Pub Date : 2019-04-24DOI: 10.5545/sv-jme.2019.6040
M. Di̇rek, M. S. Mert, Eren Soylu, F. Yüksel
The European Union brings some restrictions to the use of some refrigerants, which has been higher than 150 global warming potential (GWP) value, in mobile air conditioning (MAC) systems as in directive no 2006/40/EC [1]. Then these GWP limits were extended air conditioning and refrigeration systems with regulation the Regulation (EU) No, 517/2014 [2]. Presently, most of the MAC systems use R134a as the refrigerant; however, the GWP value of the R134a is 1300 [3] and [4]. The refrigerants such as R1234yf, R1234ze(E), R152a and R444A, can be considered as alternative refrigerants having low GWP for automotive air conditioning systems. Table 1 shows the thermophysical properties of the above-mentioned refrigerants. Among them, R1234ze(E) can be used instead of R134a due to the their similar properties [5]. However, the cooling performance of R1234ze(E) is 30 % lower in average than that of R134a when used in a similar medium capacity vapor compression system [6] to [8]. Furthermore, the performance of R1234ze(E) can be improved when the mixture of some refrigerants used to obtain required properties. The R444A consists of 83 % R1234ze(E), 12 % R32 and 5 % R152a, (by mass) and its GWP value is 93 [4] and [9] which meets the European regulations. Devecioğlu and Oruç [10] calculated the performance parameters of R1234yf, R444A and R445A for a MAC system. It was found that the R444A and R445A have lower cooling capacity, but higher coefficient of performance (COP) than that of R1234yf. Lee et al. [11] investigated the performance of R444A, R445A, R152a, and R1234yf in an automotive air conditioning (AAC) system as an alternative to R134a. The highest COP was obtained when the system was working with R152a. Cheng et al. [9] tested an air source heat pump (HP) system using the different concentrations of R32/R1234ze(E) mixture numerically. It was determined that the heating and cooling capacities were improved compared to the R134a baseline system. Meng et al. [12] determined the performance of a refrigeration system using the mixture of R152a and R1234ze(E) refrigerants as an alternative to R134a. The mixture of 50 % R1234ze(E) and 50 % R152a was found to be the best alternative for R134a. It was demonstrated that the cooling capacity of R1234ze(E)/R152a mixture was very similar to R134a and can be used without any change in the compressor. Li et al. [13] reported that R134a Experimental Investigation of an Automotive Air Conditioning System Using R444A and R152a Refrigerants as Alternatives of R134a Direk, M. – Mert, M.S. – Soylu, E. – Yüksel, F. Mehmet Direk* – Mehmet Selçuk Mert – Eren Soylu – Fikret Yüksel Yalova University, Faculty of Engineering, Turkey
欧盟在2006/40/EC指令[1]中对移动空调(MAC)系统中高于150全球变暖潜能值的制冷剂的使用进行了一些限制。然后，这些GWP限值是根据法规(EU) No . 517/2014[2]扩展的空调和制冷系统。目前，大多数MAC系统使用R134a作为制冷剂;而R134a的GWP值为1300[3]和[4]。R1234yf、R1234ze(E)、R152a、R444A等制冷剂可作为汽车空调系统低GWP值的替代制冷剂。上述制冷剂的热物理性质如表1所示。其中R1234ze(E)由于性能相似，可以代替R134a[5]。然而，R1234ze(E)在类似介质容量的蒸汽压缩系统[6]~[8]中使用时，其冷却性能比R134a平均低30%。此外，R1234ze(E)的性能可以通过与其他制冷剂混合使用而得到改善。R444A由83%的R1234ze(E)、12%的R32和5%的R152a(质量)组成，其GWP值为93[4]和[9]，符合欧洲法规。Devecioğlu和Oruç[10]分别计算了一个MAC系统的R1234yf、R444A和R445A的性能参数。结果表明，R444A和R445A的制冷量低于R1234yf，但性能系数(COP)高于R1234yf。Lee等人研究了R444A、R445A、R152a和R1234yf作为R134a替代品在汽车空调(AAC)系统中的性能。当系统与R152a一起工作时，获得了最高的COP。Cheng等人使用不同浓度的R32/R1234ze(E)混合物对空气源热泵(HP)系统进行了数值测试。经确定，与R134a基准系统相比，加热和冷却能力得到了改善。孟等人。[12]确定了使用R152a和R1234ze(E)制冷剂的混合物替代R134a的制冷系统的性能。发现50% R1234ze(E)和50% R152a的混合物是R134a的最佳替代品。结果表明，R1234ze(E)/R152a混合物的冷却能力与R134a非常相似，无需更换压缩机即可使用。Li et al.[13]报道R444A和R152a制冷剂替代R134a汽车空调系统的R134a实验研究Direk, M. - Mert, M.S. - Soylu, E. - yksel, F. Mehmet Direk* - Mehmet seluk Mert - en Soylu - Fikret yksel，土耳其ksel Yalova大学工程学院，土耳其
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Pub Date : 2019-04-15DOI: 10.5545/SV-JME.2018.5726
Youhang Zhou, Yong Li, Hanjiang Liu
According to the change in contact position between the drill edge and the workpiece, drilling machining is classified into three stages, namely, drilling guide, drilling, and drilling out [1]. In the monitoring of drilling, the signal features corresponding to the previous stage are extracted, and the mapping model is established to monitor the drilling process [2]. This can lay a theoretical foundation for realizing highprecision drilling quality analysis; the premise is how to achieve feature enhancement by implementing signal de-noising effectively in a complicated drilling environment. As it is an advanced sensor-and-signal processing technology, a growing number of scholars have been extensively adopting various kinds of sensors to ascertain the drilling process and drilling quality. The monitoring and prediction of tool wear and breakage in drilling are mainly done indirectly through thrust force [3] to [5]. Ferreiro et al. [6] and [7] and Peña et al. [8] completed the burr monitoring by extracting the features from the spindle torque signal in the drilling process. Ramirez et al. [9] established a temperature model for the drilling tool and combined the cutting force signal and temperature signal characteristics to evaluate the surface quality of the drilled surface. Xiao et al. [10] via constructing a valuable indicator, i.e., the wavelet energy ratio around the natural frequency of boring bar vibration signal to monitor tool wear and surface finish quality for deep hole boring, developed a method to monitor and evaluate tool wear during drilling through the monitoring of vibration and acoustic emission signals [11] and [12]. It is well known that the key to achieving the quality monitoring of drilling is to extract abnormal features from the monitoring signals, but the signal features representing drilling quality are often very weak, so it is necessary to pre-process the signal to intensify its features. The above researches on abnormal state monitoring and diagnosis during the machining process can be divided into two classifications: extracting the evident features of monitoring signals to determine abnormal tool damage and drilling quality, and ascertaining the tool wear and the quality of drilling trends by anatomizing the overall monitoring signal. The results of these studies have good guidance significance to ensure high-precision drilling quality. However, they cannot predict or inform when and where tool breakage and quality is abnormal. Therefore, it is of great necessity to ascertain the feature extraction problem of the drilling process signal, establish a mapping model of the monitoring signal and the drilling process, and accurately identify the time and location of abnormal Feature Enhancement Method for Drilling Vibration Signals by Using Wavelet Packet Multi-band Spectral Subtraction Zhou, Y. – Li, Y. – Liu, H. Youhang Zhou1,2,* – Yong Li1 – Hanjiang Liu1 1Xiangtan University, School of Mechanical Engineering, China 2X
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Pub Date : 2019-04-15DOI: 10.5545/SV-JME.2019.5998
A. Filip, C. Morariu, L. Mihail, G. Oancea
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Pub Date : 2019-04-15DOI: 10.5545/SV-JME.2018.5910
K. Januševičius, Juozas Bielskus, V. Martinaitis
In September 2015, the United Nations (UN) Assembly approved the sustainable development agenda [1]. According to this agenda, member countries must take action in order to improve the sustainability of the planet. Goals up until the year 2030 were set. Multiple aspects of the 17 sustainable development goals determined by the UN were aimed at increasing the utilisation of renewable energy and improving energy efficiency [2]. It is clear that these goals could only be met by using complex measures, in terms of the most influential consumers, i.e. the built environment, due to its high environmental impact [3]. In EU households, heating and hot water alone account for 79 % (in industry 70.6 %) of total final energy consumption. Thus, it is important to focus on heating demands [4]. Approximately 84 % of heating and cooling is still generated from fossil fuels, while only 16 % is generated from renewable energy. In order to fulfil the EU’s climate and energy goals, the heating and cooling sector must sharply reduce its energy consumption and decrease its use of fossil fuels [5]. Integrated design efficiency and final product quality are highly dependent on primary actions at the initial stages of any project. According to value engineering principles [6], a function could be satisfied in different ways that allow for different performances. Those aspects determine the pathway characterized by [7], which specified that alternatives should be considered at the initial stage of design. In this phase, solutions can be integrated at the lowest resource cost. In this context, the cost of considering different design alternatives becomes an important aspect of an efficient design process. When designing sustainable buildings, passive and active energy conservation solutions, in combination with renewable energy utilisation, play an important role. The primary function of a complex microclimate Functionality Assessment of Building a Microclimate System Utilising Solar Energy in a Cold Climate Januševičius, K. – Bielskus, J. – Martinaitis, V. Karolis Januševičius1,* – Juozas Bielskus2 – Vytautas Martinaitis1 1 Vilnius Gediminas Technical University, Faculty of Environmental Engineering, Lithuania 2 Vilnius Gediminas Technical University, Civil Engineering Research Centre, Lithuania
2015年9月，联合国大会通过了可持续发展议程[1]。根据这一议程，成员国必须采取行动，以改善地球的可持续性。制定了到2030年的目标。联合国确定的17项可持续发展目标的多个方面都旨在增加可再生能源的利用和提高能源效率[2]。很明显，这些目标只能通过使用复杂的措施来实现，就最具影响力的消费者而言，即建筑环境，因为它对环境的影响很大[3]。在欧盟家庭中，仅供暖和热水就占最终能源消耗总量的79%(在工业中为70.6%)。因此，关注供热需求是很重要的[4]。大约84%的供暖和制冷仍然来自化石燃料，而只有16%来自可再生能源。为了实现欧盟的气候和能源目标，供暖和制冷部门必须大幅减少能源消耗，减少化石燃料的使用[5]。综合设计效率和最终产品质量高度依赖于任何项目初始阶段的主要行动。根据价值工程原理[6]，可以通过不同的方式来满足一个函数，从而实现不同的性能。这些方面决定了[7]所描述的路径，这说明在设计的初始阶段应该考虑备选方案。在此阶段，可以以最低的资源成本集成解决方案。在这种情况下，考虑不同设计方案的成本成为有效设计过程的一个重要方面。在设计可持续建筑时，被动式和主动式节能解决方案，结合可再生能源的利用，发挥着重要作用。寒冷气候下利用太阳能构建复杂小气候系统的主要功能评估Januševičius, K. - Bielskus, J. - Martinaitis, V. Karolis Januševičius1，* - Juozas Bielskus2 - Vytautas Martinaitis1立陶宛维尔纽斯Gediminas技术大学环境工程学院2立陶宛维尔纽斯Gediminas技术大学土木工程研究中心
{"title":"Functionality assessment of building a micro-climate system utilising solar energy in a cold climate","authors":"K. Januševičius, Juozas Bielskus, V. Martinaitis","doi":"10.5545/SV-JME.2018.5910","DOIUrl":"https://doi.org/10.5545/SV-JME.2018.5910","url":null,"abstract":"In September 2015, the United Nations (UN) Assembly approved the sustainable development agenda [1]. According to this agenda, member countries must take action in order to improve the sustainability of the planet. Goals up until the year 2030 were set. Multiple aspects of the 17 sustainable development goals determined by the UN were aimed at increasing the utilisation of renewable energy and improving energy efficiency [2]. It is clear that these goals could only be met by using complex measures, in terms of the most influential consumers, i.e. the built environment, due to its high environmental impact [3]. In EU households, heating and hot water alone account for 79 % (in industry 70.6 %) of total final energy consumption. Thus, it is important to focus on heating demands [4]. Approximately 84 % of heating and cooling is still generated from fossil fuels, while only 16 % is generated from renewable energy. In order to fulfil the EU’s climate and energy goals, the heating and cooling sector must sharply reduce its energy consumption and decrease its use of fossil fuels [5]. Integrated design efficiency and final product quality are highly dependent on primary actions at the initial stages of any project. According to value engineering principles [6], a function could be satisfied in different ways that allow for different performances. Those aspects determine the pathway characterized by [7], which specified that alternatives should be considered at the initial stage of design. In this phase, solutions can be integrated at the lowest resource cost. In this context, the cost of considering different design alternatives becomes an important aspect of an efficient design process. When designing sustainable buildings, passive and active energy conservation solutions, in combination with renewable energy utilisation, play an important role. The primary function of a complex microclimate Functionality Assessment of Building a Microclimate System Utilising Solar Energy in a Cold Climate Januševičius, K. – Bielskus, J. – Martinaitis, V. Karolis Januševičius1,* – Juozas Bielskus2 – Vytautas Martinaitis1 1 Vilnius Gediminas Technical University, Faculty of Environmental Engineering, Lithuania 2 Vilnius Gediminas Technical University, Civil Engineering Research Centre, Lithuania","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131928030","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 : 2019-03-30DOI: 10.5545/SV-JME.2018.5865
Kaikai Luo, Yong Wang, Hou-lin Liu, M. Dular, Jie Chen, Zi-long Zhang
Spraying a coating on the surface of wet parts of a solid-liquid two-phase flow centrifugal pump could effectively increase its service life. To research the effect of coating thickness on the performance of the pump, a solid-liquid two-phase flow pump with a speed of n s = 81.5 was chosen, and polyurethane coatings with different thicknesses were sprayed on the surface of the blades of the impeller. The influence of coating thickness on the performance of the pump was tested under the condition of a water medium. Combined with numerical simulation, the internal flow, pressure fluctuations and radial force of the model pump were further analysed in detail. Keeping the blade outlet angle unchanged, the head and efficiency of the pump decrease with the increase of the coating thickness, and the amplitude of the decrease increases with the increase of the coating thickness. The peak value of pressure fluctuations increases with the increase of coating thickness. The pressure value on the impeller inlet increases first and then decreases with the increase of coating thickness. Radial force of impeller increases with the increase of coating thickness, and the radial force distributes in the triangle, which is the same as the number of blades.
{"title":"Effect of Coating Thickness on a Solid-Liquid Two-Phase Flow Centrifugal Pump under Water Medium","authors":"Kaikai Luo, Yong Wang, Hou-lin Liu, M. Dular, Jie Chen, Zi-long Zhang","doi":"10.5545/SV-JME.2018.5865","DOIUrl":"https://doi.org/10.5545/SV-JME.2018.5865","url":null,"abstract":"Spraying a coating on the surface of wet parts of a solid-liquid two-phase flow centrifugal pump could effectively increase its service life. To research the effect of coating thickness on the performance of the pump, a solid-liquid two-phase flow pump with a speed of n s = 81.5 was chosen, and polyurethane coatings with different thicknesses were sprayed on the surface of the blades of the impeller. The influence of coating thickness on the performance of the pump was tested under the condition of a water medium. Combined with numerical simulation, the internal flow, pressure fluctuations and radial force of the model pump were further analysed in detail. Keeping the blade outlet angle unchanged, the head and efficiency of the pump decrease with the increase of the coating thickness, and the amplitude of the decrease increases with the increase of the coating thickness. The peak value of pressure fluctuations increases with the increase of coating thickness. The pressure value on the impeller inlet increases first and then decreases with the increase of coating thickness. Radial force of impeller increases with the increase of coating thickness, and the radial force distributes in the triangle, which is the same as the number of blades.","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130159892","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 : 2019-03-24DOI: 10.5545/sv-jme.2018.5788
Roman Pawel Jedrzejczyk, M. Alb
{"title":"Active Structural Derivator in the Design Crystallization Phase of L7e Vehicle Structures","authors":"Roman Pawel Jedrzejczyk, M. Alb","doi":"10.5545/sv-jme.2018.5788","DOIUrl":"https://doi.org/10.5545/sv-jme.2018.5788","url":null,"abstract":"","PeriodicalId":135907,"journal":{"name":"Strojniški vestnik – Journal of Mechanical Engineering","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122993121","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 : 2019-03-24DOI: 10.5545/sv-jme.2018.5856
Velibor Karanović, M. Jocanović, S. Baloš, D. Knežević, I. Macuzic
0 INTRODUCTION It is very difficult to predict and precisely determine the impact of fluid cleanliness on the system operation or its components, due to many factors and a variety of hydraulic system applications. The hydraulic fluid contamination is an issue that can shorten the working life of hydraulic components, which has a direct impact on maintenance costs [1] to [3]. Also, contamination can be considered as a hydraulic system “intruder”, which has a direct or indirect influence on system behaviour and parameters such as precision, response time, repeatability, controllability, etc. [4] and [5]. Many well-regarded companies and other institutions dealing with manufacturing, maintenance and testing of hydraulic systems and equipment, based on their own experience from practice and experimental research, claim that the working fluid contamination represents the main cause of failures in 70 % to 80 % cases [2] and [6] to [9]. Additionally, the requirements for more precise control and higher efficiency of hydraulic systems, have resulted in the decreased clearances between working elements of hydraulic components and the increased working pressure values [10]. Due to the decreased clearance size, the adverse impact of micron-size solid contaminants becomes evident. Although it is wellknown that solid contaminants are destructive to hydraulic system components, as well as to the working fluid itself, there was no internationally accepted method for objectively determination of contamination tolerance for systems or each component separately [11], until 2017. In 2013, was initiated and consequently published ISO 12669:2017 standard, developed for determining the required cleanliness level (RCL) for a system [12]. This standard is now under review for five years period. Due to the lack of a standard procedure, the RCL choice is based on the system designer experience or on the third person recommendation (such as components manufacturer) and his experience. This doesn’t mean that optimal cleanliness level was selected for the specific system operation. The RCL selection by this method is strongly subjective, for which reason it does not provide consistency. Consequently, many system designers, as well as the users of hydraulic systems, are unsure and confused about the appropriate cleanliness level Impact of Contaminated Fluid on the Working Performances of Hydraulic Directional Control Valves Karanović, V. – Jocanović, M. – Baloš, S. – Knežević, D. – Mačužić, I. Velibor Karanović1,* – Mitar Jocanović1 – Sebastian Baloš1 – Darko Knežević2 – Ivan Mačužić3 1University of Novi Sad, Faculty of Technical Sciences, Serbia 2University of Banja Luka, Faculty of Mechanical Engineering, Bosnia and Herzegovina 3University of Kragujevac, Faculty of Engineering, Serbia
由于许多因素和各种液压系统应用，预测和精确确定流体清洁度对系统运行或其组件的影响是非常困难的。液压油污染问题会缩短液压元件的工作寿命，直接影响维修成本[1]~[3]。此外，污染可被视为液压系统的“入侵者”，它对系统行为和精度、响应时间、可重复性、可控性等参数有直接或间接的影响[4]和[5]。许多从事液压系统和设备制造、维护和测试的知名公司和其他机构，根据自己的实践和实验研究经验，声称工作液污染是70%至80%的故障的主要原因[2]和[6]至[9]。此外，对液压系统更精确控制和更高效率的要求，导致液压元件工作元件之间的间隙减小，工作压力值增加[10]。由于清除尺寸的减小，微米级固体污染物的不利影响变得明显。众所周知，固体污染物对液压系统部件和工作液本身都具有破坏性，但直到2017年，国际上还没有公认的方法来客观地确定系统或每个部件的污染公差[11]。2013年，发起并随后发布了ISO 12669:2017标准，用于确定系统所需的清洁度水平(RCL)[12]。这项标准目前正在进行为期五年的审查。由于缺乏标准程序，RCL的选择是基于系统设计人员的经验或第三方的建议(如组件制造商)和他的经验。这并不意味着为特定的系统操作选择了最佳清洁度级别。这种方法的RCL选择是非常主观的，因此它不能提供一致性。因此，许多系统设计师，以及液压系统的用户，不确定和困惑的适当的清洁度水平污染流体对液压换向阀的工作性能的影响karanoviki, V. - jocanoviki, M. - balosi, S. - Knežević， D. - Mačužić， I. Velibor Karanović1，* - Mitar Jocanović1 - Sebastian Baloš1 - Darko Knežević2 - Ivan Mačužić3 1诺维萨德大学，技术科学学院，塞尔维亚2巴尼亚卢卡大学，3克拉古耶瓦茨大学工程学院，塞尔维亚
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Pub Date : 2019-03-24DOI: 10.5545/SV-JME.2018.5651
P. Koc
Existing piping systems sometimes need to operate at larger mechanical loads than they are originally designed to. Often, these beyond-the-original-design loads lessen the margin against piping failure so much that performing recalculations using original analysis methods cannot qualify the pipeline. To demonstrate suitability of the existing pipeline to increased loads and to avoid piping hardware modification, more advanced analysis methods need to be employed. In this paper, a single detail from the beyondthe-original-design analysis [1] of a buried thin-wall water pipeline in nuclear power plant (NPP) Krško is shown. That analysis, the description of which is beyond the aim of this paper, demonstrated that the most critical part of the system is the penetration of the buried pipeline into a power plant’s concrete building. Namely, because of a supposed beyond-theoriginal-design earthquake, relative displacements between the building’s basement wall and the surrounding soil evolve, which in turn imposes large deformation on a buried pipe at the site of the building wall’s penetration. The most significant mode of deformation is pipe denting at the pipe-to-concretewall seal location. Pipe denting strongly influence pipeline’s strength and fatigue life; therefore, the topic was addressed by researchers in the past [2] and [3] and is still attractive today [4] to [6]. The solutions to the problem are in the form of a pure theoretic analysis [2], or as guides extracted from recapitulation of many experiments [3], or, recently, from experiments supplemented with numerical analyses [4] to [6]. All researchers agree that the excessive size of the dent, the abrupt change of the dented surface curvature and the pre-existing pipe damage on the dent spot severely lessen pipe strength and fatigue life. Because the denting is a problem still under research, it is not included in piping structural design codes yet, therefore leaving the structural engineer on thin ice. The aim of this paper is twofold: describing the experimental-numerical analysis of the dented section of a pipeline at NPP Krško and demonstrating the pipeline qualification with the applicable American Society of Mechanical Engineers (ASME) Code [7] (which is the obligatory code for NPP Krško), although no rule regarding dents is given in [7]. An Exacting Wall-Penetration Pipe Analysis Koc, P. Pino Koc* University of Ljubljana, Faculty of Mathematics and Physics, Slovenia
现有的管道系统有时需要在比最初设计的更大的机械载荷下运行。通常，这些超出原始设计的载荷会大大减少管道故障的余量，以至于使用原始分析方法进行重新计算无法使管道合格。为了证明现有管道对增加载荷的适用性，并避免管道硬件的修改，需要采用更先进的分析方法。本文给出了核电厂(NPP) Krško埋地薄壁输水管道的超原设计分析[1]中的一个细节。该分析的描述超出了本文的目的，它证明了该系统最关键的部分是埋地管道渗透到电厂的混凝土建筑中。也就是说，由于假定的超出原设计的地震，建筑物的地下室墙壁和周围土壤之间的相对位移发生变化，这反过来又对建筑物墙壁穿透部位的埋管施加了巨大的变形。最重要的变形模式是管道与混凝土墙密封位置的管道凹痕。管道凹痕严重影响管道的强度和疲劳寿命;因此，这一课题在过去[2]和[3]都有研究者提出，在今天[4]到[6]仍然具有吸引力。这个问题的解决方案以纯理论分析[2]的形式存在，或者作为从许多实验的重述中提取的指南[3]，或者最近从实验中补充了数值分析[4]到[6]。研究人员一致认为，过大的凹痕、凹痕表面曲率的突变以及凹痕处原有的管道损伤严重降低了管道的强度和疲劳寿命。由于凹痕是一个仍在研究中的问题，它还没有包括在管道结构设计规范中，因此使结构工程师如履薄冰。本文的目的有两个:描述核电站Krško管道凹陷部分的实验-数值分析，并通过适用的美国机械工程师学会(ASME)规范[7](这是核电站的强制性规范Krško)证明管道的资格，尽管在[7]中没有给出关于凹痕的规则。Koc, P. Pino Koc*卢布尔雅那大学，数学与物理学院，斯洛文尼亚
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Pub Date : 2019-02-15DOI: 10.5545/SV-JME.2018.5823
G. Filo, E. Lisowski, D. Kwiatkowski, J. Rajda
This article discusses the possibility of increasing the speed of movement of a single-sided hydraulic cylinder piston rod using a fluid stream from the return line. Directing the return stream back to the supply line instead of the fluid reservoir causes significant increase in the inflow rate to the actuator. This situation may arise when the piston rod of the cylinder is not fully loaded on part of the movement range. As part of this work, we proposed a solution in the form of a novel control valve, consisting of a throttle valve and a differential valve controlled by the pressure difference between the supply line and the return line. A geometric model was created using SolidWorks, then a simulation model was made in Matlab/Simulink. Next, simulations were carried out to prove that the use of the return fluid stream gives a possibility of a significant increase in the piston rod speed. The results of the numerical analyses were verified on a test bench where the valve prototype was tested. Speed characteristics of the piston rod against both payload force and throttle valve setting were determined. High convergence with the simulation results was obtained. It has also been confirmed that the proposed solution can be advantageous in practical applications.
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Pub Date : 2019-02-15DOI: 10.5545/sv-jme.2018.5677
Irina Stefanova Aleksandrova
The optimum conditions for dressing grinding wheels determined and recommended in the literature are valid only for particular types and tools of dressing and grinding. In this paper, an attempt has been made to optimize the dressing process parameters in fine cylindrical grinding. To define the optimum values of the dressing process variables (radial feed rate of diamond roller dresser frd , dressing speed ratio qd , dress-out time td , diamond roller dresser grit size/grinding wheel grit size ratio qg , type of synthetic diamonds and direction of dressing), a multi-objective optimization has been performed based on a genetic algorithm. In the capacity of the optimization parameter, a generalized geometric-mean utility function has been chosen, which appears to be a complex indicator characterizing the roughness and accuracy of the ground surface, the grinding wheel lifetime and the manufacturing net costs of the grinding operation. The optimization problem has been solved in the following sequence: 1) a model of the generalized utility function has been created reflecting the complex effect of the dressing system parameters; 2) the optimum conditions of uni-directional and counter-directional dressing of aluminium oxide grinding wheels by experimental diamond roller dressers of synthetic diamonds of АС32 and АС80 types and different grit size at which the generalized utility function has a maximum have been determined; 3) a Pareto optimum solution has been found (frd = 0.2 mm/min; qd = 0.8; td = 4.65 s; qg = 2.56), which guarantees the best combination between the roughness and the deviation from cylindricity of the ground surface, the grinding wheel lifetime and the manufacturing net costs of the grinding operation.
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