Fast Calculation Model Research Articles

A fast calculation method for internal blast shock wave in confined structures

Internal explosions are more complicated and destructive than external explosions. It is hard to give accurate predictions of the internal blast load by existing simplified models. In the present work, a fast calculation method for the shock wave of internal blast within a confined space was developed. Firstly, the theoretical bases of this method, the reflection addition rules and the image burst theory, were introduced and validated. Then, the concept of the influence region of image burst for internal blast calculation was proposed, and the detailed calculation method for internal blast load was presented. In addition, the internal blast loads inside a typical cubic structure and a tunnel model were calculated using this developed method, respectively. Moreover, comparison studies between the calculated results and experimental data as well as numerical simulation results were conducted. It was found that the results of the fast calculation model are in good agreement with those of the blast experiment and fine numerical simulation, but the fast calculation takes only less than 2 min. Finally, the advantages and defects of the present method were discussed and further study advices were suggested to improve the accuracy.

A multivariable control strategy based on fuzzy logic interference rule for a solar-driven, direct air-cooled H[formula omitted]O-LiBr absorption chiller

The operation of a solar-driven H2O-LiBr Absorption Chiller (AbC) is subjected to various limitations regarding its ability to satisfy efficiently the required cooling demand while avoiding certain internal conditions, such as H2O-LiBr solution crystallization and water freezing. These circumstances would lead to problematic situations and jeopardize the continuous operation of the system. Thus, the development of accurate control strategies is an issue of interest. A new operational control strategy approach is introduced and tested through simulation studies, by employing a transient model of the entire solar cooling application. A prototype under development is used for the parametrization of the direct air-cooled AbC model used in the simulations. The developed control strategy aims to minimize the electrical consumption of the auxiliary components of the AbC (i.e., fan, pumps) during the partial load operation period, by using a fuzzy logic interference rule for determining the cooling capacity demand and then applying an optimization algorithm for determining the velocity of the auxiliary components. Within the proposed control strategy, a fast-calculation model is embedded, which predicts the chiller’s capacity under variable external conditions and partial load operation. The electrical COP is increased up to 2.2 times with respect to a baseline case, based on a basic two-step control strategy, while allowing the chiller to operate smoother, minimizing the crystallization and freezing risk.

A fast computational method for internal temperature field in Oil-Immersed power transformers

In order to improve the computational efficiency of the steady-state temperature rise of oil-immersed power transformer windings, this paper proposes a temperature field reduced order model(ROM) based on proper orthogonal decomposition (POD) and response surface method(RSM). The method takes the operating conditions of the transformer as input and uses the POD method as a carrier, and establishes a fast calculation model of the steady-state temperature field through RSM, thus achieving fast calculation from transformer operating data to the entire temperature field. The paper first analyzes the reduction characteristics of the POD method, and then introduces the RSM to establish the correlation between the POD modal coefficients and the transformer conditions. Compared with traditional surrogate models, this method can obtain high-precision surrogate relationships with a small number of sample points, and the time cost of establishing is relatively low. The method aims to quickly obtain the POD modal coefficients through the winding conditions, thereby skipping the complex nonlinear calculation and efficiently reconstructing the winding temperature field with the reduced modal. The related examples show that the method has good computational accuracy and efficiency. In a 2D forced oil circulation cooling model, out of 100 test conditions, the error is not more than 2.0 K compared with the full-order calculation, and the total calculation time is only 3.13 s. Finally, based on a 35 kV natural oil circulation cooling transformer, a temperature rise test platform is constructed to verify the effectiveness of the method. The experimental results show that the calculated error of the ROM is not more than 5 K compared with the experimental results, and the single-step calculation time is only 0.73 s, which has greatly improved the computational efficiency compared with full-order calculation of the same scale. The proposed method in this study achieves a second-level calculation efficiency for the transformer winding temperature, providing a feasible solution for digital online monitoring of transformer temperatures.

A fast calculation model for interior ballistics simulation of a recoilless launch system with high chamber pressure

Recoilless launch system is economical and convenient. This paper provided a recoilless launch system with high chamber pressure based on the theory of recoilless gun. A program for interior ballistics simulation of the launch system based on the mixed propellent was designed. The curves of chamber pressure and projectile velocity on time and projectile travels were provided by the program. And the phenomena of different combustion stages presented by the curve are discussed. The simulation results reached the set indicators, and it was consistent with the actual interior ballistics. The designed model has certain reference value for real-time simulation and fast computation.

A modeling method for the DC side simplified impedance of line commutated converter based on the simplified switching function

With a large amount of new energy access and the wide application of high voltage direct current (HVDC) transmission technology based on line commutated converter (LCC), it is of great significance to study the impedance frequency characteristics of the converter to analyze the stability of the LCC-HVDC system. Due to the complexity and inefficiency of the existing modeling techniques, in this paper, a simplified impedance modeling method for the DC side of LCC based on the simplified switching function is proposed. Firstly, the commutation process of LCC is deduced according to the converter valve opening sequence and circuit principle, and the simplified switching function of LCC is proposed. Next, based on the dynamic phasor method, through the analysis and calculation of harmonic transmission between the AC and DC sides of LCC, the simplified impedance of the DC side of LCC is obtained. Then, a simulation model is established in PSCAD, and the impedance scanning results of the simulation model show that the error is small between the method proposed in this paper and the method without simplification, which verifies the validity of the proposed model. The proposed method can reduce modeling complexity and provide a fast calculation model of the DC side impedance of LCC for analyzing the stability of large complex transmission systems.

A Prediction Model of Effective Thermal Conductivity for Metal Powder Bed in Additive Manufacturing

In current research, many researchers propose analytical expressions for calculating the packing structure of spherical particles such as DN Model, Compact Model and NLS criterion et al. However, there is still a question that has not been well explained yet. That is: What is the core factors affecting the thermal conductivity of particles? In this paper, based on the coupled discrete element-finite difference (DE-FD) method and spherical aluminum powder, the relationship between the parameters and the thermal conductivity of the powder (ETCp) is studied. It is found that the key factor that can described the change trend of ETCp more accurately is not the materials of the powder but the average contact area between particles (aave) which also have a close nonlinear relationship with the average particle size d50. Based on this results, the expression for calculating the ETCp of the sphere metal powder is successfully reduced to only one main parameter d50 and an efficient calculation model is proposed which can applicate both in room and high temperature and the corresponding error is less than 20.9% in room temperature. Therefore, in this study, based on the core factors analyzation, a fast calculation model of ETCp is proposed, which has a certain guiding significance in the field of thermal field simulation.

Fast and efficient simulation of the dynamical response of coaxial magnetic gears through direct analytical torque modelling

Coaxial magnetic gears have been of great interest amongst researchers and the industry since their introduction two decades ago. Although magnetic gears suffer from slippage at high torques and in general have lower torque density compared to their mechanical counterparts, they surpass their performance in terms of attained speeds, versatility, vibration attenuation, backdrivability and efficiency. Increasing the torque density is a major issue in magnetic drivetrains that has been extensively discussed in the literature. However, the calculation of the torque is typically performed through FEA and/or numerical methods, thus increasing the computational cost especially in dynamical simulations where the applied torques at the two rotors have to be calculated at each time step. The objective of this work is to introduce an analytical 2D model for fast and efficient calculation of the applied torques for every rotation angle, geometry configuration and constitutive parameters of the magnets using the Maxwell Stress Tensor. The results obtained from the model were compared against those obtained from FEA. The calculated torques at the inner and outer rotor were in perfect agreement with FEA, however the analytical model was more than two orders of magnitude faster. In addition, an analytical calculation of the torque ripple in coaxial magnetic gear drives is made possible using the proposed model. An investigation of the influence of the modulator ring on stall torque was performed illustrating that there is an optimum length value for the ferromagnetic segment to maximize torque density. Furthermore, the motion equations of the coaxial magnetic gear drive were formulated and a model was developed to simulate the dynamical response of the system without the requirement of torque calculation at each time step that significantly decreases computational cost. The slip effect was investigated and the resulting transmission error was determined.

A global model for fast calculation of the thermal response factor of large-scale boreholes heat exchangers combining the FLS model, the 2D heat equation and a three-points method

In order to progress towards more energy efficient buildings, vertical ground coupled heat pumps are a promising solution. Optimisation of both the design and operation of boreholes heat exchangers is a key factor to reduce energy consumption of such systems. This requires a fast evaluation of the thermal response factor of the ground heat exchanger, particularly if it contains numerous boreholes and operates for multiple years. To overcome this challenge, this article reports a new global model combining the finite line source (FLS) model, the two-dimensional (2D) heat conduction equation, and a newly developed three-points method. The borehole field is sorted in increasing distance categories, each being simulated with varying timesteps. The 2D heat conduction equation is used to determine: 1) when the detailed calculation needs to be performed; and 2) the growth of the timestep. A three-points method avoiding double integration of the temperature profiles is proposed to evaluate the borehole wall temperature. The global model calculation time and accuracy were evaluated. The thermal response factor calculation for a square field of 26×26 boreholes for one simulated year took 4s, showing a calculation time reduction factor of around 1,000,000, and relative errors smaller than 2 % compared to the original FLS model with superposition principle. For 20 simulated years, the proposed model took only 1min. It is appropriate for various boreholes configurations. Its features such as accuracy, speed and load-independency are essential for its integration into building energy simulation tools.

TransDose: a transformer-based UNet model for fast and accurate dose calculation for MR-LINACs

Objective. To present a transformer-based UNet model (TransDose) for fast and accurate dose calculation for magnetic resonance-linear accelerators (MR-LINACs). Approach. A 2D fluence map from each beam was first projected into a 3D fluence volume and then fed into the TransDose model together with patient density volume and output predicted beam dose. The proposed TransDose model combined a 3D residual UNet with a transformer encoder, where convolutional layers extracted the volumetric spatial features, and the transformer encoder processed the long-range dependencies in a global space. Ninety-eight cases with four tumor sites (brain, nasopharynx, lung, and rectum) treated with fixed-beam intensity-modulated radiotherapy were included in the dataset; 78 cases were used for model training and validation; and 20 cases were used for testing. The ground-truth beam doses were calculated with Monte Carlo (MC) simulations within 1% statistical uncertainty and magnetic field strength B = 1.5 T in the superior and inferior direction. Beam angles from the training and validation datasets were rotated 2–5 times, and doses were recalculated to augment the datasets. Results. The dose-volume histograms and indices between the predicted and MC doses showed good consistency. The average 3D γ-passing rates (3%/2 mm, for dose regions above 10% of maximum dose) were 99.13 ± 0.89% (brain), 98.31 ± 1.92% (nasopharynx), 98.74 ± 0.70% (lung), and 99.28 ± 0.25% (rectum). The average dose calculation time, which included the fluence projection and model prediction, was less than 310 ms for each beam. Significance. We successfully developed a transformer-based UNet dose calculation model—TransDose in magnetic fields. Its accuracy and efficiency indicated its potential for use in online adaptive plan optimization for MR-LINACs.

A Novel Moving Load Integration Method for Real-Time Hybrid Shaking Table Test of High-Speed Maglev Vehicle–Bridge Interaction System

Real-time hybrid shaking table test for high-speed maglev vehicle–bridge interaction (VBI) system is an important method to study dynamic response of the system. Numerical experiments are usually conducted in advance to guarantee the test performed smoothly. This paper presents a novel moving load integration method combined with a truncated bridge model for fast calculation of bridge responses, and presents a framework for performing numerical experiment of a real-time hybrid test of VBI system. A realistic numerical experiment is conducted on a real-time simulator, i.e. xPC Target, integrating three commercial software, i.e. SIMPACK, ANSYS, and MATLAB-Simulink[Formula: see text], to model a real TR08 single-carriage maglev train, a 5-spans bridge and 28 shaking tables, respectively. The driving speed is 400–600[Formula: see text]km/h and the time step size in the test is 1/256[Formula: see text]s. The accuracy of moving load integration method with truncated bridge model is verified, the effects of speed on the dynamic responses of VBI systems are studied, the time delay of shaking tables and compensation algorithm is investigated, and the effects of local nonlinearity of the bridge on system responses are studied. This paper provides a practical method and valuable reference for the real-time hybrid shaking table test of vehicle–bridge coupled systems.

A New Urban Waterlogging Simulation Method Based on Multi-Factor Correlation

Waterlogging simulation is a key technology for solving urban waterlogging problems. The current waterlogging modeling process is relatively complex and requires high basic data, which is not conducive to rapid modeling and popularization. In this study, we evaluated the correlation between rainfall and waterlogging water using the following factors: terrain, evaporation, infiltration, pipe drainage capacity, and river flood water level. By quantifying the influence value of each factor on rainfall, we established a simplified model for fast calculation of waterlogging depth through input rainfall. Waterlogging data was collected from Guangzhou, China to set up the multi-factor correlation model, and verify the simulation results of the model. After the original rainfall is added/deducted, the added/loss value, the relationship between net rainfall, and maximum water depth is better than that between original rainfall and maximum water depth. Establishing a stable multi-factor correlation model for a waterlogging point requires at least three historical waterlogging event data for parameter calibration by sensitivity analysis. Comparing the simulation of four waterlogging points, the multi-factor correlation model (error = −13%) presented the least error in simulating the maximum water volume, followed by the Mike Urban model (error = −19%), and finally the SWMM model (error = 20%). Furthermore, the multi-factor correlation model and SWMM model required the least calculation time (less than 1 s), followed by the Mike Urban model (About half a minute). By analyzing the waterlogging data of Guangzhou, 42 waterlogging points with modeling conditions were screened out to further validate the multi-factor correlation model. Each waterlogging point was modeled based on the historical field, and the last rainstorm was used for model verification. The mean error of the comparison between the simulated maximum waterlogging and the measured maximum waterlogging was 3%, and the R2 value was 0.718. In summary, the multi-factor correlation model requires fewer basic data, has a simple modeling process and wide applicability, and makes it easy to realize the intelligent parameter adjustment, which is more suitable for the urgent requirements of current urban waterlogging prediction. The model results may prove accurate and provide scientific decision support for the prevention and control of urban waterlogging.

Rule-based generation of HVAC duct routing

Traditional manual duct design can result in fan energy waste due to ducts network imbalance and human design error. This paper aims to develop an automated duct routing method, which is able to connect air diffusers across space with the consideration of duct pressure balance, construction obstacles, air resistance reduction and minimising construction costs. Treating air diffusers as nodal connections of a graph, the method uses a rule-based traversal algorithm (RBTA) and a fast resistance calculation model (FRCM) to generate the duct network. The methodology is tested on six different building layouts for the automatic design of ducts in a room and the results meet designer's requirements. Compared with the traditional manually designed duct network, the new duct network is more balanced and costs less. The automated approach cuts design time by more than ten folds and avoid human mistake and error in the traditional design process.

Evaluation of defect depth in ferromagnetic materials via magnetic flux leakage method with a double Hall sensor

In the magnetic flux leakage (MFL) testing method, a linear mapping is used for the direct evaluation of defects by applying a single Hall sensor to measure the signal under a certain lift-off value. Inevitably, the uncertainty of the lift-off value in practical testing affects the accuracy of the estimated defect size. To overcome this uncertainty in the lift-off value, this paper proposes a double Hall sensor configuration with a fixed lift-off interval, and establishes an evaluation method for the defect depth through the MFL signals measured by this sensor. The effectiveness of the proposed evaluation method is verified by theoretical analysis, with the double Hall sensor providing two different lift-off values above the surface of the specimen that characterize the tested defect. Based on the error between the measured signal characteristics induced by the tested defect and the predicted values from a fast calculation model, a particle swarm optimization algorithm is employed to realize accurate evaluation of the defect depth. Theoretical research shows that the characteristic values measured by the double Hall sensor enable the defect depth to be accurately estimated. The use of a double Hall sensor with a fixed lift-off interval allows the proposed evaluation method to compensate for the unknown lift-off value in practical testing.

Experimental investigation on ceiling temperature characteristics induced by weak and strong fire plumes in tunnel fires equipped with two-point extraction ventilation using smoke extraction channel

In this paper, maximum excess temperature and longitudinal temperature decay induced by weak and strong fire plumes were discussed in tunnel fires with two-point extraction ventilation using the smoke extraction channel. First, a model for maximum excess temperature was developed based on theoretical analysis and experimental phenomenon. Subsequently, the characteristics of maximum excess temperature and longitudinal temperature decay were analyzed. Experimental results showed that the maximum excess temperature for the weak plume is higher than that predicted by the previous model due to the existence of the smoke extraction channel. The maximum excess temperature for the strong plume is much higher. Moreover, the function of maximum excess temperature for the weak plume was similar to the previous model, while that for the strong plume was different from the previous model when the fire was located at the tunnel center. Besides, exhaust rate and longitudinal fire location far from the vent did not have a considerable impact on the maximum excess temperature and longitudinal temperature decay in the fire section induced by weak plume or strong plume. Finally, new prediction models for maximum excess temperature induced by the weak and strong fire plume were validated according to experimental data. Moreover, a fast calculation model driven by experimental data was established to predict longitudinal temperature decay.

Reduction of cogging torque and electromagnetic vibration based on different combination of pole arc coefficient for interior permanent magnet synchronous machine

Cogging torque and electromagnetic vibration are two important factors for evaluating permanent magnet synchronous machine (PMSM) and are key issues that must be considered and resolved in the design and manufacture of high-performance PMSM for electric vehicles. A fast and accurate magnetic field calculation model for interior permanent magnet synchronous machine (IPMSM) is proposed in this article. Based on the traditional magnetic potential permeance method, the stator cogging effect and complex boundary conditions of the IPMSM can be fully considered in this model, so as to realize the rapid calculation of equivalent magnetomotive force (MMF), air gap permeance, and other key electromagnetic properties. In this article, a 6-pole 36-slot IPMSM is taken as an example to establish its equivalent solution model, thereby the cogging torque is accurately calculated. And the validity of this model is verified by a variety of different magnetic pole structures, pole slot combinations machines, and prototype experiments. In addition, the improvement measure of the machine with different combination of pole arc coefficient is also studied based on this model. Cogging torque and electromagnetic vibration can be effectively weakened. Combined with the finite element model and multi-physics coupling model, the electromagnetic characteristics and vibration performance of this machine are comprehensively compared and analyzed. The analysis results have well verified its effectiveness. It can be extended to other structures or types of PMSM and has very important practical value and research significance.

Fast calculation model for heat and mass transfer in a deep-buried underground air tunnel using Z-transfer coefficient method

Deep-buried tunnels are widely used in underground space for transportation and air ventilation. Accurately predicting the heat and mass transfer process of the ventilation in a tunnel is conducive to the design optimization of air conditioning and utilization of thermal pressure for underground buildings. The air condensation process has an important impact on the variation of air parameters in the tunnel. The Z-transfer coefficient method cannot accurately calculate the air parameters when the air condensation process occurs. To resolve this problem, in this study, the computational domain is redefined and a fast calculation model is proposed for heat and mass transfer in a deep-buried underground tunnel. The calculation results of this model are in good agreement with the field test results. Moreover, when calculating the hourly parameters of ventilation for a year, the running time of the new model is less than half of the finite difference method model. Considering the hourly parameters of ventilation for a certain number of days, the new model has a higher calculation efficiency. In addition, a case study was conducted to demonstrate the significance of considering the air condensation process in the model. If the calculation results of the model considering air humidity and condensation are taken as a reference, the absolute error of air temperature at the tunnel exit and the relative error of the thermal pressure, calculated by the model ignoring air humidity, can respectively reach 1.94 °C and 34%.

A mathematical model for sidelobe level optimization of variable inclination continuous transverse stub antenna

AbstractA mathematical model of variable inclination continuous transverse stub (VICTS) antenna for low sidelobe design is proposed in this paper. VICTS antenna is an antenna with continuous transverse stubs on the parallel-plate waveguide and additional branches attached to the transverse stubs to generate radiation. The antenna using this technique has high aperture efficiency and keeps a significant solution for high-gain antenna. However, the sidelobe level (SLL) of this antenna is relatively high and increases continuously as the pitch angle decreases. This paper presents a fast calculation model for the SLL of VICTS antennas using leaky-wave theory and antenna array theory. The full-wave simulation results and model calculation results are in good agreement, so this model can be used for SLL suppression of VICTS antennas in different frequency bands. By controlling the aperture field distribution to be tapered, the SLL is suppressed to − 23.7 dB using this mathematical model.

Research on fast real-time calculation model for transient temperature rise of power cables in ducts

A straightforward and fast transient temperature rise calculation model is necessary for electrical engineers to manage power cable load. A self-heating lumped parameter model (LPM) without the requirement of monitoring cable surface temperature is developed to evaluate the real-time transient temperature rise of the power cable in ducts. A mutual-heating lumped parameter model to describe the mutual heat interaction between any two cables is proposed in this paper as well. The transient temperature rise of any power cable in duct is the sum of the self-heating temperature rise and the mutual-heating temperature rise from all the other power cables in ducts. All parameters of these two models are obtained by transient thermal circuit analysis, CYMCAP calculation results and generic algorithm. A case study has been conducted to verify the feasibility of the proposed LPMs and the self and mutual temperature rise for each cable in ducts have been obtained. These results agree with the accurate data obtained from CYMCAP well, indicating that LPM can be used as a fast and straightforward tool to calculate the transient temperature rise of power cables in duct.

Rotor topology optimization of a synchronous reluctance motor based on deep neural network model

Synchronous Reluctance Motors (SynRMs) have been widely used in some industrial fields because of their attractive characteristics, such as high efficiency, low cost, and simple structure. In order to reduce the torque ripple of the SynRMs, a non-parametric model is usually used to optimize the rotor structure. However, the conventional method has the problems of the low-accuracy and poor generalization ability. In this paper, an optimization method of the rotor structure is proposed to reduce the torque ripple by utilizing the deep learning algorithm. Firstly, the sample data of the relationship between the rotor structural parameters and torque ripple are obtained with the finite element analysis (FEA). The fast calculation model is established by the deep neural network (DNN). Then, with the goal of not weakening the torque density and minimizing the torque ripple, the immune clone algorithm (ICA) is utilized to optimize the structural parameters of the rotor at different operating points. Finally, the correctness and validity of the method are verified by the simulation analysis. It is concluded that the accuracy of the model established by DNN is acceptable. The proposed method can significantly reduce the torque ripple and increase the torque density.

Research on the safety assessment of RC workshop buildings in earthquake site based on the fuzzy comprehensive evaluation

AbstractThe safety assessment of damaged buildings in earthquake site, which is always performed by experienced experts and is very important during the postearthquake emergency period. However, the conclusions often vary from person to person because of the limited number of experts and the differences in their knowledge, backgrounds, specific research directions, and practical field experience. Therefore, it is necessary to find a fast and accurate calculation model. A single‐story reinforced concrete column workshop is taken as an example in this paper. The earthquake damage assessment analysis and component detail earthquake damage are appraised according to the experts' previous earthquake experience and the qualitative provisions in the standard “Post‐earthquake Field Works, Part 2: Safety Assessment of Buildings” (GB18208.2‐2001). Based on these, the detail seismic damage is quantified. A mathematical model for the safety assessment of the single‐story reinforced concrete column workshop is established by quantifying the relevant qualitative provisions in the national standards and applying the two‐level fuzzy comprehensive evaluation method. The model is simple to use, which enables the general safety evaluators to share the experts' experience and minimizes the differences among the assessment results of different evaluators.