Turboexpander Research Articles

Cavitation Suppression and Design Optimization in a Cryogenic Liquid Turbine Expander Based on Thermodynamic Cavitation and Entropy Production Analysis

Abstract Cryogenic liquid turbine expanders have emerged quite recently as a replacement of J–T valve for enhancing energy efficiency of industrial systems, such as air separation units (ASUs) and Supercritical Compressed Air Energy Storage systems. In the liquid turbine expander, the rotating impeller-induced swirling flow and cavitation are essentially significant and intensive, which requests some in-depth work toward a thorough understanding flow physics and then effective attenuation. This study aims at effectively mitigating the swirling flow and cavitation. The entropy production analysis method (EPAM) is proposed to characterize the swirling flow and cavitation. It is then incorporated with the improved cavitation and turbulence models and validated through the simulation of the Hord's liquid nitrogen hydrofoil. To mitigate the swirling flow and subsequent cavitation, the design optimization method is developed, in which a novel optimization objective function is constituted by incorporating the local entropy production rate and vapor volume fraction to capture the mechanical energy dissipation and cryogenic cavitating flow physics; the non-uniform relational B-Splines and free form deformation (NURBS–FFD) parametric method is used to facilitate a flexible variation in impeller blade and diffuser vane geometries. It is solved within cfx frame by means of the particle swarm optimization (PSO) algorithm coupling the Kriging-based adaptive surrogate model. With the design optimization, the impeller and vaned diffuser tube geometries are collaboratively fine-tuned, and the mechanical energy dissipation and cavitating flow across both the impeller and vaned diffuser tube is effectively mitigated.

Design and off-design system simulation of concentrated solar super-critical CO2 cycle integrating a radial turbine meanline model

The proper design of a Concentrated solar power (CSP) plant and the associated thermal energy storage requires a careful analysis of the yearly expected irradiance and environmental conditions. System simulations based on accurate components models allow the prediction of the performance of the plant and the analysis of the components interactions. The simulations of various scenarios provide information that will help tuning the design of the components to improve the performance of the whole system at design and off-design conditions. In this paper, the focus is set on the radial turbine expander which is one of the most important component. Classical system simulation approaches use map based performance model for the turbine. This require to generate the performance map either with meanline models, CFD simulations or experiments. This is not very convenient when iterating on the system design and if the actual turbine does not exist yet. In this work, a meanline model for radial inflow turbine operating with real gas has been implemented in MODELICA language for the first time to the authors’ best knowledge. This turbine model has been coupled with the available CSP sCO2 Brayton cycle model in MODELON ThermalPower library. A parametric study on a virtual test bench show the turbine performances for various rotational speed and inlet guide vane angle. The study focus then on the performance prediction of on and off design of the system with a 8 MW turbine obtained with a simple preliminary design calculation. The investigations showed that for the varying load conditions in the solar plant system, an improved operating point has been identified by adjusting the rotational speed and the inlet guide vane angle. Future work will focus on the use such system model with multi objective meta heuristic optimization.

Peak regulation performance study of the gas turbine combined cycle based combined heating and power system with gas turbine interstage extraction gas method

Improving the peak regulation performance of the gas turbine combined cycle (GTCC)-based combined heating and power (CHP) system helps to increase the integration of renewable energy. A new method of the gas turbine (GT) interstage extraction gas is proposed to improve the peak regulation performance of the GTCC-based CHP system. The effect of the GT interstage extraction gas method on both the gas turbine expansion ratio and gas turbine extraction gas temperature are studied, and the heat and power operation regions of the GTCC-based CHP system are obtained. Finally, using a heating characteristic day as an example, the peak regulation performance and natural gas consumption changes of the GTCC-based CHP system are analysed. The results indicate that the GT interstage extraction gas method helps to expand the heat and power operation regions of the GTCC-based CHP system under the same output power. During the entire heating season from Nov.15th to Mar.15th, under the GT interstage extraction gas method, the integration of renewable energy is increased by 72071 MW, the natural gas consumption is decreased by 861.74 × 104 m3 and the profit is decreased by $4.72 × 105.

Abidjan, Metropole Nationale Et Internationale

Abidjan is a city that has known an exceptional destiny. It has known thanks to its port, an extraordinary development polarizing a vast demographic pool which goes beyond national borders. This rapid and continuous development from 1950 resulted from an influx of migrants, a large proportion of whom were foreigners. The engine of the spatial expansion of the city was above all the effort to create equipment and port and industrial spaces. Everything is done to make Abidjan a growth pole and a reflection of Ivorian urbanization. It has become in less than a century a great African metropolis, which is growing year after year. This article aims to show the features of the Abidjan metropolis. To achieve this, first-hand observation and documentary research were carried out. It emerges from this analysis that the centralization of trade and administration in this city and the shortcomings of the distribution system in the interior of the country confirm the industrialists in the idea that the Ivorian capital remains the best place for investment. This overwhelming primacy over others at all levels leads to rapid demographic and spatial growth. Today, Abidjan is a megacity due to its size, extent and population. It currently has nearly 5 million inhabitants (RGPH, 2014). With its 70,000 ha, it is five times larger than Paris, capital of France and the largest French-speaking city in West Africa (Chenal, 2009, p.114).

Neural network modeling for rigorous simulation of mid-pressure reciprocating expansion engines performance

In the Natural Gas (NG) distribution network, the town border stations are used to reduce NG pressure. Currently, pressure reduction is done by using throttling valves that cause a significant amount of physical exergy loss. Reciprocating Expansion Engine (REE) is a new tool to recover this pressure exergy. This study presents a thermodynamic evaluation to simulate the REE rigorously. The GERG-2008 equation of state (EOS) as an accurate model is used to calculate NG thermodynamic properties. As the utilization of GERG-2008 EOS requires specific inputs (pressure, temperature and mole fraction), the Try & Error method is utilized (while the inputs are density, specific internal energy, and NG composition). An Artificial Neural Network (ANN) method is also developed as an additional and alternative tool to overcome a basic limitation of the Try & Error method (knowing the NG composition). The validation results show that the error of the ANN and Try & Error methods for temperature, pressure calculation are reported 0.03%, 0.08%, and 0.04%, 0.9%, respectively. Also, the results show that the NG compositions have a significant impact on REE performance so that the indicated work for Khangiran and Bidboland NG mixtures are reported 165 and 143 kJ/kg, respectively.

Статистическая математическая модель расчета коэффициента полезного действия компрессоров турбодетандерных агрегатов: усовершенствование и идентификация

Despite their small size turbo expander units used for transportation and processing oil and gas have a capacity of up to 5.5 MW. Designing new turbo-expander units includes several stages, one of which is the variant calculation of the compressor for the given parameters. For calculating the efficiency of the compressor by its main parameters a specialized statistical model is used. The efficiency of stages designed according to a single unambiguous methodology depends on the design parameters and similarity criteria. The generalization of experience in designing turbo-expander units allowed improving the statistical mathematical model used in the Universal Modeling Method, taking into account the specifics of compressors. The new version of the mathematical model correctly takes account of losses in the inlet nozzle, the method of manufacturing the impeller, the diffuser type, etc. The resulting mathematical model includes 22 empirical coefficients. To select the correct values of the coefficients, the results of 26 acceptance tests of turbo-expander compressors were used. The error of the new statistical model with the selected of empirical coefficient values was 1.8%, which is sufficient for its practical application in project activities.

Potential of capturing transportation wasted heat for better fuel economy and electricity generation: Comprehensive testing

This study is experimentally exploring the feasibility of organic Rankine cycle (ORC) as a waste heat recovery (WHR) technology in internal combustion engines, aiming at improving engine’s power, fuel consumption and CO2 emissions. Exhaust gases of a heavy-duty diesel engine are used as heat source of the ORC system. However, as the engine’s operating conditions vary, powertrain performance changes substantially. Therefore and in order to provide a thorough overview, the system was tested at different engine points. The expansion machine is a custom-designed radial inflow turbine that is operating with NOVEC 649 as the working fluid. In order to assure a steady state testing, a thermal oil loop was installed between the exhaust gas and the ORC loop. For a robust study, the test results were compared with CFD ones. The coupled engine-ORC system presented an expansion power, turbine efficiency and thermal efficiency of 7.6 kW, 48% and 6.2%, respectively, when the turbine is running at maximum speed. The results also revealed that ORC systems have a promising influence in reducing the fuel consumption of diesel engine and providing extra power. Maximum percentages of improvements of BSFC and powertrain power were, respectively, 2.74 and 7.8% compared to engine without ORC.

Experimental and numerical approach for characterization and performance evaluation of cryogenic turboexpander under rotating condition

A small-scale radial expansion turbine is distinguished by its ease of production, higher efficiency, and reliability. Such turbines have been successfully used in cryogenic turboexpander systems for refrigeration and liquefaction of the process gas. This paper presents a methodology for design optimization, numerical, and experimental investigation of a radial turbine and nozzle (turboexpander), the most necessary and extortionate component of a nitrogen liquefaction system based on Claude cycle. The initial investigation starts with the preliminary design of a turboexpander using an in-house developed Matlab® code. Then, a Sobol method-based optimization approach has been proposed to determine the normalized sensitivity index and optimal range of major non-dimensional and geometrical variables for the better off-design performance of the turboexpander. After that, different losses of the turbine have been determined using an optimum set of loss correlations which is incorporated into the preliminary design process. This approach can overcome the optimization issues caused by the high sensitive design parameters, which may not be addressed through conventional methods, and ameliorates the off-design performance of the turboexpander (improves power output, total-to-static efficiency, and diminishing the turbine losses by 14.28%, 3.89%, and 9.61% respectively) as compared to the initial design. Based on this, three turboexpander systems are designed and a comparative numerical study has been conducted to study the flow field phenomenon and their thermodynamic performance at three operating pressure and cryogenic temperature (16 bar & 150 K, 8 bar & 120 K, and 4.5 bar & 95 K) using ANSYS CFX®. Finally, the Claude cycle-based experimental facility has been established to determine the thermal performance of the turboexpander at various operating pressure (16 and 8 bar), rotational speeds (120,612, 102,419, and 80,914 rpm), inlet temperatures (150 and 120 K), and mass flow rates (0.01–0.10 kg/s). The results illustrate that the predicted performance from the numerical simulation shows good agreement with the experimental results. Additionally, error analysis of experimental parameters has also been discussed.

Design Concepts of Transition Metal Dichalcogenides for High-Performance Aqueous Zn-Ion Storage.

Aqueous Zn-ion batteries (AZIBs) are considered as promising large-scale energy storage devices due to their high safety and low cost. Transition metal dichalcogenides (TMDs) as the potential aqueous Zn-storage cathode materials are under the research spotlight because of their facile 2D ion-transport channels and weak electrostatic interactions with Zn2+ . In this concept article, we summarize the intrinsic structural features and aqueous Zn-storage mechanisms of the TMDs-based electrodes. More significantly, the latest design concepts of TMDs materials for high-performance AZIBs are discussed in detail from three aspects of interlayer expansion engineering, phase transition engineering, and structure defects engineering. Finally, the current challenges facing TMDs cathodes and possible remedies are outlined for future developments towards efficient, rapid, and stable aqueous Zn-ion storage.

Integrating the Synergy of the Gut Microbiome into Regenerative Medicine: Relevance to Neurological Disorders.

A new paradigm of cell therapy-based approaches as a solution to several diseases caused by damage or loss of cells/tissues leading to organ failure heralded the birth of a new branch in medicine called regenerative medicine (RM), which was further fueled by in vitro cell expansion and tissue engineering (TE) technologies, including the ability to grow embryonic stem cells, induce pluripotent stem cells, and so on. RM addresses organ failure by repair, regeneration, or restoration, rejuvenation using cells, stem cells, or progenitor cells as tools having added cell-derived products also as a tool, and extracellular matrix component–based support, either direct or indirect (e.g., matrix induced autologous chondrocyte implantation) using scaffolds. Now, the main objective of RM is to solve the functional loss of cells that have evolved from cells as tools to cell-derived factors and scaffolds per se as tools. In this context, an important yet indispensable group of cells that constitute the major portion of the human body in terms of the number of cells having several essential roles to play, both directly and indirectly, starting from digestion and the immune system to the growing evidence of influencing neuronal function, aging, and carcinogenesis has been ignored. We would like to focus on these in this review as they should essentially be considered as a tool of RM, especially for neurological disorders for their vital role. What we are indicating is the second genome or the gut microbiome.

천연가스 정압소에 설치한 터보팽창형 유도발전기의 계통 연계 시 과도특성 해석

A new type of power generation facility with TEG that utilizes waste pressure energy during the decompression process of liquid natural gas, and the problem of instantaneous voltage sag should be reviewed in advance for grid-connected operation mode. This study implemented an EMTP/RV simulation model and conducted a time-domain simulation for verifying transient characteristics of turbo expander driven a squirrel cage induction generator in a gas governor station. The simulation results for the case studies including parallel operation condition, reactive power compensation, and three-phase short-circuit fault condition were reviewed based on the grid code and finally contributed to propose the conceptual method for grid-connected operation of TEG.

Comparable transforming growth factor beta-mediated immune suppression in ex vivo-expanded natural killer cells from cord blood and peripheral blood: implications for adoptive immunotherapy

T cell-based therapies like genetically modified immune cells expressing chimeric antigen receptors have shown robust anti-cancer activity in vivo, especially in patients with blood cancers. However, extending this approach to an “off-the-shelf” setting can be challenging, as allogeneic T cells carry a significant risk of graft-versus-host disease (GVHD). By contrast, allogeneic natural killer (NK) cells recognize malignant cells without the need for prior antigen exposure and have been used safely in multiple cancer settings without the risk of GVHD. However, similar to T cells, NK cell function is negatively impacted by tumor-induced transforming growth factor beta (TGF-β) secretion, which is a ubiquitous and potent immunosuppressive mechanism employed by most malignancies. Allogeneic NK cells for adoptive immunotherapy can be sourced from peripheral blood (PB) or cord blood (CB), and the authors’ group and others have previously shown that ex vivo expansion and gene engineering can overcome CB-derived NK cells’ functional immaturity and poor cytolytic activity, including in the presence of exogenous TGF-β. However, a direct comparison of the effects of TGF-β-mediated immune suppression on ex vivo-expanded CB- versus PB-derived NK cell therapy products has not previously been performed. Here the authors show that PB- and CB-derived NK cells have distinctive gene signatures that can be overcome by ex vivo expansion. Additionally, exposure to exogenous TGF-β results in an upregulation of inhibitory receptors on NK cells, a novel immunosuppressive mechanism not previously described. Finally, the authors provide functional and genetic evidence that both PB- and CB-derived NK cells are equivalently susceptible to TGF-β-mediated immune suppression. The authors believe these results provide important mechanistic insights to consider when using ex vivo-expanded, TGF-β-resistant PB- or CB-derived NK cells as novel immunotherapy agents for cancer.

Design of thrust bearing for hydrogen liquefaction turbine

With rapid development of hydrogen energy industry, liquid hydrogen, as a carrier with the highest energy storage density, is an effective way to ensure the large-scale application of hydrogen energy. Thrust bearing, which is the core component of hydrogen liquefaction turbine expander, has always been difficult to design. In this paper, the stress characteristics of the thrust bearing for hydrogen liquefaction are analyzed, and the analysis for designed prototype is performed. The numerical simulation results are compared with the design method. Results show the optimum clearance of thrust bearing and clearance of closed bearing has obvious influence on the peak value and position of stiffness caused by eccentricity. Numerical simulation results reflect the internal flow structures in bearing clearance, while the maximum stiffness is relatively conservative compared to analysis of radius ratio.

Thermal performance analysis of a solar-driven supercritical CO2 split-flow recompression Brayton cycle

ABSTRACT Solar is a clean and renewable energy, and is considered as the desired heat source of supercritical CO2 Brayton cycle. The heliostat field and cavity receiver of DAHAN tower solar thermal power station in China are used for analyzing the geometric relations between the sun, heliostat field and the receiver. The ray-tracing method is applied to establish a model to calculate the heat flux distribution of heating surface in the receiver. According to the absorbed heat, the supercritical CO2 split-flow recompression Brayton cycle model can be built via the Aspen HYSYS software. The uneven distribution on the heating surfaces represents a higher heat flux at the center of the spot and a lower heat flux away from the spot. The maximum heat flux is 224 kW·m−2 at 9:00 am, 349 kW·m−2 at 12:00 noon, and 215 kW·m−2 at 3:00 pm. Based on this distribution, the thermal efficiency of DAHAN tower solar thermal power station can be obtained by modeling. Compared with the steam Rankine cycle, the thermal efficiency of supercritical CO2 Brayton split-flow recompression cycle has a 50% increment. Subsequently, the effects of the split-flow ratio, the inlet temperature and pressures of turbo expander and main compressor, and the heat absorption on the thermal performance of system are obtained. Finally, the optimal parameters are obtained as follows: the split-flow ratio is 0.605, and the inlet pressures of turbo expander and main compressor are 24 and 7.9 MPa, respectively. These interesting findings are particularly significant for the application of supercritical CO2 split-flow recompression Brayton cycle system and the operating parameters’ selection in solar thermal power generation stations.

Effects of Freeze–Thaw Cycles on Volume Change Behavior and Mechanical Properties of Expansive Clay with Different Degrees of Compaction

Freeze–thaw (F-T) cycles are one of the main deterioration factors for the performance of expansive clay in seasonally frozen soil regions. This study designed a unidirectional environmental boundary loading device for F-T cycle tests. Laboratory tests were conducted to quantitatively evaluate the effects of the F-T cycle on volume change behavior and mechanical properties of expansive clay with different degrees of compaction below the canal in Xinjiang. The SEM image processing was performed with the Image-Pro Plus image processing software to get pore parameters. The results showed that during the F-T cycle, the volume change of the sample gradually changes from contraction to expansion as the degree of compaction increases. As the degree of compaction increases, the hardening characteristics of the expansive clay are weakened, and the F-T cycle promotes the softening of the stress–strain relationship. The first F-T cycle resulted in a significant decrease of failure strength, and the failure strength of different compaction degrees decreased by 56.07%–67.54% after seven cycles. The failure strain and resilient modulus of the samples are attenuated to varying degrees after F-T cycles. The correlation rate between the porosity and the attenuation rate of the failure strength is 0.719–0.882, the corresponding weight reaches 0.419–0.445, and there is an excellent linear relationship between them. The research offers some important insights into the construction and maintenance of expansive clay engineering such as the Xinjiang Canal.

Design and performance analysis of the thrust gas bearing with single orifice for helium turbine

Thrust bearing is an important component for the stability of helium turbo-expander, and is a critical part to ensure the stable operation of helium refrigerator. A thrust bearing with single orifice is designed at the end of the fan brake for a home-made 500W@4.5K helium turbine. This design optimizes the mechanical structure of the rotor and improves the overall stability of the helium turbine. To increase the axial capacity, the static and dynamic calculation model of this thrust bearing is established to analyse the performance. This paper describes the variation curve of parameters and studies the influence of temperature on bearing performance by numerical simulation method. The analysis as more simple and efficient method is used to obtain the important parameters of this thrust gas bearing with single orifice, which meets the demand of the whole engineering design for helium turbine expander.

Design and analysis of the helium purification system for the NSRRC cryogenic system

Helium is an expensive consumable in cryogenic facilities and is used widely in space, medical and energy research. At NSRRC, liquid helium is used as a coolant for superconducting magnets and SRF cavities . Minor contaminants such as nitrogen, oxygen, moisture and oil will be picked up when liquid helium circulates in large scale cryogenic systems and such contaminants can crystalize and cause damage to the cold box turbo expanders resulting in system damage and failure . Therefore, a helium purification system is designed as an integral part of the cryogenic system to conserve helium by providing 99.9995% pure helium to the liquefier after eliminating contaminants. The NSRRC helium purification process is based on two principles, the first one being a cryo-sorption device using activated charcoal and a molecular sieve and the other being a cryo-condensation unit using a tubular heat exchanger. The purifier has been designed to purify impure helium with overestimated contaminants of as much as 2.5% nitrogen and 2.5% oxygen with a mass flow rate of 475 nm3/hr and delivering a pressure of 17 bar(a) of impure helium to the purifier, the actual impurity will be much lower than the actual design contaminants. In this paper, calculation and design of the helium purification system and components composed of one double pipe counter flow heat exchanger, one vessel and tube heat exchanger, one pre-cooler and one charcoal vessel will be discussed together with charcoal mass requirement calculations and design of other components. In NSRRC, helium is liquefied and is used as a coolant for the SRF system and for cryogenic undulators. During a cryogenic cycle in the cryogenic system, helium may pick up contaminants such as moisture, oxygen, oil, and nitrogen, which have a higher freezing point than liquid helium and will crystalize. These frozen impurities will then affect plant capacity and operation such as alternating flow characteristics, damaging moving parts like turbines in the cold box causing the overall cooling efficiency to drop. Eliminating the contaminants is therefore very important for the cryogenic system.

Experimental study of different structural parameters on gas lubricated spiral groove thrust bearing for cryogenic turbo expander

With the development of high speed and miniaturization of turbo expander, the gas-lubricated spiral groove dynamic pressure gas bearing plays an important role. An experimental study on the gas-lubricated spiral groove gas thrust bearing is carried out to research the relationship between the bearing loading capacity and the structural parameters such as the spiral angle, the groove length ratio, the groove width ratio and the rotating speed. The contrast experiment of spiral groove structure on thrust disc and bearing end face was also carried out. The experimental results show that the optimum spiral angle is 20°, the optimum groove length ratio is 0.61∼0.68, the optimum groove width ratio is 0.5∼0.55, and the new structure of the spiral groove on the thrust disc will increase the bearing loading capacity by 7.6% than the traditional structure.

Numerical Investigations of Wake Expansion in the Offshore Wind Farm Using a Large Eddy Simulation

Due to abundant wind resources and land saving, offshore wind farms have been vigorously developed worldwide. The wake of wind turbines is an important topic of offshore wind farms, in which the wake expansion is a key issue for the wake model and the layout optimization of a wind farm. The large eddy simulation (LES) is utilized to investigate various offshore wind farms under different operating conditions. The numerical results indicate that it is more accurate to calculate the wake growth rate using the streamwise turbulence intensity or the total turbulence intensity in the environment. By fitting the results of the LES, two formulae are proposed to calculate the wake growth rate of the upstream wind turbine. The wake expansion of the downstream wind turbine is analyzed, and the method of calculating the wake growth rate is introduced. The simulation indicates that the wake expansion of the further downstream wind turbines is significantly reduced. The smaller lateral distance of wind turbines in the offshore wind farm has the less wake expansion of the wind turbines. The wake expansion under different inflow wind speeds is also analyzed, while the wake expansion of wind turbines under more complex conditions needs to be further studied.

Modeling and Economic Operation of Energy Hub Considering Energy Market Price and Demand

This paper discusses the economic operation strategy of the energy hub, which is being established in South Korea. The energy hub has five energy conversion devices: a turbo expander generator, a normal fuel cell, a fuel cell with a hydrogen outlet, a small-scale combined heat and power device, and a photovoltaic device. We are developing the most economically beneficial operation strategy for the operators who own the hub, without making any systematic improvements to the energy market. First, sixteen conversion efficiency matrices can be achieved by turning each device (except the PV) on or off. Next, even the same energy must be divided into different energy flows according to price. The energy flow is controlled to obtain the maximum profit, considering the internal load of the energy hub and the price fluctuations of the energy market. Using our operating strategy, the return on investment period is approximately 9.9 years, which is three years shorter than that without the operating strategy.