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A Novel Method for the Application of the ECMS(Equivalent Consumption Minimization Strategy)to Reduce Hydrogen Consumption in Fuel Cell Hybrid Electric Vehicles

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Fluid Dynamics & Materials Processing 2022年第4期18卷 867-882页

作者： Wen Sun Hao Liu Ming Han Ke Sun Shuzhan Bai Guoxiang Li School of Energy and Power Engineering Shandong UniversityJinan250061China

Fuel cell hybrid electric vehicles are currently being considered as ideal means to solve the energy crisis and global warming in today’s society.In this context,this paper proposes a method to solve the problem related to the dependence of the so-called optimal equivalent factor(determined in the framework of the equivalent consumption minimum strategy-ECMS)on the working conditions.The simulation results show that under typical conditions(some representative cities being considered),the proposed strategy can maintain the power balance;for different initial battery’s states of charge(SOC),after the SOC stabilizes,the fuel consumption is 5.25 L/100 km.

关键词： energy management fuel cell hybrid electric vehicle dynamic programming adaptive equivalent consumption minimum strategy

Multi-domain physics-informed neural network for solving heat conduction and conjugate natural convection with discontinuity of temperature gradient on interface

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Science China(Technological Sciences) 2022年第10期65卷 2442-2461页

作者： WANG TongSheng WANG ZhiHeng HUANG Zhu XI Guang School of Energy and Power Engineering Xi’an Jiaotong UniversityXi’an 710049China

Deep learning has been increasingly recognized as a promising tool in solving kinds of physical problems beyond powerful approximations. A multi-domain physics-informed neural network(mPINN) is proposed to solve the non-uniform heat conduction and conjugate natural convection with the discontinuity of temperature gradient on the interface. Local radial basis function method(LRBF) is applied to compute the case without the analytical solution and is regarded as the benchmark solver.Each physical domain matches a private neural network and all neural networks are connected by the shared information of temperature and heat flux on the interface. Joint training and separate training are utilized to minimize the loss function, which usually consists of the residual of boundary conditions, interface conditions and governing equations. Joint training minimizes the sum of all losses from neural networks with one shared optimizer, while separate training owns its private optimizer. Local adaptive activation function(LAAF) is used to accelerate the convergence and acquire a lower loss value when compared with its fixed counterpart. The numerical experiments on three types of residual points, uniform, Gauss-Lobatto and random, are conducted and it can be concluded that the uniform residual points can obtain the most accurate solution than the random and Gauss-Lobatto. Joint training is more accurate than the separate training when the number of residual points is relatively small,while the separate training performs better than the joint training for the large number of residual points. Numerous test cases on multi-domain heat transfer and fluid flow show the accuracy of the proposed m PINN. Local and global heat transfer rates show good agreements with the results from LRBF. Excepting the forward problems, the thermal conductivity ratio, the constant source and the characteristic parameters of natural convection are accurately learned from sparsely distributed data points.

关键词： multi-domain physics-informed neural network heat conduction conjugate natural convection interface condition

Indoor Environment Control Effect Based on Multi-Impeller Air Conditioner

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Journal of Thermal Science 2022年第6期31卷 2137-2154页

作者： WANG Jiahao LIU Xiaomin TIAN Chenye WU Liming XI Guang School of Energy and Power Engineering Xi’an Jiaotong UniversityXi'an 710049China

Air conditioner is the key air supply device to improve the indoor air heat transfer cycle and thermal environment. In this paper, according to the similarity theory, six kinds of the multi-impeller air conditioners(MIAC) with different numbers of axial-flow impeller are first proposed based on air conditioners with cross-flow fan(CFAC). The effects of different multi-impeller air supply modes on the indoor airflow field and temperature field are investigated by using the numerical simulation method. The validity of the computational model and method is verified by comparing the experimental measurements and numerical results. Compared with other air supply modes, the air supply distance is relatively far and the indoor environment is also improved obviously when the six-impeller air conditioner(SIAC) is used. The independent multiple impellers and outlets of SIAC make the mutual interference between the outlet airflow less, which effectively reduces the friction between the airflow and the degree of loss along the way and makes the cold and heat exchange of the whole indoor space more sufficient. The indoor thermal environment is also analyzed by using the PMV-PPD method and prototype experiment. Under the working condition of no wind, the indoor thermal comfort of human body with SIAC is better than that of CFAC. Especially in the horizontal plane of 0.6 m above the human foot, the indoor thermal environment improvement effect is the most obvious. Simultaneously, the temperature difference along the indoor height direction with the SIAC is only 1.7℃, which is 70% lower than that of the CFAC. The blowing angle between the left and right side of the SIAC is 106°, which is 31% higher than that of the CFAC. Therefore, the overall thermal comfort of the six-impeller mode is better, and the control effect of indoor environment is satisfactory.

关键词： air conditioner multi-impeller indoor thermal environment thermal comfort numerical simulation experimental test

A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses

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Science China(Technological Sciences) 2024年第1期67卷 295-310页

作者： YU MinJie ZHANG MingHui XU Lei CUI HaiChuan LIU ZhiChun LIU Wei School of Energy and Power Engineering Huazhong University of Science and TechnologyWuhan 430074China

Regenerators play a vital role in enhancing the overall performance of Stirling engines.Hence,this paper performed an energy and exergy analysis to elucidate the significance of regenerator characteristics concerning system performance,contributing to the optimal regenerator’s design and selection.The relationship between regenerator structure,regenerator exergy destruction,and output power,thermal efficiency,and exergy efficiency for Stirling engines was established by integrating the thermal model of Stirling engines with a mathematical model of regenerators.In contrast to cross-flow and parallel-flow regenerators,a novel concept of inclined-flow regenerators,featuring a matrix surface inclined in the direction of gas flow,was developed to achieve higher and more balanced engine output power and energy utilization efficiency.A comprehensive investigation was conducted into the effects of matrix structure types and regenerator geometries on the performance of both regenerators and engines.The results reveal that,following structural optimization,Stirling engines equipped with the inclined-flow regenerator demonstrate a substantial 16.6%,38.3%,and 37.2%increase in power output,thermal efficiency,and exergy efficiency,respectively,compared to those equipped with cross-flow regenerators.In contrast,when compared to engines fitted with parallel-flow regenerators,they experience a 13.5%reduction in power output but achieve remarkable enhancements of 45.4%and 36.7%in thermal and exergy efficiency,respectively.This study introduces new insights into selecting regenerator structures for enhancing the output performance of Stirling engines.

关键词： Stirling engine inclined-flow regenerator adiabatic model exergy analysis

Performance Study and Multi-Objective Optimization of a Two-Temperature CO_(2) Refrigeration System with Economizer Based on Energetic, Exergetic and Economic Analysis

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Journal of Thermal Science 2022年第5期31卷 1416-1433页

作者： LIU Guangdi ZHAO Hongxia WANG Zheng ABDULWAHID Alhasan Ali HAN Jitian School of Energy and Power Engineering Shandong UniversityJi’nan250061China

A two temperature CO_(2) refrigeration system with economizer is proposed and compared with the traditional dual-temperature CO_(2) refrigeration system based on energy consumption,exergy and economic analysis.Using genetic algorithm multi-objective optimization method,taking the COP,exergy loss and total economic cost as the objective functions to find the best design conditions of the two systems.The Pareto fronts are obtained at different ambient temperatures.Technique for order preference by similarity to an ideal solution decision-making method is adopted to determine the optimum state points.The simulation results show that when operating at different ambient temperatures,the introduction of economizer can improve COP,reduce exergy loss and the overall economic cost rate of the two-temperature CO_(2) refrigeration system.In addition,economic analyses take the impact of carbon dioxide emission cost and electricity price into consideration.The results indicate that with the increase of CO_(2) emission cost and electricity price,the hourly economic cost of both systems increases,but the hourly economic cost of the two-temperature CO_(2) refrigeration system with economizer system is always lower than that of conventional two-temperature CO_(2) refrigeration system.

关键词： two-temperature refrigeration CO_(2) multi-objective optimization energy exergetic economic cost

A surface parametric control and global optimization method for axial flow compressor blades

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Chinese Journal of Aeronautics 2019年第7期32卷 1618-1634页

作者： Jinxin CHENG Jiang CHEN Hang XIANG School of Energy and Power Engineering Beihang University

An aerodynamic optimization method for axial flow compressor blades available for engineering is developed in this paper. Bezier surface is adopted as parameterization method to control the suction surface of the blades, which brings the following advantages:(A) significantly reducing design variables;(B) easy to ensure the mechanical strength of rotating blades;(C) better physical understanding;(D) easy to achieve smooth surface. The Improved Artificial Bee Colony(IABC) algorithm, which significantly increases the convergence speed and global optimization ability, is adopted to find the optimal result. A new engineering optimization tool is constructed by combining the surface parametric control method, the IABC algorithm, with a verified Computational Fluid Dynamics(CFD) simulation method, and it has been successfully applied in the aerodynamic optimization for a single-row transonic rotor(Rotor 37) and a single-stage transonic axialflow compressor(Stage 35). With the constraint that the relative change in the flow rate is less than0.5% and the total pressure ratio does not decrease, within the acceptable time in engineering, the adiabatic efficiency of Rotor 37 at design point increases by 1.02%, while its surge margin 0.84%,and the adiabatic efficiency of Stage 35 0.54%, while its surge margin 1.11% after optimization, to verify the effectiveness and potential in engineering of this new tool for optimization of axial compressor blade.

关键词： Aerodynamic optimization Bezier surface Compressor Global optimization Surface parametric control

CFD Analysis of an 800 kV HVDC Transformer Using Rapeseed Oil as the Cooling Fluid

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CSEE Journal of power and energy Systems 2022年第5期8卷 1508-1518页

作者： Edgardy M.Gutierrez Diaz Gaosheng Wei Liu Cui Key Laboratory of power Station energy Transfer Conversion and System(Ministry of Education) School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China Department of power engineering School of Electrical EngineeringBicentenary University of AraguaTurmero 2115Venezuela

This study aims to analyze rapeseed oil’s effectiveness as a coolant of a high-voltage direct current(HVDC)converter transformer while comparing it with mineral oil.We employed a numerical model,assisted by Computational Fluid Dynamics(CFD)tools,to simulate the convective heat transfer inside a HVDC converter transformer,which is an oil-directed air forced(ODAF)type.The model seeks to obtain the temperature and velocity fields at the critical points of the fluid domain.The simulation domain reproduces a 2D cross-sectional model in the center of the structure.The results show that rapeseed oil requires more time to gain heat from the core and windings due to its lower thermal conductivity.However,the average temperature of rapeseed and mineral oils will not significantly differ once the channel temperature reaches a stable value.It indicates that the rapeseed oil can effectively replace mineral oil under the same heating conditions.Also,a slower flow of the rapeseed oil allows the fluid to smoothly enter the cooling channel.Therefore,the rapeseed oil cools these channels by pushing the fluid in them and absorbs heat from the sources earlier than mineral oil.The improvement in cooling indicates that rapeseed oil is better than mineral oil as a coolant and electrical insulating fluid for power transformers.

关键词： CFD analysis cooling fluid HVDC transformer rapeseed oil

Introduction of fretting-contact-induced crack closure: Numerical simulation of crack initiation and growth path in disk/blade attachment

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Chinese Journal of Aeronautics 2019年第8期32卷 1923-1932页

作者： Chen HU Dasheng WEI Yanrong WANG Xianghua JIANG School of Energy and Power Engineering Beihang University

Fretting fatigue crack initiation and growth in titanium alloy dovetail assembly was investigated by the Finite Element Method(FEM). Firstly, contact stress was calculated precisely with an elastic–plastic material model. Secondly, the location and angle of crack initiation were determined by the parameter of the maximum shear stress range on the critical plane, and the angle of crack growth was predicted by the Maximum Tangential Stress(MTS) criterion, which showed agreement with experimental observation. Finally, the fretting-contact-induced crack closure behavior was simulated by the node release technique in software ABAQUS with both elastic and elastic–plastic material models. The simulation shows that the variation of the contact status between fretting surfaces will result in crack closure even for the elastic material model. The fretting crack closure ratio decreases as the crack grows out of the contact area and it has great impact on the effective range of Stress Intensity Factor(SIF) as well as the crack growth rate.

关键词： Crack closure Crack growth Crack initiation Finite element method Fretting fatigue

Conductive and tribological properties of TiN-Ag composite coatings under grease lubrication

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Friction 2021年第4期9卷 774-788页

作者： Feihu LIN Yanqiu XIA Xin FENG school of energy power and Mechanical engineering North China

TiN-Ag composite coatings were prepared by pulsed bias arc ion plating.X-ray diffraction(XRD)and energy dispersive X-ray spectroscopy(EDS)were applied to analyze the compositions of the coatings.Tribological properties of the coatings were studied using an MFT-R4000 ball-on-disk friction tester in the presence of lubricating greases containing multilayer graphene.Scanning electron microscopy(SEM),Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS)were used to analyze the worn surface compositions of the lubricating films.The results show that with the decrease in Ag in the film,hardness increased but electrical conductivity decreased.The coating with 10 at%Ag content shows the best friction-reducing and anti-wear properties,which can be attributed to the moderate content of Ag embedded in the TiN crystal gap that enhanced the grain bonding force to improve the anti-wear and self-lubricating ability.Graphene can be adsorbed on the coating as a solid lubricant.

关键词： silver tribology contact resistance lubricating grease