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Improving thermal efficiency and stability of laser welding process for magnesium alloy by combining power modulation and subatmospheric pressure environment

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Journal of Magnesium and Alloys 2022年第10期10卷 2788-2800页

作者： Jie Ning Suck-Joo Na Lin-Jie Zhang Xiang Wang Jian Long Won-Ik Cho State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China BIAS-Bremer Institut für angewandte Strahltechnik GmbH Klagenfurter Straße 528359 BremenGermany

The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor *** solve the problem,the effects of subatmospheric environment on LW process,technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were *** AZ31magnesium(Mg)alloy was used as the test *** test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal *** the keyhole depth greatly rises,significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole ***,the hump-shaped surface morphology of the welded seam is formed;moreover,the weld width in local zones in the lower part of the welded seam remarkably *** LW in subatmospheric environment,the weld penetration can be further greatly increased through power ***,power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment,thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded ***,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was *** was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

关键词： Laser welding Subatmospheric environment Power modulation Highly reflective materials thermal efficiency Stability

Experimental study on the effects of HP and LP EGR on thermal efficiency and emissions of a two-stage turbocharged diesel engine

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Science China(Technological Sciences) 2014年第2期57卷 379-389页

作者： WU BinYang PU YouZhe YU XiaoYang SU WanHua State Key Laboratory of Engines Tianjin University

An experimental study was performed to compare the effects of high-and low-pressure exhaust gas recirculation loops(HP and LP EGR loops)on thermal efficiency and emissions of a diesel *** were conducted on a 12-L six-cylinder turbocharged diesel engine under various operating *** found that at a low speed of 1100 r/min,1 MPa BMEP,the LP EGR loop could achieve higher brake thermal efficiency and lower emissions than the HP *** is because the lower enthalpy available at the turbine inlet of the HP EGR loop increased the fuel/oxygen equivalence *** the HP EGR,the gross indicated thermal efficiency was reduced by 1%,but pumping losses were only reduced by 0.5%,compared to the LP EGR *** a higher speed of 1600 r/min,1 MPa BMEP,the HP EGR loop attained a higher brake thermal efficiency and lower emissions because of the relatively sufficient flow through the *** the HP EGR loop,the gross indicated thermal efficiency was only reduced by 0.5%and pumping losses were reduced by 1.5%,compared to the LP EGR *** fuel consumption and a longer ignition delay made the distribution of fuel/oxygen equivalence ratio more homogeneous,leading to lower *** data also showed that at the high speed of 1600 r/min,0.55 MPa BMEP,the brake thermal efficiency of the HP EGR loop first increased,then decreased as the EGR rate ***,under all conditions,a reasonable match of both EGR loops could achieve a good balance between fuel consumption and emissions of NOx and soot.

关键词： HP EGR LP EGR two-stage turbocharger system thermal efficiency emissions

Effect of Non-Convective Zone Thickness on thermal efficiency of Salt Gradient Solar Ponds

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Energy Engineering 2021年第4期118卷 1185-1195页

作者： Nan Li Ruiyang Xu Caihong Zhang Guoping Wu School of Vehicles and Energy Yanshan UniversityQinhuangdao066004China Architecture Department Shijiazhuang Institute of Railway TechnologyShijiazhuang050541China

An improved radiation transmission and thermal efficiency model for solar ponds has been proposed based on both the Hull Model and Wang/Seyed-Yagoobi Model in this *** new model is more accurate to actual measured conditions because multiple reflections and turbidity effects are *** penetration,thermal conductivity loss and thermal efficiency under different Non-Convective Zone thicknesses are numerically analyzed and thoroughly *** results show thatΔT/I0 plays a critical role for the thermal efficiency of solar ***,it is found through calculation that there is an optimum thickness of the Non-Convective *** the Non-Convective Zone thickness is less than this critical threshold,both temperature and thermal efficiency are decreased with increasing ***,when the Non-Convective Zone thickness is greater than this critical threshold,the increasing turbidity within a certain range will be beneficial to improve the thermal efficiency of solar *** addition,optimum Non-Convective Zone thickness is also related to the temperature,turbidity,salinity variation and bottom reflectivity.

关键词： Solar pond Non-Convective Zone thickness thermal efficiency bottom reflective

Theoretical and experimental research on effect of fins attachment on operating parameters and thermal efficiency of solar air collector

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Information Processing in Agriculture 2018年第4期5卷 411-421页

作者： Ali Daliran Yahya Ajabshirchi Department of Agricultural Machinery University of TabrizTabrizIran

Flat plate air collector is a type of heat exchanger which absorbs radiated solar energy and exchanges it to *** to low efficiency of this type of collectors,a suitable approach is investigated in this paper so as to increase thermal performance of the *** efficiency of solar collector for two models C1(without fins)and C2(with fins)both of 1 m^2 surface area with forced convection flow is studied theoretically and *** fins are attached over back board in air channel to create turbulence in air *** order to measure air temperature,17 thermal sensors(LM35)are exploited,among which 11 were mounted on absorber plate and the remaining 6 on the back *** design of experimental model are performed in Solidwork and programming of theoretical work in Matlab *** this research,a fan with constant mass flow rate of 0.033 kg/s is utilized for producing air *** indicate that applying fins in air channel not only reduces Nusselt number from 19.67 to 16.23,but also due to decreasing hydraulic diameter and creating air flow turbulence,causes increase of heat transfer coefficient from absorber plate to air flow and consequently reduction of total heat loss and higher outlet air *** difference of outlet air temperature between experimental and theoretical results for both collectors(C1 and C2)was recorded respectively as 7.6% and 9.4%.thermal efficiency was respectively calculated 30% and 51% for experimental types with and without fins and 33% and 55% for those of theoretical work which generally seem reasonable.

关键词： Solar air collector Fins thermal efficiency Energy efficiency Renewable energy

Effects of different combustion modes on the thermal efficiency and emissions of a diesel pilot-ignited natural gas engine under low-medium loads

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Journal of Central South University 2022年第7期29卷 2213-2224页

作者： JIN Shou-ying LI Jin-ze ZI Zhen-yuan LIU Ya-long WU Bin-yang State Key Laboratory of Engines Tianjin UniversityTianjin 300072China

Research on dual-fuel(DF)engines has become increasingly important as engine manufacturers seek to reduce carbon dioxide *** are significant advantages of using diesel pilot-ignited natural gas engines as DF ***,different combustion modes exist due to variations in the formation of the *** research used a simulation model and numerical simulations to explore the combustion characteristics of high-pressure direct injection(HPDI),partially premixed compression ignition(PPCI),and double pilot injection premixed compression ignition(DPPCI)combustion modes under a low-medium *** results revealed that the DPPCI combustion mode provides higher gross indicated thermal efficiency and more acceptable total hydrocarbon(THC)emission levels than the other *** to its relatively good performance,an experimental study was conducted on the DPPCI mode engine to evaluate the impact of the diesel dual-injection strategy on the combustion *** the DPPCI mode,a delay in the second pilot ignition injection time increased THC emissions(a maximum value of 4.27g/(kW·h)),decreased the emission of nitrogen oxides(a maximum value of 7.64 g/(kW·h)),increased and then subsequently decreased the gross indicated thermal efficiency values,which reached 50.4%under low-medium loads.

关键词： diesel pilot-ignited natural gas engine direct injection of natural gas combustion mode thermal efficiency emissions

thermal efficiency Prediction Model of Cement Clinker Production Based on Fuzzy C-Means Monitoring Clustering

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Thermal Efficiency Prediction Model of Cement Clinker Produc...

Adverse Effects of Condenser Cooling Seawater Temperature,Fouling,and Salinity on the Output Power and thermal efficiency of BWR NNPs

第三十九届中国控制会议

作者： Zhao Liu Xiaohong Wang Hongliang Yu Renpeng Xing School of Automation and Electrical Engineering University of Jinan Institute of Automation Qilu University of Technology (Shandong Academy of Sciences)

It is difficult to predict the thermal efficiency of cement clinker production on line. A thermal efficiency prediction model based on clustering algorithm is established to solve the problem. Firstly, aiming at the shortcomings of fuzzy c-means clustering and unsupervised clustering, an improved fuzzy c-means supervised clustering algorithm is proposed. Secondly, based on the characteristics of parameters and data of cement clinker production process, a supervised distributed support vector predictive model is established. Finally, the simulation results show that the prediction accuracy of this algorithm is high and it can be used for real-time prediction of thermal efficiency.

关键词： Cement Clinker Production Fuzzy C-means Supervised Clustering thermal efficiency Prediction Model

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Journal of Mechanical Materials and Mechanics Research 2022年第1期5卷 21-39页

作者： Said M.A.Ibrahim Ismail M.A.Aggour Mechanical Engineering Department Faculty of EngineeringAl-Azhar UniversityCairoEgypt

Increasing the thermal efficiency in newly designed power stations is a *** the efficiency in existed plants close to the rated one is of paramount *** research contributes to investigating the adverse effects of changes in condenser seawater coolant characteristics,(temperature,fouling,and salinity),on the thermal performance of a Boiling Water Reactor Nuclear Power Plant(BWR)NPP.A mathematical model is developed to relate seawater cooling temperature,fouling,and salinity to output power and thermal *** model also explains the impact of the condenser performance on power and *** thermal efficiency of the considered BWR NPP is reduced by 2.26%for a combined extreme increases in the condenser cooling seawater temperature,fouling factor of seawater and treated boiler feed water,and salinity by 10°C,0.0002,0.00001 m2K/W,and 100 g/kg,respectively.A rise in the condenser efficiency from 40%-100%results in an increase in the output power by 7.049%,and the thermal efficiency increases by about 2.62%.Conclusions are useful for reactor’s design.

关键词： BWR NPP thermal efficiency Temperature Fouling Salinity

Effects of R134a Saturation Temperature on a Shell and Tube Condenser with the Nanofluid Flow in the Tube Using the thermal efficiency and Effectiveness Concepts

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World Journal of Nano Science and Engineering 2021年第1期11卷 1-24页

作者： Élcio Nogueira Department of Mechanics and Energy State University of Rio de Janeiro DEM/FAT/UERJ Resende Brazil

The work’s objective is to analyze the influence of the saturation temperature of the R134a refrigerant on the thermal performance of a shell and tube type condenser, with water and aluminum oxide (Al2O3) nanoparticles flowing into the tube. For analysis, the heat exchanger is subdivided into three regions: subcooled liquid, saturated steam, and superheated steam. The shell and tube heat exchanger assumed as the basis for the study has 36 tubes, with rows of 4 tubes in line and three passes into the tube in each region. The parameters used to analyze the performance are efficiency and effectiveness, through variations of quantities such as saturation temperature, the nanofluid’s mass flow rate, fraction in the nanoparticles’ volume, and the number of passes in the tube in each region of the heat exchanger. The obtained results demonstrate that the efficiency is relatively high in all the analyzed situations. In each saturation temperature, the effectiveness can be increased by introducing fractions of nanoparticles in the water or increasing the number of passes in the tube.

关键词： Shell and Tube Condenser R134a Nanofluid thermal efficiency thermal Effectiveness

Data-Driven thermal efficiency Modeling and Optimization for Co-firing Boiler

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Data-Driven Thermal Efficiency Modeling and Optimization for...