This paper presents a transcritical / supercritical CO2 (sCO2) recompression Brayton cycle using a novel rotary liquid piston compressor (LPC). This new type of multi-phase compressor utilizes a pumped motive fluid that interfaces with... more
This paper presents a transcritical / supercritical CO2 (sCO2) recompression Brayton cycle using a novel rotary liquid piston compressor (LPC). This new type of multi-phase compressor utilizes a pumped motive fluid that interfaces with sCO2 in a rotating ducted cylinder for efficient CO2 compression at lower hardware costs. The energy required to pump the motive fluid can be significantly lower than that required to compress CO2 in a traditional compressor. The compressor utilizes a low compressibility, low diffusivity, low solubility liquid as the motive fluid to pressurize process fluid (sCO2) stream. Its use as a replacement for the main compressor in a recompression sCO2 Brayton cycle is expected to reduce compression power by more than 10% while maintaining robust operation over a wide range of ambient temperatures and CO2 densities that are typical for dry-cooled sCO2 cycles in arid climates. The new rotary liquid piston compressor also eliminates the need for gas lubricated b...
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A novel rotary liquid piston multi-phase pump that transfers pressure energy from high pressure motive fluid stream to a low pressure process fluid stream within a high speed multi-ducted rotor is presented. The multiple ducts in the... more
A novel rotary liquid piston multi-phase pump that transfers pressure energy from high pressure motive fluid stream to a low pressure process fluid stream within a high speed multi-ducted rotor is presented. The multiple ducts in the rotor act like cylinders of a rotating liquid piston pump with the liquid-to-liquid interface between the working fluid and the motive fluid acting like a piston. This novel pump has promise to solve challenges typically seen in multi-phase pumping and in trans-critical and supercritical CO2 compression systems, na m el y, risks due to phase change, two-phase compression inefficiencies, rotordynamic instabilities and sealing challenges etc. In this design the entrance and exit flow angles impart momentum to the rotor and the rotor achieves a self-sustained rotation without external power. The rotational speed dictates the volumetric efficiency, travel distance of the liquid piston within the ducts and the zero-mixing effectiveness of the design. This cr...
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L'invention concerne un ensemble joint d'etancheite pour une machine tournante. L'ensemble joint d'etancheite comprend de multiples segments (16) de dispositif d'etancheite disposes en circonference entre un logement... more
L'invention concerne un ensemble joint d'etancheite pour une machine tournante. L'ensemble joint d'etancheite comprend de multiples segments (16) de dispositif d'etancheite disposes en circonference entre un logement stationnaire et un rotor. Chacun des segments (16) de dispositif d'etancheite comprend un element d'interface avec le stator. Le segment de dispositif d'etancheite comprend aussi un patin comportant une ou plusieurs dents de labyrinthe tournees vers le rotor et une zone (32) de surface porteuse de charge, lequel le patin admettant un fluide haute pression dans la partie amont de la dent de labyrinthe (20) la plus en avant et un fluide basse pression dans la partie aval de la dent de labyrinthe la plus en arriere. Le segment de dispositif d'etancheite comprend en outre un joint d'etancheite secondaire (28) en contact avec l'element d'interface stator a une extremite radialement exterieure et en contact avec un nez sureleve ...
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Ausfuhrungsformen der vorliegenden Offenbarung sind auf eine Gleitringdichtung gerichtet, die einen Statorring enthalt, der eingerichtet ist, um um einen Rotor einer Turbine angeordnet zu werden, wobei der Statorring ein erstes... more
Ausfuhrungsformen der vorliegenden Offenbarung sind auf eine Gleitringdichtung gerichtet, die einen Statorring enthalt, der eingerichtet ist, um um einen Rotor einer Turbine angeordnet zu werden, wobei der Statorring ein erstes Ringsegment und ein zweites Ringsegment aufweist, die eingerichtet sind, um gemeinsam den Statorring zu bilden, wobei das erste und das zweite Ringsegment in Umfangsrichtung geteilt sind und wenigstens ein Lagerelement aufweisen, das zwischen dem ersten und dem zweiten Ringsegment angeordnet ist, und wobei das wenigstens eine Lagerelement eingerichtet ist, um eine relative axiale Bewegung zwischen dem ersten und dem zweiten Ringsegment an Verbindungsstellen zwischen dem ersten und dem zweiten Ringsegment zu ermoglichen.
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This paper presents a hybrid finite element - finite volume algorithm for solving multi-scale fluid-structure interaction during transient operation of a hydraulic rod seal. The elasto-hydrodynamic model consists of analyses of the... more
This paper presents a hybrid finite element - finite volume algorithm for solving multi-scale fluid-structure interaction during transient operation of a hydraulic rod seal. The elasto-hydrodynamic model consists of analyses of the macro-scale structural mechanics of the seal deformations, a macro-scale elastic contact mechanics at the seal-rod interface, the micro- scale fluid mechanics of the lubricating film in the sealing zone, the micro-scale statistical contact mechanics of the contacting asperities on the seal lip and the micro-scale elastic deformation mechanics of the sealing zone, all incorporated in a single hybrid iterative computational framework to solve these highly coupled nonlinear multiphysics equations simultaneously. Finite element calculations using COMSOL's PDE and Structural Mechanics modules are coupled with finite volume calculations in MATLAB to form a hybrid MATLAB based framework. The hybrid method facilitates an online calculation of micro-scale defo...
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This paper focuses on the development of a structural health monitoring system based on guided Lamb waves propagating over the structure and a network of surface acoustic sensors in communication at high frequencies. A time-of-flight... more
This paper focuses on the development of a structural health monitoring system based on guided Lamb waves propagating over the structure and a network of surface acoustic sensors in communication at high frequencies. A time-of-flight (ToF), algorithm and a probabilistic diagnostic imaging and calibration method is developed to detect miniscule material losses or material adhesion as well as the defects like small scale holes and cracks in turbomachinery components like blades, rotors, plates and pipes. Using an advanced ToF algorithm, precise differences in timescales for arrival of symmetric / antisymmetric lamb wave packets are found for all possible combinations of actuator-sensor pairs. This leads to a deterministic mathematical construct for damage localization for various actuator-sensor pairs at focal points. In the probabilistic diagnostic imaging (PDI) method, field value is assigned based on fusion of wave signals rendered by various actuator-sensor paths to indicate the p...
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Supercritical carbon dioxide (sCO2) power cycles could be a more efficient alternative to steam Rankine cycles for power generation from coal. In this paper, the end seal layout for a nominally 500 MWe sCO2 turbine is presented and the... more
Supercritical carbon dioxide (sCO2) power cycles could be a more efficient alternative to steam Rankine cycles for power generation from coal. In this paper, the end seal layout for a nominally 500 MWe sCO2 turbine is presented and the shaft end sealing requirements for such utility-scale sCO2 turbines are discussed. Shaft end leakage from a closed-loop sCO2 cycle and the associated recompression load can result in net cycle efficiency loss of about 0.55% points to 0.65% points for a nominally 500 MWe sCO2 power cycle plant. Low-leakage hydrodynamic face seals are capable of reducing this leakage loss (and net cycle efficiency loss), and are considered a key enabling component technology for achieving 50–52% or greater thermodynamic cycle efficiencies with indirect coal-fired sCO2 power cycles. In this paper, a hydrodynamic face seal concept is presented for end seals on utility-scale sCO2 turbines. A 3D computational fluid dynamics (CFD) model with real gas CO2 properties is develo...
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Flame spread characteristics are studied for water-in-oil emulsion layers floating on top of a water body — similar to a scenario in which an accidental oil spill occurs in open, rough sea. A comprehensive mathematical model is developed... more
Flame spread characteristics are studied for water-in-oil emulsion layers floating on top of a water body — similar to a scenario in which an accidental oil spill occurs in open, rough sea. A comprehensive mathematical model is developed and numerical solution is obtained for the ignition and flame spread process which takes into account the emulsion break up into oil and water due to heating, oil vaporization, combustion of oil vapor mixed with air in open atmosphere, radiative and convective heat feed back from flames to the condensed phase (consisting of emulsion, oil, and water), and continuation of the emulsion breaking resulting in flame spread till the oil is consumed. Numerical results are compared with experiments conducted on Arabian Medium Crude oil emulsions made with up to 20% weathered oil (light fraction evaporated, by volume), having up to 50% water content in the emulsions. The flame spread rate decreased as the water content and the weathering level increased, with a reasonable agreement between experiments and model. The long term objective of this work is to assist the application of in situ burning as a measure for the cleanup of weathered and emulsified oils.Copyright © 2005 by ASME
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Abstract Viscoelastic effects on the performance of a hydraulic rod seal are examined using a visco-elastohydrodynamic model. The model consists of coupled macro and micro scale deformation and contact mechanics analyses and micro scale... more
Abstract Viscoelastic effects on the performance of a hydraulic rod seal are examined using a visco-elastohydrodynamic model. The model consists of coupled macro and micro scale deformation and contact mechanics analyses and micro scale fluid mechanics analysis. Dynamic mechanical analysis and a constrained optimization method are used to extract the spectrum of relaxation time scales and corresponding instantaneous elastic moduli associated with the seal polymer, required by the model. Simulation results show that the seal performance, including leakage prevention and friction force, depends on the relationship between the characteristic time constants of the polymer’s molecular chains and the seal cycle frequency.
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Research Interests: Engineering, Mechanical Engineering, Fluid Mechanics, Modeling, Contact Mechanics, and 15 moreStructural Analysis, Finite Element Analysis, Cavitation, Injection Molding, Structure Analysis, Steady state, Finite Volume, Mass Conservation, Finite Volume Method, Cavitacion, Transient Response, Flow Rate, Pressure Distribution, Elastohydrodynamic Lubrication, and Reynolds equation
Three mixed lubrication models of a reciprocating hydraulic rod seal are described: a steady-state elastic model, a transient elastic model, and a transient viscoelastic model. These models are used to simulate a U-cup rod seal utilized... more
Three mixed lubrication models of a reciprocating hydraulic rod seal are described: a steady-state elastic model, a transient elastic model, and a transient viscoelastic model. These models are used to simulate a U-cup rod seal utilized in an injection moulding application. Results characterizing the leakage and friction force, as well as the detailed behaviour of the sealing zone, are presented.
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A soft elastohydrodynamic model of a reciprocating elastomeric hydraulic rod seal has been developed. It consists of coupled fluid mechanics, contact mechanics, and deformation analyses. The model has been used to analyze a U-cup lip seal... more
A soft elastohydrodynamic model of a reciprocating elastomeric hydraulic rod seal has been developed. It consists of coupled fluid mechanics, contact mechanics, and deformation analyses. The model has been used to analyze a U-cup lip seal in an injection molding application with a time-varying sealed pressure and rod velocity. Results include the histories of the hydraulic fluid flow rate, fluid transport, mean shear stress on rod, sealing zone length, and friction force on rod, as well as distributions of the fluid pressure, film thickness, and contact pressure.
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A visco-elastohydrodynamic model of a hydraulic rod seal during transient operation has been developed. The model includes analyses of the macro- and microscale deformation mechanics and contact mechanics, and the microscale fluid... more
A visco-elastohydrodynamic model of a hydraulic rod seal during transient operation has been developed. The model includes analyses of the macro- and microscale deformation mechanics and contact mechanics, and the microscale fluid mechanics. Viscoelasticity enters the analysis through the deformation mechanics and through the contact mechanics. A hybrid finite element-finite volume computational framework is developed to solve the highly coupled governing equations. Viscoelasticity is seen to affect the leakage and friction characteristics of the seal through its effects on the changing fluid pressure and contact pressure distributions as the rod velocity and sealed pressure change during a cycle. Compared with purely elastic behavior, viscoelasticity increases the fluid pressure and the contact pressure significantly in the sealing region closest to the sealed end, shifts the fluid pressure peaks away from the sealed end during the instroke, and enhances the cavitation during the o...
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Supercritical CO2 power cycles could be a more efficient alternative to steam Rankine cycles for power generation from coal. However, CO2 turbomachinery for this application has not yet been designed. This paper summarizes a scale-up of... more
Supercritical CO2 power cycles could be a more efficient alternative to steam Rankine cycles for power generation from coal. However, CO2 turbomachinery for this application has not yet been designed. This paper summarizes a scale-up of the 10MWe Southwest Research Institute (SwRI) and General Electric (GE) Sunshot CO2 turbine design to the maximum size possible, nominally about 50MWe. The thermodynamic cycle and turbine design are described. This non-reheat recompression cycle can achieve >49% cycle efficiency at ISO conditions with wet cooling. Scale-up of the Sunshot turbine beyond 50MWe is limited by the availability of long, large diameter rotor forgings and requires a change to an assembled rotor design. A clean-sheet conceptual design of a 450MWe assembled turbine rotor is also presented. It appears possible to package this reheat turbine rotor into a single casing at 3600 rpm and still maintain rotordynamic stability. This reheat recompression cycle can achieve 51.9% cycl...
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Component design, maturation and material development for sCO2 turbomachines in the 10MW to 500 MW range have been identified to be in the critical path for the successful implementation sCO2 power plants. However, the performance and... more
Component design, maturation and material development for sCO2 turbomachines in the 10MW to 500 MW range have been identified to be in the critical path for the successful implementation sCO2 power plants. However, the performance and life limiting mechanisms of these components in high pressure, high temperature sCO2 environment are not well understood. These mechanisms are governed by multi-scale coupled physics interactions combined with strong perturbations in performance variables around the critical point. In this paper, some of the work done by GE, under U.S. DOE PREDICTS program, in developing performance and life prediction models for Hybrid Gas Bearing (HGB) and Dry Gas Seal (DGS) is presented. From a system perspective, HGB can provide substantial benefits (~3 to 5%) to the modular CSP operation, while use of DGS limits the leakage losses (~2-3% improvement in cycle efficiency for 10 MW scale) as well as the windage losses in the generator (increase in generator efficienc...
CSP plants using supercritical CO2 (sCO2) power cycle can potentially achieve high thermal conversion efficiency at low capital cost due to compact turbomachinery and other components. An sCO2 expander and improved heat exchanger is... more
CSP plants using supercritical CO2 (sCO2) power cycle can potentially achieve high thermal conversion efficiency at low capital cost due to compact turbomachinery and other components. An sCO2 expander and improved heat exchanger is expected to provide a major stepping stone for achieving CSP power at $0.06/kW-hr LCOE, energy conversion efficiency > 50%, and total power block cost < $1,200/kW installed. However the life limiting mechanisms of these turbomachines in high pressure, high temperature sCO2 environment are not well understood. To understand the effect of high pressures, high temperatures and sCO2 chemical kinetics on crack initiation, crack propagation and low cycle fatigue (LCF) life of these turbomachines, a novel experimental setup is developed. Advanced microstructure and spectroscopic analyses are conducted that shed light on some key differences between various Ni base alloys in terms of oxidation morphology, chemical species diffusion and trapping, the format...
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U.S. Department of Energy (DOE) has recently sponsored research programs to develop megawatt scale supercritical CO2 (sCO2) turbine for use in concentrated solar power (CSP) and fossil based applications. To achieve the CSP goal of power... more
U.S. Department of Energy (DOE) has recently sponsored research programs to develop megawatt scale supercritical CO2 (sCO2) turbine for use in concentrated solar power (CSP) and fossil based applications. To achieve the CSP goal of power at $0.06/kW-hr LCOE and energy conversion efficiency > 50%, the sCO2 turbine relies critically on extremely low leakage film riding seals like dry gas seal (DGS). Although DGS technology has been used in other applications before. making it successful for stringent conditions of an sCO2 turbo-expander is challenging. This paper presents results from a multi-scale coupled physics model that predicts the performance of DGS under a typical sCO2 turbine mission cycle and addresses some of the risks specific to operation in sCO2. Real gas equations of state are incorporated in the models to capture large discontinuities in fluid properties close to the critical point. A novel experimental setup is developed to observe and characterize transition of CO...
Research Interests: Engineering and Physics
A neural network based method is developed that can learn the underlying physics of hydraulic turbocharger (a radial pump coupled with a radial turbine) from a set of sparse experimental data and can predict the performance of a new... more
A neural network based method is developed that can learn the underlying physics of hydraulic turbocharger (a radial pump coupled with a radial turbine) from a set of sparse experimental data and can predict the performance of a new turbocharger design for any given set of previously unseen operating conditions and geometric parameters. The novelty of the algorithm is that it learns the underlying physical mechanisms from a very sparse data spanning a broad range of flow rates and geometrical size brackets and uses these deeper common features recognized through a “mass-learning process” to predict the full performance curves for any given single geometry. The deep learning algorithm is able to accurately predict the key performance parameters like total efficiency of the turbocharger, its operating speed, pressure rise provided by the radial pump of the turbocharger and the shaft power produced by the radial turbine of the turbocharger for any given input combination of pump and tu...
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure... more
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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Dry gas seals (DGS) are widely used in turbomachinery applications. They are recently being also recommended for sealing novel super critical CO2 turbomachinery space. However, these seals can render interesting behavior under certain... more
Dry gas seals (DGS) are widely used in turbomachinery applications. They are recently being also recommended for sealing novel super critical CO2 turbomachinery space. However, these seals can render interesting behavior under certain operating conditions which needs to be carefully monitored so that intended level of dynamic characteristics can be achieved. The ability of these seals to maintain low leakage by riding at small clearances makes them an attractive solution where secondary flows need to be minimized. To understand the significance of some of the key design features of these seals, in this work an analysis on a gas lubricated spiral groove dry gas seal is presented. Equations in polar coordinates governing the compressible flow through the DGS gap and a numerical method to solve such non-linear partial differential equation is presented. The resulting sets of equations are solved for hydrodynamic pressure distribution and the axial separation force and the film stiffnes...