Three-dimensional Simulation Model Research Articles

Active Control of Longitudinal Combustion Instability in Bluff-Body Stabilized Premixed Flames with Multiple Neural Network Controller

ABSTRACT The suppression performance of multiple neural network controller on the longitudinal combustion instability is investigated in the Volvo bluff-body stabilized premixed flame. Two controlled plant models, e.g. one-dimensional (1D) reduced order acoustic network model and three-dimensional (3D) large eddy simulation model are adopted to verify this control strategy. In order to build the reduced order Volvo acoustic network model, large eddy simulation is adopted to extract the characteristics of system heat release under wide bandwidth and construct the flame transfer functions. For the 1D acoustic network model, this controller can completely eliminate the pressure oscillation using fuel valve as actuator. For the 3D large eddy simulation model that mimics the real-time oscillating characteristics, clustered prediction method and amplitude limiting method are adopted in multiple neural network control strategy to better account for the nonlinear characteristics of the 3D Volvo flame. This control strategy enables the modulation of the phase relationship between the heat release rate oscillation and pressure oscillation by introducing small perturbations to the inlet equivalence ratio, and attenuates the amplitude of the second harmonic of the unstable mode effectively.

Finite Element Analysis of Relative Slip Between Tight Tops and the Human Body

To investigate the fabric performance of tight tops and the influence of clothing pressure on the relative slip between clothing and the human body, a simulation model based on finite element analysis is proposed. This model simulates the relative slip distance under dynamic conditions. Initially, a three-dimensional model for numerical simulation was established through reverse engineering. Subsequently, material properties and boundary conditions were defined. Finally, the model was analyzed using ANSYS Workbench, and the obtained results were compared with the stretch ratio of the skin on the human back. The results indicate that, under constant conditions, the Young’s modulus of the fabric has a greater influence on the slip and shows a significant positive correlation, with correlation coefficients ( R) all exceeding 0.99. The impact of clothing pressure on sliding is relatively small, and the sliding distance decreases with an increase in clothing pressure. In addition, it has been demonstrated that there is a significant correlation ( p < 0.05) between the relative sliding distance of clothing and the stretch ratio of the skin. The study could provide a helpful guideline for the design of smart clothing, and it can provide valuable insights for various applications, such as sportswear and medical apparel.

Performance enhancements of power density and exergy efficiency for high-temperature proton exchange membrane fuel cell based on RSM-NSGA III

In this study, a three-dimensional simulation model was developed and a multi-objective optimization of a single-channel high-temperature proton exchange membrane fuel cell (PEMFC) was carried out by the response surface methodology (RSM) and the non-dominated genetic algorithm III (NSGA III). Firstly, five main influencing factors including operating temperature (T), operating pressure (p), gas diffusion layer porosity (εGDL), proton exchange membrane (PEM) thickness (Mmem) and anode stoichiometry ratio (λa) were identified. The optimization objectives include three cell performance evaluation indexes: power density (wpow), system efficiency (ηsystem), and exergy efficiency (ηexergy). Secondly, the prediction accuracies of the RSM and artificial neural network (ANN) for the three performance evaluation indexes of high-temperature PEMFC were compared. Finally, the optimal solution from the Pareto solutions derived through RSM-NSGA III. The results show that the maximum wpow, maximum ηsystem and maximum ηexergy are 0.793 W cm−2, 22.31 % and 54.69 %, respectively. The optimal result obtained by combining EWM and VIKOR is wpow = 0.6726 W cm−2, ηsystem = 19.44 % and ηexergy = 54.01 %, respectively. The corresponding condition is T = 447.18 K, p = 1.15 atm, εGDL = 0.617, Mmem = 0.0412 mm, and λa = 1.26, respectively. Moreover, the suggestions are provided for the design of more efficient high-temperature PEMFC.

Encapsulation structure and in-situ embedding test and model study of a new type of road piezoelectric energy collector

In recent years, research on road piezoelectric energy harvesters (RPEH) has made great progress in the field of road vibration energy harvesting. However, the research on the packaging structure and embedding method of RPEH is not comprehensive. In this paper, a new type of transducer unit structure is developed, which can improve the electrical energy output compared with the drum piezoelectric transducer, and its waterproof performance of the transducer unit is tested under different water depth and duration. Then, a new RPEH package structure is made, and the output performance is compared with the three commonly used package structures in the current research, and the field construction of RPEH with different embedding methods is carried out on the actual road to evaluate the electrical energy output capacity of RPEH under different embedding methods, and the best construction method of RPEH is summarized through durability test. Finally, the three-dimensional simulation model of RPEH with different construction methods is established, and the stress and voltage are analyzed by finite element method to verify the best embedding method. The test results show that the piezoelectric output efficiency of the new transducer unit is increased by 38.9 %, and it still has good electrical energy output after 24 h immersion at a depth of 1.5 m, and its waterproof level reaches IPX8. Under larger excitation frequency and load, the indoor output of RPEH in the new package structure has better output performance in indoor test. The bolt-spring package is used to apply pre-pressure to RPEH, and the output efficiency of RPEH is improved. When the excitation conditions are 10 kN, 10 Hz, the output power is increased by 11.1 %, 127.3 % and 247.4 % compared with the other three package structures. The maximum power of RPEH is 3.41 W by placing concrete on the bottom surface of RPEH sponge washer and using asphalt as the pavement layer to ensure the durability of piezoelectric pavement. The finite element analysis illustrates the strain and voltage variation of piezoelectric pavement with different embedment modes, and the simulation results are consistent with the test results. The research results provide an important basis for the design of RPEH packaging structure and embedding method in road piezoelectric engineering.

Numerical simulation and optimisation design for ventilation and heat dissipation in high-temperature and high-load indoor substations

Under high-temperature and high-load operational conditions, inadequate ventilation and suboptimal cooling arrangements within indoor substations result in high oil temperatures, posing a threat to the secure and steady operation of transformers. In this paper, the ventilation and heat dissipation effect of a 110 kV indoor substation is studied by the computational fluid dynamics method. Initially, the three-dimensional simulation model of the main transformer chamber is constructed to mirror the actual substation structure. Subsequently, the impact of the upper outlet on ventilation and heat dissipation is explored. The results show that the proximity of the upper outlet to the fan on the side wall prompts the fan to draw air from the upper outlet, diminishing the air volume entering the lower intake outlet by 38.8 %. It proves detrimental to the transformer's heat dissipation efficiency. Lastly, with the upper outlet closed, the study delves into the impact of various configurations of intake and exhaust ports on optimizing ventilation and heat dissipation. A total of six cases of two scenarios for the air inlet location and three exhaust vent positions are explored. According to the simulation results, the optimal case of substation ventilation and heat dissipation is obtained by considering four evaluation parameters.

Temperature distribution analysis and mechanical property prediction of wire loops in the Stelmor air-cooling system

During the Stelmor air-cooling process, the temperature distribution has a significant impact on the wire loops' final mechanical properties. The temperature distribution during air-cooling process is accurately solved by establishing three-dimensional model and Computational Fluid Dynamics (CFD) simulation. It is also found that the heat transfer coefficient on the cross section of the wire loop is very different, with a difference of 70–100 Wm−2K−1. The average value of the surface heat transfer coefficient of the wire loops section is used to replace the surface heat transfer coefficient of the wire loops, which improves the temperature distribution calculation accuracy, which is not considered by previous scholars. The finite difference method is used to calculate the mathematical model of the temperature distribution during the Stelmor air-cooling process. It is found that the maximum temperature difference of the wire during the cooling process is 90–110 K. The prediction model of mechanical property of wire after air-cooling was established, and distribution of mechanical property of the wire loops was obtained, and the reason for the uneven distribution of mechanical property of the wire loops was found.

A Novel Numerical Model Considering Unsaturated Soil Properties and Computational Study on Heat and Moisture Transfer Characteristics of Helix Ground Heat Exchanger

Abstract A novel three-dimensional numerical simulation model for the helix ground heat exchanger was proposed in this paper, which takes into account unsaturated soil properties. This model is more suitable for real working conditions. To validate its accuracy, a miniature model heat transfer experimental platform was constructed. Additionally, the study conducted simulation research using three types of soil with significantly different thermal and moisture characteristics. Moreover, the comprehensive thermal conductivity and water diffusion coefficient of these three soil types were determined by relevant literature and experimental tests. The aim was to comprehensively explore the impact of different soil types on the heat and mass transfer of the helix ground heat exchanger. The results indicate that the numerical model developed in this paper accurately captures the heat and mass transfer characteristics of the helix ground heat exchanger to a certain extent. Increasing the comprehensive thermal conductivity and water diffusion coefficient of the soil can significantly enhance the heat exchange capacity of the exchanger. For instance, under sandy loam conditions, the heat exchange capacity is approximately 20.73% higher compared to clay loam conditions. The study also identifies two distinct areas around the helix ground heat exchanger: the severe change region and the soft change region. In the severe change region, there is a notable decrease in soil water content near the exchanger, which inevitably weakens the thermal conductivity of the soil. It is advised to minimize this effect through measures like active water spraying.

A three-dimensional numerical model for computing the actual voltage induced in a Barkhausen surface coil

This investigation presents a novel three-dimensional simulation model designed for the analysis of Magnetic Barkhausen Noise (MBN). The model’s formulation is directly deduced from Maxwell’s equations, establishing a Boundary Value Problem (BVP) with boundary conditions tailored to a specific configuration involving a lengthy steel rod encased within a solenoid, subjected to sinusoidal current excitation, all contained within an air enclosure. This chosen configuration holds physical equivalence to the majority of setups commonly utilized in Barkhausen experiments. Utilizing the proposed three-dimensional model, it became feasible, for the first time, to computationally assess the voltage induced in the coil by the flux emanating from all spatial directions. The findings indicate that the MBN signal is primarily generated by the flux rate aligned with the direction of the applied field. Nevertheless, simulations confirm additional contributions to the signal originating from magnetic flux in directions significantly deviating from the applied field direction. It is demonstrated that these contributions from lateral flux significantly influence the angular dependence of the Barkhausen signal energy, showcasing a notable alignment between the proposed model and experimental results. The results underscore the capability of the proposed model to facilitate the simulation of Barkhausen Noise.

Numerical study on dynamic flow of flexible extension nozzle in rocket motors

The use of extension nozzles in rocket propulsion systems is one of the effective methods to increase the geometric expansion ratio and thrust of the nozzle. As a new type of extension nozzle, the flexible extension nozzle can achieve continuous changes in nozzle expansion ratio. To explore the characteristics of the flow field structure at the “bulge” structure and the step structure in the actual configuration of the flexible extension nozzle, and the impact on the performance of the nozzle, a three-dimensional numerical simulation model of the flexible extension nozzle was first established to study the flow field at the “bulge” structure, and then a two-dimensional unsteady numerical simulation model was established by using the coupling technology of dynamic grid and overlapping grid to study the flow field at the step structure. The results show that during the unfolding of the nozzle surface, a complex flow structure of “expansion fan-mixing layer-shock-vortex” were formed in the step area at the junction of the fixed section and the moving extension section. The specific impulse loss of the 3D model is larger than that of the 2D model due to the consideration of the “bulge” structure. The flow loss of the “bulge” structure and the step structure to the nozzle is 0.73% and 0.65% respectively.

Use of virtual reality in physical rehabilitation: A narrative review

Virtual reality (VR) has emerged as an innovative technology in various fields. It transforms how we experience and interact with the world, and it has also developed into physical rehabilitation. Rehabilitation has also evolved from mere exercises to using technology while giving exercises to patients. VR is a technology that can enhance treatment and improve outcomes. VR uses computer-generated three-dimensional interactive simulation models, allowing users to engage in environments resembling real-world objects and events. An extensive literature search was conducted on SCOPUS, PubMed, the Web of Science and relevant rehabilitation databases. The keywords ‘virtual reality’, ‘rehabilitation’ and ‘physical therapy’ were employed to identify pertinent studies. The inclusion criteria encompassed research investigating the use of VR in rehabilitating musculoskeletal, neurological and cardiovascular conditions. VR has been used in various rehabilitation domains. It is effectively used in balance and gait training, cognition and memory training, pain management, muscle strengthening, etc. It has also been shown to improve adherence to exercises. VR training in physical therapy represents a transformative advancement in rehabilitation. Integrating VR technology offers many benefits, including enhanced engagement, customised therapy regimens and a safe environment for patients to practice and improve their physical abilities. The evidence from various studies indicates its potential to improve outcomes for individuals with a wide range of physical impairments.

Design, thermal-mechanical coupling analysis, and optimization of polymeric matrix composite sandwiches with a lattice core exposed to a high temperature

This study presents the design of a sandwich structure tailored for post-heat transfer applications subjected to out-of-plane compression. A three-dimensional finite element simulation model was developed to analyze the temperature distribution within the sandwich structure and investigate the effects of high-temperature exposure on its mechanical behaviors. The structure was subjected to a temperature of 300 °C for 400 s, and the temperature distribution at the upper connection point between the top face sheet and the struts of the core was determined. Subsequently, upon returning the sandwich to ambient temperature, a comprehensive calculation of its mechanical properties was conducted and then enhanced by applying different optimization techniques. The results demonstrate that filling the core with Saffil alumina fibers in the presence of a 1.5 mm a thermal barrier coating of Superwool 607 helps increase the mechanical properties of the sandwich structure by around 55%.

Thermal and Mechanical Stress Analysis in Aircraft Hybrid Panels with Multi-Bolt Joints.

This study investigates the thermal stress and bolt load distribution in a hybrid panel structure of an aircraft mechanical joint under extreme temperatures. The hybrid panel structure comprises two aluminum alloy splices, six T-shaped composite stringers, and two composite skins, secured together with 96 bolts. This study analyzed the strain induced by thermal stress on composite materials and metals within the structure across temperatures, employing temperature environment tests ranging from room temperature to -54 °C, alongside a carrying capacity test at -54 °C. Furthermore, a three-dimensional simulation model of the panel structure was developed, incorporating considerations for contact, metal elastoplasticity, and the progressive damage failure of composite materials. This model facilitated the determination of thermal stress and bolt load distribution patterns. The results indicate a strong consistency between the finite element analysis outcomes and the experimental data. Temperature variations exacerbate the uneven distribution of bolt loads, concentrating the load near the edges of the hybrid structure while diminishing it in the center. The bolt load distribution parallel to the mechanical load direction forms an "M" shape, with a maximum load magnitude of approximately 31 kN. Perpendicular to the mechanical load, the bolt load undergoes significant changes, especially at the edges, reaching a maximum of about 20 kN, which warrants attention. The bolt-load distribution of the structure with the increase in mechanical load at -54 °C tends to be consistent with that at room temperature.

Influence of Magnetic Field Configuration in Helicon-Negative Ion Source on Increase of the Efficiency of NNBI Heating System

The influence of the magnetic field configuration on the performance of a helicon-based negative ion source is investigated with simulation experiments. Using COMSOL Multiphysics software, a three-dimensional simulation model for a negative ion source, based on a helicon plasma source, is presented in two magnetic field configurations: uniform and nonuniform configurations. The helicon plasma source employed a Nagoya-type antenna to apply radio-frequency (RF) power at a frequency of 13.56 MHz. The injected gas is hydrogen with a flow of 10 standard cubic centimeters per minute. Using a three-dimensional model, helicon wave propagation in the presence of a magnetic filter and the energy absorption mechanism in the helicon system are investigated. In this context, in the presence of the two magnetic field configurations, the influence of the important parameters’ working pressure and RF power on the optimization of negative ion production under volume mode is studied. Six electromagnetic coils at the same current are used for producing the magnetic field in both cases of uniform and nonuniform configurations. The variation of the electron density and electron temperature, in both regions of driver and expansion, are calculated and represented with respect to the different power and the gas pressure. The simulation results of the negative ion density in the expansion region for the uniform and nonuniform magnetic field configurations are compared. The results indicate that at the same applied current of coils, the negative ion density in the presence of the nonuniform magnetic field is about 1.75 times higher than the negative ion density of the uniform case. Moreover, the results show that the negative ion density is decreased by decreasing the magnetic field of the driver region in the nonuniform cases.

Electric-thermal-mechanics modeling for in-process phenomena during micro resistance spot welding spark plug of Pt and Inconel600

The spark plug is one of the important components in the gasoline engine's combustion chamber. To reduce vehicle emissions, the platinum spark plug is selected due to its good performance. Due to the high productivity of resistance spot welding (RSW), a micro-scale RSW process is employed to assemble the platinum tip to Inconel600 part in the production of spark plugs. In order to understand the electric-thermal-mechanics phenomena during micro resistance spot welding spark plug for controlling the welding quality and saving electric energy, a three-dimensional simulation model and the in-house finite element program JWRIAN-RSW3D were developed. The potential history and upper electrode displacement results were verified with experiments. Numerical case studies were made to investigate the influence magnitude of welding current on the electric-thermal-mechanics phenomena. The developed model reveals inside phenomena to clearly understand the welding mechanism for potential, current density, temperature, electrode displacement and their distribution/history as well as the molten zone. The comprehensive phenomena of maximum temperature distribution on both base metals and Inconel600 were clarified using a top perspective, revealing differences in distribution on the contact surface between horizontal and vertical sections. To achieve a complete welding joint, the molten zone on the contact area is required carefully in order to facilitate the bonding of both base metals. Based on simulation results for three welding conditions, the alternating current at the magnitude of 1.2 kA with the welding time of 0.1 s is recommended to obtain the welded joint with minimized energy consumption in production.

Simulation-Based Thermal Fatigue Validation Test Development for Exhaust Manifold

Abstract Exhaust manifolds in diesel engines undergo continuous thermal cycle loading of varying thermal cycles with different mean, amplitude, and rate of temperature change created by application duty cycles. This makes analysis and testing of the exhaust manifold to meet the thermal mechanical fatigue life expectation of different applications challenging. In this paper, a simulation-based product development approach, which uses application duty cycles, simulation models of different capabilities, including three-dimensional Finite element simulation model, one-dimensional (1D) physis-based damage model to develop an abusive thermal cycle engine test for validating exhaust manifold, is presented.

The influence of hydraulic fracture and reservoir parameters on the storage of CO2 and enhancing CH4 recovery in Yanchang formation

The demand for a clean energy source from shale is growing day-to-day since it is not harmful to the environment like other fossil fuels. Further, shale reservoirs offer long-term geo-carbon dioxide (CO2) storage. Innovations in horizontal drilling and multi-stage hydraulic fracturing have made shale gas extraction and geo-CO2 storage economically viable. A three-dimensional Yanchang shale formation simulation model in Ordos's basin was developed using CMG-GEM, considering adsorption/desorption, diffusion, geomechanics, permeability changes, and non-Darcy flow. Two horizontally drilled wells, each 510 m long, were fractured and positioned 90 m apart. CO2 gas was injected into Well-2, producing methane (CH4) in Well-1. After simulation for 30 years, the cumulative mass of CH4 produced was 1.07×10+5kg, the cumulative mass of CO2 produced was 2.3×10+4kg, which is 1.14% of the mass injected, the cumulative mass of CO2 injected was 2.01×10+6kg and cumulative mass of CO2 gas stored was 1.987×10+6kg which is 98.86% of the injected mass of CO2 gas. The natural fracture system was the dominant factor of enhanced shale gas recovery and CO2 injection in the Yanchang shale formation. A sensitivity analysis was conducted with CMG-CMOST, examining the influence of reservoir and hydraulic fracture parameters in the storage of CO2 and enhancing CH4 recovery. Natural fracture porosity had the most significant impact on CH4 production and CO2 storage, followed by fracture permeability and half-length leading for hydraulic fracture parameters, with fracture conductivity being the least influential parameter. The approach used in this study applies to tight shale oil and gas formations in various sedimentary basins worldwide, enabling a more comprehensive understanding of reservoirs and hydraulic fracture parameters that can enhance oil and natural gas production.

Liquid metal-enhanced thermoelectric generator for high-temperature thermal harvesting

It is a challenge to achieve high output power of the thermoelectric generator (TEG) for high-temperature waste heat recovery due to the working fluids with low thermal conductivity (such as air) or low tolerance of temperature (water or oil). In this paper, the gallium-based liquid metal (LM) with a high boiling point (>1000 ℃) and thermal conductivity (>20 W/mK) are introduced to significantly enhance heat charging and discharging at the hot/cold sides of TEG. We also developed an electromagnetic induction pumping method for the effective LM-driven flow at high temperatures. A three-dimensional coupling multi-parameter optimization simulation model of LM-based TEG was developed to reveal the internal heat transfer and power generation mechanism for clarifying the impact factors of the performance. The results have shown that the power generation capacity can be effectively improved by increasing the inlet temperature (Thot-in). It is worth noting that the temperature difference (ΔT) of the TEG module is severely limited by the thermal resistance (Rcapacity) of the LM heat capacity, such as, when the flow rate of 2 L/min, the Rcapacity accounts for 90.6 % (0.020 ℃/W). It is easier to achieve a larger open circuit voltage by increasing the height of the thermoelectric leg, but the Pmax is constantly weakened. Compared with Xceltherm 600 and Solar salt, LM heat transfer fluid has more obvious advantages in enhancing the power generation performance of the system. The LM-based TEG experiment platform was established to study heat transfer and power generation characteristics. The results have demonstrated that good consistency was proved by comparing experimental and numerical data. And the Pmax of the LM-based TEG system is 0.16 W/cm2 at ΔT of 136 ℃. LM-based TEG can open new perspectives for broad applications in high-temperature waste heat recovery.

Research on the influence and optimization of sunshade effect on radiative cooling performance

Intense solar radiation is the main reason why radiative cooling is difficult to achieve during the daytime, as the radiative heat flux from the sun will offset the heat emitted by the cooler. Most previous studies have focused on providing coolers with high solar reflectance and high mid-infrared spectral emissivity by designing photonic structures. In this study, a macroscopic sunshade device based on the solar visual motion trajectory is proposed to reduces the direct solar radiation received by the cooler surface through setting a blocking on the solar path, while hardly affecting the radiative capacity of the cooler. Here, we built a three-dimensional sunshade device simulation model based on the surface-to-surface radiative heat transfer module in COMSOL Multiphysics® software, which can effectively improve the cooling performance of the cooler. Then, using polished aluminum plates, black paint-coated cooler, and reflective radi-cool film to test the impact of macroscopic sunshade device based on the solar apparent motion trajectory on improving the cooling performance of difference coolers. The results verified the effectiveness of the proposed sunshade devices in improving radiative cooling performance, and the results showed that the maximum temperature reduction could reach 3.35 °C, 26.96 °C, and 3.42 °C, respectively.

A numerical simulation method for solving electromagnetic-mechanical coupling field

A new numerical simulation method based on the finite volume method has been proposed to address the challenges associated with the pseudo-oscillation phenomenon that occurs with an increased Péclet number, as well as determining an appropriate time step for electromagnetic-mechanical coupled physical field calculations. This method utilizes the concept of upwind from Computational Fluid Dynamics (CFD) to solve Maxwell's equations, a finite-volume method for discretizing the electromagnetic diffusion equations. Through computing typical electromagnetic field problems such as TEAM problem 9–1 and comparing the results to the literature, it has been confirmed that this method has sufficient computational accuracy to solve electromagnetic field numerical simulation problems containing moving conductors. Additionally, a three-dimensional simulation model of the electromagnetic coil gun has been established to verify the viability of the proposed method for solving magnetic field problems under the electromagnetic launch (EML) system. The study also examined the change in magnetic field strength and current density of the EML device during the launching process. The results lay the foundation for the technical application of this method.

Optimizing Hydrogen and Ammonia Injection Timing for Enhanced Mixture Formation in Internal Combustion Engines

Hydrogen and ammonia are two carbon-free alternative fuels for engines. They represent some of the most viable pathways toward achieving our objectives of energy conservation and reducing emissions. To research the quality of the hydrogen-ammonia-air mixture formation under different hydrogen/ammonia injection timing, a three-dimensional simulation model for a PFI(Port Fuel Injection) hydrogen internal combustion engine with the inlet, outlet, valves and cylinder was established using Converge software. Research focused on the space distribution characteristics and variation law of velocity field, concentration field and turbulent kinetic energy under different injection timings in order to reveal the influence of these parameters on hydrogen-ammonia-air mixture formation process. The results showed that hydrogen injection should be neither too early nor too late. Backfiring can be initiated too early or too late. Therefore, the optimum starting point for hydrogen/ammonia injection should be 338°CA.