Pub Date : 2021-01-24DOI: 10.5545/SV-JME.2020.7076
D. Grguraš, L. Sterle, Aleš Malneršič, Luka Kastelic, C. Courbon, F. Pušavec
Single-channel supply of pre-mixed liquid carbon dioxide (LCO2) and minimum quantity lubrication (MQL) represents a state-of-the-art LCO2 assisted machining. However, to fully understand and optimize cooling and lubrication provided by the LCO2 + MQL, a fundamental media flow analysis is essential, yet not researched enough. Therefore, in this paper, media flow velocity and oil droplet size were analysed in supplying line and at the nozzle outlet using high-speed camera and proprietary single-channel system. Results indicate that pre-mixed media flow velocity is mainly influenced by the LCO2 expansion rate upon the nozzle outlet, wherein oil droplet size is largely dependent on the solubility between oil and LCO2. Media flow velocity increases significantly from an average of 40 m/s in the supplying line to the excess of 90 m/s at the nozzle outlet due to the pressure drop and LCO2 expansion. Furthermore, this volume expansion causes the oil droplet to increase to the point of critical, unstable droplet size. Afterward, the unstable oil droplet breaks up into smaller oil droplets. It was found, that nonpolar oil, with greater solubility in LCO2, compared to the polar oil, provides droplets as small as 2 μm in diameter. Smaller oil droplets positively reflect on tool wear and tool life in LCO2 assisted machining, as the longest tool life was achieved by using the nonpolar oil for pre-mixed LCO2 + MQL.
{"title":"Media Flow Analysis of Single-Channel Pre-Mixed Liquid CO2 and MQL in Sustainable Machining","authors":"D. Grguraš, L. Sterle, Aleš Malneršič, Luka Kastelic, C. Courbon, F. Pušavec","doi":"10.5545/SV-JME.2020.7076","DOIUrl":"https://doi.org/10.5545/SV-JME.2020.7076","url":null,"abstract":"Single-channel supply of pre-mixed liquid carbon dioxide (LCO2) and minimum quantity lubrication (MQL) represents a state-of-the-art LCO2 assisted machining. However, to fully understand and optimize cooling and lubrication provided by the LCO2 + MQL, a fundamental media flow analysis is essential, yet not researched enough. Therefore, in this paper, media flow velocity and oil droplet size were analysed in supplying line and at the nozzle outlet using high-speed camera and proprietary single-channel system. Results indicate that pre-mixed media flow velocity is mainly influenced by the LCO2 expansion rate upon the nozzle outlet, wherein oil droplet size is largely dependent on the solubility between oil and LCO2. Media flow velocity increases significantly from an average of 40 m/s in the supplying line to the excess of 90 m/s at the nozzle outlet due to the pressure drop and LCO2 expansion. Furthermore, this volume expansion causes the oil droplet to increase to the point of critical, unstable droplet size. Afterward, the unstable oil droplet breaks up into smaller oil droplets. It was found, that nonpolar oil, with greater solubility in LCO2, compared to the polar oil, provides droplets as small as 2 μm in diameter. Smaller oil droplets positively reflect on tool wear and tool life in LCO2 assisted machining, as the longest tool life was achieved by using the nonpolar oil for pre-mixed LCO2 + MQL.","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126938653","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}
Pub Date : 2020-12-15DOI: 10.5545/sv-jme.2020.6910
Xibing Li, Zhenglei Yu, Xizhao Li, Weixiang Li, Tengyue Zou
The present paper focuses on the manufacturing of micro-groove heat pipes on hydrostatic thrust bearings of heavy machinery. Special multitooth tools were designed for plough-extrusion forming heat pipes on flat copper. Experimental results were conducted to determine whether the plough-extrusion forming could achieve better performance than traditional wire electrical discharge. Furthermore, the processing using multi-tooth tool with 10 mm length, 55 tooth number, 0.25 mm tooth depth and 0.22 tooth top width was found to achieve the best performance among the six optional tools. The 50 mm/min forming speed was determined to acquire the best surface quality of the microgroove structure. Through heat transfer testing, the theoretical model for a micro-groove heat pipe made by plough-extrusion forming was also verified.
{"title":"Plough-extrusion Forming for Making Micro-groove Heat Pipes on Hydrostatic Thrust Bearings of Heavy Machinery","authors":"Xibing Li, Zhenglei Yu, Xizhao Li, Weixiang Li, Tengyue Zou","doi":"10.5545/sv-jme.2020.6910","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6910","url":null,"abstract":"The present paper focuses on the manufacturing of micro-groove heat pipes on hydrostatic thrust bearings of heavy machinery. Special multitooth tools were designed for plough-extrusion forming heat pipes on flat copper. Experimental results were conducted to determine whether the plough-extrusion forming could achieve better performance than traditional wire electrical discharge. Furthermore, the processing using multi-tooth tool with 10 mm length, 55 tooth number, 0.25 mm tooth depth and 0.22 tooth top width was found to achieve the best performance among the six optional tools. The 50 mm/min forming speed was determined to acquire the best surface quality of the microgroove structure. Through heat transfer testing, the theoretical model for a micro-groove heat pipe made by plough-extrusion forming was also verified.","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127192957","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}
Pub Date : 2020-12-15DOI: 10.5545/sv-jme.2020.6714
Jianyong Liu, Jianfei Sun, U. Zaman, Wuyi Chen
In this paper, vibration-free milling cutters (variable helix (VH) and variable pitch (VP) end mills) and standard (SD) end mills are used to machine TB6 (Ti-10V-2Fe-3Al) titanium alloy in order to study the influence of wear and geometric structure parameters of milling cutters on chatter, cutting force and surface integrity of machined surfaces. The results of the tests show that the wear of milling cutters has a significant influence on the chatter, cutting force, roughness, residual stress, and microhardness. Geometric structure parameters of milling cutters also have a clear impact on both chatter and cutting force. Also, chatter and cutting force have significant effects on roughness and residual stress, which are in turn affected by tool geometric structure parameters, separately.
{"title":"Influence of Wear and Tool Geometry on the Chatter, Cutting Force, and Surface Integrity of TB6 Titanium Alloy with Solid Carbide Cutters of Different Geometry","authors":"Jianyong Liu, Jianfei Sun, U. Zaman, Wuyi Chen","doi":"10.5545/sv-jme.2020.6714","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6714","url":null,"abstract":"In this paper, vibration-free milling cutters (variable helix (VH) and variable pitch (VP) end mills) and standard (SD) end mills are used to machine TB6 (Ti-10V-2Fe-3Al) titanium alloy in order to study the influence of wear and geometric structure parameters of milling cutters on chatter, cutting force and surface integrity of machined surfaces. The results of the tests show that the wear of milling cutters has a significant influence on the chatter, cutting force, roughness, residual stress, and microhardness. Geometric structure parameters of milling cutters also have a clear impact on both chatter and cutting force. Also, chatter and cutting force have significant effects on roughness and residual stress, which are in turn affected by tool geometric structure parameters, separately.","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123381130","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}
Pub Date : 2020-11-15DOI: 10.5545/sv-jme.2020.6836
Nedzad Rudonja, Milan Gojak, I. Zlatanović, R. Todorovic
In this article is presented a thermodynamic analysis of a cascade heat pump system designed for using in high-temperature heating systems. The own thermodynamic model was built by using properties of working fluids from the CoolProp base. The cascade heat pump was designed to use ambient air as heat source with temperature t_amb= –20 °C and for heating water in the high-temperature heating system up to 70 °C. The projected heating capacity of the cascade heat pump was 100 kW. The coefficient of performance (COP) of the cascade heat pump system due to use of different working mediums combinations in cycles of the cascade heat pump was investigated. For the best combination of working fluids (mediums) sub-cooling, super-heating, pressure loss in compressor’s suction line, as well as exergy efficiency of the heat pump were analysed as a function of the mean temperature of the cascade heat exchanger.
{"title":"Thermodynamic Analysis of a Cascade Heat Pump Incorporated in High-Temperature Heating System","authors":"Nedzad Rudonja, Milan Gojak, I. Zlatanović, R. Todorovic","doi":"10.5545/sv-jme.2020.6836","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6836","url":null,"abstract":"In this article is presented a thermodynamic analysis of a cascade heat pump system designed for using in high-temperature heating systems. The own thermodynamic model was built by using properties of working fluids from the CoolProp base. The cascade heat pump was designed to use ambient air as heat source with temperature t_amb= –20 °C and for heating water in the high-temperature heating system up to 70 °C. The projected heating capacity of the cascade heat pump was 100 kW. The coefficient of performance (COP) of the cascade heat pump system due to use of different working mediums combinations in cycles of the cascade heat pump was investigated. For the best combination of working fluids (mediums) sub-cooling, super-heating, pressure loss in compressor’s suction line, as well as exergy efficiency of the heat pump were analysed as a function of the mean temperature of the cascade heat exchanger.","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114372206","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}
Pub Date : 2020-11-15DOI: 10.5545/sv-jme.2020.6868
Tianxin Li, Hang Xu, Meng Tian
Due to the complexity of load distribution and contact conditions, as well as the lack of effective analysis methods, the theoretically designed rotary vector (RV) cycloidal-pin drive with good meshing characteristics shows poor loaded performance in practical applications. In this paper, an effective analysis method based on the minimum energy principle is proposed, which can accurately obtain the real loaded characteristics in line with the actual operations. In the process of loaded analysis, through the innovative introduction of the minimum energy principle, the actual number of teeth engaged simultaneously was accurately determined, which directly affects the quality of meshing. The results of simulation and measurement experiment demonstrate the correctness and practicability of the theoretical analysis method and the effectiveness of the introduction of the minimum energy principle. This study solves the problem that the actual meshing performance is inconsistent with the theoretical analysis results, and provides an effective way for the improvement and pre-control of the transmission accuracy and meshing quality of the robot RV reducer.
{"title":"A Loaded Analysis Method for RV Cycloidal-pin Transmission Based on the Minimum Energy Principle","authors":"Tianxin Li, Hang Xu, Meng Tian","doi":"10.5545/sv-jme.2020.6868","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6868","url":null,"abstract":"Due to the complexity of load distribution and contact conditions, as well as the lack of effective analysis methods, the theoretically designed rotary vector (RV) cycloidal-pin drive with good meshing characteristics shows poor loaded performance in practical applications. In this paper, an effective analysis method based on the minimum energy principle is proposed, which can accurately obtain the real loaded characteristics in line with the actual operations. In the process of loaded analysis, through the innovative introduction of the minimum energy principle, the actual number of teeth engaged simultaneously was accurately determined, which directly affects the quality of meshing. The results of simulation and measurement experiment demonstrate the correctness and practicability of the theoretical analysis method and the effectiveness of the introduction of the minimum energy principle. This study solves the problem that the actual meshing performance is inconsistent with the theoretical analysis results, and provides an effective way for the improvement and pre-control of the transmission accuracy and meshing quality of the robot RV reducer.","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130304888","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}
Pub Date : 2020-11-15DOI: 10.5545/sv-jme.2020.6795
M. Dobeic, V. Butala, M. Prek, J. Leskovšek, Žiga Švegelj
From a sociological and economic perspective, odour pollution is one of the most complex problems in the field of air quality. Therefore, various approaches and odour impact criteria are particularly relevant when assessing odour exposure in the areas of different land use. The number of odour assessment methods is limited, and the lack of analytical techniques to determine odour concentration makes odour assessment even more complex. It is essential to analyse the spatial and temporal distribution of odour concentrations in order to assess odour nuisance in the ambient air. Since sampling of odorous air in the field for subsequent determination of odour concentrations in a laboratory by dynamic olfactometry is time-consuming, two approaches are used to assess odour concentrations in ambient air: estimating odour concentration by field inspection and calculation of odour concentrations using atmospheric dispersion models. The latter is the most commonly used technique. Our study aimed to provide fundamentals for an odour regulatory framework in Slovenia. While a multitude of approaches is presently applied to establish odour regulation framework, a broader approach remains lacking. Various odour emission sources were identified to evaluate available methods and techniques to assess odour impact. The impact area was selected to analyse and compare the impact of different odour sources in terms of odour concentration, odour frequency, odour offensiveness, land use, and receptor location. Finally, odour impact criteria were set according to odour offensiveness and concentration, percentile compliance level and land use.From a sociological and economic perspective, odour pollution is one of the most complex problems in the field of air quality. Therefore, various approaches and odour impact criteria are particularly relevant when assessing odour exposure in the areas of different land use. The number of odour assessment methods is limited, and the lack of analytical techniques to determine odour concentration makes odour assessment even more complex. It is essential to analyse the spatial and temporal distribution of odour concentrations in order to assess odour nuisance in the ambient air. Since sampling of odorous air in the field for subsequent determination of odour concentrations in a laboratory by dynamic olfactometry is time-consuming, two approaches are used to assess odour concentrations in ambient air: estimating odour concentration by field inspection and calculation of odour concentrations using atmospheric dispersion models. The latter is the most commonly used technique. Our study aimed to provide fundamentals for an odour regulatory framework in Slovenia. While a multitude of approaches is presently applied to establish odour regulation framework, a broader approach remains lacking. Various odour emission sources were identified to evaluate available methods and techniques to assess odour impact. The impact area was selected to analyse
{"title":"Fundamentals of Odour Assessment in Slovenia","authors":"M. Dobeic, V. Butala, M. Prek, J. Leskovšek, Žiga Švegelj","doi":"10.5545/sv-jme.2020.6795","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6795","url":null,"abstract":"From a sociological and economic perspective, odour pollution is one of the most complex problems in the field of air quality. Therefore, various approaches and odour impact criteria are particularly relevant when assessing odour exposure in the areas of different land use. The number of odour assessment methods is limited, and the lack of analytical techniques to determine odour concentration makes odour assessment even more complex. It is essential to analyse the spatial and temporal distribution of odour concentrations in order to assess odour nuisance in the ambient air. Since sampling of odorous air in the field for subsequent determination of odour concentrations in a laboratory by dynamic olfactometry is time-consuming, two approaches are used to assess odour concentrations in ambient air: estimating odour concentration by field inspection and calculation of odour concentrations using atmospheric dispersion models. The latter is the most commonly used technique. Our study aimed to provide fundamentals for an odour regulatory framework in Slovenia. While a multitude of approaches is presently applied to establish odour regulation framework, a broader approach remains lacking. Various odour emission sources were identified to evaluate available methods and techniques to assess odour impact. The impact area was selected to analyse and compare the impact of different odour sources in terms of odour concentration, odour frequency, odour offensiveness, land use, and receptor location. Finally, odour impact criteria were set according to odour offensiveness and concentration, percentile compliance level and land use.From a sociological and economic perspective, odour pollution is one of the most complex problems in the field of air quality. Therefore, various approaches and odour impact criteria are particularly relevant when assessing odour exposure in the areas of different land use. The number of odour assessment methods is limited, and the lack of analytical techniques to determine odour concentration makes odour assessment even more complex. It is essential to analyse the spatial and temporal distribution of odour concentrations in order to assess odour nuisance in the ambient air. Since sampling of odorous air in the field for subsequent determination of odour concentrations in a laboratory by dynamic olfactometry is time-consuming, two approaches are used to assess odour concentrations in ambient air: estimating odour concentration by field inspection and calculation of odour concentrations using atmospheric dispersion models. The latter is the most commonly used technique. Our study aimed to provide fundamentals for an odour regulatory framework in Slovenia. While a multitude of approaches is presently applied to establish odour regulation framework, a broader approach remains lacking. Various odour emission sources were identified to evaluate available methods and techniques to assess odour impact. The impact area was selected to analyse","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127788998","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}
Pub Date : 2020-10-15DOI: 10.5545/sv-jme.2020.6771
A. Kulawik, J. Wróbel
In the presented study, the cases of regeneration of the element made of C45 steel, using the MAG (Metal Active Gas) method are analysed. The base material is applied to the regeneration process. The analysis of the influence of the padding weld width (0.006 m, 0.01 m, 0.014 m) and the preheating temperature on the phase transformations and effective stresses of the regenerated layer are performed. A non-standard approach to preheating (before each padding weld after the cooling to ambient temperature) is considered. Due to the possibility of simplifying the model from 3D to 2D (symmetry of calculations for long padding welds), calculations were performed using the finite element method in the transverse to the padding direction. Each new padding weld was included as an additional area in the finite element mesh. The developed numerical model includes a temperature model, phase transformations in the liquid and solid states, and the stress model in the elastic-plastic range. The aim of the regeneration is not only to obtain the original geometry of the element, but it is also important that the filler material used (in the considered case identical to the base material) has appropriate properties. These properties largely depend on the phase composition. The used filler material affects not only the hardness, brittleness, and ductility of the material. Its kinetics and changes in the geometry can cause significant stresses and even cracks. Based on the obtained results, it can be concluded that increasing the width of the padding welds causes a decrease in the level of residual effective stress; however, it is technologically difficult to accomplish. The most unfavourable stresses occur in the initial area of the pad welding zone. For lower preheating temperatures and smaller welds, areas with possible cracks are identified. In these cases, lower preheating and tempering should be carried out, which leads to similar energy costs as at higher preheating temperatures. Due to the complex phase transformation process for medium carbon steels and the need for the process parameters control, proper regeneration is possible only in automated workstations. Keywords: computational mechanics, numerical simulation, padding weld, preheating, strain analysis, stress
{"title":"Numerical Study of Stress Analysis for the Different Widths of Padding Welds","authors":"A. Kulawik, J. Wróbel","doi":"10.5545/sv-jme.2020.6771","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6771","url":null,"abstract":"In the presented study, the cases of regeneration of the element made of C45 steel, using the MAG (Metal Active Gas) method are analysed. The base material is applied to the regeneration process. The analysis of the influence of the padding weld width (0.006 m, 0.01 m, 0.014 m) and the preheating temperature on the phase transformations and effective stresses of the regenerated layer are performed. A non-standard approach to preheating (before each padding weld after the cooling to ambient temperature) is considered. Due to the possibility of simplifying the model from 3D to 2D (symmetry of calculations for long padding welds), calculations were performed using the finite element method in the transverse to the padding direction. Each new padding weld was included as an additional area in the finite element mesh. The developed numerical model includes a temperature model, phase transformations in the liquid and solid states, and the stress model in the elastic-plastic range. The aim of the regeneration is not only to obtain the original geometry of the element, but it is also important that the filler material used (in the considered case identical to the base material) has appropriate properties. These properties largely depend on the phase composition. The used filler material affects not only the hardness, brittleness, and ductility of the material. Its kinetics and changes in the geometry can cause significant stresses and even cracks. Based on the obtained results, it can be concluded that increasing the width of the padding welds causes a decrease in the level of residual effective stress; however, it is technologically difficult to accomplish. The most unfavourable stresses occur in the initial area of the pad welding zone. For lower preheating temperatures and smaller welds, areas with possible cracks are identified. In these cases, lower preheating and tempering should be carried out, which leads to similar energy costs as at higher preheating temperatures. Due to the complex phase transformation process for medium carbon steels and the need for the process parameters control, proper regeneration is possible only in automated workstations.\u0000Keywords: computational mechanics, numerical simulation, padding weld, preheating, strain analysis, stress","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133698864","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}
Pub Date : 2020-10-15DOI: 10.5545/sv-jme.2020.6707
Yong Wang, Zi-long Zhang, Jie Chen, Hou-lin Liu, Xiang-Peng Zhang, M. Hočevar
Applying a high strength coating on a blade’s surface could significantly prolong the service life of a centrifugal pump under sediment-laden water flow because of its protection. To explore the effect of blade coating, the characteristics of energy, vibration and pressure fluctuation of a centrifugal pump (the specific speed (ns) is 81.46) with different polyurethane coating thickness coefficients were experimentally studied under sediment-laden water flow. Keeping the blade outlet angle, blade inlet angle and blade shape unchanged, the head H and efficiency η under both sediment-laden flow and clear water flow decrease significantly as the coating thickness coefficient increases. The axis rotating frequency and blade passing frequency are the main excitation frequencies of the pump vibration velocity amplitude and outlet pressure fluctuation. The vibration velocity amplitude and outlet pressure fluctuation at the frequency of 1 BPF are the largest. At the frequency of 1 axis rotating frequency, they are the second in all cases. The peak values of both vibration velocity amplitude and outlet pressure fluctuation are proportional to the coating thickness coefficient. An analysis was performed for several increasing coating thicknesses, corresponding to coating coefficients from K0 to K3. When the coating thickness coefficients are K0, K1, and K2, the peak value of vibration velocity amplitude under sediment-laden flow is larger than that under clear water flow, but the very small difference between them undercoating thickness coefficient K3. The peak values of pressure fluctuations under different flow rates decrease first and then increase with the increasing coating thickness coefficient, and lowest points are all located at the coating thickness coefficient K1.
{"title":"Effect of Blade Coating on a Centrifugal Pump Operation under Sediment-Laden Water Flow","authors":"Yong Wang, Zi-long Zhang, Jie Chen, Hou-lin Liu, Xiang-Peng Zhang, M. Hočevar","doi":"10.5545/sv-jme.2020.6707","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6707","url":null,"abstract":"Applying a high strength coating on a blade’s surface could significantly prolong the service life of a centrifugal pump under sediment-laden water flow because of its protection. To explore the effect of blade coating, the characteristics of energy, vibration and pressure fluctuation of a centrifugal pump (the specific speed (ns) is 81.46) with different polyurethane coating thickness coefficients were experimentally studied under sediment-laden water flow. Keeping the blade outlet angle, blade inlet angle and blade shape unchanged, the head H and efficiency η under both sediment-laden flow and clear water flow decrease significantly as the coating thickness coefficient increases. The axis rotating frequency and blade passing frequency are the main excitation frequencies of the pump vibration velocity amplitude and outlet pressure fluctuation. The vibration velocity amplitude and outlet pressure fluctuation at the frequency of 1 BPF are the largest. At the frequency of 1 axis rotating frequency, they are the second in all cases. The peak values of both vibration velocity amplitude and outlet pressure fluctuation are proportional to the coating thickness coefficient. An analysis was performed for several increasing coating thicknesses, corresponding to coating coefficients from K0 to K3. When the coating thickness coefficients are K0, K1, and K2, the peak value of vibration velocity amplitude under sediment-laden flow is larger than that under clear water flow, but the very small difference between them undercoating thickness coefficient K3. The peak values of pressure fluctuations under different flow rates decrease first and then increase with the increasing coating thickness coefficient, and lowest points are all located at the coating thickness coefficient K1.","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127373845","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}
Pub Date : 2020-10-15DOI: 10.5545/sv-jme.2020.6883
Oscar Tenango-Pirin, Elva Reynoso-Jardón, J. C. García, Y. Mariaca, Yuri Sara Hernández, R. Ñeco, Omar Dávalos
Thermal barrier coatings play a key role in the operational life of microturbines because they reduce thermal stress in the turbine components. In this work, numerical computations were carried out to assess new materials developed to be used as a thermal barrier coating for gas turbine blades. The performance of the microturbine components protection is also evaluated. The new materials were 8YSZ, Mg2SiO4, Y3Ce7Ta2O23.5, and Yb3Ce7Ta2O23.5. For testing the materials, a 3D gas microturbine model is developed, in which the fluid-structure interaction is solved using CFD and FEM. Temperature fields and stress magnitudes are calculated on the nozzle and blade, and then these are compared with a case in which no thermal barrier is used. Based on these results, the non-uniform temperature distributions are used to compute the stress levels in nozzles and blades. Higher temperature gradients are observed on the nozzle; the maximum temperature magnitudes are observed in the blades. However, it is found that Mg2SiO4 and Y3Ce7Ta2O23.5 provided better thermal insulation for the turbine components compared with the other evaluated materials. Mg2SiO4 and Y3Ce7Ta2O23.5 presented the best performance regarding stress and thermal insulation for the microturbine components. Keywords: thermal barrier coating, gas microturbine, turbine blade, thermal stress
{"title":"Effect of Thermal Barrier Coating on the Thermal Stress of Gas Microturbine Blades and Nozzles","authors":"Oscar Tenango-Pirin, Elva Reynoso-Jardón, J. C. García, Y. Mariaca, Yuri Sara Hernández, R. Ñeco, Omar Dávalos","doi":"10.5545/sv-jme.2020.6883","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6883","url":null,"abstract":"Thermal barrier coatings play a key role in the operational life of microturbines because they reduce thermal stress in the turbine components. In this work, numerical computations were carried out to assess new materials developed to be used as a thermal barrier coating for gas turbine blades. The performance of the microturbine components protection is also evaluated. The new materials were 8YSZ, Mg2SiO4, Y3Ce7Ta2O23.5, and Yb3Ce7Ta2O23.5. For testing the materials, a 3D gas microturbine model is developed, in which the fluid-structure interaction is solved using CFD and FEM. Temperature fields and stress magnitudes are calculated on the nozzle and blade, and then these are compared with a case in which no thermal barrier is used. Based on these results, the non-uniform temperature distributions are used to compute the stress levels in nozzles and blades. Higher temperature gradients are observed on the nozzle; the maximum temperature magnitudes are observed in the blades. However, it is found that Mg2SiO4 and Y3Ce7Ta2O23.5 provided better thermal insulation for the turbine components compared with the other evaluated materials. Mg2SiO4 and Y3Ce7Ta2O23.5 presented the best performance regarding stress and thermal insulation for the microturbine components.\u0000Keywords: thermal barrier coating, gas microturbine, turbine blade, thermal stress","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117192666","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}
Pub Date : 2020-10-15DOI: 10.5545/sv-jme.2020.6853
F. Cianetti
Fatigue damage and, in general, fatigue behaviour is not simple to observe or estimate during the operational life of a generic vibrating mechanical system. There are a lot of theoretical or numerical methods that allow to evaluate it or by knowing a priori the loading conditions and obtaining output stress states by adopting numerical models of the mechanical system or by directly experimentally measuring and acquiring stress/strain states. A few examples of instruments (e.g. rain flow recorders) or measurement chains dedicated to estimate it in time domain or frequency domain are found in the literature but none that fully both observes the system dynamic behaviour and estimates the related actualized cumulated damage, and, thus, none that can estimate the residual life of the system itself. In this paper, a simple time-domain method, designed to monitor the instantaneous fatigue behaviour by definition of the instantaneous and cumulated potential damage or of equivalent damage signal amplitude is presented, based on rain-flow counting method and a damage linear cumulation law and starting from system dynamics signals. This methodology was designed to overestimate real damage to alert the system manager before any crack starts and to be simply translated into electronic boards that can be mounted on generic mechanical systems and linked to one of the sensors that usually monitor system functionality. Keywords: fatigue; damage; rain flow counting; random loads
{"title":"How to Experimentally Monitor the Fatigue Behaviour of Vibrating Mechanical Systems?","authors":"F. Cianetti","doi":"10.5545/sv-jme.2020.6853","DOIUrl":"https://doi.org/10.5545/sv-jme.2020.6853","url":null,"abstract":"Fatigue damage and, in general, fatigue behaviour is not simple to observe or estimate during the operational life of a generic vibrating mechanical system. There are a lot of theoretical or numerical methods that allow to evaluate it or by knowing a priori the loading conditions and obtaining output stress states by adopting numerical models of the mechanical system or by directly experimentally measuring and acquiring stress/strain states. A few examples of instruments (e.g. rain flow recorders) or measurement chains dedicated to estimate it in time domain or frequency domain are found in the literature but none that fully both observes the system dynamic behaviour and estimates the related actualized cumulated damage, and, thus, none that can estimate the residual life of the system itself.\u0000In this paper, a simple time-domain method, designed to monitor the instantaneous fatigue behaviour by definition of the instantaneous and cumulated potential damage or of equivalent damage signal amplitude is presented, based on rain-flow counting method and a damage linear cumulation law and starting from system dynamics signals. This methodology was designed to overestimate real damage to alert the system manager before any crack starts and to be simply translated into electronic boards that can be mounted on generic mechanical systems and linked to one of the sensors that usually monitor system functionality.\u0000Keywords: fatigue; damage; rain flow counting; random loads","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121749577","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：