A revised Tesla Turbine concept for 2-phase applications

The Tesla turbine is an original expander working on the principle of torque transmission by wall shear stress. The principle – demonstrated for air expanders at lab scale has some attractive features when applied to two-phase expanders: it is suitable for handling limited flow rates (as is the case for machines in the range from 500W to 5 kW), it can be developed to a reasonable size (rotor of 0.1 to 0.25 m diameters), with acceptable rotational speeds (which range from 500 to 10000 rpm). The original concept was revisited, designing it for two-phase operation and considering not only the rotor configuration but the whole machine. The flow model was developed using complete real fluid assumptions including several new concepts such as bladed channels for the stator, labyrinth seals, and a rotating diffuser. Preliminary design sketches are presented, and results discussed and evaluated.

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Modeling of Wall Friction for Multispecies Solid-Gas Flows

Journal of Fluids Engineering ◽

10.1115/1.3242608 ◽

1986 ◽

Vol 108 (4) ◽

pp. 486-488 ◽

Cited By ~ 1

Author(s):

E. D. Doss ◽

M. G. Srinivasan

Keyword(s):

Shear Stress ◽

Flow Model ◽

Flow Characteristics ◽

Wall Friction ◽

Gas Flows ◽

Two Phase ◽

One Dimensional ◽

Friction Models ◽

Wall Interaction ◽

The One

The empirical expressions for the equivalent friction factor to simulate the effect of particle-wall interaction with a single solid species have been extended to model the wall shear stress for multispecies solid-gas flows. Expressions representing the equivalent shear stress for solid-gas flows obtained from these wall friction models are included in the one-dimensional two-phase flow model and it can be used to study the effect of particle-wall interaction on the flow characteristics.

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Comparative Study of Loss-of-Coolant Accident Using MAAP4.03 and RELAP5/MOD3.2.2

10th International Conference on Nuclear Engineering, Volume 3 ◽

10.1115/icone10-22439 ◽

2002 ◽

Author(s):

Chang Hwan Park ◽

Doo Yong Lee ◽

Ik Jeong ◽

Un Chul Lee ◽

Kune Y. Suh ◽

...

Keyword(s):

Flow Model ◽

Correction Term ◽

Sensitivity Study ◽

Severe Accident ◽

Primary System ◽

Two Phase ◽

Flow Rates ◽

Flow Models ◽

Loss Of Coolant Accident ◽

Loss Of Coolant

Analysis was performed for a large-break loss-of-coolant accident (LOCA) in the APR1400 (Advanced Power Reactor 1400 MWe) with the thermal-hydraulic analysis code RELAP5/ MOD3.2.2 and the severe accident analysis code MAAP4.03. The two codes predicted different sequences for essentially the same initiating condition. As for the break flow and the emergency core cooling (ECC) flow rates, MAAP4.03 predicted considerably higher values in the initial stage than RELAP5/ MOD3.2.2. It was considered that the differing break flow and ECC flow rates would cause the LOCA sequences to deviate from one another between the two codes. Hence, the break flow model in MAAP4.03 was modified with partly implementing the two-phase homogeneous critical flow model and adopting a correction term. The ECC flow model in MAAP4.03 was also varied by changing the hardwired friction factor through the sensitivity study. The modified break flow and ECC flow models yielded more consistent calculational results between RELAP5/MOD3.2.2 and MAAP4.03. It was, however, found that the resultant effect is rather limited unless more mechanistic treatments are done for the primary system in MAAP4.03.

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Local Concentrating, Not Shear Stress, That May Lead to Possible Instability of Protein Molecules During Syringe Injection: A Fluid Dynamic Study with Two-Phase Flow Model

PDA Journal of Pharmaceutical Science and Technology ◽

10.5731/pdajpst.2018.009357 ◽

2019 ◽

Vol 73 (3) ◽

pp. 260-275 ◽

Cited By ~ 3

Author(s):

Lei Xing ◽

Yue Li ◽

Tonglei Li

Keyword(s):

Shear Stress ◽

Flow Model ◽

Two Phase Flow ◽

Fluid Dynamic ◽

Dynamic Study ◽

Phase Flow ◽

Two Phase ◽

Protein Molecules ◽

Syringe Injection

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A two-phase dilatant debris flow model based on full scale shear stress and pore pressure measurements

10.5194/egusphere-egu2020-21752 ◽

2020 ◽

Author(s):

Guillaume Meyrat

Keyword(s):

Shear Stress ◽

Debris Flow ◽

Pore Pressure ◽

Debris Flows ◽

Flow Model ◽

Fluid Composition ◽

Geophysical Research ◽

Two Phase ◽

Non Linear ◽

Fluid Pore Pressure

Since 2004, observations of shear and normal stresses have been collected at the base of naturally-triggered debris flows at the Illgraben observation station (Wallis, Switzerland) [1].&#160;&#160; Because flow height and the normal force are simultaneously measured, and limited observations of basal fluid pore pressure are available, it is possible to investigate how the solid/fluid contents of the flow influence the measured shear stress.&#160; The experimental results have emphasized two debris flow properties: (1) Debris flows are characterized by rocky or boulder-rich front, following by a fluidized tail. Consequently, the mass density varies from large values at the front of the flow to lower values towards the tail. A comparison between different debris flow events, however, likewise reveals that the streamwise change in density can vary dramatically between two different events. (2) The relationship between the measured shear and normal tress is highly non-linear.&#160;Operating on the assumption that the streamwise change in density (or equivalently change in streamwise composition) is primarily responsible for the observed non-linear stress behavior, we develop a rheological model describing two-phase debris flow motion. The underlying idea behind the model is that the granular content of the flow can dilate, changing the solid/fluid composition of the flow, and thereby alter the bulk flow density. The model allows us to estimate the correct debris flow composition for different classes of debris flow varying from granular to muddy fluid. Based on these results, we are then able to reproduce the measured shear stress data when we simulate the measured events numerically.&#160; The results appear to confirm dilatant-type flow models proposed by Takahashi [2], and later developed in detail by Iverson and George [3]. The model is used to back-calculate recent debris flow events that occurred near Davos Switzerland in 2018/2019.&#160;&#160;&#160;REFERENCES<ol><li>McArdell, B.W., Bartelt, P. and Kowalski, J. (2007): Field observations of basal forces and fluid pore pressure in a debris flow, Geophysical Research Letters, Vol. 34, No. L07406.</li> </ol>&#160;<ol><li>Takahashi, T. (2007): Debris flows: mechanics, prediction and countermeasures, Taylor and Francis / Balkema, 448pp.</li> </ol>&#160;<ol><li>George, D. L., & Iverson, R. M. (2011). A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure. Italian journal of engineering geology and Environment, 43, 415-424.</li> </ol>

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Choked Expansion of Subcooled Water and the I.H.E. Flow Model

Journal of Heat Transfer ◽

10.1115/1.3450795 ◽

1978 ◽

Vol 100 (2) ◽

pp. 275-280 ◽

Cited By ~ 15

Author(s):

R. L. Collins

Keyword(s):

Sound Speed ◽

Flow Model ◽

Maximum Error ◽

Saturation Line ◽

Two Phase ◽

Pressure Derivative ◽

Flow Rates ◽

The Past ◽

Liquid Saturation ◽

Reservoir Conditions

The isentropic, homogeneous, equilibrium (I.H.E.) model for two-phase flows is discussed with special regard to recent experimental and theoretical information. Over the past years, the I.H.E. model has been misrepresented many times and its deficiencies have been overstated. More recent studies have indicated that the I.H.E. model may be quite valid for certain types of flows and this paper is presented to amplify these results. It is noted here that the I.H.E. model, under certain reservoir conditions, will over-predict flow rates, that an essential discontinuity of the I.H.E. sound speed may play an important role in choking, that the mass flux-pressure derivative is not continuous at the saturation line, and that the maximum error of the I.H.E. flow rate is about 60 percent at the liquid saturation line.

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An Analytical Two-Phase Flow Model for Prediction of Leakage in Wet Gas Labyrinth Seals and Pocket Damper Seals. Is Simplicity Still Desired?

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4051916 ◽

2021 ◽

Author(s):

Jing Yang ◽

Luis San Andres

Keyword(s):

Analytical Model ◽

Flow Model ◽

Two Phase Flow ◽

Volume Fraction ◽

Gas Mixture ◽

Phase Flow ◽

Rotor Speed ◽

Labyrinth Seals ◽

Two Phase ◽

Wet Gas

Abstract Current and upcoming two-phase pump and compression systems in subsea production facilities must demonstrate long-term operation and continuous availability. Annular pressure seals, limiting secondary flow, also influence the dynamic stability of turbomachinery. Hence, it becomes paramount to quantify the leakage and dynamic performance of annular seals operating with a liquid in gas mixture (wet gas). The paper develops a simple analytical model predicting the leakage and cavity pressures for Labyrinth seals and pocket damper seals (PDSs) operating with two-phase flow. The model adapts Neumann's equation with a homogeneous flow model. Predicted leakage for a four-blade PDS operating under a low supply pressure (2.3 and 3.2 bar) and a low rotor speed (5,250 rpm) agree well with experimental results for both a pure gas and a wet gas conditions. For an eight-blade PDS supplied with air at 62.1 bar, discharge pressure 31.1 bar and rotor speed of 15 krpm, the analytical model predicts leakage that is just 2% larger than a CFD prediction. For the PDS supplied with an oil in gas mixture having gas volume fraction = 0.92 ~ 0.98, the simple model delivers leakage that is up to ~ 6% lower than published CFD results. Throughout the life of an oil well that sees radical changes in gas and liquid composition as well as pressure conditions, the expedient model, quick and accurate to estimate leakage in wet gases seals, can be readily integrated into an engineering routine or practice.

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