Two-phase Conditions Research Articles

A generalized machine learning-assisted phase-equilibrium calculation model for shale reservoirs

In compositional reservoir simulation, a significant portion of the CPU time is consumed in phase equilibrium calculations. Previous studies have incorporated the machine learning (ML) technique to accelerate and stabilize the phase equilibrium calculations. However, there are two main limitations: 1) previous work mainly focuses on conventional reservoirs, which cannot be extended to unconventional reservoirs; 2) previous studies are limited to fluid compositions with specific hydrocarbon components that narrows their application. In this paper, we propose a novel ML-assisted framework for phase equilibrium calculations in shale reservoirs. A general set of pseudo-components is considered to allow users to customize the composition of hydrocarbon mixtures. A pore size-dependent EOS is applied to simulate the fluid phase behavior in nano-scale conditions. In the stability test, the multilayer perceptron (MLP) is trained to predict the fluid phase state: single-phase or two-phase. For the fluid labeled as two-phase condition, the phase-split computation is performed to obtain the equilibrium ratio. Instead of using the initial estimate from the stability test, the MLP and the physics-informed neural network (PINN) are applied to obtain the initial estimates for the minimization program. The results show that, with the assistance of ML technique, we are able to reduce the computation time needed for the nano-scale phase equilibrium calculations by more than two orders of magnitude while maintaining 97% accuracy. Compared with MLP, PINN can accurately predict the equilibrium ratios with a limited range of input variables but require more training time. The progress of this study present a ML-assisted framework for phase equilibrium calculations and the generalized proxy phase-equilibrium calculator can be compiled into reservoir simulator to accelerate flash calculation.

Analysis of a Stator-Rotor-Stator Spinning Disk Reactor in Single-Phase and Two-Phase Boiling Conditions Using a Thermo-Fluid Flow Network and CFD

Cryogenic liquid propellants are used in liquid rocket engines to obtain high specific impulse. The flow rates are controlled by turbopumps that deliver liquid propellant to the engine at high pressure levels. Due to the very low saturation temperature of the cryogenic propellant, in the first phases of the transient operation, in which the engine is at ambient temperature, its surfaces are subject to boiling conditions. The effect of boiling on the heat transfer between the solid and the fluid needs to be well characterized in order to correctly predict the cryopump metal temperature temporal evolution and the necessary amount of propellant. With the aim of benchmarking numerical tools against experimental data, a representative test case was chosen. This consists of a stator-rotor-stator spinning disc reactor studied under single-phase and two-phase heat transfer conditions. The numerical approaches used are represented by a 1D network solver, where the pressure drop and heat transfer are calculated by correlations, and Computational Fluid Dynamics (CFD) simulations, carried out with ANSYS Fluent. Both the numerical tools returned a reasonable agreement in single-phase conditions, also thanks to the use of adequate correlations in the flow network solver and typical conditions for the CFD simulations. Two-phase conditions on the contrary are more challenging, with underpredictions up to 20% and 80%, respectively. The issues are ascribable to the use of correlations that are inadequate to capture the two-phase phenomena occurring in the srs reactor and numerical limitations in the actual implementation of the boiling model in the CFD solver.

A computational study of curvature effect on pressure drop of gas-liquid two-phase flow through 90 degree elbow

The CFD analysis of air-water two-phase flows was performed in a 90o vertical to horizontal elbows made of PVC with four different inside diameters (25 mm, 50 mm, 75 mm, and 100 mm) with six different curvature radius to diameter ratios (R/D) 1, 2, 4, 6, 8, and 10. Pressure drops were investigated at various upstream and downstream locations using computational, experimental, empirical methods. The most effective method in investigating and determining total pressure drop of two-phase flow in pipes and bends is considered to be computational study. The CFD simulations were performed using ANSYSY 19.2 FLUENT and a mixture model. The studies were conducted under the following two-phase conditions: mass quality from 1-50% and mass flux from 350-1000 kg/m2s. The results show that the impact of these significant parameters are important and dramatic specially at high curvature radius, mass flux and mass quality. The results of the CFD study demonstrated a substantial loss in energy and pressure as the fluid exits the elbow section, and also a higher drop in pressure observed at higher air velocity. Also, higher pressure drops were obtained with increasing pipe diameter in one side, and with decreasing R/D on the other side. Finally, the current results were verified with the empirical and experimental studies and a good agreement were obtained.

Influence of the balance hole on the performance of a gas–liquid two–phase centrifugal pump

Centrifugal pumps are prone to vibration due to unstable impeller forces under gas–liquid two-phase conditions. The balance hole can balance the axial force on the impeller and improve the operation stability of the pump. In this study, the influence of the balance hole on the performance of the multiphase pump is studied. By parameterizing the balance hole, the influences of the radial position, circumferential position and diameter of the balance hole on the external characteristics, gas-phase distribution and axial force of the multiphase pump are investigated. Results show that the balance hole degrades the centrifugal pump performance at small gas volume fraction (GVF). At high GVF, when the balance hole is located in the gas phase accumulation zone and the diameter is above 6 mm, the performance of the centrifugal pump will be improved. The balance hole can improve the distribution of gas-phase in the impeller, but the effect is limited to the local area around the balance hole. The effect of the balance hole on the axial force weakens as the centre position of the balance hole moves from the impeller inlet to the impeller outlet, increases with increased hole diameter and is less influenced by circumferential position.

Numerical Investigation on a Twin-Screw Multiphase Pump Under low IGVF

A three-dimensional transient numerical model was developed to obtain the two-phase flow characteristics in a twin-screw multiphase pump based on dynamic mesh technology and the multiphase flow model. The pump performance under different inlet gas volume fractions (IGVF) was predicted by the numerical model and was tested. Then, the numerical model was validated after comparing the simulation and experimental results. After that, the flow field in the pump under 10% IGVF was analyzed. When the IGVF is 10%, the pressure increases step by step and is symmetrical from both ends to the middle of the screw rotors. The pressure distribution through a single working chamber is uniform. It falls rapidly at the inlet of the tooth tip gap and then drops linearly in the gap channel. At the outlet of the tip gap, the pressure temporarily falls due to the high-speed jet. The GVF distribution in the working chamber is uneven. The leakage flow is laminar in the tip gap, and the liquid concentrates on the top of the gap. When the last working chamber connects with the discharge chamber, the discharge jet flow causes the vortices in the discharge pipe. The gas gradually moves to the center of the vortices, forming four gas-phase aggregation regions. The velocity of the interlobe leakage is the largest. The maximum velocity appears at the second cross-section and reaches 35m/s. This research can be used to improve the performance of the twin-screw multiphase pump under two-phase working conditions.

A 3-D multiphase model of proton exchange membrane electrolyzer based on open-source CFD

In this study, a 3-D multiphase model of the proton exchange membrane (PEM) electrolyzer is developed on an open-source computational fluid dynamics (CFD) platform, OpenFOAM. A pseudo-coupling method is presented to consider the detailed two-phase distribution conditions at the interface between the flow channel and liquid/gas diffusion layer (L/GDL) in anode flow channel of a 3-D PEM electrolyzer model. The detailed two-phase distribution conditions can be obtained by high-speed optical images or volume of fluid (VOF) simulation results. Through this method, it is possible to predict the effect of two-phase flow existing in the anode flow channel on the transport phenomena in the porous electrode, and thus cell performance. The 3-D model is validated with experimental test results at three current density conditions (0-1, 0-2, 0-3 A cm−2) considering the existence of two-phase flow. It is found that if the two-phase flow in the anode flow channel is neglected, the simulation polarization curves will deviate from the experimental test results, especially at high current density conditions. In contrast, the simulated polarization curves manage to fit the experimental data accurately with the pseudo-coupling method, indicating that it is necessary to consider the effect of two-phase flow. In addition, this pseudo-coupling model can not only take the multi-phase mass transport into consideration but also the distribution of temperature and current density inside a PEM electrolyzer. With the help of this model, a novel double-layer flow field is proposed to enhance the performance of electrolyzer. It is found that the cell performance of the proposed flow field is 0.171 V better that of the traditional parallel flow field at 3 A cm−2. Also, the temperature distribution and current density distribution of the new flow field are more uniform, which could benefit the durability and performance of PEM electrolyzer.

On-Water Selectivity Switch in Microdroplets in the 1,2,3-Triazole Synthesis from Bromoethenesulfonyl Fluoride.

Water profoundly affects many organic reactions by accelerating them or changing their selectivity. Performing reactions "on-water" offers an intriguing opportunity to influence chemical reactivity. A nebulizer plume is an efficient way of generating microdroplets─the uniquely complex reaction environment which opens alternative possibilities that are not readily accessible in bulk emulsions. We describe the on-water switch of chemoselectivity in the formation of triazoles controlled by the on-water environment in dual spray. These conditions facilitate elimination of H-SO2F from the triazoline intermediate, whereas the reaction in organic solvents results in the exclusive HBr elimination. The influence of two-phase conditions was investigated to obtain the best reaction efficiency, and the crucial importance of the water/organic interface interactions was verified by pH variation and D2O use.

Numerical assessment of a two-phase Tesla turbine: Parametric analysis

• Tesla turbine performance analysis in two-phase condition via CFD and analytical model. • The phase change model is adapted to R404a based on saturation temperature. • 1D-homogeneous analytical model estimation is comparable with 3D nonhomogeneous model. • The surface roughness effect is more pronounced at lower gaps between the disks. • The two-phase tesla turbine produced ~ 0.8 W and torque of 3.6 mN-m at 2000 RPM. The scenarios on the future energy systems invariably point to heat pumps as an emerging technology to reach efficiency goals alongside energy and CO 2 reduction targets. Moreover, they may progressively foster the use of chillers and refrigeration units. In this study, a technology that could enhance the efficiency of systems based on inverse cycles is analysed. Particularly, the two-phase flow behaviour of a Tesla turbine is numerically investigated. The main objectives are to clarify the role of the second phase, the actual operating range, and examine the flow mixing. Two computational approaches are developed, relying on a customised home-built mathematical model and CFD analyses carried out with a commercial software. The calculations are performed for two-phase R404a fluid over significant ranges of rotational speed, plate gap size, and plate roughness. All the critical liquid–vapour interactions are determined and discussed utilising the CFD solution of the Eulerian-Eulerian approach with a frame motion technique. The other model is a homogeneous finite-difference solution, and the mass transfer is directly determined based on the phase diagram of the fluid neglecting other phase-interaction parameters. The two approaches are compared to some available experimental results from the literature, revealing an excellent agreement. The results show the average power output of 0.8 W with a delivered torque of 3.6 mN-m at a rotational speed of about 2000 RPM. The numerical analysis explains the different effects of the two-phase conditions on the turbine efficiency, paving the way to an accurate design of boundary layer turboexpanders operating under these conditions.

Optimal tuning of PI controllers using adaptive particle swarm optimization for doubly-fed induction generator connected to the grid during a voltage dip

This paper proposes the adaptive particle swarm optimization (APSO) technique to control the active and reactive power produced by a variable wind energy conversion system and the exchanged power between the electric grid and the system during a voltage dip (VD). Besides, to get the variable speed wind energy maximum power, a maximum power point (MPP) methodology is utilized. The system under study is a 5 MW wind turbine connected via a gearbox to a doubly-fed induction generator (DFIG). The DFIG stator is branched directly to the electrical network, while the Back-to-Back converters couple the rotor to the grid. The decoupled vector control of the rotor side converter and the grid side converter is established primarily by a conventional proportional-integral (PI) and a second level by an intelligent PI whose gains are tuned using the proposed control. The performances and results obtained by APSO tuned PI controllers are analyzed and compared with those attained by classical PI controllers through the MATLAB/Simulink. The superiority of the advised technique is examined during a two-phase short-circuit fault condition and confirmed by the reduced oscillations.

Study on the Effect of Gas-Liquid Two-Phase Medium on PAT Performance

A pump as turbine is optimized firstly, then the distribution of gas, the vortex structure evolution, the force characteristic and energy conversion characteristic are analyzed under pure liquid and gas-liquid two-phase conditions. The result manifests that because of the existence of gas, the pressure gradient decreased and the normal flow of high-pressure fluid in the turbine is inhibited by gas. The radial force vector, the time domain value and the main frequency amplitude are all smaller than that of pure liquid condition, and hydraulic vibration is more likely to be caused by the flow uncertainty of gas. The energy conversion performance of the unit is worse.

Effect of Gas Volume Fraction on the Energy Loss Characteristics of Multiphase Pumps at Each Cavitation Stage

In the process of conveying a medium, when the inlet pressure is low, the cavitation phenomenon easily occurs in the pump, especially in the gas–liquid two-phase working condition. The occurrence of the cavitation phenomenon has a great impact on the performance of the multiphase pump. In this paper, the SST (sheard stress transport) k-ω turbulence model and ZGB (Zwart–Gerber–Belamri) cavitation model were used to simulate the helical axial flow multiphase pump (hereinafter referred to as the multiphase pump), and the experimental verification was carried out. The effect of gas volume fraction (GVF) on the energy loss characteristics in each cavitation stage of the multiphase pump is analyzed in detail. The study shows that the critical cavitation coefficient of the multiphase pump gradually decreases with the increase in GVF, which depresses the evolution of cavitation, and the cavitation performance of the multiphase hump is improved. The ratio of total loss and friction loss to total flow loss in the impeller fluid domain gradually increases with the development of cavitation, and the pressurization performance of the multiphase pump gradually decreases with the development of cavitation. The results of the study can provide theoretical guidance for the improvement of the performance of the multiphase pump.

Effect of Synergistic Aging on Bauxite Residue Dust Reduction Performance via the Application of Colloids, an Orthogonal Design-Based Study.

The application of polymer colloids is a promising approach for bauxite residue dust pollution control. However, due to the existence of synergistic aging, the efficiency of colloid dynamic viscosity to predict the dust control performance of bauxite residue is unclear. Previous studies were also rarely performed under synergistic aging conditions. Thus, this paper investigates the relationship between colloids’ viscosity and dust control performance under synergistic aging modes. Results illustrated that the binary colloid achieved better dust control performance than unitary colloid for their higher viscosity and penetration resistance. For both unitary and binary colloid, higher viscosity results in better crust strength. A logarithmic relationship was found for viscosity and dust erosion resistance under unitary aging. However, Only the dynamic viscosity of colloids in solid-liquid two-phase conditions, rather than dissolved in deionized water, can effectively predict the dust control performance under synergistic aging conditions.

Static Characteristics and Leakage Rates of Smooth Annular Seals Based on a New Solution Method for Gas-Liquid Two-Phase Conditions

This paper proposes a new solution method for the leakage and static characteristics of smooth annular seal under a homogeneous gas-liquid two-phase flow based on a bulk-flow model. In this solution method, the Rayleigh–Plesset equation is introduced into the governing equations to describe the behavior of bubbles considering mixture compressibility. Detailed comparisons between Childs’ experimental leakage rates and predicted ones based on the proposed method are conducted, and the predicted results show good agreement with the experimental results, with a maximum error of 11.2%. Moreover, static characteristics of the seal, including leakage rates, gas volume fraction (GVF) distribution, pressure distribution, mixture density, and viscosity within the seals, are investigated based on the present method. The results show that as the inlet gas volume fraction increases from 0% to 10%, the local gas volume fraction of each axial position will increase, however, the seal leakage, mixture density, and mixture viscosity will decrease. Bubble radius has little effect on the leakage rates and the static characteristics of the seals. Additionally, comparisons between the characteristics of the model seals with different clearances show that the leakages of the seals with bigger clearance behave more sensitively to the inlet GVF changes.

Numerical and experimental research on the erosion of solid-liquid two-phase flow in transport butterfly valve based on DEM method

PurposeThe purpose of this paper is to analyze the mechanism of particle erosion in butterfly valve pipelines under hydraulic transportation conditions. The results will affect the sealing and safety of butterfly valve pipelines and hopefully serve as reference for the anti-erosion design of butterfly valve pipelines.Design/methodology/approachThrough the discrete element method (DEM) simulation that considers the force between particles, the detached eddy simulation (DES) turbulence model based on realizable k-epsilon is used to simulate the solid-liquid two-phase flow-induced erosion condition when the butterfly valve is fully opened. The simulation is verified by building an experimental system correctness. The solid-liquid two-phase flow characteristics, particle distribution and erosion characteristics of the butterfly valve pipeline under transportation conditions are studied.FindingsThe addition of particles may enhance the high-speed area behind the valve. It first increases and then decreases with increasing particle size. With increasing particle size, the low-velocity particles change from being uniformly distributed in flow channel to first gathering in the front of the valve and, then, to gathering in lower part of it. Fluid stagnation at the left arc-shaped flange leads to the appearance of two high-speed belts in the channel. With increasing fluid velocity, high-speed belts gradually cover the entire valve surface by focusing on the upper and lower ends, resulting in the overall aggravation of erosion.Originality/valueConsidering the complexity of solid-liquid two-phase flow, this is the first time that the DEM method with added inter-particle forces and the DES turbulence model based on realizable k-epsilon has been used to study the flow characteristics and erosion mechanism of butterfly valves under fully open transportation conditions.

Fluid evolution in the Beidabate porphyry Cu-Mo deposit, Xinjiang, northwest China: Evidence from fluid inclusions and H-O-C-S isotopes

• A fluid evolution model for Beidabate deposit is presented. • The model relies on fluid phase separation. • The precipitation mechanism for Mo and Cu is proposed. The Beidabate deposit is a porphyry Cu-Mo deposit located in the West Tianshan Orogenic Belt , Xinjiang Uygur Autonomous Region. The fluid evolution path and Cu-Mo mineralization mechanism remain obscured by multiple hydrothermal pulses. Systematic fluid inclusion and H-O-C-S isotope analyses were performed on five identifiable mineralization stages. Variations in fluid composition, temperature, and pressure record the fluid evolution path: (1) During the formation of barren quartz veins (stage I), fluid inclusions were trapped under single- to two-phase transitional conditions, as evidenced by the presence of intermediate-density inclusions as well as coexisting daughter mineral-bearing inclusions and vapor-rich inclusions (boiling FIAs). Fluid phase separation occurred at temperatures of 387–412 °C and pressures of 180–300 bar. (2) Fluid inclusions in K-feldspar-quartz veins (stage II) and molybdenite-quartz veins (stage III) were trapped under two-phase conditions. Boiling FIAs were also recognized, with homogenization temperatures of 306–368 °C and entrapment pressures of 80–200 bar. Fluid boiling is the main precipitation mechanism of molybdenite . (3) Fluid inclusions in pyrite-chalcopyrite-quartz veins (stage IV) and fluorite-chalcopyrite veins (stage V) are predominantly liquid-rich and CO 2 -bearing inclusions, which represent extraneous fluids. These inclusions homogenized at temperatures of 192° to 285 °C, and minimum entrapment pressures of 40–50 bar. Fluid mixing is the main precipitation mechanism of chalcopyrite . H-O-C-S isotope data (δ 18 O = 3.2 to 15.2‰, δD = −103.6 to −75.1‰, δ 13 C = −24.2 to −9.7‰ and δ 34 S = 4.6 to 7.0‰) indicate that the ore-forming fluids have a predominantly magmatic signature with subsequent dilution by late meteoric water and intense water–rock interaction. We established a genetic model of the Beidabate porphyry Cu-Mo deposit with the aim of providing insight into prospecting at a regional scale.

Development of ejector performance map for predicting fixed-geometry two-phase ejector performance for wide range of operating conditions

Recent studies have expanded the operational envelope of ejector by utilizing both pressure recovery and liquid recirculation mechanisms. This necessitates finding a consistent representation of fixed-geometry ejector performance data using only operational variables for predicting ejector performance. Taking inspiration from the compressor performance maps, the study explores the appropriate motive, performance, and characterization variable for representing ejector performance while conducting experiments on a transcritical CO2 ejector system. The existing ejector efficiency is revisited by conducting ejector power analysis. Two possible motive variables, along with a new ejector efficiency is introduced. The trends of existing and new ejector efficiencies are studied in controlled motive variable experiments while changing suction flow conditions. The ejector performance can be represented with the help of a single curve, termed as ejector performance map, using the new ejector efficiency as performance variable and the volumetric entrainment ratio as characterization variable. The prediction accuracy for both the single-phase and the two-phase suction inlet conditions are evaluated while developing performance map using only the single-phase suction inlet data points. The methodology can predict 89.3% of the data within 20% accuracy. The applicability of the methodology is assessed for other datasets involving different refrigerants, cycle architectures, and applications. The proposed ejector performance map can be utilized in numerical ejector system analysis for investigating new cycle architectures based on ejector experimental data, thus, improving system model fidelity. It can also help system design engineers in making ejector system selection decisions after thorough system performance analysis.

Effective and economic microbial lipid biosynthesis for biodiesel production by two-phase whole-cell biocatalytic process

Efficient and economical production of renewable fuels and chemicals requires the co-utilization of sugars derived from lignocellulosic biomass as feedstock. Herein, Rhodosporidium toruloides cells were employed to produce microbial lipid via co-fermentation of lignocellulosic biomass-derived non-sterile sugars. In this study, we found that Rhodosporidium toruloides was very effective lipid biosynthesis yeast for co-fermenting of lignocellulosic biomass-derived sugars through the two-phase whole-cell biocatalytic process. Moreover, under the two-phase biosynthesis condition, the lipid production of non-sterile fermentation was higher than that of sterile fermentation. Accordingly, the two-phase whole-cell biocatalytic process for lipid biosynthesis can reduce the energy consume for the sterilization. Especially high lipid productivity was achieved from mixed sugars solution without sterility in bioreactor. After incubation for 47 h in bioreactor, the biomass, lipid and lipid contents were achieved in 56.8 gL-1, 92.7 gL-1 and 61.3%, respectively. Co-fermenting of lignocellulosic biomass-derived sugars may reduce the cost of lipid production. Fermentation of non-sterile condition can further decrease the cost of sterilization steam and cooling water by 357 RMB/ton (about 55 USD/ton). The composition of fatty acid was consistent with common plant oils and was suitable as feedstock for biodiesel production. The results of the present work show that the two-phase whole-cell biocatalytic process has a great potential in industrial lipid biosynthesis for biodiesel production.

Unlock the Potentials to Further Improve CO2 Storage and Utilization with Supercritical CO2 Emulsions When Applying CO2-Philic Surfactants

Supercritical CO2 (ScCO2) emulsion has attracted lots of attention, which could benefit both climate control via CO2 storage and industry revenue through significantly increased oil recovery simultaneously. Historically, aqueous soluble surfactants have been widely used as stabilizers, though they suffer from slow propagation, relatively high surfactant adsorption and well injectivity issues. In contrast, the CO2-soluble surfactants could improve the emulsion performance remarkably, due to their CO2-philicity. Here, comprehensive comparison studies are carried out from laboratory experiments to field scale simulations between a commercially available aqueous soluble surfactant (CD 1045) and a proprietary nonionic CO2-philic surfactant whose solubility in ScCO2 and partition coefficient between ScCO2/Brine have been determined. Surfactant affinity to employed oil is indicated by a phase behavior test. Static adsorptions on Silurian dolomite outcrop are conducted to gain the insights of its electro-kinetic properties. Coreflooding experiments are carried out with both consolidated 1 ft Berea sandstone and Silurian dolomite to compare the performances as a result of surfactant natures under two-phase conditions, while harsher conditions are examined on fractured carbonate with presence of an oleic phase. Moreover, the superiorities of ScCO2 foam with CO2-philic surfactant due to dual phase partition capacity are illustrated with field scale simulations. ScCO2 and WAG injections behaviors are used as baselines, while the performances of two types of CO2 emulsions are compared with SAG injection, characterized by phase saturations, CO2 storage, oil production, CO2 utilization ratio and pressure distribution. A novel injection strategy, named CO2 continuous injection with dissolved surfactant (CIDS), which is unique for a CO2-philic surfactant, is also studied. It is found that the CO2-soluble surfactant displays much lower oil affinity and adsorption on carbonate than CD 1045. Furthermore, in a laboratory scale, a much higher foam propagation rate is observed with the novel surfactant, which is mainly ascribed to its CO2 affinity, assisted by the high mobility of the CO2 phase. Field scale simulations clearly demonstrate the potentials of CO2 emulsion on CO2 storage and oil recovery over conventional tertiary productions. Relative to traditional aqueous soluble surfactant emulsion, the novel surfactant emulsion contributes to higher injectivity, CO2 storage capability, oil recovery and energy utilization efficiency. The CIDS could further reduce water injection cost and energy consumption. The findings here reveal the potentials of further improving CO2 storage and utilization when applying ScCO2-philic surfactant emulsion, to compromise both environmental and economic concerns.

Test Results for the Static and Rotordynamic Characteristics of a Long (L/D = 0.75) Smooth Seal in Two-Phase (Mainly Gas) Conditions With a 62-Bar Inlet Pressure

Abstract Recent multiphase-pump developments encountered several rotordynamic issues with smooth balance-piston seals, creating a need to better understand the performance of annular seals under multiphase-flow operation. This paper presents measurements of static and dynamic characteristics of a long smooth seal (L/D = 0.75, D = 114.686 mm, and Cr = 0.200 mm) operating under pure- and mainly air condition in which air is mixed with silicone oil (PSF-5cSt). Tests are performed at a supply pressure of 62.1 bars-g, three rotation speeds (5, 10, and 15 krpm), three pressure ratios (PRs) (0.6, 0.5, 0.4), for a range of inlet liquid volume fraction (LVFi) from 0% to 8%. The results are then compared to: (1) the previous test reported by Zhang et al. (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) with similar testing condition but a different seal geometry (L/D = 0.65, D = 89.306 mm, and Cr = 0.188 mm) and (2) the predictions from a bulk-flow model developed by San Andrés (2012, “Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals,” ASME J. Eng. Gas Turbines Power, 134(2), p. 022503). Results show a significant increase of direct dynamic stiffness KΩ as LVFi increases, especially at low PR. Test results reported by Zhang et al. (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) has an opposite tendency of KΩ as an impact of increasing LVFi values. Concerning cross-coupled dynamic stiffness kΩ and cross-coupled damping c, the results from Zhang et al. (2017) and the present results agree to the effects of changing speed, PR, and LVFi under pure- and mainly air conditions. As LVFi increases, direct damping C increases while test results reported by Zhang et al. (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) showed no significant increase. A steady-state computational fluid dynamics (CFD) result for a testing case suggests a significant difference happening inside the two seals (present seal and Zhang et al.'s (2017, “Experimental Study of the Static and Dynamic Characteristics of a Long Smooth Seal with Two-Phase, Mainly-air Mixtures,” ASME J. Eng. Gas Turbines Power, 139(12), p. 122504) seal). A full investigation in CFD is needed. Except for the direct dynamic stiffness and the impact of changing LVFi on the cross-coupled dynamic stiffness, the bulk-flow model of San Andrés (2012, “Rotordynamic Force Coefficients of Bubbly Mixture Annular Pressure Seals,” ASME J. Eng. Gas Turbines Power, 134(2), p. 022503) predicts decently the tendencies and magnitudes of the rotordynamic coefficients.

Performance evaluation of a Terry GS-2 steam impulse turbine with air-water mixtures

• A Terry GS-2 turbine was tested under gas mass fractions from 1.00 to 0.05. • Terry turbine performance degrades with decreasing gas mass fraction. • Results demonstrate capabilities for extended use in nuclear plant systems. Terry steam turbines are widely used in various industries because of their robust design. Within the nuclear power generation industry, they are used in the Reactor Core Isolation Cooling System to remove decay heat during reactor isolation events. During the Fukushima Daiichi nuclear power station disaster in Japan in 2011, the Reactor Core Isolation Cooling System and associated Terry turbine operated for over 70 hours in Unit 2; this runtime is well beyond the expected operating duration. Theories suggest the turbine was subjected to a two-phase inlet flow, which could degrade the turbine performance. In this work, an experimental test rig was constructed to test a full-scale Terry model GS-2 steam turbine under two-phase air/water flows. Steady-state efficiency and torque performance maps of the turbine were developed over a range of turbine inlet pressures (1.38–4.83 bar or 20–70 psia), air mass fractions (0.05–1.0) and rotational speeds up to 4000 RPM. Turbine performance followed expected trends with torque varying linearly and efficiency varying quadratically with rotational speed. In addition, high-speed images of the two-phase flow entering the turbine were also analyzed to understand how changes in inlet pressure and air mass fraction affect the flow regime and homogenization. The present tests with air–water two-phase mixtures are an important step towards providing an understanding of the full-scale Terry turbine’s behavior and performance curves under two-phase conditions. The results of this work will be combined with air/water and steam/water data gathered using a small-scale Terry ZS-1 steam turbine in order to understand the scaling relationship between large and small size Terry turbines and fluid pairs. The combined data set will enable further development of analytical models over a wide range of conditions and may be used to provide technical justification for expanded use of the Terry turbines in nuclear power plant safety systems and other systems.