Search

Aluminum alloy die casting has achieved rapid development in recent years and has been widely used in all walks of life. However, due to its high pressure and high-speed technological characteristics, avoiding hole defects has become a problem of great significance in aluminum alloy die casting production. In this paper, the filling visualization dynamic characterization experiment was innovatively developed, which can directly study and analyze the influence of different injection rates on the formation and evolution of alloy flow patterns and gas-induced defects. As the injection speed increased from 1.0 m/s to 1.5 m/s, the average porosity increased from 7.49% to 9.57%, marking an increase in the number and size of the pores. According to the comparison with Anycasting, simulation results show that a liquid metal injection speed of 1.5 m/s when filling the flow front vs. the previous injection rate of 1.0 m/s caused fractures when filling at the same filling distance. Therefore, the degree of the broken splash at the flow front is more serious. Combined with the analysis of transport mechanics, the fracturing is due to the wall-attached jet effect of the liquid metal in the filling process. It is difficult for the liquid metal to adhere to the type wall in order to fuse with subsequent liquid metal to form cavity defects. With an increase in injection velocity, the microgroup volume formed via liquid breakage decreases; thus the volume of air entrapment increases, finally leading to an increase in cavity defects. [ABSTRACT FROM AUTHOR]

Diesel engine combustion is dependent mainly on the fuel injection characteristics, particularly the injection pressure and rate, which directly affect the engine efficiency and emissions. Herein, an electrically controlled supercharger is added to a traditional high-pressure common rail system to form an ultrahigh-pressure common rail system. Then, the variations in the spray, combustion, and emission characteristics of a diesel engine with a variable fuel injection rate are analyzed. Moreover, a simulation model for a diesel engine combustion chamber is built and verified by experimental results for numerical analysis. The results reveal that the injection rate can be flexibly adjusted via regulation when the solenoid valves are opened on the electrically controlled supercharger. Specifically, (1) the boot-shaped injection rate has greater potential than the traditional rectangular injection rate in terms of combustion and emission; (2) the main injection advance angle at the boot-shaped injection rate can be properly increased to improve combustion; and (3) the pilot injection quantity and advance angle are strongly coupled with the boot-shaped injection rate, potentially enhancing the mixing efficiency of fuel and air in the cylinder to achieve favorable emission results. This paper provides good guidance for the reliable design and optimization of noble-metal-based diesel engines. [ABSTRACT FROM AUTHOR]

A viable green energy source for heavy industries and transportation is hydrogen. The internal combustion engine (ICE), when powered by hydrogen, offers an economical and adaptable way to quickly decarbonize the transportation industry. In general, two techniques are used to inject hydrogen into the ICE combustion chamber: port injection and direct injection. The present work examined direct injection technology, highlighting the need to understand and manage hydrogen mixing within an ICE's combustion chamber. Before combusting hydrogen, it is critical to study its propagation and mixture behavior just immediately before burning. For this purpose, the DI-CHG.2 direct injector model by BorgWarner was used. This injector operated at 35 barG and 20 barG as maximum and minimum upstream pressures, respectively; a 5.8 g/s flow rate; and a maximum tip nozzle temperature of 250 °C. Experiments were performed using a high-pressure and high-temperature visualization vessel available at our facility. The combustion mixture prior to burning (spray) was visually controlled by the single-pass high-speed Schlieren technique. Images were used to study the spray penetration (S) and spray volume (V). Several parameters were considered to perform the experiments, such as the injection pressure (Pinj), chamber temperature (Tch), and the injection energizing time (Tinj). With pressure ratio and injection time being the parameters commonly used in jet characterization, the addition of temperature formed a more comprehensive group of parameters that should generally aid in the characterization of this type of gas jets as well as the understanding of the combined effect of the rate of injection on the overall outcome. It was observed that the increase in injection pressure (Pinj) increased the spray penetration depth and its calculated volume, as well as the amount of mass injected inside the chamber according to the ROI results; furthermore, it was also observed that with a pressure difference of 20 bar (the minimum required for the proper functioning of the injector used), cyclic variability increased. The variation in temperature inside the chamber had less of an impact on the spray shape and its penetration; instead, it determined the velocity at which the spray reached its maximum length. In addition, the injection energizing time had no effect on the spray penetration. [ABSTRACT FROM AUTHOR]

OBJECTIVE This study evaluated the effects of scanning position and contrast medium injection rate on pulmonary CT perfusion (CTP) images in healthy dogs. ANIMALS 7 healthy Beagles. METHODS Experiments involved 4 conditions: dorsal and sternal recumbency at 2.5 mL/s (first) and sternal recumbency with additional rates of 1.5 and 3.5 mL/s (second). Various parameters, including the initial time of venous enhancement (Tv), peak time of arterial enhancement (PTa), and peak enhancement values of the artery, were measured. The PTa to Tv interval was calculated. Perfusion mapping parameters (pulmonary blood flow, pulmonary blood volume, mean transit time, time to maximum, and time to peak) were determined in different lung regions (left and right dorsal, middle, and ventral). RESULTS There are significant variations in most perfusion mapping parameters based on the pulmonary parenchymal location. Dorsal recumbency had a lower peak value of arterial enhancement than sternal recumbency. Pulmonary blood flow in the dorsal region and mean transit time and time to maximum in all regions showed no significant differences based on position. Pulmonary blood volume and time to peak varied with scanning position. The PTa to Tv interval did not differ based on the injection rate, but the injection time at 1.5 mL/s was longer than at other rates. All perfusion mapping parameters of the ventral region increased with higher injection rates. CLINICAL RELEVANCE The recommended CTP imaging approach in dogs is a low injection rate of 1.5 mL/s in the sternal recumbency. This study provides reference ranges for perfusion parameters based on the pulmonary parenchymal location, contributing to the acquisition and application of pulmonary CTP images for differential diagnosis in small-breed dogs. [ABSTRACT FROM AUTHOR]

Copyright of Irrigation & Drainage is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Simultaneous multiple-fracture treatments in horizontal wellbores have become an essential technology for the economic development of shale gas reservoirs. During hydraulic fracturing, fracture initiation and propagation always induce additional stresses on the surrounding rock. When multiple fractures develop simultaneously, the development of some fractures is limited due to the stress-shadow effect. An in-depth understanding of the multiple-fracture propagation mechanism as reflected by fracture morphology and flow rate distribution can help to set reasonable operation parameters for improving the uniformity of multiple fractures and forming a complex fracture network according to the different in situ stress conditions in a reservoir to increase the shale gas recovery and reduce the cost. In this study, a two-dimensional (2D) fracture propagation model was developed based on the extended finite element method (XFEM). Then, the influences of various factors, including geological and operational factors, on the development of multiple fractures were studied. The results of numerical simulations showed that increasing the cluster spacing or injecting fracturing fluid with lower viscosity can help reduce the stress-shadow effect. In the case of smaller in situ stress differences, the deflection of the fractures was larger due to the stress-shadow effect. As the stress difference increased, the direction of the propagation of the fracture was gradually biased towards the direction of maximum horizontal stress. In addition, the injection rate had some effects on the fracture morphology and flow rate distribution. However, as the injection rate increased, the dominant fracture developed rapidly, and the fracture length significantly increased. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing has been widely used to enhance reservoir permeability during the extraction of shale gas. As one of the external input parameters, injection rate has a significant impact on formation breakdown pressure and the complexity of hydraulic fractures. To gain deeper insights into the effect of injection rate on breakdown pressure and fracture morphology, we conducted five hydraulic fracturing experiments on Changning shale in the laboratory. We used five different injection rates between 3 and 30 mL/min to fracture cylindrical core samples with 50 mm in diameter and 100 mm in length. We monitored acoustic emissions and surface displacements during the tests, and analyzed the fracture pattern post mortem by using a fluorescent tracer. We find a semi-logarithmic relationship between the breakdown pressure and the injection rates. Second, we find that it is the injection rate that dictates sample deformation and crack formation during breakdown rather than the fluid volume injected during the whole process. The analysis of amplitudes and frequency of acoustic signals indicates that hydraulic fracturing of Changning shale is overall dominated by tensile fractures (> 60%). However, at low injection rates, shear events are facilitated before rock breakdown. On the other hand, high injection rates result in reducing fracture tortuosity and surface roughness due to limited fluid infiltration in the relatively short injection window. We close this study with a conceptual model to explain the difference between fluid infiltration (low injection rates) and the loading rate effect (high injection rate) in low-permeability shale rocks. The findings obtained in this study can help to adjust injection rates in the field to economically and safely produce gas from shale. Highlights: Rock expansion upon breakdown is dominated by instantaneous crack opening caused by injection rates. Low injection rates reduce the breakdown strength by activating shear cracks in a larger fluid infiltration zone. High injection rates have limited effects on fracture morphology. A theoretical model is proposed to elucidate the competing mechanism between fluid infiltration and the loading rate effect. [ABSTRACT FROM AUTHOR]

During the refining stage of electric arc furnace (EAF) operation, molten steel is stirred to facilitate gas/steel/slag reactions and the removal of impurities, which determines the quality of the steel. The stirring process can be driven by the injection of oxygen, which is carried out by burners operating in lance mode. In this study, a computational fluid dynamics (CFD) platform is used to simulate the liquid steel flow dynamics in an industrial-scale scrap-based EAF. The CFD platform simulates the three-dimensional, transient, non-reacting flow of the liquid steel bath stirred by oxygen injection to analyze the mixing process. In particular, the CFD study simulates liquid steel flow in an industrial-scale EAF with three asymmetric coherent jets, which impacts the liquid steel mixing under different injection conditions. The liquid steel mixing is quantified by defining two variables: the mixing time and the standard deviation of the flow velocity. The results indicate that the mixing rate of the bath is determined by flow dynamics near the injection cavities and that the formation of very low-velocity regions or 'dead zones' at the center of the furnace and the balcony regions prevents flow mixing. This study includes a baseline case, where oxygen is injected at 1000 SCFM in all the burners. Two sets of cases are also included: The first set considers cases where oxygen is injected at a reduced and at an increased uniform flow rate, 750 and 1250 SCFM, respectively. The second set considers cases with non-uniform injection rates in each burner, which keep the same total flow rate of the baseline case, 3000 SCFM. Comparison between the two sets of simulations against the baseline case shows that by increasing the uniform flow rate from 1000 to 1250 SCFM, the mixing time is reduced by 10.9%. Moreover, all the non-uniform injection cases reduce the mixing time obtained in the baseline case. However, the reduction in mixing times in these cases is accompanied by an increase in the standard deviations of the flow field. Among the non-uniform injection cases, the largest reduction in mixing time compared to the baseline case is 10.2%, which is obtained when the largest flow rates are assigned to coherent jets located opposite each other across the furnace. [ABSTRACT FROM AUTHOR]

The permeability of reservoirs is a key factor affecting the exploitation and utilization of geothermal resources. This test used a core flow meter and other advanced experimental devices to investigate the evolution of the permeability characteristics of loose sandstone samples (with a diameter of 25 mm and a length of 50 mm) in the Zijiao Town area under various temperatures, confining pressures, injection rates, and cyclic loading and unloading conditions. The results show that (1) as the temperature increases, the overall trend of rock permeability decreases, which is mainly related to the thermal expansion of rock particles. In addition, the higher the temperature, the greater the gravel outflow. (2) The critical pressure for pore closure in the unconsolidated sandstone in the region is approximately 15 MPa. (3) The permeability change of loose sandstone under low injection rate conditions is relatively small and can be neglected. However, there is reason to believe that under high-flow injection conditions, the permeability of this type of rock mass will undergo significant changes. (4) Under the condition of loading and unloading, the permeability ratio curve of the unloading stage at three temperatures is almost a straight line. The higher the temperature, the smaller the slope, and the permeability at 20 °C with the highest recovery degree is only about 50% of the initial one. [ABSTRACT FROM AUTHOR]

Abstract The stress field is a critical factor for fracture propagation in hydraulic fracturing. Attention should be paid to fracture propagation with the nonuniform stress field. A stress field with gradient was established to investigate the influence of the nononuniform stress on fracture propagation. Based on the three‐dimensional block distinct element model the fracture propagation law with nononuniform stress was obtained. The mechanism of stress gradient and magnitude of uneven fracture propagation was revealed. Aiming at the uneven propagation, the influence of elastic modulus and construction parameters was analyzed. The results show that the influence of the elastic modulus follows the χ2 distribution equation and the influence of construction parameters can be expressed by the product of the injection rate and fluid viscosity. This conclusion is of theoretical significance for fracturing with nonuniform in situ stress.

Tingting Li,1,2 Wenjing Han,1,2 Xinlu Yang,1 Yu Wang,1 Li Peng,1 Lingwei He,1 Lianjia Hu,1 Jiayuan Liu,1 Min Xia,1 Sheng Wang1,2 1Department of Anesthesiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, People’s Republic of China; 2Department of Anesthesiology, Anhui Provincial Hospital Affiliated to Anhui Medical University, Hefei, People’s Republic of ChinaCorrespondence: Sheng Wang, Department of Anesthesiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, No. 17 Lujiang Road, Luyang District, Hefei, Anhui Province, People’s Republic of China, Tel +86 191 5600 7726, Email iamsheng2020@ustc.edu.cnPurpose: This study aimed to explore the effects of different injection rates of propofol on postoperative cognition in elderly patients undergoing laparoscopic inguinal hernia repair.Methods: A total of 180 elderly patients who planned to undergo laparoscopic inguinal hernia repair were randomly divided into three groups: slow injection of propofol (VS-Group, 30 mg kg− 1 h− 1); medium injection of propofol (VM-Group, 100 mg kg− 1 h− 1) or fast injection of propofol (VF-Group, 300 mg kg− 1 h− 1). Propofol was induced by microinfusion pump, and the depth of anesthesia was monitored by bispectral index (BIS). Propofol and remifentanil were continuously infused during anesthesia maintenance and adjusted according to BIS. The primary outcome was the use of the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA) to measure the incidence of postoperative cognitive decline (POCD) in elderly patients on the first and seventh postoperative day. Secondary outcomes included induced dose of propofol, incidence of burst suppression and maximum electroencephalographic (EEG) effect of propofol (BIS-min) during induction.Results: The incidence of POCD on the first and seventh day postoperatively was similar among the three groups (P > 0.05). However, with the increase of propofol injection rate, induced dose of propofol, incidence of burst suppression and BIS-min during induction, the number of patients requiring vasoactive agents were significantly increased (P < 0.001). Multivariate regression analysis showed that the brief duration of burst suppression during induction did not affect the occurrence of POCD, while age and duration of hospitalization were risk factors for POCD.Conclusion: For elderly patients undergoing laparoscopic inguinal hernia repair, lowering the injection rate of propofol (such as 30 mg kg− 1 h− 1) cannot decrease the incidence of early POCD, but reduces induction dose of propofol and use of vasoactive drugs, making the patient’s hemodynamics more stable.Keywords: propofol, injection rate, bispectral index, burst suppression, elderly, postoperative cognitive decline

Diesel engine combustion is dependent mainly on the fuel injection characteristics, particularly the injection pressure and rate, which directly affect the engine efficiency and emissions. Herein, an electrically controlled supercharger is added to a traditional high-pressure common rail system to form an ultrahigh-pressure common rail system. Then, the variations in the spray, combustion, and emission characteristics of a diesel engine with a variable fuel injection rate are analyzed. Moreover, a simulation model for a diesel engine combustion chamber is built and verified by experimental results for numerical analysis. The results reveal that the injection rate can be flexibly adjusted via regulation when the solenoid valves are opened on the electrically controlled supercharger. Specifically, (1) the boot-shaped injection rate has greater potential than the traditional rectangular injection rate in terms of combustion and emission; (2) the main injection advance angle at the boot-shaped injection rate can be properly increased to improve combustion; and (3) the pilot injection quantity and advance angle are strongly coupled with the boot-shaped injection rate, potentially enhancing the mixing efficiency of fuel and air in the cylinder to achieve favorable emission results. This paper provides good guidance for the reliable design and optimization of noble-metal-based diesel engines.

A viable green energy source for heavy industries and transportation is hydrogen. The internal combustion engine (ICE), when powered by hydrogen, offers an economical and adaptable way to quickly decarbonize the transportation industry. In general, two techniques are used to inject hydrogen into the ICE combustion chamber: port injection and direct injection. The present work examined direct injection technology, highlighting the need to understand and manage hydrogen mixing within an ICE’s combustion chamber. Before combusting hydrogen, it is critical to study its propagation and mixture behavior just immediately before burning. For this purpose, the DI-CHG.2 direct injector model by BorgWarner was used. This injector operated at 35 barG and 20 barG as maximum and minimum upstream pressures, respectively; a 5.8 g/s flow rate; and a maximum tip nozzle temperature of 250 °C. Experiments were performed using a high-pressure and high-temperature visualization vessel available at our facility. The combustion mixture prior to burning (spray) was visually controlled by the single-pass high-speed Schlieren technique. Images were used to study the spray penetration (S) and spray volume (V). Several parameters were considered to perform the experiments, such as the injection pressure (Pinj), chamber temperature (Tch), and the injection energizing time (Tinj). With pressure ratio and injection time being the parameters commonly used in jet characterization, the addition of temperature formed a more comprehensive group of parameters that should generally aid in the characterization of this type of gas jets as well as the understanding of the combined effect of the rate of injection on the overall outcome. It was observed that the increase in injection pressure (Pinj) increased the spray penetration depth and its calculated volume, as well as the amount of mass injected inside the chamber according to the ROI results; furthermore, it was also observed that with a pressure difference of 20 bar (the minimum required for the proper functioning of the injector used), cyclic variability increased. The variation in temperature inside the chamber had less of an impact on the spray shape and its penetration; instead, it determined the velocity at which the spray reached its maximum length. In addition, the injection energizing time had no effect on the spray penetration.

The stress field is a critical factor for fracture propagation in hydraulic fracturing. Attention should be paid to fracture propagation with the nonuniform stress field. A stress field with gradient was established to investigate the influence of the nononuniform stress on fracture propagation. Based on the three‐dimensional block distinct element model the fracture propagation law with nononuniform stress was obtained. The mechanism of stress gradient and magnitude of uneven fracture propagation was revealed. Aiming at the uneven propagation, the influence of elastic modulus and construction parameters was analyzed. The results show that the influence of the elastic modulus follows the χ2 distribution equation and the influence of construction parameters can be expressed by the product of the injection rate and fluid viscosity. This conclusion is of theoretical significance for fracturing with nonuniform in situ stress. [ABSTRACT FROM AUTHOR]

Copyright of Oilfield Chemistry is the property of Sichuan University, Oilfield Chemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the injection processes and spray behavior of diesel fuel (DF), rapeseed oil (RO) and their fuel blends (RO25, RO50, RO75) have been qualitatively and quantitatively analyzed to identify the differences in the injection rate and the spray parameters. The volumetric and mass injection rates, the spray penetration, the spray cone angle and the spray area under non-evaporation conditions in a nitrogen-filled camber were analyzed. The results showed that rapeseed oil leads to a decrease in the peak injection rate due to its higher density and viscosity. Moreover, rapeseed oil and its blends with mineral diesel oil exhibited smoother rising slopes at the start of injection. The spray tip penetration was the longest for the rapeseed oil and the spray tip penetrations of the fuel blends RO25, RO50 and RO75 were arranged between the values of DF and RO. As the injection pressure increased, the differences in the spray tip penetrations diminished. Increasing the amount of rapeseed oil in fuel blends resulted in a smaller spray cone angle compared to diesel fuel. The spray area of all tested fuels increased significantly with increasing spray tip penetration, the spray area of RO was consistently lower than that of diesel fuel. [ABSTRACT FROM AUTHOR]

Simultaneous multiple-fracture treatments in horizontal wellbores have become an essential technology for the economic development of shale gas reservoirs. During hydraulic fracturing, fracture initiation and propagation always induce additional stresses on the surrounding rock. When multiple fractures develop simultaneously, the development of some fractures is limited due to the stress-shadow effect. An in-depth understanding of the multiple-fracture propagation mechanism as reflected by fracture morphology and flow rate distribution can help to set reasonable operation parameters for improving the uniformity of multiple fractures and forming a complex fracture network according to the different in situ stress conditions in a reservoir to increase the shale gas recovery and reduce the cost. In this study, a two-dimensional (2D) fracture propagation model was developed based on the extended finite element method (XFEM). Then, the influences of various factors, including geological and operational factors, on the development of multiple fractures were studied. The results of numerical simulations showed that increasing the cluster spacing or injecting fracturing fluid with lower viscosity can help reduce the stress-shadow effect. In the case of smaller in situ stress differences, the deflection of the fractures was larger due to the stress-shadow effect. As the stress difference increased, the direction of the propagation of the fracture was gradually biased towards the direction of maximum horizontal stress. In addition, the injection rate had some effects on the fracture morphology and flow rate distribution. However, as the injection rate increased, the dominant fracture developed rapidly, and the fracture length significantly increased.

The permeability of reservoirs is a key factor affecting the exploitation and utilization of geothermal resources. This test used a core flow meter and other advanced experimental devices to investigate the evolution of the permeability characteristics of loose sandstone samples (with a diameter of 25 mm and a length of 50 mm) in the Zijiao Town area under various temperatures, confining pressures, injection rates, and cyclic loading and unloading conditions. The results show that (1) as the temperature increases, the overall trend of rock permeability decreases, which is mainly related to the thermal expansion of rock particles. In addition, the higher the temperature, the greater the gravel outflow. (2) The critical pressure for pore closure in the unconsolidated sandstone in the region is approximately 15 MPa. (3) The permeability change of loose sandstone under low injection rate conditions is relatively small and can be neglected. However, there is reason to believe that under high-flow injection conditions, the permeability of this type of rock mass will undergo significant changes. (4) Under the condition of loading and unloading, the permeability ratio curve of the unloading stage at three temperatures is almost a straight line. The higher the temperature, the smaller the slope, and the permeability at 20 °C with the highest recovery degree is only about 50% of the initial one.

Resistivity will have different response characteristics to the hydraulic fracture propagation process. In this work, a resistivity testing system for hydraulic fracturing specimens was established. Resistivity and acoustic emission (AE) information were jointly analysed to determine the dynamic response characteristics of resistivity during hydraulic fracture propagation. The results show that the water and fracture exert a competitive influence on the connection structure of the circuit, and there are two significant peak resistivity points in the curve, presenting a double peak therein. The peak resistivity data of the specimen with a larger fracture area are much different from the initial value. With the increase of the rate of injection, the range of variation of the highest value that can be reached with the specimen resistivity decreases. High resistivity rates or high resistivity fluctuations exhibit rapid a release of fracture energy. The fracture failure mode dominated by shear fractures makes the formation produce a “series+parallel” electrical connection structure; a calculation model of formation resistivity based on shear and tensile failure was proposed to characterize the proportion of different types of hydraulic fractures and elucidate the control effect of matrix resistivity on the electrical performance of the overall circuit structure.

Artificial recharge of groundwater increases the water level in an aquifer, which can be used for water security in a drought-prone region. This study was conducted to identify the interval of injection wells in a small basin upstream of a watershed. For the pilot test, 11 injection wells were installed, in which individual and simultaneous injections were performed. The rates of the individual and simultaneous injections ranged from 0.49–38.13 and 0.04–11.48 m3/d, respectively. Simultaneous injection resulted in a reduced injection rate of approximately 4.4–95.4% compared to that of individual injection owing to the interference effect of the injection wells. Moreover, the hydraulic conductivity of each well and the radius of influence were used to analyze the interference effect during injection using the Thiem-Dupuit equation. The interference effect between injection wells was evaluated by increasing the space from 2 to 15 m at four recharge lines (total length: 340 m) within the study area, and the expected injection rate was calculated as the rates of 220.85–58.95 m3/d. On the other hand, construction cost for installing injection wells became higher at 2 m interval than at 15 m. Therefore, there was no significant increase in construction cost per 1-m3 injection volume as well as decrease in total injection rate if the well interval was > 5 m and the optimum interval of injection well was suggested to be at least 5 m. Drought-prone areas are generally excluded from water-welfare benefits and are economically fragile; consequently, when developing an artificial recharge facility, injection wells should be designed considering the security of suitable amount of water with economic feasibility. [ABSTRACT FROM AUTHOR]

This study emphasized on the removal performance of polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) and mercury by different activated carbon injection (ACI) rates from a full-scale (700 t/d) MSW incinerator. The result exhibited that the emission standard of PCDD/Fs and mercury could be met when the ACI rate reached 50 mg/Nm3 and 30 mg/Nm3, respectively. Lower chlorinated PCDD/Fs and PCDFs showed higher removal efficiencies compared with highly chlorinated PCDD/Fs and PCDDs, which could be attributed to the larger competitiveness of highly volatile congeners in AC adsorption than the lower volatile ones. AC turned out to have different adsorption selectivity for CP-routes PCDD/Fs congeners, among which 1379-TCDD was preferred to be absorbed while others exhibited little or poor selectivity for AC adsorption. The removal efficiency of PCDD/Fs was positively correlated with ACI rate at 99% confidence interval with a linear relationship (R2 = 0.98). Also, the outlet concentration of mercury decreased with the increase of ACI rate in a nearly linear function (R2 = 0.96). These results will be meaningful for the rational use of AC for pollutants control. [ABSTRACT FROM AUTHOR]

Background: Contrast reflux, which is the retrograde movement of contrast against flow direction, is commonly observed during angiography. Despite a vast body of literature on angiography, the hemodynamic factors affecting contrast reflux have not been studied. Numerous methods have been developed to extract flow from angiography, but the reliability of these methods is not yet sufficient to be of routine clinical use. Purpose: To evaluate the effect of baseline blood flow rates and injection conditions on the extent of contrast reflux. To estimate arterial flow rates based on measurement of contrast reflux length. Materials and methods: Iodinated contrast was injected into an idealized tube as well as a physiologically accurate model of the cervico‐cerebral vasculature. A total of 194 high‐speed angiograms were acquired under varying "blood" flow rates and injection conditions (catheter size, injection rate, and injection time). The length of contrast reflux was compared to the input variables and to dimensionless fluid dynamics parameters at the catheter‐tip. Arterial blood flow rates were estimated using contrast reflux length as well as a traditional transit‐time method and compared to measured flow rates. Results: Contrast reflux lengths were significantly affected by contrast injection rate (p < 0.0001), baseline blood flow rate (p = 0.0004), and catheter size (p = 0.04), but not by contrast injection time (p = 0.4). Reflux lengths were found to be correlated to dimensionless fluid dynamics parameters by an exponential function (R2 = 0.6–0.99). When considering the entire dataset in unison, flow estimation errors with the reflux‐length method (39% ± 33%) were significantly higher (p = 0.003) than the transit‐time method (33% ± 36%). However, when subgrouped by catheter, the error with the reflux‐length method was substantially reduced and was significantly lower (14% ± 14%, p < 0.0001) than the transit‐time method. Conclusion: Results show correlations between contrast reflux length and baseline hemodynamic parameters that have not been reported previously. Clinically relevant blood flow rate estimation is feasible by simple measurement of reflux length. In vivo and clinical studies are required to confirm these correlations and to refine the methodology of estimating blood flow by reflux. [ABSTRACT FROM AUTHOR]

The relevance of the research is caused by the fact that the presence of natural fracturing in complex carbonates reservoirs is the main factor that affects the shape and propagation of the network of hydraulic fractures. In such cases, when a hydraulic fracture collides with natural fracturing, there may be a different nature of their interaction, for example, displacement, intersection, etc. Consequently, hydraulic fracturing in complex carbonate reservoirs, characterized by the presence of natural fracturing, can lead to the formation of not a symmetric fracture in its classical sense, but their complex network. Based on field observations (microseismic monitoring and studies of the void space of rocks), various degrees of complexity of hydraulic fractures have been established: from a simple relatively flat single fracture to a rather complex network of fractures. The main aim of the study is to assess the formation of complex networks of hydraulic fractures in naturally fractured carbonate reservoirs. Object: complex carbonate reservoir with a system of natural fractures. Methods: analysis of production, technological, hydrodynamic data and the results of microseismic monitoring in the process of hydraulic fracturing. Results. It was found that hydraulic fracturing in complex carbonate reservoirs often does not lead to the formation of a fracture in its classical sense – two wings propagating symmetrically from the wellbore, which is confirmed by the results of the analysis of the pressure build-up curves in diagnostic logarithmic coordinates. Hydraulic fractures can propagate into the formation directly from wells – targets of influence (classical representation), or through the existing network of natural fractures located in the drainage zone. To involve a significant number of natural fractures and other types of voids in the filtration process during hydraulic fracturing, it is advisable to pump the fracturing fluid at low speeds. Control over the development of hydraulic fractures should be based on reliable information about the natural fracturing of the reservoir before the event, and regulation – through monitoring the dynamics of pressure and injection rate, which confirms the research results.

In this study, the CO2 carbonatization potential of the Deccan basalt formation in Eastern India is evaluated by establishing a hydro-chemical field-scale model based on the geological, hydrological, and geochemical parameter of the basalt in the Mandla lobe. The reliable initial mineral thermodynamic parameters are obtained by validating the laboratory scale experiment of CO2-water-basalt reaction with a numerical method. Over 50% of injected carbon mineralized within 140 days for the Deccan basalt in the Mandla lobe, and the majority of CO2 is sequestered as ankerite, siderite, and calcite, which occupy a percent of 65%, 28%, and 7%, respectively. Clay minerals, including smectite and chlorite, are important secondary minerals contributing to the process of CO2 storage in the basaltic reservoir. Clay precipitation can promote the dissolution of silica- and aluminum-rich plagioclase and release Ca2+ to enhance the carbonatization of CO2 to Ca carbonates but competes for Fe2+ and Mg2+ from siderite and magnesite. Clay precipitation also impacts the CO2 carbonatization efficiency by changing the basalt conductivity. CO2 carbonatization efficiency was found to increase with the reduction of injection rate. However, slow flow rate can increase the pore clogging risk and induce large pressure build-up. This is the first field-scale assessment of CO2 mineralization potential of the Deccan basalt, which is one of the largest terrestrial flood basalt formations in the world. The results can provide valuable information and scientific support for India and global carbon mitigation. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article is devoted to computer of the atomization, combustion, and evaporation processes of liquid fuel drops (heptane) at high turbulence. The paper describes main characteristics and methods of atomization of liquid fuels and shows the types of special devices used in fuel supply injection systems. As proposed in the paper mathematical model of the combustion of liquid fuel injections at high turbulence consists of the laws of conservation of mass, momentum, transfer of kinetic energy, and conservation concentration of the mixture components. Also, when setting up computational experiments, the chemical model of reacting systems, the turbulence model, and the equations describing evaporation, heat transfer, interaction with the gaseous medium were taken into account. As a result of the computational experiments performed to study the liquid fuel droplets' injection rate influence on the processes of its spraying combustion, the optimal combustion mode was established. The obtained data that determine the optimal mode are confirmed by a graphical interpretation of the distribution of temperature fields, the number combustion products, and particles along the height of the model combustion chamber. These results contribute to a deep study and construction of the liquid fuels' combustion theory, and an understanding complex thermal and physical phenomena in combustion chambers. [ABSTRACT FROM AUTHOR]

In this study, the injection processes and spray behavior of diesel fuel (DF), rapeseed oil (RO) and their fuel blends (RO25, RO50, RO75) have been qualitatively and quantitatively analyzed to identify the differences in the injection rate and the spray parameters. The volumetric and mass injection rates, the spray penetration, the spray cone angle and the spray area under non-evaporation conditions in a nitrogen-filled camber were analyzed. The results showed that rapeseed oil leads to a decrease in the peak injection rate due to its higher density and viscosity. Moreover, rapeseed oil and its blends with mineral diesel oil exhibited smoother rising slopes at the start of injection. The spray tip penetration was the longest for the rapeseed oil and the spray tip penetrations of the fuel blends RO25, RO50 and RO75 were arranged between the values of DF and RO. As the injection pressure increased, the differences in the spray tip penetrations diminished. Increasing the amount of rapeseed oil in fuel blends resulted in a smaller spray cone angle compared to diesel fuel. The spray area of all tested fuels increased significantly with increasing spray tip penetration, the spray area of RO was consistently lower than that of diesel fuel.

In the present study, entropy generation in a non-axisymmetric steady-state incompressible viscous flow over a single rotating porous disk is investigated analytically. The dimensionless form of the local and total entropy generation caused by frictional and thermal effects are derived. The effects of the injection rate and Brinkman number on the entropy generation are revealed. It is found that there exists an optimal injection rate for each Brinkman number, which minimizes the total entropy generation. [ABSTRACT FROM AUTHOR]

Copyright of Acta Geoscientica Sinica is the property of Acta Geoscientica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the influence of different fracturing fluid injection rates on various fracturing parameters of cement-sand slurry specimens, besides the fracture shapes and extension patterns produced by the specimens under this condition. The experimental study was carried out by configuring square cement-sand slurry specimens with the same cement and sand ratio, combined with ISCO injection pump, acoustic emission equipment, and CT scanning equipment. The test results showed that the fracture initiation time and initiation duration of specimens gradually decreased; in addition, the fracture initiation pressure gradually increased as the injection rate increased. In addition, the shape of fractures produced by fracturing changes from irregular to regular with increasing injection rate; the complexity of the fracture network changes from complex to simple with increasing injection rate. In this paper, acoustic emission and CT technology are combined with the test, so as to more scientifically and intuitively explore the influence mechanism of injection rate on hydraulic fracturing of specimens and fracture expansion research. In addition, adjusting the injection volume of fracturing fluid plays an important role in improving mining efficiency and economic cost. This is an important reference for the use of hydraulic fracturing in a large number of rock projects such as deep coal resource extraction as well as coalbed methane development. [ABSTRACT FROM AUTHOR]

Copyright of China Plastics / Zhongguo Suliao is the property of Journal Office of CHINA PLASTICS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tight heterogeneous glutenites are typically characterized by highly variable lithology, low/ultra-low permeability, significant heterogeneity, and a less-developed natural fracture system. It is of great significance for economic development to improve hydraulic fracture complexity and stimulated reservoir volume. To better understand the hydraulic fracturing mechanism, a large-scale experimental test on glutenite specimens was conducted and the hydraulic fracture propagation behaviors and focal mechanism were analyzed. A three-dimensional numerical model was developed to reproduce the hydraulic fracture evolution process and investigate the effects of operating procedures on hydraulic fracture geometry and stimulated reservoir volume. A simultaneous variable injection rate and fluid viscosity technology was proposed to increase the hydraulic fracture complexity and stimulated reservoir volume. The results indicate that four fracturing behaviors can be observed, namely, penetration, deflection, termination, and bifurcating, in the laboratory experiment. Tensile events tend to appear during the initiation stage of hydraulic fracture growth, while shear events and compressive events tend to appear during the non-planar propagation stage. The shear and compressive mechanisms dominate with an increase in the hydraulic fracture complexity. The variable injection rate technology and simultaneous variable injection rate and fluid viscosity technology are effective techniques for fracture geometry control and stimulated reservoir volume enhancement. The key to improve hydraulic fracture complexity is to increase the net pressure in hydraulic fractures, cause evident pressure fluctuations, and activate or communicate a wide range of natural discontinuities. The results can provide a better understanding of the fracture geometry control mechanism in tight heterogeneous glutenites, and offer a guideline for treatment design and optimization of well performance. [ABSTRACT FROM AUTHOR]

High pressure common rail system can precisely control the injection time and injection pressure to improve the thermal efficiency of the engine. The injection characteristics of the system can affect the combustion and emission process of the engine. Injection stability is defined as variation characteristics of injection. This could have an unignored influence on combustion and engine output, while few study has been published. The primary objective is to establish evaluation systems and methods for injection stability. Then to study injection stability of the high pressure common rail system. Firstly, several parameters that have an important influence on the emission and combustion are identified. Based on the characteristics data obtained, it is verified that the stability parameters are in accordance with the normal distribution. Then, the five characteristic stability parameters of close speed of injection, cycle injection mass, injection delay, maximum injection rate and open speed of injection were quantitatively analyzed by using range, relative range, kurtosis and variance. It is found that the close speed of injection is greatly depend on injection pressure, the range of close speed varies from 1.8 to 5.1 mg/ms when rail pressure varies from 60 MPa to 160 MPa at 0.6 ms energizing time. The stability of injection mass depends on energizing time, the relative range in short energizing time can be four times than long energizing time. The maximum injection rate has similar characteristics with injection mass, it is also depends on energizing time. The range of maximum injection rate is reduced from the average of 0.6–0.7 mg/ms to 0.3 or even 0.2 mg/ms with the increase of energizing time. The injection delay and open speed of injection seems to be greatly affected by pressure fluctuation, since the observed data present complex rules. Pressure fluctuation in common rail can affect injection stability a lot. [ABSTRACT FROM AUTHOR]

The stringent emission regulations diesel engines are required to meet have resulted in the usage of multihole and ultramultihole injectors, nowadays. In this research study, a double-layered eight-hole diesel injection nozzle was investigated both numerically and experimentally. A three-dimensional model of the nozzle which was validated with experimental results was used to analyze the injection characteristics of each hole. The validation was conducted by comparing experiment and simulation injection rate results, acquired simultaneously from all the holes of the injector and the model. The fuel flow rates of the lower layered holes are higher than those of the upper layered holes. Two different needle eccentricity models were established. The first model only included the lateral displacement of the needle during needle lift. The needle reached maximum displacement at full needle lift. The second model considered the needle inelastic deformation into consideration. The needle radially displaces and glides along with the needle seat surface during needle lift. When the eccentricity reached a maximum in the radial direction, the needle began to lift upward vertically. The differences in injection characteristics under the different eccentricity models were apparent. The results indicated that the cycle injection quantity, fuel injection rate, and cavitation of each hole were affected during the initial lifting stages of the needle lift. As the eccentricity of the needle increases, the injection rate uniformity from the nozzle hole deteriorates. The result showed that the upper layered holes were affected by the needle eccentricity during needle lift. [ABSTRACT FROM AUTHOR]

Background: During diagnostic cerebral angiography, the contrast bolus injected into a vessel can cause substantial changes in baseline pressures and flows. One potential, and serious complication is the re-rupture of aneurysms due to these injections. The goals of this in vitro study were to evaluate the effect of injection conditions on intraneurysmal pressure changes during angiography. Methods: A silicone replica of a complete circle of Willis model with ophthalmic, anterior communicating, and basilar tip aneurysms was connected to a physiologically accurate flow pump. Contrast injections were performed under different conditions (carotid or vertebral vessel imaging, catheter diameter, injection rate, injection time, and arterial blood flow rate) and the pressure in each aneurysm was recorded before and during each injection. The effect of injection conditions on percentage increase in aneurysm pressures was statistically assessed. Additionally, the effect of the distance between the aneurysm and the catheter-tip on aneurysmal pressures was assessed. Results: Mean intraneurysmal pressures during injection (84.5 ± 10.8 mmHg) were significantly higher than pre-injection pressures (80.4 ± 10.6 mmHg, p < 0.0001). Only 3 of the 5 conditions – carotid injections, higher injection rates, and smaller catheter diameters – significantly increased intraneurysmal pressures. The catheter-tip distance showed no correlation to pressure increases. Conclusions: Increasing contrast injection rates and decreasing catheter diameters are correlated to intraneurysmal pressure increases during angiography irrespective of the distance to the catheter tip. Future in vivo studies are required to confirm these findings and determine whether the amplitude of pressure increases with commonly used injection rates can be clinically detrimental. [ABSTRACT FROM AUTHOR]

Carbonate rocks contain about 60 % of global oil and gas reserves. Stimulation of wells tapping into carbonate reservoirs is often performed using hydrochloric acid treatments based on the chemical reaction of hydrochloric acid with carbonate minerals. Carbonate reservoirs generally exhibit significant inhomogeneity, therefore the acid being injected into the formation causes uneven rock dissolution in the near-wellbore region, resulting in the emergence of highly conductive flow channels (wormholes) with complex geometry. They ensure a good hydrodynamic connection between the well and the formation. Each specific rock-acid compound system has an optimum injection rate which can help form long weakly ramified wormholes at minimum acid injection volume. The optimum injection rate value is influenced by many factors, such as pressure, temperature, acid concentration, solution composition, mineral composition of rock etc. As of today, laboratory research is the main method to determine the optimum parameters for treating the near-wellbore formation region with acid. The paper summarises the results of the analysis examining the influence of various factors on the optimum injection rate and the amount of injected pore volumes of an acid compound until a wormhole breakthrough. It is shown that the factors have a cumulative effect on the effectiveness of the acid treatment and have to be considered simultaneously in laboratory tests. The results of the performed analysis have been taken into account when planning further laboratory research. Within the design scope of hydrochloric acid treatments in wells of one of Iraq’s carbonate fields, laboratory tests have been conducted to assess the impact of acid concentration and injection rate on the effectiveness of acid stimulation in the conditions that were expected in case of the hydrochloric acid treatment. The determined injection parameters help obtain an optimum structure of wormholes at a minimum acid injection volume. The results of the performed research have been successfully used to design hydrochloric acid treatments in wells of the field under study.

Objective: The injection rate of the local anesthetic may affect the level and the time of onset of sensory block. The aim of this prospective study was to investigate the effects of two different injection rates of local anesthetic solution (0.5% heavy bupivacaine) on the onset of sensory block, and the incidence and the onset of hypotension in pregnant women undergoing spinal anesthesia for elective Cesarean delivery. Methods: A total of 67 patients were randomized into two groups: 120-second injection time (Group Slow; n = 33) and 15-second injection time (Group Fast; n = 34). Maximum level of sensory and motor block, time to sensory block at the level of T6, hemodynamic parameters, use of ephedrine and incidence of side effects were recorded at measurement time points. Results: Maximum level of the sensory block was similar in both groups. The time to achieve adequate and maximum sensory block level was shorter in Group Slow(S) (p = 0.004 and 0.037, respectively). Incidence of hypotension was similar, but hypotension occurred earlier in Group Fast(F) (p = 0.011). Requirement for ephedrine and incidence of nausea and vomiting was similar. Conclusions: This study reveals that 120-second injection duration during spinal anesthesia is associated with shorter time to achieve the maximum sensory block level and slower onset of hypotension. It means that prolonging the duration of local anesthetic injection to 120-seconds is advantageous compared with 15-seconds in caesarean section.

A novel method is proposed for the quantitative characterization of the unique simultaneous plasticizing and filling phenomenon in ultrasonic plasticization micro-injection molding (UPMIM). The injection rate is redefined as the mass flow rate during the melt filling in the cavity. The shape of the cavity was designed as a mechanical test sample scaled down from the standard tensile specimen. The micro-molded specimens were subjected to tensile tests and Gel Permeation Chromatography (GPC) measurements to analyze their mechanical properties and possible macromolecular alterations, respectively. The influence of process parameters on the injection rate and mechanical properties was obtained by orthogonal and single factor experiments. The results show that the simultaneous plasticizing and filling process can be quantitatively characterized by the injection rate which is significantly affected by the plunger speed. With the capability of the present experimental setting, a maximum injection rate of 237 mg/s for polypropylene can be achieved via process optimization. Particularly, it was confirmed that higher injection rates can be utilized for increased molding efficiency while without undermining the mechanical properties of micro-molded specimens according to the tensile tests and GPC measurements.

Dikes feed most eruptions, so understanding their mechanism of propagation is fundamental for volcanic hazard assessment. The variation in geometry of a propagating dike as a function of the injection rate remains poorly studied. Here we use experiments injecting water into gelatin to investigate the variation of the thickness, width and length of a flux-driven dike connected to its source as a function of the injection time and intruded volume. Results show that the thickness of vertically propagating dikes is proportional to the injection rate and remains constant as long as the latter is constant. Neither buoyancy nor injected volume influence the thickness. The along-strike width of the dike is, however, proportional to the injected volume. These results, consistent with the inferred behavior of several dikes observed during emplacement, open new opportunities to better understand how dikes propagate and also to forecast how emplacing dikes may propagate once their geometric features are detected in real-time through monitoring data.

This study provides guidance for the effective application of dendritic hydrophobically associating polymer (DHAP) solutions to establish flow resistance in porous media. The solution properties (viscoelasticity, rheological properties, hydrodynamic size, and static adsorption capacity) of a DHAP were evaluated. The seepage characteristics of the porous medium were also studied. The effects of solution concentration, the permeability of the porous medium, and the injection rate of the polymer solution on the establishment of flow resistance were analyzed. The results showed that the elastic modulus of DHAP was dominant over the viscosity modulus, and the rheological behavior and hydrodynamic size were not greatly affected by the solution concentration. The adsorption characteristics of DHAP on the porous medium indicated multimolecular-layer adsorption. The equilibrium adsorption capacity was approximately 1100 μg/g. When DHAP at a concentration of 2000 mg/L passed through a 2500-mD porous medium at a flow rate of 0.1 mL/min, the injection pressure increased with cumulative injection volume, and it was difficult to achieve injection equilibrium. Increasing the injection rate caused the injection pressure to increase more quickly, making it easier to reach injection equilibrium. As the injection velocity increased, the resistance factor of the polymer solution in the porous medium first decreased and then became stable. Thus, high-speed DHAP injection reduced the resistance factor in the porous medium, while low-speed DHAP injection resulted in higher flow resistance. [ABSTRACT FROM AUTHOR]

This paper presents a detailed model of a common rail diesel injector and its validation using injection rate measurement. A new method is described for injector nozzle flowrate determination using simulation and measurement tools. The injector model contains fluid dynamic, mechanic and electro-magnetic systems, describing all-important internal processes and also includes the injection rate meter model. Injection rate measurements were made using the Bosch method, based on recording the pressure traces in a length of fuel during injections. Comparing the results of the simulated injection rate meter, simulated injector orifice flow and injection rate measurements, the simulated and measured injection rates showed good conformity. In addition to this, the difference between nozzle flow rate and the measured flow rate is pointed out in different operating points, proving, that the results of a Bosch type injection rate measurements cannot be directly used for model validation. However, combining injector, injection rate meter simulation and measurement data, the accurate nozzle flow rate can be determined, and the model validated. [ABSTRACT FROM AUTHOR]

In order to study the influence factors of particle carrying capacity of foam fluid during the reverse circulation washing process, a model of reverse circulation well washing by foam fluid was established based on finite element method. The influence of injection temperature and foam quality on the particle carrying capacity of foam fluid was analyzed. The numerical simulation results show that the injection temperature of foam fluid increases from 15 °C to 80 t, the carrying rate decreases by about 7. 3%. The foam quality of foam fluid increases from 0. 65 to 0.95, the particle carrying rate increases by about 8. 3%. The results show that the particle carrying capacity of foam fluid decreases with the injection temperature increase during the reverse circulation washing process of foam fluid. The foam quality of foam fluid has a greater influence on the particle carrying capacity than the injection temperature. The viscosity is an important factor to determine the particle carrying capacity of foam fluid when other conditions are unchanged. [ABSTRACT FROM AUTHOR]