Frontiers in Mechanical Engineering最新文献_第10页

Design Bushfire Selection for Bushfire Protection in Adaptation to Global Warming 适应全球变暖的林火防护设计选择

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-21 DOI: 10.3389/fmech.2019.00027

Grahame Douglas, Yaping He

引用次数: 1

Nanoscale Friction: Phonon Contributions for Single and Multiple Contacts 纳米级摩擦:声子对单接触和多接触的贡献

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-16 DOI: 10.3389/fmech.2019.00023

J. Streator

引用次数: 2

Roughness of Deposited Carbon-Based Coatings and Its Statistical Characteristics at Nano and Microscales 沉积碳基涂层的粗糙度及其在纳米和微米尺度上的统计特性

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-14 DOI: 10.3389/fmech.2019.00024

F. Borodich, E. Brousseau, A. Clarke, A. Pepelyshev, J. C. Sánchez-López

{"title":"Roughness of Deposited Carbon-Based Coatings and Its Statistical Characteristics at Nano and Microscales","authors":"F. Borodich, E. Brousseau, A. Clarke, A. Pepelyshev, J. C. Sánchez-López","doi":"10.3389/fmech.2019.00024","DOIUrl":"https://doi.org/10.3389/fmech.2019.00024","url":null,"abstract":"Topography of surfaces may influence many processes in tribology including friction and adhesion. Its influence is usually taken into account in various statistical models of rough surfaces. Most of these models are based on an explicit or implicit assumption of normality of the asperity heights or similar assumptions that involve Gaussian distributions. Recently it has been shown that the height distribution of surfaces prepared by grinding are not Gaussian at both nano and micro-scales, while topography of epoxy resin replicas of polishing papers having nominal asperity sizes up to several micrometers, was Gaussian. Here we study roughness of carbon-based coatings deposited by direct current pulsed magnetron sputtering with and without substrate bias voltage at micro and nano-scale. First the heights of the nano-asperities were determined by AFM (Atomic Force Microscopy). Then the heights of the micro-asperities were measured by a profilometre (a stylus). Finally the same regions measured by stylus were again studied by AFM. Standard statistical parameters of surfaces are determined at each scale. It has been also shown that the stylus measurements did not cause plastic deformations because the distributions of heights at nano-scale were the same. Using the experimental data obtained, the assumption of the normal distribution for the roughness heights has been studied by application of various modern tests of normality. It was found that the surfaces satisfy the assumption of normality of the heights at both levels. Hence, some of the standard statistical models of contact between rough solids can be applied to these intact surfaces.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"64 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78781919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

Measurement and Prediction of Discharge Coefficients in Highly Compressible Pulsating Flows to Improve EGR Flow Estimation and Modeling of Engine Flows 高可压缩脉动流中流量系数的测量和预测，以改进EGR流量估计和发动机流量建模

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-13 DOI: 10.3389/fmech.2019.00025

I. Brahma

{"title":"Measurement and Prediction of Discharge Coefficients in Highly Compressible Pulsating Flows to Improve EGR Flow Estimation and Modeling of Engine Flows","authors":"I. Brahma","doi":"10.3389/fmech.2019.00025","DOIUrl":"https://doi.org/10.3389/fmech.2019.00025","url":null,"abstract":"An assumption of constant discharge coefficient (Cd) is often made when modeling highly compressible pulsating engine flows through valves or other restrictions. Similarly, orifices and flow nozzles used for real-time EGR flow estimation are often calibrated at a few steady-state points with one single constant Cd that minimizes the error over the selected points. This assumption is based on near constant Cd observed at high Reynolds number for steady flow. It has been shown in this work that this assumption is not reasonable for pulsating flow, particularly at large amplitudes and low flow rates. The discharge coefficient of a square-edged orifice placed in the exhaust stream of a diesel engine produced Cd’s varying between 0.60-0.90 for the resulting critical/near-critical flows. A novel pulsating flow measurement apparatus that allowed independent variation of pressure, flow rate and frequency and allowed reproducible measurements independent of transducer characteristics, produced Cd’s in the range of 0.25-0.60 with a similar square-edge orifice. The variation in Cd was characterized by two dimensionless variables that normalized the standard deviation of the pulsating signal with dynamic pressure and average differential pressure drop respectively. The results raise important questions that can potentially initiate fundamental work to fill the gap in the literature that exists for highly compressible pulsating flows.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"126 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77076043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

Effect of Surface Layers in Sliding Contact of Viscoelastic Solids (3-D Model of Material) 粘弹性固体滑动接触中表层的影响(材料三维模型)

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-09 DOI: 10.3389/fmech.2019.00026

E. Torskaya, F. Stepanov

引用次数: 13

A Bio-Diesel Chemical Kinetic Mechanism Based on Decoupling Methodology and Detailed H2/O2/CO/C1~C3 Mechanism 基于解耦方法的生物柴油化学动力学机理及H2/O2/CO/C1~C3机理研究

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-07 DOI: 10.3389/fmech.2019.00021

S. Yang, M. Jia

{"title":"A Bio-Diesel Chemical Kinetic Mechanism Based on Decoupling Methodology and Detailed H2/O2/CO/C1~C3 Mechanism","authors":"S. Yang, M. Jia","doi":"10.3389/fmech.2019.00021","DOIUrl":"https://doi.org/10.3389/fmech.2019.00021","url":null,"abstract":"Biodiesel is a renewable, clean-burning diesel replacement, and may have superior brake thermal efficiency with certain blends compared to traditional diesel counterpart at higher compression ratios. The combustion chemistry process of biodiesel, which has not been well understood, is of great interests to some engine researchers. Researchers have developed some complicated chemical kinetic mechanisms for bio-diesel, which cannot be used in engine CFD with current computational resources. The present work aims to construct a new chemical kinetic mechanism with a medium size for biodiesel combustion. Since 2016, H2/O2/CO/C1 and C2-C3 detailed sub-mechanisms (the C3 model contained in AramcoMech2.0) have been developed for accurately predicting laminar flame speeds, ignition delay times, and important species evolutions, and have been validated against a large array of experimental measurements over a wide range of conditions. In this paper, a 3-component biodiesel surrogate chemical kinetic mechanism constructed in 2015 based on decoupling methodology has been combined with the new ‘core’ H2/O2/CO/C1~C3 detailed mechanism to generate a new bio-diesel chemical kinetic mechanism. In the surrogate mechanism construction, three skeletal sub-mechanisms are used for the three biodiesel components (MD, MD5D, and n-decane). The final mechanism, which has 183 species and 1002 reactions, has been validated with available experiment data. It will be validated extensively with more experimental biodiesel data and applied to engine CFD for understanding biodiesel combustion.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"219 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76920274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Quantifying the Underlying Causes of a Discrepancy Between Predicted and Measured Energy Use 量化预测与测量能源使用差异的潜在原因

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-03 DOI: 10.3389/fmech.2019.00020

Chris van Dronkelaar, M. Dowson, C. Spataru, E. Burman, D. Mumovic

{"title":"Quantifying the Underlying Causes of a Discrepancy Between Predicted and Measured Energy Use","authors":"Chris van Dronkelaar, M. Dowson, C. Spataru, E. Burman, D. Mumovic","doi":"10.3389/fmech.2019.00020","DOIUrl":"https://doi.org/10.3389/fmech.2019.00020","url":null,"abstract":"Simulation is commonly utilised as a best practice approach to assess building performance in the building industry. However, the built environment is complex and influenced by a large number of independent and interdependent variables, making it difficult to achieve an accurate representation of real-world building energy in-use. This gives rise to significant discrepancies between simulation results and actual measured energy consumption, termed ‘the performance gap’. The research presented in this paper quantified the impact of underlying causes of this gap, by developing building simulation models of four existing non-domestic buildings, and then calibrating them towards their measured energy use at a high level of data granularity. It found that discrepancies were primarily related to night-time use and seasonality in universities is not being captured correctly, in addition to equipment and server power density being underestimated (indirectly impacting heating and cooling loads). Less impactful parameters were among others; material properties, system efficiencies and air infiltration assumptions.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"44 11","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3389/fmech.2019.00020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72368083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 7

Pressure- and Temperature-Dependent Viscosity Measurements of Lubricants With Polymeric Viscosity Modifiers 使用聚合粘度调节剂的润滑油的压力和温度依赖性粘度测量

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-05-01 DOI: 10.3389/fmech.2019.00018

B. LotfizadehDehkordi, P. Shiller, G. Doll

{"title":"Pressure- and Temperature-Dependent Viscosity Measurements of Lubricants With Polymeric Viscosity Modifiers","authors":"B. LotfizadehDehkordi, P. Shiller, G. Doll","doi":"10.3389/fmech.2019.00018","DOIUrl":"https://doi.org/10.3389/fmech.2019.00018","url":null,"abstract":"The pressure–viscosity coefficient, α, is a measure of the pressure dependence of the viscosity of the liquid in elastohydrodynamic lubrication (EHL). There seems to be confusion around the understanding of the pressure–viscosity response in the inlet zone. In this paper the values of α were obtained from measurements of viscosity as a function of pressure and offers a understanding on the piezoviscous effect at various inlet pressures for those liquids. Moreover, the viscosities of several commercial engine oils and laboratory blends of mineral and synthetic base oils with polymer additives were measured at pressures up to 1 GPa and at temperatures of 40°C, 75°C, and 100°C. It was observed in some of these materials The significant changes within viscosity are temperature- and pressure-dependent. Analysis of the experimental results indicated that the solidification (significant increase viscosity) is due to liquid-solid phase transitions occurring in the lubricant’s polymer additives. Thus, this paper gives evidence on the role of molecular weight and concentration of polymer and its influence on the pressure- and temperature-dependent onset of the phase transitions. This transition has not been discussed in the open literature and is not accounted for in current bearing design using the Barus equation or the modified Yasatomi equation and may be the cause of some bearing damage modes.","PeriodicalId":53220,"journal":{"name":"Frontiers in Mechanical Engineering","volume":"192 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2019-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76967614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Modeling for Design Optimization of Piston Crown Geometry Through Structural Strength and Lubrication Performance Correlation Analysis 基于结构强度与润滑性能相关性分析的活塞冠几何形状优化设计建模

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-04-30 DOI: 10.3389/fmech.2019.00017

P. Mishra, Santosh Kumar

引用次数: 4

Grease Lubrication of Self-Mated 60NiTi Bearing Materials 自配60NiTi轴承材料的润滑脂润滑

IF 2.3

Frontiers in Mechanical Engineering Pub Date : 2019-04-18 DOI: 10.3389/fmech.2019.00013

Azhar Vellore, Nicholas Walters, A. Martini

引用次数: 0