Emel Ceyhun Sabir and Erdem Koç
The main purpose of the study is to develop a theoretical model being capable of analysing the sealing and hydrodynamic‐hydrostatic lubrication mechanisms occuring between the…
Abstract
Purpose
The main purpose of the study is to develop a theoretical model being capable of analysing the sealing and hydrodynamic‐hydrostatic lubrication mechanisms occuring between the mating surfaces of mechanical face seals.
Design/methodology/approach
The theoretical model developed is based on solving the governing basic lubrication equation (Reynolds differential equation) by employing a finite difference method. The main lubrication machanism is assumed to be converging‐diverging wedge which is formed by the relative tilt of the sealing surfaces. The non‐dimensional Reynolds equation was solved to give the pressure distribution and consequently the load and moment acting on the movable seal ring. The aim of the model is to predict the non‐dimensional hydrodynamic and hydrostatic load carrying capacity of the system.
Findings
Theoretical model developed is capable of estimating the hydrodynamic and hydrostatic behaviour of mechanical radial face seals. It is shown that a converging‐diverging wedge mechanism produces hydrodynamic pressure which in turn maintains the seperation of the surfaces. The tilt appears to be caused mainly by bearing misalignment. It has been shown that hydrostatic load or pressure centre is an important parameter for load balance of moving seal ring. It is easy and useful to calculate the dimensional parameters defined taking into account the different geometrical and operating parameters.
Originality/value
This paper offers a quick and easy opportunity to examine the hydrodynamic behaviour of movable seal ring of a mechanical face seal and provides a considerable contribution to the lubrication and sealing research area. With the general theoretical model developed, the behaviour of the seal ring can be modelled and estimated.
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Fazıl Canbulut, Cem Sinanoğlu, Şahin Yıldırım and Erdem Koç
A neural network is employed to analyze axial piston pump of hydrostatic circular recessed bearing. Owing to complexity of the system, the neural network is used to predict the…
Abstract
A neural network is employed to analyze axial piston pump of hydrostatic circular recessed bearing. Owing to complexity of the system, the neural network is used to predict the bearing parameters of the experimental system. The system mainly consists of cylinder block, piston, slipper, ball‐joint and swash plate. The neural model of the system has three layers, which are input layer with one neuron, hidden layer with ten neurons and output layer with three neurons. It can be outlined from the results for both approaches neural network could be modeled bearing systems in real time applications.
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Fazil Canbulut, Cem Sinanoğlu and Erdem Koç
The purpose of this paper is to investigate experimentally slippers, which have an important role on power dissipation in the swash plate axial piston pumps. Since slippers affect…
Abstract
Purpose
The purpose of this paper is to investigate experimentally slippers, which have an important role on power dissipation in the swash plate axial piston pumps. Since slippers affect the performance of the system considerably, the effects of surface roughness on lubrication have been studied in slippers with varying hydrostatic bearing areas and surface roughness.
Design/methodology/approach
An experimental set‐up was designed to determine the performance of slippers, which are capable of increasing the efficiency of axial piston pumps, in different conditions.
Findings
The findings suggest that the frictional power loss has been caused by surface roughness, capillary tube diameter, and the size of the hydrostatic bearing area, supply pressure and the relative velocity. In the case of the 0.7 and 9.5 μm surface roughness more power is needed to overcome the friction force between slippers and slipper plates, but less power loss occurs with the slippers with surface roughness of 1.5 μm. The slippers with surface roughness of 1.5 μm are considered, because of the optimum power loss. Moreover, the power loss decreases with increasing capillary tube diameter and supply pressure.
Originality/value
In order to investigate slipper behaviour under different operating conditions, with different capillary tube size and supply pressure an experimental work was carried out for finding exact design parameters of the real time system.
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Fazil Canbulut, Erdem Koç and Cem Sinanoğlu
The purpose of this paper is to experimentally and theoretically investigate slippers, which have an important role on power dissipation in the swash plate axial piston pumps.
Abstract
Purpose
The purpose of this paper is to experimentally and theoretically investigate slippers, which have an important role on power dissipation in the swash plate axial piston pumps.
Design/methodology/approach
The slipper geometry and working conditions affected on the slipper performance have been analyzed experimentally. The model of the slipper system has been established by original neural network (NN) method.
Findings
First, the effects of the slipper geometry with smooth and conical sliding surfaces on the slipper performance were experimentally analyzed. Smooth sliding surface slippers showed a better performance then the conical surface ones. According to the results, the neural predictor would be used as a predictor for possible experimental applications on modeling this type of system.
Originality/value
This paper discusses a new modeling scheme known as artificial NNs an experimental and a NN approach have been employed for analyzing axial piston pumps. The simulation results suggest that the neural predictor would be used as a predictor for possible experimental applications on modeling bearing system.
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Erdem Koç and Emel Ceyhun Sabir
The main purpose of the research work carried out is to investigate the hydraulic balance conditions of the sealing ring of a mechanical radial face seal in terms of the residual…
Abstract
Purpose
The main purpose of the research work carried out is to investigate the hydraulic balance conditions of the sealing ring of a mechanical radial face seal in terms of the residual load acting on the ring by employing the theoretical model developed mentioned in the first part of the investigation.
Design/methodology/approach
The end load balance conditions for the movable seal ring have been examined by considering the residual load acting on the ring under all running conditions. The main lubrication and sealing mechanism is assumed to be due to the existence of the relative tilt between the mating surfaces, which is formed by the bearing misalignment. The aim of the theoretical model developed is to predict the necessary minimum film thickness between the relatively moving surfaces by considering the non‐dimensional running (operating) conditions and the geometrical parameters defined. The theoretical model is based on the main differential equation (Reynolds' equation) which is achieved by adopting the standard finite difference form.
Findings
Under the combination of the hydrostatic clamping forces and hydrodynamic restoring forces, an equilibrium position is reached with the seal ring displaced from its central position. At a particular non‐dimensional pressure, the seal ring comes into contact with the stationary plate and this limits the upper value of pressure that can be resisted by the mechanical seal type examined without metal‐metal contact. With the theoretical model developed, it was found that the minimum film thickness between the realtively moving surfaces could be predicted.
Originality/value
This paper provides a considerable scientific contribution to the field of lubrication and sealing aspect of the mechanical radial face seals. The results presented in the first part of the investigation and the remarks outlined in this paper would be considered as a design tool for the seal designers with special reference to ring behaviour under hydrodynamic and hydrostatic conditions.
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The purpose of this paper is to investigate the hydrodynamic performance of a single‐screw extruder with special reference to metering region.
Abstract
Purpose
The purpose of this paper is to investigate the hydrodynamic performance of a single‐screw extruder with special reference to metering region.
Design/methodology/approach
The hydrodynamic analysis of a single screw extruder is carried out by dimensional and non‐dimensional parameters defining the polymer flow behaviour. The flow types formed in the extruder channel are defined and the relationship between the flow with the extruder geometry is examined.
Findings
The theoretical model developed is capable of estimating the hydrodynamic behaviour of extruder metering region. With the model developed, extruder geometry and polymer flow rate under different operating conditions can be predicted.
Originality/value
This paper offers a quick and easy opportunity to examine the hydrodynamic behaviour of extruder metering region. With the theoretical model developed, the behaviour of the flow in extruder can be modelled and estimated.
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The purpose of this paper is to investigate the design dimensions in pressure or metering region of a single‐screw extruder by determining viscous power loss. The paper is the…
Abstract
Purpose
The purpose of this paper is to investigate the design dimensions in pressure or metering region of a single‐screw extruder by determining viscous power loss. The paper is the second part of a series.
Design/methodology/approach
Viscous power loss formed in the extruder screw channel and the radial clearance is determined and evaluated in terms of non‐dimensional parameters in order to obtain a theoretical model.
Findings
The theoretical model developed is capable of estimating the viscous power loss in the extruder metering region. With the model developed, extruder geometry and viscous power loss under different operating conditions can be predicted.
Originality/value
This paper offers a quick and easy opportunity to examine the viscous power loss in the extruder.
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Yan Li, Ming K. Lim, Weiqing Xiong, Xingjun Huang, Yuhe Shi and Songyi Wang
Recently, electric vehicles have been widely used in the cold chain logistics sector to reduce the effects of excessive energy consumption and to support environmental…
Abstract
Purpose
Recently, electric vehicles have been widely used in the cold chain logistics sector to reduce the effects of excessive energy consumption and to support environmental friendliness. Considering the limited battery capacity of electric vehicles, it is vital to optimize battery charging during the distribution process.
Design/methodology/approach
This study establishes an electric vehicle routing model for cold chain logistics with charging stations, which will integrate multiple distribution centers to achieve sustainable logistics. The suggested optimization model aimed at minimizing the overall cost of cold chain logistics, which incorporates fixed, damage, refrigeration, penalty, queuing, energy and carbon emission costs. In addition, the proposed model takes into accounts factors such as time-varying speed, time-varying electricity price, energy consumption and queuing at the charging station. In the proposed model, a hybrid crow search algorithm (CSA), which combines opposition-based learning (OBL) and taboo search (TS), is developed for optimization purposes. To evaluate the model, algorithms and model experiments are conducted based on a real case in Chongqing, China.
Findings
The result of algorithm experiments illustrate that hybrid CSA is effective in terms of both solution quality and speed compared to genetic algorithm (GA) and particle swarm optimization (PSO). In addition, the model experiments highlight the benefits of joint distribution over individual distribution in reducing costs and carbon emissions.
Research limitations/implications
The optimization model of cold chain logistics routes based on electric vehicles provides a reference for managers to develop distribution plans, which contributes to the development of sustainable logistics.
Originality/value
In prior studies, many scholars have conducted related research on the subject of cold chain logistics vehicle routing problems and electric vehicle routing problems separately, but few have merged the above two subjects. In response, this study innovatively designs an electric vehicle routing model for cold chain logistics with consideration of time-varying speeds, time-varying electricity prices, energy consumption and queues at charging stations to make it consistent with the real world.
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Fabián Castaño and Nubia Velasco
To solve the problem, a mathematical model is proposed; it relies on a directed acyclic graph (DAG), in which arcs are used to indicate whether a pair of appointments can be…
Abstract
Purpose
To solve the problem, a mathematical model is proposed; it relies on a directed acyclic graph (DAG), in which arcs are used to indicate whether a pair of appointments can be assigned to the same route or not (and so to the same care worker). The proposed model aims at minimizing the personnel required to meet daily demand and balancing workloads among the workers while considering the varying traffic patterns derived from traffic congestion.
Design/methodology/approach
This paper aims at providing solution approaches for addressing the problem of assigning care workers to deliver home health-care (HHC) services, demanding different skills each. First, a capacity planning problem is considered, where it is necessary to define the number of workers required to satisfy patients' requests and then, patients are assigned to the care workers along with the sequence followed to visit them, thus solving a scheduling problem. The benefits obtained by permitting patients to propose multiple time slots where they can be served are also explored.
Findings
The results indicate that the problem can be efficiently solved for medium-sized instances, that is, up to 100 daily patient requests. It is also indicated that asking patients to propose several moments when they can receive services helps to minimize the need for care workers through more efficient route allocations without affecting significantly the balance of the workloads.
Originality/value
This article provides a new framework for modeling and solving a HHC routing problem with multiskilled personnel. The proposed model can be used to identify efficient daily plans and can handle realistic characteristics such as time-dependent travel times or be extended to other real-life applications such as maintenance scheduling problems.
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Gizem Erdem, Ommay Aiman Safi and Esma Betül Savaş
Peer mentoring programs in higher education settings support incoming students in their transition and adaptation to college life. Mentoring program evaluation research primarily…
Abstract
Purpose
Peer mentoring programs in higher education settings support incoming students in their transition and adaptation to college life. Mentoring program evaluation research primarily focuses on student outcomes and documents mentoring relationship quality (MRQ) as an important component of programs that facilitate change. The current study examines MRQ in a college peer mentoring program and explores its association with mentors’ and mentees’ perceptions of family relationships.
Design/methodology/approach
The sample included 629 first-year students (Mage = 18.4 and 54.2% female) and 88 mentors (Mage = 20.6 and 65.9% female). Each mentor was matched with eight to 10 incoming students in the same department. Dyadic data were collected prior to the program (pre-test) and at the end of the fall semester (mid-program) and spring semester (post-test). At pre-test assessment, mentors and mentees rated their family relationships, perceived trust, loyalty, and fairness in their families. At follow-up assessments, mentees reported their MRQ, mentoring duration, and mentoring activities.
Findings
A multilevel modeling analysis revealed that mentees’ and mentors’ perceptions of loyalty in their families predicted higher levels of MRQ at the end of the program. However, mentors’ perceived trust in their families was negatively associated with MRQ.
Originality/value
This study adds to the youth mentoring literature by focusing on family-of-origin experiences of both mentors and mentees from a dyadic and relational perspective. These findings have implications for future research and the practice of formal mentoring programs in college settings.