Energy Science & Engineering最新文献

Effective hole cleaning is essential to drilling success, with poor cuttings transport leading to reduced penetration rates, stuck pipe, and increased non-productive time. The Drilling Cuttings Carrying Index (CCI) indicates the efficiency of hole cleaning. To ensure optimal hole cleaning, it should be greater than or equal to 1. Achieving a high CCI typically requires either the deployment of high-capacity rigs and robust surface equipment with increased volumes of drilling fluid, or the adjustment of drilling fluid properties—particularly rheology—to improve cuttings transport performance. This study proposes a data-driven optimization of the CCI to enhance hole cleaning performance in a Middle Eastern oil field. Real field data from 15 depths across three formations were used to assess CCI, revealing suboptimal values below the critical threshold of 1. To improve CCI, key fluid and operational parameters—flow rate, plastic viscosity, and yield point—were optimized through Monte Carlo simulations using Oracle Crystal Ball. A total of 80 simulations were conducted for each depth to identify optimal parameter combinations that enhance cuttings transport efficiency. The optimized CCI values across all depths (440–2900 m) were determined, indicating satisfactory hole cleaning and offering a practical approach for improving wellbore cleaning. The defined optimal CCI values will contribute to optimized hole cleaning and reduced drilling costs in future drilling campaigns.

To address the challenge of monitoring the stress evolution in flexible-molded concrete pier columns during secondary mining in coal pillarless mining operations, this study aims to develop and validate a real-time monitoring method based on distributed fiber optic sensing (DFOS) technology. With an engineering background of the Zhaozhuang coal mine as the engineering background of coal pillar mining without coal pillar mining along the hollow stay pillar, on-site research, laboratory tests, theoretical analysis, and on-site tests were adopted to study how to accurately, comprehensively, and accurately grasp the stress distribution of soft-molded concrete pier columns and its evolution characteristics under the influence of secondary quarrying movement in coal pillar mining without coal pillar mining along the hollow stay pillar. The results of the study show that the calibration test determines the characterization formula between the optical fiber phase change and the stress of the flexible concrete pier column. The stress monitored by the optical fiber is highly consistent with the measured stress in the value and trend. Downhole observations were found to be consistent with the fiber-optic monitoring data, and timely measures were taken, and comparison of fiber-optic monitoring and traditional stress gauge monitoring results showed consistency.

A new interleaved high step-up DC–DC converter is presented in this paper, providing very high voltage conversion, significantly lowering the voltage stress across semiconductor components, and minimizing conduction losses. In this topology, an active snubber circuit guarantees zero-voltage switching (ZVS) of the main switches over a wide load range, while the auxiliary switch achieves complete zero-current switching (ZCS) operation without contributing to additional power losses in the converter. Since the duty cycle of the auxiliary switch is small, the auxiliary circuit remains active in the converter for a short duration. The use of fixed-frequency PWM control enables an optimized design of the magnetic components while keeping the control implementation relatively simple. In addition, because the input and output terminals share a common ground, the control circuit does not require input-side isolation, thereby further simplifying the overall system design. The theoretical analysis is validated by a 250 W prototype with 20 V input to 600 V output voltage with a 100 kHz switching frequency.

To ensure sustainable management of energy systems and maintain their benefits over time, it's imperative to prioritise science-based decision-making models throughout energy policy formulation and management processes, however, there is a significant research gap regarding energy modelling in Somalia. Therefore, this study developed three scenarios namely: Business as usual (BAU), Renewable Energy Technologies (RET) and visionary transition scenario (VTS) for supply side to fulfil projected demand. Considering, CO₂ emissions resource potential, and techno-economic parameters. The novelty of this study lies in being the first comprehensive application of the Long-Range Energy Alternatives Planning (LEAP) model for Somalia's electricity sector, integrating environmental, economic, and technological perspectives to support sustainable energy transition policies. Using the LEAP model, electricity demand was projected to increase from 133.2 GWh in 2020 to 1814.2 GWH in 2050, representing a growth of approximately 13.62 times compared to the base year, with an estimated annual rise of 1.88% under the BAU and other scenarios in this study. In RET scenario, where 70.3% of electricity generation comes from renewable sources, carbon dioxide (CO2) emissions are forecasted to be significantly lower compared to the BAU scenario in the year 2050, with emissions reaching 1406.3 thousand metric tonnes which is 1.56 times smaller than the BAU scenario for the same time. CO2 emissions in VTS scenario are estimated to be net-zero by 2050, driven by a complete shift from fossil fuels to renewable energy sources. Greenhouse gas emissions for each scenario were evaluated using the IPCC Tier 1 methodology, and the economic assessment based on Net Present Value (NPV) analysis shows that the VTS scenario offers the most cost-effective and sustainable pathway. Overall, the findings highlight that expanding solar and wind energy can enable Somalia to achieve a low-carbon and economically resilient electricity system, offering crucial insights for national policymakers and future sustainable development planning.

In this study, a novel optimization approach is proposed for cleanroom ventilation systems with a specific focus on plastic injection molding machines used in pharmaceutical manufacturing. The research uses MATLAB-based numerical modeling to analyze the effects of air changes per hour (ACH), fresh air intake percentage, and internal heat generation on energy consumption. Three different climatic conditions—winter, mild spring, and summer—are examined to determine the optimal operating parameters for heating, ventilation, and air conditioning (HVAC) systems. The results indicate that adjusting ACH and fresh air intake percentages dynamically based on seasonal variations reduces heating and cooling loads significantly. In winter conditions, a 50% fresh air intake at an ACH of 50 minimizes heating demand by utilizing internally generated heat. In summer, increasing fresh air intake optimally lowers cooling demand by exhausting excess equipment-generated heat. Moreover, implementing intelligent control strategies based on real-time temperature monitoring reduces unnecessary energy consumption while maintaining required cleanroom standards. These findings demonstrate that strategic HVAC adjustments can enhance energy efficiency, reducing overall heating and cooling loads without compromising cleanroom air quality and regulatory compliance.

This study introduces an advanced adaptive protection approach for AC power systems, designed to address key limitations in current clustering-based relay coordination methods. Using K-means, hierarchical, and spectral clustering techniques, the proposed scheme classifies grid operating conditions more effectively, ensuring that relay settings adapt to different network scenarios. A key feature of this study is a practical method for identifying the optimal number of clusters and selecting the fine-tuning relay settings using the Genetic and Tug of War Optimisation algorithms, which improves the speed of fault detection and isolation over twenty different network topologies. The proposed scheme supports standard and non-standard Overcurrent Relay (OCR) characteristics, in which the IEC inverse-time curve is expanded beyond its conventional pickup-current limit to capture higher fault-current levels in renewable-integrated networks, ensuring faster and more selective relay operation. In Clustering 1 (Topology 1), the total tripping time was reduced to 23.15 s, while Clustering 2 (Topology 16), involving more relays, recorded 29.77 s. The total tripping time for Clustering 3 (Topology 2) was 29.34 s. Hardware-in-the-Loop (HIL) testing verified the real-time performance of the proposed scheme, showing high performance with simulation results and less than 2% deviation in relay tripping times. These outcomes demonstrate the scheme's ability to deliver reliable and responsive protection across various grid environments.

This study addresses the challenges of deformation failure and the difficulty in controlling the surrounding rock in the 2453 floor roadway of a coal mine in Hunan Province, influenced by mining activities. Conducting an in-depth investigation into the evolution law of the principal stress and stability control technologies for the surrounding rock of the floor roadway under the influence of mining. The research employs a combination of on-site investigations, laboratory tests, numerical simulations, and industrial trials. The results indicate that high horizontal tectonic stress and the characteristics of soft rock can easily lead to significant deformation of the surrounding rock in the roadway. By monitoring the principal stress in each part of the surrounding rock from the excavation of the 2453 floor roadway to the completion of upper coal seam mining, we obtained the evolution of the principal stress in the surrounding rock influenced by mining activities. During the mining process, the plastic zone in the “butterfly leaf” region of the surrounding rock in the roadway exhibits malignant extension; however, the depth and extent of the plastic zone on the sides remain largely unchanged. Based on this, a comprehensive support technical scheme is proposed, featuring “full-face high pre-tightening force bolt supporting + enhancing the support with long anchor cables at the key part of the plastic zone in roadway + grouting” as the main supporting body, complemented by “metal mesh + shotcrete” as auxiliary support measures. On-site monitoring has shown that the new support scheme more effectively controls the stability of the surrounding rock.

The current study analyzes the performance and emission attributes of different blends (0%, 20%, 40%, 60%, 80%, and 100% being termed as MB0, MB20, MB40, MB60, MB80 and MB100, respectively) of biodiesel derived from Raphanus Sativus, Jatropha, and Balanites aegyptiaca seeds with conventional diesel. The MB0 blend was pure diesel, and the MB100 blend was pure biodiesel (with no diesel). Critical performance parameters like Brake Thermal Efficiency (BTE), Brake Specific Fuel Consumption (BSFC), and Exhaust Gas Temperature (EGT) were evaluated experimentally. Moreover, the environmental effects were assessed by measuring emission characteristics such as Carbon Monoxide (CO), Hydrocarbons (HC), Nitrogen Oxides (NO_x), and Smoke Opacity. The results indicated that the mixed biodiesel blend MB20 exhibited a higher BSFC by 5.08% and a lower BTE by 3.13% compared to diesel at maximum load. The emission characteristics are much better performed by MB20 when compared with diesel. Additionally, the study examined the influence of diethyl ether as an oxygenated additive on the targeted biodiesel blend. The improved biodiesel blend (MB20) was blended with 5%, 10%, and 15% DEE, and MB95E5, MB90E10, and MB85E15 were prepared. Incorporating diethyl ether dramatically changed combustion behavior. The performance and emission characteristics were substantially changed. The results are presented and discussed here.

This paper presents the Lyapunov stability scheme based nonlinear power transfer matrix (NLPTM) model for controlling and modeling the permanent magnet synchronous generator (PMSG) based wind turbine. The proposed model considers active and reactive power as system state variables; thus, the rotor flux has no impact on the changes in stator active and reactive powers. This approach is based on a nonlinear technique employed on the machine-side ac/dc converter (MSC) and the grid-side dc/ac converter (GSC) of the PMSG wind turbine to reduce the oscillating current during the energy conversion process. The effectiveness of the proposed Lyapunov-integrated NLPTM approach is evaluated on a nonlinear controller-integrated PMSG wind system through simulation and is validated against an existing control scheme under transient operating conditions. The results proved the proposed approach's superiority in enhancing the power flow and suppressing the transient currents to improve the stability of the PMSG wind turbine.

During ultra-deep well drilling, the narrow safety density window of the drilling fluid makes it prone to complex conditions such as gas invasion. The high-temperature and high-pressure environment causes changes in the properties of the drilling fluid, making the gas invasion process highly covert and increasing the difficulty of well control. To address the challenge of accurately predicting gas migration velocity under gas invasion conditions in ultra-deep wells, this study considers the impact of temperature and pressure on the properties of the drilling fluid. A fluid state equation for ultra-deep wells was established. Based on the coupling effects of various parameters, a gas migration velocity model applicable to multi-well types and multi-factor coupling influences was developed. This model can calculate conditions for high-viscosity drilling fluids and analyze the impact of different parameters on gas migration velocity in vertical and horizontal wells. Additionally, suppression methods for gas migration velocity in ultra-deep wells were proposed. The study shows that an increase in drilling fluid viscosity, drilling fluid density, annular backpressure, and gas-liquid density ratio reduces the gas content in the wellbore and suppresses the increase in gas migration velocity. An increase in formation permeability results in a higher gas content in the wellbore, promoting an increase in gas migration velocity. The impact of drilling fluid displacement on wellbore gas content is complex. To reduce gas migration velocity, high-density and high-viscosity drilling fluids can be used, along with appropriate increases in wellhead backpressure and drilling fluid flow rate, to prevent gas invasion. This study helps to better understand the multiphase flow characteristics in the wellbore under gas invasion conditions in ultra-deep wells, ensuring the smooth operation of ultra-deep well drilling.