Verified Simulation Model Research Articles

Research on the Performance of Thermoelectric Self-Powered Systems for Wireless Sensor Based on Industrial Waste Heat.

The issue of energy supply for wireless sensors is becoming increasingly severe with the advancement of the Fourth Industrial Revolution. Thus, this paper proposed a thermoelectric self-powered wireless sensor that can harvest industrial waste heat for self-powered operations. The results show that this self-powered wireless sensor can operate stably under the data transmission cycle of 39.38 s when the heat source temperature is 70 °C. Only 19.57% of electricity generated by a thermoelectric power generation system (TPGS) is available for use. Before this, the power consumption of this wireless sensor had been accurately measured, which is 326 mW in 0.08 s active mode and 5.45 μW in dormant mode. Then, the verified simulation model was established and used to investigate the generation performance of the TPGS under the Dirichlet, Neumann, and Robin boundary conditions. The minimum demand for a heat source is cleared for various data transmission cycles of wireless sensors. Low-temperature industrial waste heat is enough to drive the wireless sensor with a data transmission cycle of 30 s. Subsequently, the economic benefit of the thermoelectric self-powered system was also analyzed. The cost of one thermoelectric self-powered system is EUR 9.1, only 42% of the high-performance battery cost. Finally, the SEPIC converter model was established to conduct MPPT optimization for the TEG module and the output power can increase by up to approximately 47%. This thermoelectric self-powered wireless sensor can accelerate the process of achieving energy independence for wireless sensors and promote the Fourth Industrial Revolution.

Multi-factor coupling optimization of heat recovery effectiveness in a transcritical CO2 heat pump

In the background of energy shortage and climate change, transcritical CO2 heat pump(HTP) technology has attracted lots of attention because of its energy-saving and environmentally friendly advantages. In this research, an experimentally verified simulation model of transcritical CO2 HTP is established to investigate multi-factor coupling optimization of heat recovery effectiveness(ηIHX). First, the coupling optimization mechanism of ηIHX and discharge pressure(pdis) is analyzed. Moreover, this research explores the influence of ηIHX on heating capacity, power consumption, discharge temperature(tdis), and internal heat exchanger(IHX) cost, and further proposes a comprehensive heat recovery index to optimize the above factors. Based on this index the optimal heat recovery effectiveness(ηIHX,opt) for each operating condition is obtained. Also, a failure boundary for the coupling optimization of the ηIHX is also indicated. In addition, the optimal discharge pressure(pdis,opt) prediction correlation for different ηIHXs is proposed, which can be used for heat recovery effectiveness collaborative optimization control. Finally, a general method for evaluating IHX is provided. Taking Xi'an as an example, the optimal heat recovery area(AIHX,opt) of this HTP system is 0.42m2, with which the optimized HTP system operates safely at extreme operating conditions, resulting in an annual lucre of 1,211 CNY.

Experimental and numerical study of in-plane uniaxial compression response of PU foam filled aluminum arrowhead auxetic honeycomb

PurposeAuxetics metamaterials show high performance in their specific characteristics, while the absolute stiffness and strength are much weaker due to substantial porosity. This paper aims to propose a novel auxetic honeycomb structure manufactured using selective laser melting and study the enhanced mechanical performance when subjected to in-plane compression loading.Design/methodology/approachA novel composite structure was designed and fabricated on the basis of an arrowhead auxetic honeycomb and filled with polyurethane foam. The deformation mechanism and mechanical responses of the structure with different structural parameters were investigated experimentally and numerically. With the verified simulation models, the effects of parameters on compression strength and energy absorption characteristics were further discussed through parametric analysis.FindingsA good agreement was achieved between the experimental and simulation results, showing an evidently enhanced compression strength and energy absorption capacity. The interaction between the auxetic honeycomb and foam reveals to exploit a reinforcement effect on the compression performance. The parametric analysis indicates that the composite with smaller included angel and higher foam density exhibits higher plateau stress and better specific energy absorption, while increasing strut thickness is undesirable for high energy absorption efficiency.Originality/valueThe results of this study served to demonstrate an enhanced mechanical performance for the foam filled auxetic honeycomb, which is expected to be exploited with applications in aerospace, automobile, civil engineering and protective devices. The findings of this study can provide numerical and experimental references for the design of structural parameters.

Development and verification of a variable friction self-centering damper

The structure of a variable friction self-centering damper (VFSCD) and the main key parameters for controlling its hysteretic performance are introduced. The performance evaluation index and calculation method of each index of the VFSCD are defined. The theoretical equation and simulation model of the VFSCD are established and compared with the test results. Based on the verified simulation model, the local behavior and stress mechanism of the key components of the VFSCD are further analyzed. The results show that the VFSCD hysteresis curves are full and have good energy dissipation capacity, and there is no residual deformation or damage to each component after unloading. With the increase in the number of wedge groups, the yield load, loading stiffness and bearing capacity of the VFSCD increase significantly, and the unloading stiffness and restoring force decrease obviously. Importantly, the test curve, the theoretical curve, and the finite element hysteresis curve are in good agreement. Although there are some errors in the test results, the theoretical curves are basically consistent with the simulation curves. The simulation model established in this research can effectively reflect the local behavior and stress mechanism of VFSCD.

A shared PV system for transportation and residential loads to reduce curtailment and the need for storage systems

This paper proposes a shared multi-stakeholder PV system for traction substations and nearby residential loads to reduce the need for storage, AC grid exchange, and curtailment. The residential stakeholders offer both the base electrical load and the solar panels installation space needed by the traction stakeholder, who brings the peak load and investments to the former.Two case studies were conducted for one year in the city of Arnhem, The cy=Netherlands, using comprehensive and verified simulation models: A high-traffic and a low-traffic substation. The results showed a positive, synergetic benefit in reducing the PV system’s excess energy and size requirement for any type of traction substations connected to any number of households.In one detailed example, the multi-stakeholder system suggested in this paper is shown to reduce curtailment by up to 80% in moments of zero-traction load. Generally, the direct load coverage of a PV system is increased by as much as 7 absolute percentage points to the single-stakeholder system when looking at energy-neutral system sizes. This multi-stakeholders system offers then an increase in the techno-economic feasibility of PV system integration in urban loads.

Gas bubble coalescence in laser directed energy deposition of irregular HDH titanium alloy powder feedstock

In this study, the synchrotron X-ray imaging technique was used to investigate the coalescence of gas bubbles during laser directed energy deposition (L-DED) of irregular hydride-dehydride (HDH) titanium alloy particles onto a titanium alloy substrate. The objective is to better understand the coalescing mechanism of gas bubbles during the L-DED process of unique feedstock materials. The coalescence frequency of gas bubbles is the percentage of bubbles merging and is dependent on collision frequency and coalescence efficiency. Forces in the melt pool flow such as Marangoni forces, buoyancy force, vaporization pressure, and acoustic waves, along with the number of generated bubbles, were the major factors for increasing the collision frequency between bubbles. In addition, the random forest model determined that the diameter of the smaller bubble during collision was the most significant factor impacting the efficiency of coalescence, which was equal to 48% when the smaller diameter was larger than a threshold of 76 μm and 3.5% and when the diameter was smaller than 76 μm. The results also showed that 6.5% of the formed bubbles in the melt pool led to coalescence. Overall, this work can help mitigate pores, verify simulation models, and promote irregular or recycled powder feedstock as effective replacement to atomized feedstock.

Simulation modeling and design of circular concrete-filled double-skin tubular slender beam-columns with outer stainless-steel tube

The stainless-steel tube has been used to construct Concrete-Filled Steel Tubular (CFST) columns because it has a high resistance to fire and corrosion, good durability, and aesthetic appearance compared to the carbon steel tube. However, there is very little published research on eccentrically loaded circular Concrete-Filled Double-skin Steel Tubular (CFDST) slender beam-columns composed of an outer stainless-steel tube and an inner carbon-steel tube. In line with this, this paper presents a fiber-based simulation model for predicting the structural performance of CFDST slender columns with external circular stainless-steel tube under eccentric compression. The simulation modeling of load-deflection curves and load-moment interaction diagrams for slender CFDST beam-columns is developed and verified by the experimental results. The verified simulation model is then used to study the effects of geometric and material properties on structural performance. The range analysis is applied to the orthogonal design to identify the relative significance of the factors that influence the structural response. The orthogonal design covers CFDST beam-columns with a hollow ratio ranging from 0.1 to 0.8. The results indicate that the column slenderness ratio is the most significant factor, followed by the loading eccentricity ratio, the outer tube thickness, stainless steel proof stress, concrete strength, and carbon steel yield strength. The accuracy of the design method specified in Australian standard AS/NZS 2327, and the proposed design methods are evaluated. The proposed equation provides accurate strength predictions of CFDST slender columns where the external skin is made of stainless steel.

Measuring and Architecting System Resilience Through Trade Study Analysis

Resilience is a dimension of trade study analysis that must be accounted for in early conceptual system design because it can influence cost, reliability, performance, and overall lifecycle cost. Traditional trade studies, which focus on risk, safety, and costs aspects analysis are no longer sufficient because they only account for predicted and known disruptions. This article proposes a practical and implementable methodology for measuring, predicting, and architecting system resilience during conceptual design that considers both known and unknown disruptions. This article extends the current literature by motivating the resilience curve using a Markov process, verifying resilience with empirical data, and incorporating the interaction between subsystems using common cause failure with the binomial failure rate. A verified simulation model is used as a predictive analysis tool and applied to an unmanned surface vehicle case study.

Novel Vision Monitoring Method Based on Multi Light Points for Space-Time Analysis of Overhead Contact Line Displacements.

The article presents an innovative vision monitoring method of overhead contact line (OCL) displacement, which utilizes a set of LED light points installed along it. A light point is an, LED fed from a battery. Displacements of the LED points, recorded by a camera, are interpreted as a change of OCL shape in time and space. The vision system comprises a camera, properly situated with respect to the OCL, which is capable of capturing a dozen light points in its field of view. The monitoring system can be scaled by increasing the number of LED points and video cameras; thus, this method can be used for monitoring the motion of other large-size objects (e.g., several hundred meters). The applied method has made it possible to obtain the following novel results: vibration damping in a contact wire is nonlinear by nature and its intensity depends on the wire vibration amplitude; the natural frequency of contact wire vibration varies, and it is a function of vibration amplitude; the natural frequency of contact wire vibration also depends on the wire temperature. The proposed method can be used to monitor the uplift of contact and messenger wires in laboratory conditions, or for experimental OCL testing, as well as for verifying simulation models of OCL.

Experimental and numerical investigation on the temperature distribution of composite box‐girders with corrugated steel webs

Although composite box-girders with corrugated steel webs have been widely applied in practical bridge constructions, the nonuniform temperature field in the composite box-girders without sufficient study may lead to negative effects on the durability of bridge structures. Thus, this paper focuses on the temperature distribution characteristics of the composite box-girder with corrugated steel webs. The temperature data of a corrugated steel web box-girder specimen has been measured. An apparent nonuniform temperature distribution of the experimented specimen under solar radiation can be observed through the measured data. Then, the numerical simulation model of the corrugated steel web composite box-girder specimen has been established and validated by the measured temperature data. Based on the verified simulation model, the temperature distribution of an actual composite box-girder has been analyzed numerically. The results show that the difference between the vertical temperature gradients along the north and south sides of the girder can reach up to 11.9°C, and the maximum vertical temperature gradient can be more than 24.0°C in summer days. Moreover, parametric studies have been carried out to reveal the impacts of material parameters on the composite box-girder's temperature distribution and the thermal loading index. Both the concrete and steel surface absorptivity show significant influences on the temperature distribution and the thermal loading index through the parametric study. It hopes that the current investigation can provide some contributions for further applications of the composite box-girder with corrugated steel web, and other researches regarding temperature field of the structures.

Theoretical and experimental study of motion suppression and friction reduction of rotor systems with active hybrid fluid-film bearings

Active bearings (including fluid film bearing) are efficient in reducing vibration and improving dynamic performances of rotary machinery. The control systems have significant influence in the working processes of rotor-bearing systems, including hydrodynamic and tribological performance. The aim of the study is to investigate the feasibility of the joint controlling of the rotor vibration and simultaneously minimizing friction losses in active hybrid bearing (AHB) – rotor systems. The theoretical and experimental results show the rotor vibrations are reduced at the energy-efficient operating modes under complex loads. The theoretical study is performed by the verified simulation models of rigid rotors with thrust and journal AHB. The artificial neural networks are proposed to calculate the bearing forces to provide a balance of accuracy and computational costs. The controller for the thrust AHB is based on the PI law, while the journal AHB controller implements an adaptive nonlinear proportional law with integrating properties. Both controllers perform well in reducing the vibration magnitudes for the systems under the periodic and constant load forces. Such rotor motion control is also able to reduce power losses caused by the viscous friction in AHB. The theoretical study shows the relations between the position of the rotor with AHBs and the magnitude of the viscou forces of the lubricant film. The minimum friction areas could be used to choose the setpoints for AHBs’ controllers for joint rotor motion and friction control.

Supercapacitor-Based Energy Storage in Elevators to Improve Energy Efficiency of Buildings

Improving energy efficiency is the most important goal for buildings today. One of the ways to increase energy efficiency is to use the regenerative potential of elevators. Due to the special requirements of elevator drives, energy storage systems based on supercapacitors are the most suitable for storing regenerative energy. This paper proposes an energy storage system consisting of a supercapacitor bank and a bidirectional six-phase interleaved DC/DC converter. The energy savings achieved by the proposed system were investigated through simulation tests. The proposed system was modeled considering all physical constraints. A simulation model of the existing faculty elevator system was created in PLECS and verified with field measurements. Reliable results were ensured by using the verified simulation model and considering all physical constraints. The operation of the proposed energy storage system was tested under various conditions. In addition, the simulation model of the elevator system with the proposed energy storage system was tested using the elevator traffic data obtained from the measurements. The simulation results show the effectiveness of the proposed energy storage system and that significant energy savings can be achieved.

Placement and sizing of solar PV and Wind systems in trolleybus grids

Reducing the environmental impact of transportation requires the successful integration of renewable energy sources into the electrical transportation networks. However, the mismatch between renewable generation and the intermittent bus schedules causes temporary absence of loads and creates considerable excess energy, potentially rendering the systems economically infeasible. So far, studies on integration of renewables in transport grids were limited to decentralized solar PV systems (placed at the substation level), using statistical or simplified models, and concerned mainly with increasing the trolleygrid capacity. In this paper, both PV and Wind systems are considered and studied as to maximize their direct utilization by using verified simulation models for six different sizing and placement scenarios. The Dutch trolleygrid of Arnhem is used as a case study. Scenarios I to V looked at a decentralized renewable sources placement and ultimately concluded that PV systems at low-traffic substations are best sized for complete energy-neutrality, with daily storage systems. On the other hand, those at high-traffic substations should be without storage and sized below their energy-neutrality point — ideally, using the Marginal Utilization approach (scenario III). Finally, the Centralized (Aggregated) Energy-Neutral Wind and PV Approach of scenario VI offers the best outcome, with a hybrid solution of 53% PV and 47% Wind. This scenario offers a 54.1% direct bus load coverage. In comparison, scenario I, which had attempted a grid energy-neutrality in a decentralized manner, had only achieved 32.4% direct load coverage. The outcome of scenario VI can even be pushed to values above 80% by installing storage systems.

Thermal modeling and designing of microchannel condenser for refrigeration applications operating with isobutane (R600a)

• A simulation thermal model was proposed for the microchannel condensers. • Isobutane (R600a) was considered as the working fluid. • A new heat transfer coefficient correlation was employed in the simulation model. • The thermal simulation model validated against experimental data. • Microchannel condenser designs were discussed with the verified simulation model. The present study has focused on thermally performance modeling and designing of microchannel condenser (MC-C). It is aimed at contributing to new MC-C designs for refrigeration applications working with isobutane (refrigerant R600a). To this purpose, a novel thermal simulation model has been developed as a design tool to predict the heat capacity, outlet temperature and pressure of the MC-C. The existing correlations in the literature about heat transfer and pressure drop of refrigerant flow inside the microchannel have been evaluated to improve the accuracy of the thermal simulation model. A new heat transfer coefficient correlation has been employed in the model with the purpose of further improvement of the accuracy. An experimental study has been performed to validate thermal simulation model results. It is found that the model predicted isobutane temperature at the outlet of the MC-C and heat transfer capacity with deviations in the range of ±2% and ±1%, respectively. The model has an average of 6.8% MAE for the prediction of the isobutane pressure at the outlet of the MC-C The theoretical air-cooled MC-C designs have been performed to investigate the effect of hydraulic diameter microchannels and pass arrangement on heat transfer performance. The theoretical air-cooled MC-C designs have been modeled and discussed with the experimentally validated thermal simulation model for refrigeration applications. According to the model results, although the heat transfer coefficient inside microchannels increases as the hydraulic diameter decreases, heat transfer capacity decreases. When the pass arrangement is modeled, it is concluded that the designs with high tube numbers in the passes at which vapor quality is still high exhibit higher heat transfer capacity in the MC-C.

Numerical Optimization for the Impact Performance of a Rubber Ring Buffer of a Train Coupler

Shock and vibration caused by mechanical motion bring huge potential threats to the service life and assembly reliability of mechanical systems. Rubber materials have been widely used in aircraft, trains, and other engineering fields, due to their excellent properties in shock and vibration absorption. This paper aimed to study the rubber ring buffer applied to a certain type of Chinese locomotive. Firstly, the finite element model was established and verified through experimental data. Based on the verified simulation model, the influence of the constitutive parameters (C01/C10 ratio height H and contour radius R) of the rubber ring on its energy absorption and peak crushing force under impact loading was studied in a numerical environment. Finally, the design of the experiment was carried out by the optimized Latin hypercube method, and the response surface model was established, which intuitively demonstrated the influence of the relevant parameters of the rubber ring on the change trend of the energy absorption and peak force. Based on the proxy model, the parameters that improve the crashworthiness of the rubber ring buffer were found quickly by the NSGA-II optimization algorithm, and the problems of a long calculation time and low optimization efficiency when using the conventional finite element method were avoided. The optimization results stated that when H = 107.57 mm and R = 85.70 mm, C01/C10 = 0.0571 of the energy absorption of the optimized buffer was increased by 59.03%, and the peak force was decreased by 14.37%, compared with the original structure. The optimized rubber ring buffer is expected to reduce the peak crushing force, enhance the energy absorption capacity, and mitigate the damage to the train system caused by shock and vibration.

Standoff tracking control of underwater glider to moving target

The standoff tracking control of underwater glider to moving targets has non-negligible potentials in oceanic observations. To perform such operations, this study presents an integrated standoff tracking method that focuses on dealing with the coupled motions and under-actuated characteristics of the gliders as well as offsetting the dilemma caused by lacking of navigation system. The proposed approach contains guidance algorithm, basic controller, and reinforcement learning optimizer to improve the tracking accuracy. The verified simulation model for the OUC-III glider is utilized to develop the algorithm and evaluate the effectiveness of tracking. The adaptive navigation law called Lyapunov guidance vector field method generates the desired heading in this framework. The guidance only requires positioning information that is accessible through dead-reckoning. For the deficiency that the glider’s state controlled by the proportional integral differential controller can not immediately reach the required state, the reinforcement learning optimizer is introduced. The gliding status constitutes optimizer input while the compensating rotation signals are outputted to actuate the movable mass. The reward function of the optimizer is designed for maintaining the glider position error within 1 m with respect to the standoff circle. On this basis, the objective is set to maximize the rewards and consequently to guarantee the best accuracy. Three reinforcement learning algorithms are adopted and tested in our proposed framework. In the training phase, the training speeds of composite methods and pure reinforcement learning algorithms are compared. To test the stability, we design different types of moving targets, standoff radium and disturbance in the validation simulation, which have not appeared in the training. This study can provide patterns and solutions for the standoff tracking applications of underwater gliders. Also, it enlarges the glider’s scope of deployment based on the existing hardware.

Performance investigation on a coaxial-nozzle ejector for PEMFC hydrogen recirculation system

The ejector driven by the high-pressure gas potential energy from the hydrogen storage tank can reliably recirculate the unconsumed hydrogen in the proton exchange membrane fuel cell (PEMFC) system. However, the fixed-geometry ejector cannot maintain consistently high performance among the whole power output range in the PEMFC system due to its shortage of limited operating range. In this paper, a coaxial two-nozzle ejector, satisfying the requirements of the PEMFC system under different power outputs, is developed for hydrogen recirculation. The proposed ejector is investigated numerically based on an experimentally verified simulation model to reveal the flow distribution and predict its performance. The simulation results show that the proposed ejector can work in a wide power range of 17.90–84.00 kW within a suitable supply hydrogen pressure range of 4–7 bar. More importantly, the ejector can not only maintain a recirculation ratio above 0.9 in the wide output power range but a high recirculation ratio greater than 2.0 in the low power output. The proposed ejector broadens the working range of a single ejector used in the PEMFC system, which significantly promotes the development of fuel cell being widely adopted in automobiles.

Evaluation of in situ Thermomechanical Stress–Strain in Power Modules Using Laser Displacement Sensors

Digital design has been successfully employed in development of new compact wide bandgap power modules, achieving unprecedented switching speeds while maintaining low thermal resistance. Owing to the achieved performance, the next step in the field is ensuring that proposed designs are mechanically robust and reliable. The new power module structures lack the long history of experimental experience as is the case with conventional silicon power modules. To limit the number of physical prototypes that needs to be built and to speed up development time, having a verified simulation model of the thermomechanical behavior is of great value to designers. In this article, a finite element simulation of the thermomechanical induced stress and strain is presented of an integrated GaN full-bridge switching cell. The simulated strain of the power module is verified by an experimental test. During the test, one of the semiconductor devices of the module is subjected to a power loss. A laser displacement sensor is used to measure the in situ deflection of the ceramic substrate caused by the temperature increase. The experimental results confirm the ability of the simulation model to accurately predict the deflection within an error of only 7.3%.

Design and Numerical Simulation of a Ball Cutting Type Energy Absorber Device

This paper is verified by numerical simulation and experiment. Based on the principle of energy absorption in metal cutting process, this paper presents a new type of energy absorption structure, which can improve the collision performance of urban rail vehicles. The structure is composed of solid energy absorption tube, hard ball, anti-crawling board and mounting board. Based on the nonlinear dynamic simulation theory and the explicit algorithm of finite element software ABAQUS, the finite element model of the structure of the cutting type energy absorber was established, and the energy absorption process was simulated. Based on the verified simulation model, the influences of the design parameters such as the cutting depth and the number of balls on the energy absorption process are analyzed. It is found that the design parameters affect the cutting force and energy absorption, and the structure has a good energy absorption effect during the collision.

DEM simulation model to optimise shutter hole position of a centrifugal fertiliser distributor for precise application

The purpose of this study is to analyse the distribution pattern of centrifugal fertiliser distributor with two shutter holes and obtain the optimal position of the shutter holes for improved distribution uniformity. A simulation model of the centrifugal fertiliser distributor was generated by discrete element method (DEM). The behaviour of fertiliser particles on the spinner was analysed by the simulation and the simulation model was verified through a stationary distribution pattern test. The distributor design was modified using the verified simulation model to improve the distribution uniformity. The simulation results of the existing fertiliser distributor showed the amount of fertiliser applied on the right side of the machine was 1.59 times higher than the amount applied on the left (R/L ratio) and the coefficient of variation (CV) was 34.88% at stationary condition indicated non-uniform fertiliser distribution. As the position of the shutter holes was moved in the direction of rotation of the spinner (i.e. clockwise) the amount of fertiliser distributed towards the right side decreased. The shutter hole position accordingly adjusted to improve fertiliser distribution uniformity. When the optimal position of the shutter hole was used under stationary condition, the R/L ratio was close to 1.0, whilst the CV value decreased by approximately 50%. The optimal solution was also suitable during continuous application when applying at a width of 8 m since CV values were