Field Operating Conditions Research Articles

Determination of Temperature‐ and Carrier‐Dependent Surface Recombination in Silicon

Knowledge regarding the temperature dependence of the surface recombination at the interface between silicon and various dielectrics is critically important as it 1) provides fundamental information regarding the interfaces and 2) improves the modeling of solar cell performance under actual operating conditions. Herein, the temperature‐ and carrier‐dependent surface recombination at the silicon–oxide/silicon and aluminum–oxide/silicon interfaces in the temperature range of 25−90 °C using an advanced technique is investigated. This method enables to control the surface carrier population from heavy accumulation to heavy inversion via an external bias voltage, allowing for the decoupling of the bulk and surface contributions to the effective lifetime. Thus, it offers a simple and versatile manner to separate the chemical passivation from the charge‐assisted population control at the silicon/dielectric interface. A model is established to obtain the temperature dependence of the capture cross sections, a critical capability for the optimization of the dielectric layers and the investigation of the fundamental properties of the passivation under field operating conditions.

On the future sustainable ultra-high-speed maglev: A superconductor magnet technology enabling high energy efficiency and robustness

The blooming ultrahigh-speed SC maglev (superconducting magnetically levitated train) prompts green travel worldwide. We utilized high-temperature superconductor (HTS) magnets and have developed an energy-economical SC maglev prototype (Energ. Convers. Manage. (291)117247). In this paper, as a continuation, we further improve and maximize the performance of its key part – the HTS magnets, especially in compact high magnetic field and energy density operating conditions, by innovating an HTS magnet technology named the Shunted Extreme-NI Concept. The operational energy-robustness, -density, and -economy of HTS magnets, compared to the conventional type, are improved by 96.8%, 66.7%, and 52.5%, respectively. For a full-scale maglev equipped with this technology, the estimated energy consumption per passenger kilometer can be further reduced to below 20% of that of airplanes under the same cruising speed of 1000 km/h. This work is dedicated to advancing the energy performances of HTS magnets, heading to the future sustainable maglev transportation.

勺轮式排种器在振动条件下的排种性能试验研究

The seeder was tested and evaluated for field operations vibration characteristics in light of the issue that the spoon-wheel maize precision seeder vibrates due to the field operating conditions, which impairs the performance of the seed-metering device. During field testing, it was discovered that the seed-metering device vibrated greater as the forward speed increased, resulting in a higher peak vibration acceleration. However, fluctuations in forward speed did not affect the frequency distribution of the peak vibration acceleration. Time-domain and spectrogram investigations revealed that the vibration frequency of the seed-metering device was predominantly within 0~10 Hz for seeder operating speeds ranging from 2~6 km/h, with acceleration values spanning from 0.85~1.86 m/s2. An electromagnetic seeding test stand was established in response to the discoveries. The essential variables governing the seeding performance of the spoon-wheel seed-metering device were then investigated using orthogonal tests, such as forward speed, vibration frequency, and vibration acceleration. The empirical results elucidated a hierarchical relationship between these factors and seeding quality. Specifically, vibration frequency emerged to be the predominant factor, followed by vibration acceleration, and forward speed. The seeding quality of the seed-metering device was negatively correlated with increases in forward speed and vibration acceleration, which led to a lower qualified rate, higher leakage rate, and variation coefficient. Overall, the qualified rate, leakage rate, and variation coefficient were all significantly influenced by the three factors.

Study on the process technology of energy saving and consumption reducing for municipal sludge-based biochar

Taking the production process of sludge-based biochar as the research object, based on the measured data of engineering field operation, the thermal balance models of sludge carbonization and cooling conveying system, pyrolysis gas incineration and waste heat recovery system, flue gas treatment and deodorization system were established respectively. The energy loss points in the process of operation were determined and calculated. The results show that the energy consumption loss of sludge-based biochar production process is 23550 MJ/h under the field operation conditions of feeding 2920 kg/h of dry sludge (moisture content 30 %), 19.65 kg/h of natural gas and 67 kg/h of fresh water, producing 1500 kg/h of sludge-based biochar (moisture content 4.5 %) and carbonization temperature 450 °C. Compared with the sludge drying incineration process, it can save energy and reduce consumption by 52.2 %, and the calorific value of sludge-based biochar is 7.04 MJ/kg, which is 49.6 % higher than that of dry sludge.

A self-enhanced electrochemiluminescence array chip for portable label-free detection of SARS-CoV-2 nucleocapsid protein with smartphone

SARS-CoV-2 antigen detection plays a key role in the rapid diagnosis of COVID-19. However, current clinically used immunoassays are often limited by assay throughput, sensitivity, accuracy, and field operating conditions. To address these challenges, we constructed a self-enhanced electrochemiluminescence (ECL) array chip (SE2AC) for highly sensitive and label-free detection of SARS-CoV-2 nucleocapsid protein (N protein) with a facile and portable assay setup. Firstly, the self-enhanced ECL nanomaterials with inherent film-forming properties were synthesized by co-doping Ru(bpy)32+ and polyethyleneimine (PEI) in silica nanoparticles (Ru/PEI@SiO2). Secondly, a resistance-induced potential difference-based single-electrode electrochemical system (SEES) was adapted to serve as the electrode array to facilitate one-step assembly without the need for chip alignment. Thirdly, the chip electrode array was functionalized with the synthesized self-enhanced ECL emitters and captured antibodies. In addition, a portable detection box equipped with a smartphone was 3D-printed to serve as the chip holder and “dark room” for imaging acquisition. The SE2AC performance was validated with N protein with a limit of detection (LOD) of 0.47 pg/mL in the range of 1–10,000 pg/mL. Furthermore, the chip successfully detected the viral antigen residue as low as 1.92 pg/mL from diluted rehabilitation patients’ serum samples. This is the first study reporting label-free detection of SARS-Cov-2 N protein based on a self-enhanced ECL immunosensor, which provides a novel facile method for highly sensitive diagnosis of COVID-19 with high throughput, portability, and low cost.

Reliability evaluation of DC power optimizers for photovoltaic systems: Accelerated testing at high temperatures with fixed and cyclic power stresses

This paper presents a long-term and large-scale time-to-failure reliability study to determine the acceleration factor and field-use lifetime for dc optimizers. Forty optimizers were tested at two high static temperatures (85 °C and 95 °C) and two input power profiles (fixed power and cyclic power) over a period of 6400 h. For degradation analysis, continuous electrical and thermal data were collected. On average, the dc optimizer units degraded by about 1%, while no hard failures occurred over 6400 h of high-temperature stress testing. Using the Arrhenius life-stress model along with average field measured temperature, it is predicted that the dc optimizers should be able to survive for 39–73 years in field operating conditions with a reliability of 79%, having a lower one-sided confidence bound of 90%, demonstrating similar or even exceeding the lifetime of the associated PV modules. Nevertheless, with the determined activation energy of 0.33 eV, derived from the observed degradation percentage in cyclic power profiles, the projected lifespan for dc optimizers is significantly curtailed. Under field conditions, our estimations suggest a service life ranging between 9 and 12 years. Furthermore, the cyclic power profile at higher stress temperature demonstrated higher levels of degradation compared to the fixed power profile. This implies the cyclic thermal mechanisms at higher stress temperature (which are not captured in the Arrhenius equation) account for a higher contribution to degradation. This has been confirmed through the use of Weibull distribution model where the analysis indicates that the estimated lifetime for dc optimizer can significantly decrease based on a higher stress temperature along with the power cycling of the units.

Modeling and simulation of an industrial adsorption process of dehydration of natural gas in 4A molecular sieves: Effect of adsorbent aging

Adsorption in molecular sieves is the number one choice for the dehydration of natural gas in offshore platforms. Many phenomenological and mathematical approaches have been used to describe this unit operation. However, the effect of aging on the operation performance, and consequently the adequacy of these models to describe operational field conditions, has been seldom assessed. This work presents the simulation of an industrial unit of natural gas dehydration with 4A molecular sieves in different cycle numbers using a phenomenological model. First, the most adequate equilibrium isotherm to describe experimental data of pure compound adsorption (viz., the dual-site Langmuir isotherm) was determined. Second, momentum, mass, and energy transfer equations were implemented, and the modeling of literature adsorption data was used to verify the adequacy of the developed equations. Finally, an industrial dehydration unit was modeled using the same approach, and calculated breakthrough times were compared to field data. In conclusion, the premature aging of molecular sieves in industrial operation appears as a defining factor in equipment performance.

Characterization of asphaltene removal mechanisms from well columns using surface energy

The deposition of asphaltene in well columns would compromise flow assurance and possible occurrence of under deposit corrosion. The formed deposit is the net difference between deposition and removal of asphaltene fouling. While there has been a body of research on deposition, the subjects of removal and its dominant mechanisms have received less attention. The present study therefore examines the most important removal mechanisms of shear force, rolling, and rebound under field operating conditions. To achieve this, the removal critical velocity was examined as a function of oil properties of density (870–1000 kg/m3) and viscosity (1.5–3.0 cP), casing diameter (4.5–7 in), and casing substrate (two grades of carbon steel). Experiments were used to determine the preliminary surface energy/tension characteristics of the investigated casing surfaces, crude oil sample, and crude oil-extracted asphaltene particles. The findings revealed that the casing substrate would profoundly influence the removal of asphaltene from the surface whereas the impact of oil properties and casing diameter would be meagre. Furthermore, the larger the asphaltene particles, the greater the possibility for asphaltene removal. For similar thermodynamic, hydrodynamic, and geometrical conditions, the rebound is the major mechanism for removal of asphaltene deposits, according to the predicted critical removal velocities. Finally, to calculate the proportion of precipitated asphaltene particles that would ultimately attach to the surface of the casing, the sticking probability is examined.

Biotrickling Filtration for the Reduction of N2O Emitted during Wastewater Treatment: Results from a Long-Term In Situ Pilot-Scale Testing.

Wastewater treatment plants (WWTPs) are a major source of N2O, a potent greenhouse gas with 300 times higher global warming potential than CO2. Several approaches have been proposed for mitigation of N2O emissions from WWTPs and have shown promising yet only site-specific results. Here, self-sustaining biotrickling filtration, an end-of-the-pipe treatment technology, was tested in situ at a full-scale WWTP under realistic operational conditions. Temporally varying untreated wastewater was used as trickling medium, and no temperature control was applied. The off-gas from the covered WWTP aerated section was conveyed through the pilot-scale reactor, and an average removal efficiency of 57.9 ± 29.1% was achieved during 165 days of operation despite the generally low and largely fluctuating influent N2O concentrations (ranging between 4.8 and 96.4 ppmv). For the following 60-day period, the continuously operated reactor system removed 43.0 ± 21.2% of the periodically augmented N2O, exhibiting elimination capacities as high as 5.25 g N2O m-3·h-1. Additionally, the bench-scale experiments performed abreast corroborated the resilience of the system to short-term N2O starvations. Our results corroborate the feasibility of biotrickling filtration for mitigating N2O emitted from WWTPs and demonstrate its robustness toward suboptimal field operating conditions and N2O starvation, as also supported by analyses of the microbial compositions and nosZ gene profiles.

Field Study of Photovoltaic Systems with Anti-Potential-Induced-Degradation Mechanism: UVF, EL, and Performance Ratio Investigations

The potential-induced degradation (PID) of photovoltaic (PV) modules is one of the most extreme types of degradation in PV modules, where PID-affected modules can result in an almost 25% power reduction. Understanding how module defects impact PID is key to reducing the issue. Therefore, this work investigates the impact of an anti-PID inverter on PV modules throughout three years of field operating conditions. We used electroluminescence (EL), ultraviolet fluorescence (UVF), and thermography imaging to explore the varieties of an anti-PID inverter connected to a PV string. It was discovered that a PV string with an anti-PID inverter could improve the output power of the modules by 5.8%. In addition, the performance ratio (PR) was equal to 91.2% and 87.8%, respectively, for PV strings with and without an anti-PID inverter.

A Novel Domain Adversarial Graph Convolutional Network for Insulation Defect Diagnosis in Gas-Insulated Substations

The data-driven models have achieved remarkable advancements in diagnosing gas-insulated substation (GIS) insulation defects on specific massive datasets. However, restricted by field operating conditions and sample scarcity of GIS, the above methods are difficult to achieve high-precision and robust diagnosis of GIS insulation defects on-site. To settle these problems, we propose an innovative domain adversarial graph convolutional network (DAGCN) for few-shot GIS insulation defects on-site. To improve the accuracy of GIS insulation defects diagnosis, a graph convolutional network (GCN) with multiple attention mechanisms is constructed to take advantage of node features and topology to adaptively mine defect features. Then, a novel domain adversarial (DA) tactic is introduced for GIS insulation defect diagnosis in few-shot conditions through the transfer of diagnostic knowledge. In the proposed DA, the source and target domains classifier loss are jointly optimized to realize feature migration and domain matching. Experiment results demonstrate that the DAGCN achieves reliable diagnosis of GIS insulation defect, which has obvious advantages over existing methods. Simultaneously, the DAGCN proposed can achieve satisfactory diagnosis including unlabeled field samples. Moreover, it has development potential in diagnosing unlabeled samples, thus providing a feasible solution for GIS insulation defect diagnosis and GIS operation and maintenance.

Efficacy of selected herbicides on Cuban bulrush [Oxycaryum cubense (Poepp. & Kunth) Lye

Cuban bulrush (Oxycaryum cubense) (Poepp. & Kunth) Lye is an epiphytic perennial sedge that invades aquatic habitats in the southeastern United States. Its emergent and floating growth habit allows it to form tussocks that restrict waterway access for navigation and outcompete native plant species. It is primarily managed using herbicides, and there is a need to evaluate more active ingredients for Cuban bulrush control. Three groups of single or tank mix herbicide applications were evaluated for control of Cuban bulrush in a greenhouse setting Florida. In trial 1, we evaluated operational treatments currently used by state agencies in Florida (diquat, glyphosate, 2,4-D, glyphosate þ flumioxazin, 2,4-D þ diquat, and 2,4-D þ glyphosate). In trial 2, we evaluated a recently registered synthetic auxin herbicide (florpyrauxifen-benzyl) alone or in combination with 2,4-D, imazamox, or flumioxazin. In trial 3, we evaluated several acetolactate synthase (ALS)-inhibitor herbicides (halosulfuron, imazapic, imazethapyr, bispyri-bac-sodium, imazapyr, and imazamox). Operational treat-ments and florpyrauxifen-benzyl combinations resulted in . 70% visual control 30 days after treatment (DAT) and . 90% biomass reduction of aboveground tissue 60 DAT. ALS-inhibiting herbicides resulted in slower symptom development, although there was limited regrowth (. 90% biomass reduction) 60 DAT for plants treated with imazapic, imazethapyr, imazamox, and imazapyr. Halosulfuron and bispyribac-sodium resulted in inconsis-tent levels of control between experimental runs. These small-scale results suggest that the current operational treatments as well as florpyrauxifen-benzyl combinations provide both fast and effective control of Cuban bulrush. Future work will focus on verifying these findings under operational field conditions.

Experimental Study on the Relationship Between the Change of Free available Chlorine and the Increase Rate of Disinfection by-products according to Operating Conditions of three Types of Sodium Hypochlorite

Objectives : This study was conducted to suggest field operating conditions that can minimize disinfection by-products for three types of sodium hypochlorite.Methods : In this study, changes in free available chlorine, chlorate and bromate were analyzed according to storage temperature, storage time and presence or absence of sunlight for three types of sodium hypochlorite(two types of bleach and one type of sodium hypochlorite made on-site hypochlorite generator).Results and Discussion : In the case of bleach with 12% free available chlorine, when operating with a target of 10% of more of free available chlorine, the storage time for each storage temperature was 3 days at 40℃, 13 days at 30℃, 27 days at 20℃, 85 days at 10℃, and 200 days at 5℃. In the case of bleach with 5% free available chlorine, when operating with a target of 4% of more of free available chlorine, the storage time for each storage temperature was 37 days at 35℃, 255 days at 20℃, 1,343 days at 10℃, and 4,821 days at 4℃. In the case of sodium hypochlorite with 0.8% free available chlorine made on-site hypochlorite generator, when operating with a target of 0.7% of more of free available chlorine, the storage time for each storage temperature was 10 days at 3 5℃, 42 days at 20℃, 470 days at 10℃, and 1,770 days at 4°C. As a result of evaluating the quality change according to the presence or absence of UV protection, the free available chlorine decreased rapidly when exposed to sunlight, whereas the free available chlorine decreased slowly in the case of indoor storage.Conclusion : Bleach with 12% free available chlorine can be stored for about 60 days at 15℃, and bleach with 5% free available chlorine can be used within about 6 months at 15℃. And sodium hypochlorite with 0.8% free available chlorine can be used within 10 days at room temperature. In addition, when storing sodium hypochlorite, it is suggested that it be stored indoors protected from sunlight.

An Automatic Data Augmentation Method for Working Condition Diagnosis of Rod Pumping Systems Based on Teacher Knowledge

Working condition diagnosis is an important means of evaluating the operating state of rod pumping systems. As the data source of working condition diagnosis, the quality of indicator diagrams will have a significant impact on the diagnosis results. In the actual oil field production process, the number of samples between indicator types is usually unbalanced, so it is an important means to improve the diagnostic accuracy by using data augmentation methods. However, traditional data augmentation methods require manual design, and the experimental results are not satisfactory. We propose an automatic data augmentation method based on teacher knowledge for working condition diagnosis of rod pumping systems. This method adopts an adversarial strategy for data augmentation and optimization and uses the teacher model as prior knowledge to generate information-rich transformation images for the model, thereby improving the generalization of the working condition diagnosis model. Specifically, our method makes the augmented images adversarial to the target model and recognizable to the teacher model. Compared with traditional methods, this method can automatically select the correct data enhancement method according to different indicator diagram sample sets to solve the corresponding problems. Our method has an accuracy of more than 98% in the diagnosis of actual oil field operating conditions. The experiment showed that the accuracy of this method was more than 5% higher than that of the traditional data augmentation methods in the task of condition diagnosis, which shows that this method has research and development value.

Development of technological solutions for reliable killing of wells by temporarily blocking a productive formation under ALRP conditions (on the example of the Cenomanian gas deposits)

Modern field operation conditions are characterized by a decline in gas production due to the depletion of its reserves, a decrease in reservoir pressure, an increase in water cut, as well as due to the depreciation of the operating well stock. These problems are especially specific at the late stage of development of the Cenomanian deposits of Western Siberia fields, where the anomaly factor below 0.2 prevails, while gas-bearing formations are represented mainly by complex reservoirs with high-permeability areas. When killing such wells, the classical reduction of overbalance by reducing the density of the process fluid does not provide the necessary efficiency, which requires the search for new technical and technological solutions. In order to prevent the destruction of the reservoir and preserve its reservoir properties during repair work in wells with abnormally low reservoir pressure, AO “SevKavNIPIgaz” developed compositions of special process fluids. A quantitative description of the process of blocking the bottomhole formation zone is proposed by means of mathematical modeling of injection of a gel-forming solution into a productive horizon. The well killing technology includes three main stages of work: leveling the injectivity profile of the productive strata using three-phase foam, pumping the blocking composition and its displacement with the creation of a calculated repression. Solutions obtained on the basis of a mathematical model allow optimizing technological parameters to minimize negative consequences in the well killing process.

An integrated anti-interference suppression strategy based on L-type and π type circuit series for integrated distribution box

With the wide application of intelligent distribution equipment, the operation and management level of the distribution network has been significantly improved. At present, domestic and foreign scholars' researches on the primary and secondary integration technology of distribution switch are still in its infancy. And it needs to be further discussed. Based on the structure theory of the distribution terminal acquisition unit, this paper analyzes the influence of temperature rise, pressure, and strong electromagnetic interference on the performance of primary and secondary fusion equipment under field operating conditions. To improve the operation reliability of the integrated equipment, an anti-interference suppression measure of the primary and secondary fusion distribution switch is proposed based on the series connection of L-type and π-type circuits and the accuracy detection method of the transformer. It solves the problem of high-frequency damping oscillation effectively at the input of the transformer under the condition of electromagnetic interference. This paper verifies the feasibility and effectiveness of the integrated fusion technology of the primary and secondary fusion equipment of distribution switches through theory and experiment.

Simulation of Cathode Catalyst Durability Under Fuel Cell Vehicle Operation - the Effect of Temperature

Fuel cell vehicles (FCVs) emerge to be promising candidates to produce clean power for the transportation sector in order to tackle climate change issues. Although the commercialization of polymer electrolyte membrane fuel cells (PEMFCs) has progressed in the past few decades, there are still obstacles to address, including high cost and limited hydrogen infrastructure. For heavy duty transportation applications, the PEMFC durability is also not yet proven, and extrapolating from lab data to real-world field operating conditions remains a significant challenge [1].In this work, the cathode catalyst degradation in PEMFCs is studied to make an estimation of fuel cell durability in the FCV application. The well-known Butler-Volmer approach is utilized to model platinum dissolution and redeposition, platinum oxidation and platinum ion formation during the fuel cell operation [2]. First, the model is calibrated with the results presented by Ferreira et al. [3] at 80℃; the calibrated model is then validated with Kocha’s results [4] to demonstrate the model’s capability of generating reliable results at different temperatures. In order to realistically predict the cathode degradation pattern and lifetime, the real-life fuel cell operating conditions should be obtained. Therefore, a drive cycle recorded based on a real-life transit bus operation in the city of Victoria is utilized to calculate the input fuel cell voltage profile. The procedure to calculate fuel cell operating voltage profile using the drive cycle has been thoroughly explained by Ahmadi and Kjeang [5]. This procedure employs Newton’s second law to calculate the required cell power density considering the air flow drag force counteracting the vehicle thrust. Finally, polarization curves representing the fuel cell performance are used to calculate the fuel cell voltage profile with the determined required cell power density. Polarization curves measured under a range of temperatures are employed to adequately reflect the effect of temperature on the fuel cell performance. The cell active area is considered to be 500 cm2 and the stack is assumed to contain 225 cells, representing a nominal stack power of 74 kW at 80℃. The fuel cell operation and degradation are simulated at three different temperatures: 60, 70, and 80℃. The change of remaining electrochemically active surface area (ECSA) with time is calculated as the output of the model.Temperature highly affects the electrochemical reactions of platinum dissolution in several ways. First, it affects the Tafel slope in the platinum dissolution reaction. Second, it substantially impacts on platinum degradation reaction rate constant [6]. The Arrhenius approach is taken in this study to apply the effect of temperature on the reaction rate constants. Fuel cell voltage loss over time is determined by assuming simple Tafel kinetics. The cathode lifetime is calculated at 0.6 A/cm2 and is estimated by considering 10% voltage drop as the failure criterion. Fig. 1 shows the simulated change of remaining ECSA over time and the resulting fuel cell lifetime for the three different cell temperatures. The results indicate that the cathode lifetime increases 168% when the cell temperature drops from 80℃ to 60℃ due to a significantly lower platinum degradation rate at 60℃. The results show relatively low cathode catalyst lifetimes for a transit bus. The reason is attributed to the bus drive cycle used as the model input. The drive cycle contains a great portion of deceleration and idling time which leads to a fuel cell operation close to open circuit voltage (OCV), thus experiencing a high degradation rate.In this regard, the present modeling framework could become a useful tool for fuel cell and FCV developers to predict lifetime for new products and systems prior to commercial release. Scientifically, the present model can also be used to further explore key influencing factors on fuel cell durability and develop more durable cell, stack, and system designs for a targeted FCV application. Acknowledgements This research was supported by the Natural Sciences and Engineering Research Council of Canada, Canada Research Chairs, and Simon Fraser University Community Trust Endowment Fund.

Experimental and Computational Investigation for Accelerated Testing and Characterization of Next-Generation Steam Turbine Rotors

Abstract A unique set of test protocols is developed to evaluate new materials for high-temperature and pressure applications (>700 °C and 310 bar) in next-generation thermal power plants. These protocols employ accelerated testing processes to provide a realistic estimate of a component’s life under actual field operating conditions. A state-of-the-art experimental facility to characterize turbine rotors for advanced ultra-supercritical conditions was commissioned at Bharat Heavy Electricals Limited, India. An alloy rotor mounted inside the test chamber is subjected to cyclic thermal and mechanical stresses at elevated temperatures for a predetermined number of thermal cycles to estimate its creep and fatigue life. Cyclic thermal and mechanical loads are applied by sequentially exposing rotors rotating at high speed to transient heating, steady-state soaking, and transient cooling. These transient heating and cooling processes are carefully designed to achieve specific temperature gradients inside the rotor bulk. The rotor is heated in a vacuum by thermal radiation from heater coils. In contrast, rotor cooling is accomplished by circulating relatively cold nitrogen gas through the chamber. Preliminary findings from accelerated tests are reported here. Two computational fluid dynamics (CFD) models were developed to support the transient heating and cooling experiments. Good agreement is observed between CFD simulations and measurements, validating the approach presented. This facility, established under a clean energy research initiative, plays a vital role in reducing the time and cost involved in finding suitable alloy materials, thus advancing the development of ultra-efficient thermal power plants.

Experimental Evaluation of the Rheological Properties and Influencing Factors of Gel Fracturing Fluid Mixed with CO2 for Shale Gas Reservoir Stimulation.

Foam gel fracturing fluid has the characteristics of low formation damage, strong flowback ability, low fluid loss, high fluid efficiency, proper viscosity, and strong sand-carrying capacity, and it occupies a very important position in fracturing fluid systems. The rheological properties of gel fracturing fluid with different foam qualities of CO2, under different experimental temperatures and pressures, have not been thoroughly investigated, and their influence on it was studied. To simulate the performance of CO2 foam gel fracturing fluid under field operation conditions, the formula of the gel fracturing fluid was obtained through experimental optimization in this paper, and the experimental results show that the viscosity of gel fracturing fluid is 2.5 mPa·s (after gel breaking at a shear rate of 500 s−1), the residue content is 1.3 mg/L, the surface tension is 25.1 mN/m, and the interfacial tension is 1.6 mN/m. The sand-carrying fluid has no settlement in 3 h with a 40% sand ratio of 40–70-mesh quartz sand. The core damage rate of foam gel fracturing fluid is less than 19%, the shear time is 90 min at 170 s−1 and 90 °C, the viscosity of fracturing fluid is >50 mPa·s, and the temperature resistance and shear resistance are excellent. The gel fracturing fluid that was optimized was selected as the base fluid, which was mixed with liquid CO2 to form the CO2 foam fracturing fluid. This paper studied the rheological properties of CO2 foam gel fracturing fluid with different CO2 foam qualities under high temperature (65 °C) and high pressure (30 MPa) and two states of supercooled liquid (unfoamed) and supercritical state (foamed) through indoor pipe flow experiments. The effects of temperature, pressure, shear rate, foam quality, and other factors on the rheological properties of CO2 foam gel fracturing fluid were considered, and it was confirmed that among all the factors, foam quality and temperature are the main influencing factors, which is of great significance for us to better understand and evaluate the flow characteristics of CO2 foam gel fracturing fluid and the design of shale gas reservoir fracturing operations.

Efficiency of an Inverted-Shroud Gravitational Gas Separator: Effect of the Liquid Viscosity and Inclination

Summary Gas-liquid separation is a typical process in many applications. For instance, gas separation is critical for the proper operation of electrical submergible pumps in the oil and gas industry as the pumps’ performance and lifetime are severely reduced when working with high gas/oil ratios. Gas-liquid separators are installed in oil production wells to reduce the void fraction at the pump inlet. The inverted-shroud gravitational separator stands out due to its efficiencies higher than 97%. This separator performs the gas separation process in two stages. The first is a segregation process related to inversion from liquid to gas continuous flow, whereas the second stage is related to gas entrainment associated with kinetic-energy dissipation process. The latter is more complex to model in the vertical than in the inclined separator’s position. Previous studies revealed that the liquid flow rate and separator’s inclination are relevant parameters for the gas separation efficiency (GSE). However, studies regarding the effect of the liquid viscosity on GSE are scanty. We evaluate the influence of the liquid viscosity and separator’s inclination on the GSE of an inverted-shroud separator (IS-separator) with water-air and oil-air mixtures. Efficiency maps for each inclination and empirical correlations to predict the GSE in the vertical inclination are proposed. New experimental data collected for several liquid flow rates and separator inclinations are offered in this study as a starting point to develop universal GSE maps. Different gas separation phenomena are observed depending on the flow pattern at the inner annular channel (IAC) of the separator and its inclination. The experiments conducted with the water-air mixture indicated turbulent flow, while the oil-air mixture revealed laminar flow for both inclined and vertical positions. The results suggest that the greater the liquid viscosity, the higher the GSE. The efficiency maps indicate that it is possible to reach total gas separation (TGS) for many experimental conditions. In practice, our approach proposes an alternative technology where the variables that influence the production well’s dynamic fluid level are actively controlled. Therefore, the IS-separator can operate under operational field conditions similar to those tested on a laboratory scale. This fact makes the IS-separator a promising tool for industrial applications.