High Injection Research Articles

Crystallinity and mechanical properties of polypropylene products foamed by microcellular injection molding process

AbstractMicrocellular injection molding (MIM) is a pivotal technique for lightweight molding. Polypropylene (PP) is widely used in MIM due to light weight and easy processing. The crystallinity of foamed PP products influences the load‐bearing structures and consequently mechanical properties. To address the deterioration of mechanical properties caused by internal porous structure, a novel method is proposed to regulate the crystallinity by optimizing process parameters, thereby improving mechanical properties. Wide‐angle x‐ray diffraction, mechanical testing, and melt flow simulation are applied to investigate the influence of process parameters on crystallinity and mechanical properties. Parameters are further optimized by establishing a multivariate nonlinear regression model for process parameters and crystallinity. The results show that increasing melt temperature, injection rate, mold temperature, and cooling time stimulate crystallization, enhancing strength and decreasing elongation at break. Conversely, high injection ratio of supercritical fluid obstructs crystallization, reducing strength, and increasing elongation at break. The crystallinity increases by 20.81%; the corresponding tensile, flexural, and shear strength and corresponding modulus increases by 5.39% and 10.28%, 7.60% and 18.50%, 5.00% and 11.37%, and elongation at break decreased by 5.19% through the optimization of regression model. The proposed method is feasible to upgrade the mechanical properties of foamed PP products.

Modeling the carrier density in the exciton formation zone of organic light-emitting diode under high current injection

The carrier density in exciton formation zone is the electrical parameter most relevant to the stability of organic light-emitting diode: the decrease of carrier density improves the device stability. Here, based on the general mode of carrier device lifetimes, the carrier densities in the exciton formation zone of organic light-emitting diode have been calculated at current densities (J) ≥ 2.0 kA cm−2. With J increasing, the carrier density increases accordingly. At a given J, the carrier density decreases with the emissive layer’s thickness increasing, but increases with the emissive layer’s charge carrier mobilities. The increase of the energetic disorder of emissive layer leads to a marked decrease of carrier density. Increasing the hole (electron) mobility of hole (electron) transport layer helps reduce carrier density. The current research is believed very beneficial to the development of electrically pumped organic lasers.

System and multi-physics coupling model of liquid-CO2 injection on CO2 storage with enhanced gas recovery (CSEGR) framework

Injecting CO2 into gas reservoirs can achieve CO2 Storage with enhanced gas recovery (CSEGR). The development of liquid-CO2 injection has the characteristics of high injectability, high mobility ratio, and low diffusion coefficient. Therefore, this paper established a wellbore-reservoir-thermo-hydro-mechanical-diffusion (WR-THMD) multi-physics fully coupled model of the wellbore-reservoir system, and verified the model based on field and experimental data. The mass transfer, heat transfer, and gas physical property changes in the wellbore and reservoir during the injection of liquid-CO2 were studied. The impact of different engineering parameters on improving CH4 recovery and CO2 storage is also discussed. The results show that the impact of the wellbore on the physical properties and phase state of CO2 is crucial. The injection of liquid-CO2 is beneficial to the storage of CO2 and the displacement of CH4. Lowering the injection temperature will slightly improve the injectability of liquid-CO2 and increase the CO2 storage rate by 5.13%. Using a high injection mass flow rate will effectively raise CH4 recovery rate by 15.60%, but it will weaken the injectability of CO2 and cause CO2 to break through in the production well prematurely. The research results provide important suggestions and theoretical support for the application of liquid-CO2 injection on CSEGR.

Antibacterial Micelles-Loaded Carboxymethyl Chitosan/Oxidized Konjac Glucomannan Composite Hydrogels for Enhanced Wound Repairing.

Antibacterial hydrogels have emerged as a promising approach for effective wound treatment. However, despite extensive research on the fabrication of antibacterial hydrogels, it remains challenging to develop injectable, biocompatible, transparent, and mass-producible hydrogels with antibacterial properties. In this study, we successfully fabricated an antibacterial drug-loaded composite hydrogel, named CC45/OKG40/HS, through a Schiff base reaction between carboxymethyl chitosan (CC) and oxidized konjac glucomannan (OKG), followed by the encapsulation of stevioside-stabilized honokiol (HS) micelles. The CC45/OKG40/HS hydrogel exhibited several favorable properties, including a short gel time (<10 min), high water content (>92%), injectability, good adhesiveness, self-healing ability, and high transparency. In vitro experiments confirmed its excellent antibacterial properties, antioxidant activities, and high biocompatibility (no cytotoxicity, hemolysis ratio <5%). Furthermore, in vivo evaluation demonstrated that the CC45/OKG40/HS0.5 hydrogel accelerated wound healing by relieving inflammatory responses and enhancing re-epithelization. Given its feasibility for mass production, the findings showed that the CC45/OKG40/HS hydrogel has the potential as an advanced antibacterial wound dressing for commercial use.

Analysis of the High Use of Injectable Family Planning at the Pasar Minggu District Health Center

Family planning is an action that helps individuals or couples to get certain objects,avoid undesirable birth, to get the desired birth, the interval between pregnancies, anddetermine the number of children. Preliminary study was conducted in the DistrictHealth Center Pasar Minggu obtained the number of family planning acceptors were1.556 people (January to November 2013). The purpose of this study was to determinefactors associated with high users of injection family planning in women of childbearingage such as: age, parity, knowledge, blood pressure status, breastfeedning status,education, occupation, family income, affordability means, the costs of family planning,goverment guarantees, husband’s supports, and the supports of health professionals.The method used was a survey with a cross-sectional approach. The research samplewere mothers who used contraceptives 161 acceptors. The analysis was performedusing univariate, bivariate and multivariate analyzes. The results showed 68.3%injection users. The results of the bivariate analysis of parity (p=0,040 OR=2,190CI=1,095 to 4,380), age (p=0,000 OR=4,875 CI=2,390 to 9,945), knowledge (p=0,000OR=6,009 CI=2,852 to 12,658), the status of blood pressure (p=0,000 OR=6,054CI=2,909 to 12,599), breastfeeding status (p=0,041 OR=2,132 CI=1,084 to 4,190),education (p=0,012 OR=2,526 CI=1,275 to 5,006), employment (p=0,053 OR=2,049CI=1,045 to 4,108), affordability (p=0,021 OR=2,406 CI=1,196 to 4,838), husband’ssupport (p=0,001 OR=3,637 CI=1,778 to 7,442), the government guarantees (p=0,039OR=2,143 CI=1,090 to 4,211), the costs of family planning (p=0,016 OR=2,415 CI=1,223to 4,768), the support of health professionals (p=0,024 OR= 2,440 CI=1,181 to 5,044),and family income (p=0,008 OR=2,800 CI=1,353 to 5,796). Multivariate analysis workbecomes the most dominant variables associated with high injection family planningusers. The results of this study are expected to be used as an initial overview for furtherresearch related to high injection family planning users.

Study on time-varying characteristics and flow behavior of microencapsulated polymer

Due to the challenges posed by high injection pressure and significant viscosity shear loss, conventional polymer flooding methods are unable to effectively meet the urgent demand for enhanced oil recovery in medium- and low-permeability reservoirs. Microencapsulated polymer flooding is a promising solution to address the aforementioned challenges due to its advantages of easy wellbore injection, shear resistance, and delayed thickening. However, there is a lack of research on the release behavior and time-dependent characteristics of microencapsulated polymer and its impact on flow behavior in reservoirs. To address this gap, we conducted a series of experiments, including thermal stability tests, microfluidic chip experiments, and micro-scale oil displacement experiments, to reveal the time-varying behavior generated by the triggered release of microencapsulated polymers. The results showed that microencapsulated polymer can be fully triggered after 8 days of aging at 85 °C, with a viscosity exceeding the initial viscosity by more than 25 times. The release mechanism of the polymer aligned with the Ritger-Peppas model, transitioning from super Case-II transport to anomalous transport, and finally to Fickian diffusion with increasing temperature. During the triggering process, the presence of particles stabilized shear and improved oil displacement, particularly in small pore throats. Higher triggering degrees of the solution resulted in greater flow resistance within the microchannel, effectively suppressing fluid fingering. The oil displacement effectiveness of fully triggered microencapsulated polymer was comparable to that of conventional polymers. This study provides insights into the flow behavior of microencapsulated polymer at a microscopic level, offering valuable references for its application in the field.

Intra-Articular Hyaluronic Acid for Osteoarthritis of the Hip, Shoulder, and Ankle

What Is the Issue?&#x0D; &#x0D; Osteoarthritis (OA) is a chronic disease of the joints, such as the hip, shoulder, and ankle. OA causes the joints to be painful, unstable, and less functional. In adults 55 years and younger, joint trauma is a common cause of OA.&#x0D; Hyaluronic acid (HA) is a naturally occurring molecule found in human cells that provides lubrication when injected into the joint. HA injections are a less invasive option than surgery, with potentially fewer complications.&#x0D; To support decision-making about treating hip, shoulder, or ankle OA in adults 55 years and younger, it is important to understand the potential benefits and harms of using HA in this population.&#x0D; &#x0D; What Did We Do?&#x0D; &#x0D; We reviewed the clinical effectiveness of high molecular weight (MW) injection of HA in adults between the ages of 18 and 55 years with OA of the hip, shoulder, or ankle joints to guide decisions on the use of high MW HA injection.&#x0D; An information specialist searched for peer-reviewed and grey literature sources published on January 1, 2013 to December 12, 2023. One reviewer screened citations and selected and critically appraised the included studies.&#x0D; &#x0D; What Did We Find?&#x0D; &#x0D; The evidence for this report was based on observational before-and-after studies. We found no relevant comparative studies examining the effect of high MW HA versus placebo or no treatment.&#x0D; While most studies reported post-treatment outcome improvements, it is uncertain whether high MW injection of HA improves pain, function, and disability in adults 55 years and under with hip, shoulder, or ankle OA. This is due to the low-quality evidence, small sample sizes, and methodological problems. Serious side effects of high MW HA were not reported.&#x0D; &#x0D; What Does This Mean?&#x0D; &#x0D; Due to the uncertainty of the clinical effectiveness evidence, health care providers and decision-makers may consider other factors when considering high MW IA-HA for patients with hip, shoulder, or ankle OA; these factors could include acceptability, feasibility, costs, health equity, and patient values and preferences.&#x0D; Future research from randomized studies in large populations is needed to understand the effectiveness and safety of high MW HA injections for hip, shoulder, and ankle OA.&#x0D;

Mesenchymal stem cells derived from CHIR99021 and TGF‑β induction remained on the colicomentum and improved cardiac function of a rat model of acute myocardium infarction.

Human induced pluripotent stem cells (hiPSCs) have been regarded as a potential stem cell source for cell therapy. However, the production of cells with mesenchymal potential from hiPSCs through spontaneous differentiation is time consuming and laborious. In the present study, the combined use of the GSK-3 inhibitor CHIR99021 and TGF-β was used to obtain mesenchymal stem cell (MSC)-like cells from hiPSCs. During the induction process, the transcription of epithelial-mesenchymal transition (EMT)-related genes N-cadherin and Vimentin in the transformed cells was upregulated, whereas the transcription of E-cadherin and pluripotency-related transcription factors SOX2, OCT4 and NANOG did not change significantly. This indicated that whilst cells were pluripotent, EMT was initiated by the upregulation of transcription of EMT promoting genes. Both SMAD-dependent and independent signalling pathways were significantly activated by the combined induction treatment compared with the single factor induction. The hiPSC-derived MSC-like cells (hiPSC-MSCs) expressed MSC-related markers and acquired osteogenic, chondrogenic and adipogenic differentiation potentials. After being injected into the peritoneal cavity of rats, the hiPSC-MSCs secreted angiogenic and immune-regulatory factors and remained on the colicomentum for 3 weeks. Within an 11-week period, four intraperitoneal hiPSC-MSC injections (1x107 cells/injection) into acute myocardial infarction (AMI) model rats significantly increased the left ventricular ejection fraction, left ventricular fractional shortening and angiogenesis and significantly reduced scar size and the extent of apoptosis in the infarcted area compared with that of the control PBS injection. Symptoms of hiPSC-MSC-induced immune reaction or tumour formation were not observed over the course of the experiment in the hiSPC-MSC treated rats. In conclusion, the CHIR99021 and TGF-β combined induction was a rapid and effective method to obtain MSC-like cells from hiPSCs and multiple high dose intraperitoneal injections of hiPSC-derived MSCs were safe and effective at restoring cardiac function in an AMI rat model.

Effects of reservoir fluids on sand packs consolidated by furan and epoxy resins: Static and dynamic states

One of the most effective methods for sand control is the chemical consolidation of sandstone structures. In this paper, the impacts of crude oil and brine in the static state and the impact of the flow rates of the fluids in the dynamic state have been assessed at the reservoir conditions. The analyses in this research were Young's modulus, compressive strength, porosity, and permeability which were done on core samples after and before fluid contact. Samples made with two different resins showed good resistance to crude oil in both states. No considerable change was seen in the analyses even at high crude oil injection rates in the dynamic state. Conversely, brine caused a noticeable change in the analyses in both states. In the presence of brine at the static state, Young's modulus and compressive strength respectively decreased by 37.5% and 34.5% for epoxy cores, whereas these parameters respectively reduced by 30% and 41% for furan cores. In brine presence at the dynamic state, compressive strength reduction was 10.28 MPa for furan and 6.28 MPa for epoxy samples and their compressive strength reached 16.75 MPa and 26.54 MPa respectively which are higher than the critical point to be known as weak sandstone core. Moreover, Young's modulus decrease values for furan and epoxy samples were respectively 0.37 GPa and 0.44 GPa. Therefore, brine had a more destructive effect on the mechanical characteristics of samples in the static state than the dynamic one for two resins. In addition, brine injection increased permeability by about 13.6% for furan and 34.8% for epoxy. Also, porosity raised by about 21.8% for furan, and 19% for epoxy by brine injection. The results showed that the chemical sand consolidation weakens in the face of brine production along with crude oil which can lead to increasing cost of oil production and treating wellbore again.

Polyol-assisted efficient hole transfer and utilization at the Si-based photoanode/electrolyte interface

The sluggish kinetics of the anodic oxygen evolution reaction significantly restricts the efficiency of silicon (Si)-based photoelectrochemical (PEC) cells. In this study, we employ microfabrication technology to batch-prepare reproducible Si substrates, and develop a facile electrodeposition technique to load high-quality nickel film onto the substrates. Innovatively, we introduce energetically favorable polyols (such as glycerol, propylene glycol, and ethylene glycol) into the electrolyte, resulting in a remarkably low onset potential and a high hole injection efficiency during the PEC oxidation process. Taking glycerol as an example, in-situ impendence spectra provide real-time evidence for the accelerated hole transfer and utilization at the photoanode/electrolyte interface in the presence of glycerol. Mechanistic studies further reveal that glycerol undergoes synergistic oxidation mediated by holes and catalysts. Finally, by intergrating a solar thermoelectric generator into a PEC polyol oxidation cell, the self-powered system demonstrates promising potential for producing valuable products solely by harnessing solar energy.

Analysis of Rotor Anisotropy and Position Tracking Error Prediction for Surface-Mounted PMSM Under High Frequency Signal Injection

Analysis of Rotor Anisotropy and Position Tracking Error Prediction for Surface-Mounted PMSM Under High Frequency Signal Injection

Numerical simulations of earthquake rupture induced by pressure perturbation

The subsurface fluid injection can cause pressure increase within faults, leading to earthquake occurrences. However, the factors controlling earthquake rupture due to pressure perturbation remain poorly understood. To resolve this problem, we simulate the physical processes of earthquake nucleation and rupture on strike-slip faults perturbated by pressure migration based on the slip-weakening law. Multiple kinds of factors, including background stress, fluid injection rates, the area of the pressurized region, fault geometry, and fault friction coefficients, are considered in our simulations. Our simulation results reveal that the ratio of shear stress to normal stress rather than their absolute values controls the rupture behavior. With the large stress ratios, high injection rates, and large pressurized areas, earthquakes are prone to propagate as runaway ruptures. Additionally, faults with large aspect ratios of length to width are also favorable for causing runaway ruptures. In contrast, the factors of fault strike, dip angles and friction coefficients have minor influence on rupture behavior.

Перспективы развития дизельной топливной аппаратуры в ближайшем будущем

The analysis of the positive qualities of Common Rail (CR) fuel equipment widely used in diesels today is given. The possibility of optimal diesel control, high injection pressure, elimination of repeated fuel injections, improvement of fuel efficiency, reduction of the difference in the amplitude of torque fluctuations in the cylinders, very precise regulation of the beginning of fuel supply, a high degree of diagnosability of fuel equipment, the possibility of precise regulation of the uniformity of fuel supply through the cylinders, the ability to ensure optimal regulation of the turbocharger are noted, the ability to turn off a number of cylinders and ensure that cycles are skipped when operating under partial loading conditions. Disadvantages are also presented, in particular, a large number of various elements and sensors, activators and other controls are included in the injection system, as well as the increased demands of CR-type fuel equipment on the purity and quality of diesel fuel. When operating in low-flow modes, the injection pressure is significantly reduced to a value of 60-80 MPa, which leads to fuel overspending, the cost of fuel equipment is about twice as much as classical fuel equipment, the starting properties of diesel (as evidenced by operation) decrease sharply after 500-800 hours of operation, problems arise with maintaining high pressure in the ramp (battery), possible ruptures and leakages of the high-pressure system lead to increased fire hazard of the engine. The reasons for increased carbon formation and loss of operational efficiency and reliability are listed. Using the methods of relative penalty points, the quality of traditional fuel equipment and CR-type equipment was compared. Based on the analysis, a conclusion is made about the scope of application of this new system and traditional classical fuel equipment in the near future. The operating conditions, the qualifications of the maintenance personnel, modern requirements of standards for noise, toxicity of diesel engines and their reliability indicators were taken into account.

Multiscale Model for Hydrogen Transport and Storage in Shale Reservoirs

Summary Utilizing underground geological structures for hydrogen storage is an effective approach for energy transformation. The depleted shale reservoirs can be considered as promising options for large-scale hydrogen storage because of the vast storage capacity, high containment security, and low operation cost. However, it is challenging to characterize the hydrogen transportation mechanism and estimate hydrogen storage potential in shale formations from multiscale perspectives. In this paper, we propose a multiscale model for hydrogen transport and storage in partially depleted hydraulically fractured shale reservoirs, considering the effects of gas diffusion, adsorption, slip flow, and continuous flow. By the Laplace transformation and Pedrosa substitution, a computationally effective semi-analytical solution was derived and validated with a commercial numerical simulator. A hydrogen storage capacity (HSC) assessment workflow is proposed using a typical shale reservoir in the Appalachian Basin as a case study. The results indicate that the storage capacity can reach up to 31.92×108 m3 at a high constrained injection pressure. In addition, the HSC is strongly controlled by the adsorption property, diffusion coefficient, shale composition, flow capacity between different scale media, and mobility ratio. The influence of most reservoir parameters on storage potential is negligible at low constrained pressure but critical at high constrained pressure. Such a model can be used as a robust pressure predictor and storage capacity estimator for hydrogen storage projects in partially depleted shale reservoirs.

Principle and practice of hydraulic softening top-cutting and pressure relief technology in weakly cemented strata

Extremely thick and hard roofs are difficult to break in the mining of a working face, and the large area of the suspended roof easily induces a strong ground pressure or dynamic impact disasters. The roof control of a coal mining face in a mine in western China was taken as a case study. The mineral composition, microstructure, and hydrophysical properties of the hard roof overlying the coal seam were analyzed. The characteristics of the weak-cementation strata that are prone to mud and collapse when encountering water were targeted to investigate the hydraulic softening roof-cutting and pressure relief technology. It was found that the clay mineral composition in the roof plate accounts for 60.6%. After 24 h of natural immersion, the rock strength decreased by approximately 10.3%–49%, and further immersion caused disintegration. By arranging high and low double-row water injection softening drilling holes in the cutting hole and roadway of the working face, the strength of roof rock strata in the target area was reduced, and the initial weighting step distance and weighting strength of the working face were reduced. The hydraulic softening roof-cutting pressure relief technology effectively regulated the weighting step distance of the hard roof and the peak weighting of the working face.

Simulation and performance prediction of partially naturally fractured reservoirs under solution gas drive primary recovery and gas injection processes

The study presented in this paper has multiple objectives. First, a simulation model for partially naturally fractured reservoirs under solution gas drive is developed. The model considers the major key parameters controlling fluid flow in the reservoir, including fracture intensity and distribution, instantaneous gas/oil segregation due to vertical capillary continuity, gas/oil gravity drainage, and reinfiltration of the drained oil to the lower matrix. Once the model is well-established, it is used to study the reservoir performance under two recovery processes: primary depletion and gas injection. A detailed investigation of the sensitivity of the ultimate oil recovery to the fracture intensity, oil production rates, and gas injection rates is performed. The findings of this study indicate that the ultimate oil recovery of low-fracture intensity reservoirs subjected to the depletion drive process is insensitive to production rates. However, for moderate- to high-fracture intensity reservoirs and low production rates, the recovery increases with increasing fracture intensity. Conversely, for moderate- to high-fracture intensity reservoirs and high production rates, the recovery is not significantly affected. For the gas injection mechanism, it is found that the ultimate oil recovery is a function of both the fracture intensity and gas injection rate. Furthermore, three fracture intensity ranges are identified: low, medium, and high. For the low- and high-fracture intensity ranges, the recovery increases with increasing gas injection rates and fracture intensity. However, for the medium fracture intensity ranges, the recovery behaves differently. It increases at low gas injection rates and decreases at high injection rates as the fracture intensity increases. New equations relating the cumulative oil production to the production rates, gas injection rates, and fracture intensity are also presented.

Dual External Electron Injection Barrier Layers Enable High‐Performance Near‐Infrared Organic Photodetectors Realizing Real‐Time Heart Rate Monitoring

AbstractNear‐infrared organic photodetectors (NIR‐OPDs) play important roles in medical monitoring, bio‐imaging and night vision, etc. Among them, bulk heterojunction (BHJ)‐based photodiode type NIR‐OPDs exhibit extraordinary characteristics in photoresponse and photosensitivity. However, their dark current density (Jd) often increases severely as the bias voltage increases, which seriously reduces detection sensitivity for NIR light. Here, a novel structure of dual external electron injection barrier layers (DEBLs) composed of “m‐MTDATA/DPEPO:HAT‐CN” is proposed to overcome this challenge. For DEBLs, a barrier is established with high injection barrier and long effective injection barrier width to prevent external electrons injection under bias voltage for suppressing Jd (4.22 × 10−8 A cm−2 better than 1.47 × 10−5 A cm−2 of the traditional device at −2 V). More importantly, photo‐generated carriers have almost no loss through DEBLs. Therefore, high and stable detectivity (D*) over 1013 Jones are realized under 850 nm from 0 V to nearly −1 V and even far over 1012 Jones at −2 V. More strikingly, the structure of DEBLs is proven to be effective and universal in NIR‐OPDs and the device based on it successfully realize the real‐time heart rate monitoring of various human states, which exhibits great potential in human health monitoring.

An Integrated Model for Acid Fracturing without Prepad Considering Wormhole Growth

Acid fracturing is an effective stimulation technology that is widely applied in carbonate reservoirs. An integrated model for acid fracturing without prepad treatment has been established. Compared with the previous models which use prepad for generating hydraulic fractures, this model can simultaneously simulate the fracture propagation and the acid etching of fracture surfaces, as well as the wormhole growth during acid fracturing. The influences of some essential factors have been studied through a series of numerical simulations, and the main conclusions are as follows. First, increasing the injected acid volume can expand the size of the formed hydraulic fractures and extend the propagation distance of the wormhole. Increasing the injected acid volume can also expand the etched width and extend the effective distance of the injected acid. Second, a high injection rate impels more acid to flow into the depth of a fracture before infiltration and reaction, resulting in the augmentation of a hydraulic fracture’s geometric size and the extension of the effective distance. But the maximum etched width decreases as the injection rate rises. A high injection rate can also enable wormholes to grow in the natural fracture area farther away from the hydraulic fracture inlet, but shorten the length of the original wormhole near the hydraulic fracture inlet. Third, an increase in acid viscosity can enlarge the geometric size of the hydraulic fracture and reduce the propagation distance of wormholes. In addition, an increase in the acid viscosity blocks the acid flow from fracture inlet to tip, reducing the effective distance of acid fracturing. Fourth, the natural fracture is the vital inducement of wormhole growth, and wormholes are apt to grow in the natural fracture area. Moreover, the geometric size of the hydraulic fracture and the effective distance of acid fracturing decrease with an increasing number of natural fractures. This research can provide a reference for field applications of acid fracturing without prepad.

Multi-Fracture Propagation Considering Perforation Erosion with Respect to Multi-Stage Fracturing in Shale Reservoirs

Shale gas is considered a crucial global energy source. Hydraulic fracturing with multiple fractures in horizontal wells has been a crucial method for stimulating shale gas. During multi-stage fracturing, the fracture propagation is non-uniform, and fractures cannot be induced in some clusters due to the influence of stress shadow. To improve the multi-fracture propagation performance, technologies such as limited-entry fracturing are employed. However, perforation erosion limits the effect of the application of these technologies. In this paper, a two-dimensional numerical model that considers perforation erosion is established based on the finite element method. Then, the multi-fracture propagation, taking into account the impact of perforation erosion, is studied under different parameters. The results suggest that perforation erosion leads to a reduction in the perforation friction and exacerbates the uneven propagation of the fractures. The effects of erosion on multi-fracture propagation are heightened with a small perforation diameter and perforation number. However, reducing the perforation number and perforation diameter remains an effective method for promoting uniform fracture propagation. As the cluster spacing is increased, the effects of erosion on multi-fracture propagation are aggravated because of the weakened stress shadow effect. Furthermore, for a given volume of fracturing fluid, although a higher injection rate is associated with a shorter injection time, the effects of erosion on the multi-fracture propagation are more severe at a high injection rate.

Experimental study on high pressure injection characteristics of gas fuel based on turbulent constant volume combustion bomb

In the face of strict carbon regulations, the internal combustion engine industry is turning to carbon-neutral and low-emission fuels. The experimental study of the high-pressure direct jet characteristics of gaseous fuels is still limited to the study of the high-pressure direct jet characteristics in stationary and non-uniform turbulent environments. The effect of isotropic turbulence on the high-pressure direct jet characteristics of gaseous fuels has not been thoroughly investigated. This paper investigates the high-pressure direct injection characteristics of gaseous fuels in an isotropic turbulent environment. Based on the experimental platform of turbulent constant volume combustion bomb, the effects of laminar flow environment and turbulence intensity on the high-pressure injection characteristics of gaseous fuels in turbulent environment are investigated in this paper. The results show that the turbulent environment has accelerated the axial development of high-pressure gaseous fuel injection compared to the laminar environment. The greater the velocity of the jet front, the greater the penetration distance. Under the turbulence intensity of 2.25 m/s, the penetration distance was 94.2 mm at 2.5 ms with a jet pressure of 6 MPa, which was 12.3% larger than that in the laminar flow environment (83.9 mm). Turbulence increases the radial development of the high-pressure gaseous fuel jet, facilitates radial diffusion and mixing at the jet boundary, accelerates the continuous merging and fragmentation process of the vortices at the jet boundary, enhances the entrainment of the surrounding medium gases, and contributes to the mixing of fuel and air in the jet. The stronger the turbulence intensity, the larger the near-field cone angle and far-field cone angle, and the larger the excess air coefficient. The stronger the turbulence intensity, the more the jet volume will be. This paper reveals the mechanism of background turbulence on jet development. The study is of great academic significance to enrich and deepen the theory of gaseous fuel jets.