow, are observed in the test section. Phenomena are noted, such as the aspect ratio and Reynolds number of a vapour bubble, which are in turn correlated to the associated pressure drops over time. From analysis of our results, images and video sequences with the corresponding physical data obtained, it is possible to follow visually the nucleation and subsequent both ‘free’ and ‘confined’ growth of a vapour bubble over time.

Analysis of Transient Two-Phase Flow in Pressure Safety Valve Outlet Headers

2018 ◽  
Author(s):  
Maral Taghva ◽  
Lars Damkilde
Keyword(s):  
Steady State ◽  
Shock Waves ◽  
High Speed ◽  
Two Phase Flow ◽  
Safety Valve ◽  
Strong Shock ◽  
Flow Property ◽  
Phase Flow ◽  
Transient Pressure ◽  
Two Phase

To protect a pressurized system from overpressure, one of the most established strategies is to install a Pressure Safety Valve (PSV). Therefore, the excess pressure of the system is relieved through a vent pipe when PSV opens. The vent pipe is also called “PSV Outlet Header”. After the process starts, a transient two-phase flow is formed inside the outlet header consisting of high speed pressurized gas interacting with existing static air. The high-speed jet compresses the static air towards the end tail of the pipe until it is discharged to the ambiance and eventually, the steady state is achieved. Here, this transient process is investigated both analytically and numerically using the method of characteristics. Riemann’s solvers and Godunov’s method are utilized to establish the solution. Propagation of shock waves and flow property alterations are clearly demonstrated throughout the simulations. The results show strong shock waves as well as high transient pressure take place inside the outlet header. This is particularly important since it indicates the significance of accounting for shock waves and transient pressure, in contrast to commonly accepted steady state calculations. More precisely, shock waves and transient pressure could lead to failure, if the pipe thickness is chosen only based on conventional steady state calculations.

scholarly journals Experimental Investigation of the Performance and Spray Characteristics of a Supersonic Two-Phase Flow Ejector with Different Structures

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1166 ◽  
Author(s):  
Shizhen Li ◽  
Wei Li ◽  
Yanjun Liu ◽  
Chen Ji ◽  
Jingzhi Zhang
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Fire Suppression ◽  
Cone Angle ◽  
Water Mist ◽  
Pulsation Period ◽  
Phase Flow ◽  
Two Phase ◽  
Half Cone ◽  
Half Cone Angle

A two-phase flow ejector is an important part of a water mist fire suppression system, and these devices have become a popular research topic in recent years. This paper proposes a supersonic ejector that aims to improve the efficiency of water mist fire suppression systems. The effects of ejector geometric parameters on the entrainment ratio (ER) were explored. The effects of primary flow pressure (PP) on the mixing process and flow phenomena were studied by a high-speed camera. The experimental results show that the ER first increases and then decreases with increasing PP. ER increases with increasing ejector area ratio (AR). The PP corresponding to the maximum ER of ejectors with a different nozzle exit position (NXP) is 3.6 bar. The ejector with an NXP of +1 and AR of 6 demonstrate the best performance, and the ER of this ejector reaches 36.29. The spray half-cone angle of the ejector increases with increasing ER, reaching a maximum value of 7.07°. The unstable atomization half-cone angle is mainly due to a two-phase flow pulsating phenomenon. The pulsation period is 10 ms. In the present study, a general rule that provides a reference for ejector design and selection was obtained through experiments.

6. Inviscid instability of high speed two-phase flow

1998 ◽  
Vol 1 (1) ◽  
pp. 7-7 ◽  
Author(s):  
G. H. Schnerr ◽  
S. Adam
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Inviscid Instability

Estimation of Average Void Fraction for Gas-Liquid, Two-Phase Flow in an Industrial Nozzle Assembly Using a Quick-Closing-Valve

2008 ◽  
Author(s):  
Mohammad A. Rahman ◽  
Johana Gomez ◽  
Ted Heidrick ◽  
Brian A. Fleck ◽  
Jennifer McMillan
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Two Phase Flow ◽  
Video Camera ◽  
Synchronization Error ◽  
Phase Flow ◽  
Closing Time ◽  
Two Phase ◽  
Void Fractions ◽  
Atomization Performance

Experimentally accurate void fraction measurements are a challenge in an air/water, two-phase flows through an industrial nozzle assembly, as a highly non-uniform void fraction exists in the feeding conduit prior to the nozzle. In this study, average void fractions were measured by isolating a section in the feeding conduit of a horizontal nozzle assembly, termed as the quick-closing-valve (QCV) technique. A high-speed video camera was utilized to capture the asynchronization closing time, tac. The average closing time and asynchronization for the pneumatically controlled valves were 200 ms and 2 ms, respectively. Based on the equation of 100umtac (1−α)/αlc, the synchronization error between the two valves was 1.12%, 1.26%, and 1.79% for the 1%, 2% and 4% ALR cases, respectively; here um is the mixture velocity, α is the void faction, and lc is the closing length. Higher synchronization error at 4% ALR occurs due to enhanced momentum in the flow regime. Experimental results indicate that the average α over the 33.4 cm feeding conduit (6.25 mm ID) was 76% (αtheoretical = 75%) for the 2% ALR, and 85% (αtheoretical = 83%) for the 3.3% ALR. In the two-phase, two-component flow the α affects the drop size and stability of the spray produced from an industrial nozzle assembly. Learning from this study will yield insights and conceptual understanding of two-phase flow phenomena in conduit, which would affect stability, pulsation tendency, and possibly atomization performance of the nozzle downstream. Two-phase flow nozzles have wide applications in the industries, e.g. petrochemical, pharmaceutical, and others.

Numerical Simulation and Experimental Validation on the Particle Trajectory in a Solid Propellant Rocket Chamber

2000 ◽  
Author(s):  
Yumin Xiao ◽  
R. S. Amano ◽  
Timin Cai ◽  
Jiang Li
Keyword(s):  
Numerical Simulation ◽  
Experimental Method ◽  
High Speed ◽  
Particle Trajectory ◽  
Two Phase Flow ◽  
Measurement Data ◽  
Special Method ◽  
Phase Flow ◽  
Two Phase ◽  
Particle Injection

Abstract In solid rocket motors (SRMS) using aluminized composite solid propellants and submerged nozzles a two-phase flow pattern is one of the main flow characteristics needs to be investigated. The modeling and validation of two-phase flow are the focus in this research field. In this paper the authors first traced the particle trajectory in a SRM chamber by using numerical method, and then developed a new experimental method to measure the particle trajectory in a SRM chamber to validate the numerical results. The experimental method was based on the RTR (X-ray Real-time Radiography) technique and high-speed motion analyzer. A special method was developed to imitate the particle injection on the propellant surface. The calculation results and measurement data show that the trajectory obtained by numerical simulation was in good agreement with the measured one by imposing proper boundary conditions. For particles with diameter of 75μm, the initial velocity factor of particle is approximately 0.4, and the particles pass through the centerline in both calculation and experiment. The present method can be extended to study the impingement of particles on the wall and other related two-phase flow patterns.

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