•The fluid-solid-acoustic coupling method is used to study the flow field of nozzle.•DPM-LES method can simulate nozzle flow process more accurately.•High-frequency vibration of SVC directly ...increases the dynamic pressure inside nozzle.•The increase of the orifice diameter and depth leads the SPL to first decrease and then increase.
Dust particle pollution endanger human health and cause safety hazards in industry. Twin-fluid atomization technology plays an important role in reducing the pollution of dust particles. In the current study, based on the Large Eddy Simulation (LES) model, the Discrete Phase Model (DPM) model and the Ffowcs Williams-Hawkings (FW-H) model, a fluid-solid-acoustic multi-physics coupling DPM-LES model is proposed, and the numerical simulation results under the multi-field coupling are compared and verified by experiments. Then, through the numerical simulation method, the flow field dynamic characteristics and acoustic characteristics inside and outside the gas-liquid twin-fluid nozzle (TFN) under different operating parameters and self-excited vibrating cavity (SVC) structure parameters are studied. Because the high-frequency vibration of the SVC caused by high gas flow leads to local severe turbulence and the rebound effect between the fluid and the SVC, the dynamic pressure value in most areas of the nozzle reached more than 7000 Pa. Due to the resistance of the air in the flow field and the friction and entrainment between the gas-liquid two phases during the movement, the axial distance in the atomizing flow field with a velocity exceeding 2 m/s can be as far as 2.13m when orifice depth L =1.0 mm. The SPL of the nozzle is gradually attenuated in the process of space propagation. The increased gas flow enhances turbulence, which intensifies nozzle noise. In this paper, the DPM-LES investigation on flow field dynamic and acoustic characteristics of a TFN by multi-field coupling method are studied, which can lay a theoretical foundation for the optimal design of TFN in engineering and provide a certain reference for the reduce of dust particle pollution.
•The cost feasibility of renewable energy for oil and gas field development was evaluated•The maintenance strategy is optimized to reduce the equipment cost•Real-time electricity price forecast is ...introduced to analyze the operating cost•An optimization method of maintenance strategy for multi-function combined degradation is proposed.
The development and utilization of renewable energy has become a research hotspot in recent years, and it has begun to be experimentally applied in the development of “ultra-deep water” oil and gas fields. This paper proposes an economic perspective of renewable energy in offshore oil and gas development, evaluating the economic feasibility of large, complex, and multi-equipment systems, as well as the grouping maintenance of the system with multiple types of reliability functions. Comprehensively considering the construction cost, maintenance cost and real-time electricity price cost, the reliability and maintenance cost are the objective function, and the real-time electricity price is the influencing factor. The operating costs of offshore oil and gas development over long distances and offshore wind energy are compared. The results show that grouping maintenance can greatly reduce the total cost. As an alternative energy solution, offshore wind can meet the demand for clean energy in the context of economic growth, although the total cost is higher than that of long-distance transmission.
The nonlinear capacitance model is important to predict the dynamic characteristics of SiC mosfet s. Different from the conventional modeling method extracting the parameters from the full data, this ...article proposes a modeling method based on the envelope of the switching trajectory, which greatly reduces the complexity of the model and avoids divergence during the simulation. The proposed modeling method clarifies the value range of gate-source voltage v gs and drain-source voltage v ds in each interterminal capacitance operation period, and only necessary data will be taken into consideration, whereas the unnecessary data out of switching trajectory will be discarded. In order to verify the correctness and accuracy of the proposed model, the SiC mosfet C2M0080120D (1200 V/36 A) with the nonlinear capacitances is modeled in the Pspice environment and compared with the measured results of the double-pulse experiment. The proposed model is also simulated in a full-bridge inverter. The results show that the proposed model has enough accuracy and efficiency in dynamic behavior prediction of SiC mosfet s, which would be potential for the more complex system-level simulation.
The optimal operation of the integrated electricity and heat systems (IEHS) can bring environmental benefits, reduce the operational cost, and achieve high penetration levels of renewables. This ...review aims to provide a comprehensive overview of the IEHS modeling and solution methods for the optimal operation. With respect to the optimal operation, the IEHS modeling is reviewed from five aspects, including the representation of dynamic characteristics, operational flexibility improvement, operation under uncertainty, joint dispatch of the electrical power system (EPS) and district heating system (DHS), and joint market clearing of the EPS and DHS. The solution methods for the optimal operation of the IEHS are divided in four groups according to the properties of optimization problems, i.e., methods for integrated energy flow calculation, methods for decentralized optimization, methods using relaxation and convexification techniques, and methods based on intelligent algorithms. The main characteristics, advantages, and limitations of the modeling and solution methods are detailed and compared. In the end, the current gaps and future research are summarized regarding the modeling and solution methods for the optimal operation of the IEHS.
•The IEHS modeling considers dynamic characteristics, flexibility improvement, uncertainty, and joint dispatch and clearing.•The IEHS solution methods in different situations.•Current gaps and future research of modeling and solution methods.
Material extrusion (ME), one of the most rapidly developing additive manufacturing techniques, has been widely used in the field of aerospace, medical, industrial design, and so on. Since the working ...environment is increasingly complex, it is urgent to study the ME products' dynamic performances to determine their reliability. In this article, a finite element theoretical model of ME thin plate was established with the porosity defect taken into account. A modal test system was set up and the multiple‐input single‐output method was used to obtain the measured data. The scanning electron microscopy (SEM) analysis on the samples confirmed that the dynamic characteristic was improved as the extrusion temperature increased. In addition, the sensitivity analysis was carried out on the model to predict how the samples' elastic modulus, Poisson's ratio, and density affect their dynamic characteristics. The results show that the proposed model is reliable to give accurate predictions on the dynamic characteristics of ME thin plates. With the increase of extrusion temperature, the samples' natural frequency will increase, and the vibration response will decrease. The sensitivity analysis indicates that increasing elastic modulus or Poisson's ratio can increase the natural frequency of ME thin plate but decrease the vibration response. While increasing the density will decrease both the natural frequency and vibration response.
Schematic representation of the deposition sequence and modal test system.
Water management is one of the most important issues for proton exchange membrane fuel cell stack. Liquid water accumulates in the stack may impede the transport of the reaction gas, resulting in ...unstable output performance and poor durability. In this study, Condensation mode and Condensation Circulation mode are proposed to reduce the accumulation of liquid water in the anode compartment, thus reducing the risk of flooding. Comparative research among the traditional dead-end anode (DEA) mode and presented modes are carried out on a ten-cell open-cathode PEMFC stack. The comparisons show that the proposed strategies can effectively alleviate the voltage decay caused by flooding and improve output stability. And the Condensation Circulation mode is more effective than the Condensation mode.
•Dynamic behaviors of voltage and pressure are discussed in detail.•Condensation mode and Condensation Circulation mode are applied to avoid flooding.•The proposed strategies can effectively improve the dynamic behaviors.•Condensation Circulation mode behaves better than Condensation mode.
Recycled aggregate concrete structures are advocated widely as sustainable structures mainly due to numerous benefits of concrete recycling including reducing the need of natural resources extraction ...and landfill. Furthermore, the energy and carbon implications of recycled aggregate concrete in material level and low-rise structural level have been investigated. However, little attention has been paid to investigating the effects of adoption of recycled aggregate concrete as structural material on the carbon footprint of high-rise buildings, typical of common structures in megacities such as Shanghai, China. To address this gap, this study investigates the carbon footprint of two identical twin towers, with one tower made of recycled aggregate concrete and the other made of natural aggregate concrete. The structures were designed by following Chinese building codes while optimizing the mix design of recycled aggregate concrete to achieve similar fresh and hardened concrete properties to natural aggregate concrete. The static behaviors and dynamic characteristics of structures were analyzed prior to evaluating the carbon footprint to ensure that both structures had equivalent functions. The global warming potential and cumulative energy demand indicators for the recycled aggregate concrete structure were calculated based on local data and compared with those of the same structure made with natural aggregate concrete. The results indicate that adoption of recycled aggregate concrete as structural material in the high-rise structure, in place of natural aggregate concrete, can result in up to about 2.175 × 105 kgCe decrease in carbon footprint in condition of this specific project. The effects of recycling strategy used and the transportation distances on embodied carbon and energy consumption further highlight the environmental benefits of promoting recycled aggregate concrete applications.
•Recycled aggregate concrete (RAC) was applied in a high-rise structure.•Structural performance of the RAC structure was field tested and compared.•Carbon emission reduction caused by applying RAC was evaluated and discussed.
The electric shoegear-conductor rail system (the shoe-rail system) is one of the electric energy collection devices for metro vehicles. A good interaction performance between the electric shoegear ...and the conductor rail is essential to ensure the current collection quality and operational safety. The conductor rail irregularities and vehicle-track excitation (induced by track irregularities) are the major disturbances to the shoe-rail interaction. Only the vertical effect of the vehicle-track excitation has been considered in previous studies, which cannot reproduce the realistic behavior of the shoe-rail system. To address this deficiency, this work attempts to build a spatial vehicle-shoe-rail system coupling model, including the disturbances from both the conductor rail irregularities and vehicle-track excitations. The numerical accuracy is verified by comparison with the measurement data collected from Guangzhou Metro Line 5 (Jiaokou to Wenchong section). Then, the effects of conductor rail irregularities, speed, shoe-rail structure parameters, and track irregularities on the interaction performance of the electric shoegear-conductor rail system are analyzed. The results show that the maximum contact force exceeds the safety threshold at a speed of over 120 km/h. The frequency analysis of the contact force at different speeds indicates the necessity to avoid the resonance caused by the match between the span passage frequency and the dominant natural frequency. The stochastic analysis indicates a visible dispersion in contact force standard deviation excited by track irregularities. The dispersion increases from 2.2% to 21.8% with the degradation of the track quality from level 6 to level 1. The statistical maximum of contact force will exceed the safety threshold with poor track quality.
Deformation monitoring and dynamic characteristic analysis of bridge structures are the vital and basic requirements for the safe operation of bridges. In recent years, Global Navigation Satellite ...System (GNSS) has become increasingly widely used in bridge structural health monitoring with the development of the GNSS technology, especially the continuous improvement and development of China's Beidou navigation satellite system (BDS). This article summarizes the application process of GNSS dynamic deformation monitoring and the development of GNSS deformation measurement technology of bridge structural health monitoring, the dynamic characteristic identification method and its application in bridge GNSS monitoring. The positioning solution methods for GNSS monitoring, the high sampling rate GNSS receiver for monitoring, multi-frequency and multi-system GNSS monitoring and the weakening of multipath effect of GNSS monitoring are summarized in detail. Then, the conclusions and prospects are posed for future research and related application.
The elastic ring assumes a multifunctional role, crucially providing support and reshaping oil-film thickness distribution in applications such as squeeze film dampers, demonstrating its practical ...efficacy. In this work, a magnetorheological damper (MRD) incorporating an elastic ring is proposed for the first time to improve the performance of damper. The innovative configuration of the elastic ring magnetorheological damper (ERMRD) is fabricated and integrated into a test platform of rotor system. The multi-filed coupling dynamic model of ERMRD is developed involving magnetic field interactions governed by Kirchhoff law, magnetorheological fluid flow dynamics derived from lubrication theory, and the elastic ring deformation based on thin plate theory. The intricate influence mechanisms of elastic ring and excitation current on oil-film characteristic of ERMRD, encompassing oil-film pressure, oil-film force, oil-film stiffness and damping, are investigated in detail. To substantiate the capabilities of ERMRD, it is implemented within the rotor system and a coupled dynamic model is established using Lagrange equation. This is followed by an in-depth analysis of the dynamic response using the Newmark-β method, including a comparative assessment with the conventional MRD. The results reveal that the elastic ring and excitation current influence oil-film pressure distribution in ERMRD from different perspectives, leading the oil-film force to present diverse variation characteristics. Compared to MRD, ERMRD exhibits weaker nonlinearity and superior damping performance.
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