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Editorial Office

University of Ljubljana
Faculty of Mechanical Engineering
Journal of Mechanical Engineering

Aškerčeva 6,

SI-1000 Ljubljana
Slovenia

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E: info@sv-jme.eu



The journal is subsidized by Slovenian Research Agency.

 
ISSN: 0039-2480

Journal of Mechanical Engineering 63 (2017) 2

 

 

 


 

Influence of Hydrodynamic Cavitation on Intensification of Laundry Aqueous Detergent Solution Preparation

Authors - Tadej Stepišnik Perdih* – Brane Širok – Matevž Dular


Abstract

Washing machines are one of the most energy and water demanding domestic appliances. Over years, a significant effort of the scientific community has been invested into making laundry more “sustainable”. Nevertheless, the preparation of detergent solution has been entirely overlooked step of laundering. The preparation of aqueous detergent solutions in the currently available washing machines takes up to 10 minutes. In this work, we propose a design of a special rotary hydrodynamic cavitation generator, which would impact this process. New detergent dissolution rates have been experimentally tested on the laboratory model washing machine using the designed cavitation generator. The dissolution rates have been determined from the measurements of the undissolved detergent after the specific time of treatment. Additionally, the influence of hydrodynamic cavitation on that process has been isolated and investigated. To do so, two flow regimes have been established: the regime with cavitation present and the regime where cavitation was not present. In order to evaluate cavitational intensity, pressure oscillations inside cavitation generator have been recorded. Results indicate that cavitation significantly increases the detergent dissolution rates. In the cavitation flow regime, more than 80 % of the detergent is dissolved in approximately 10 seconds. With no cavitation present, about 150 seconds are needed to dissolve the same amount of the detergent. Intensification of the process can be attributed to mechanical effects of cavitation. This research shows that use of the cavitation generators in the washing machines could lead to shorter washing programs and henceforth potential water and energy savings.

Keywords - hydrodynamic cavitation, rotary cavitation generator, cavitational intensity, washing machines, aqueous detergent solution

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)2, 83-91, SI 13
DOI:10.5545/sv-jme.2016.3970

 

pdfInfluence of Hydrodynamic Cavitation on Intensification of Laundry Aqueous Detergent Solution Preparation (.pdf 3.4MB)

 


  

Effects of Nozzle Inner Surface Roughness on the Performance of Self-Resonating Cavitating Waterjets under Different Ambient Pressures

Authors - Deng Li – Yong Kang* – Xiaolong Ding – Xiaochuan Wang – Zhenlong Fang


Abstract

The self-resonating cavitating waterjet (SRCW) has been widely used for many practical and industrial applications since the first recognition of its strong cavitation ability. To further improve the performance of SRCW under ambient pressures, the effects of nozzle inner surface roughness were experimentally studied by impinging the jets on pure aluminium specimens (1070A) at various standoff distances. The typical macroscopic appearances and mass losses of the eroded specimens were used to evaluate the performances of the jets issuing from six organ-pipe nozzles of different inner surface roughness values (0.8 μm, 1.6 μm, 3.2 μm, 6.3 μm, 12.5 μm, and 25 μm). The results show that nozzle inner surface roughness significantly influences the optimum standoff distance and the cavitation intensity, which greatly depends on the ambient pressure. Moreover, it is found that there is always an optimum surface roughness that can remarkably enhance the cavitation erosion capability under each ambient pressure. Specifically, at ambient pressures of 2 MPa and 4 MPa, the surface roughness of 6.3 μm causes the strongest cavitation intensity at standoff distances of 42 mm and 50 mm, respectively. While at ambient pressures of 6 MPa, 8 MPa, and 10 MPa, the surface roughness of 12.5 μm is the one that maximally enhances the intensity at standoff distances of 45 mm, 40 mm, and 35 mm, respectively. Furthermore, the enhanced cavitation intensity is found to improve the impingement power of the high-speed waterjet as well. The present study also helps to provide a guideline for determining the finishing accuracy of inner surface required in the fabrication of organ-pipe nozzles.

Keywords - self-resonating cavitating waterjet, surface roughness, cavitation erosion, ambient pressure, organ-pipe nozzle

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)2, 92-102, SI 14
DOI:10.5545/sv-jme.2016.3563

 

pdfEffects of Nozzle Inner Surface Roughness on the Performance of Self-Resonating Cavitating Waterjets under Different Ambient Pressures (.pdf 2.0MB)

 


 

Inverse Method for Controlling Pure Material Solidification in Spherical Geometry

Authors - Mohamed Charifi* – Rabah Zegadi


Abstract

In this study, we present the control of the solidification process of a phase-changing, pure material described in one-dimensional spherical geometry. We used an inverse global descent method in which the gradient and the adjoint equation are constructed in continuous variables of time and space. The control variable is the temperature at the fixed boundary of the solid domain. For the desired solidification front, the control was determined using information on the heat flux deduced by heat balance. The numerical resolution was based on a finite difference method in a physical domain with a moving grid related to the evolving solidification front with time. The developed numerical model was validated using an exact built solution. The numerical results of the control problem are presented for both the exact and noisy data cases. For the noisy data, a regularization method was applied. In the case of the exactdata, a rapid control determination was achieved except for time steps near the end. The random errors effects in bruited data were considerably reduced by regularization.

Keywords - phase change, interface solid/liquid, inverse problem, spherical geometry

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)2, 103-110, SI 15
DOI:10.5545/sv-jme.2016.3805

 

pdfInverse Method for Controlling Pure Material Solidification in Spherical Geometry (.pdf 465KB)

 


 

Work Hardening of Non-Axisymmetric Die-Less Spinning

Authors - Zhen Jia – Zhiren Han* – Baoming Liu – Yong Xiao


Abstract

Non-axisymmetric shell parts are widely used in the fields of aviation, aerospace and automobiles. Because of good flexibility, short production preparation period and low cost, die-less spinning has the advantages in processing those parts. However, the special work-hardening distribution being caused by its processing technology will affect the performance of these parts. Therefore, the work-hardening of nonaxisymmetric die-less spinning is studied through experiments and by using the finite element method (FEM). The law of “smaller half cone angle (HCA) with bigger work-hardening” is found by testing the surface hardness of the spun workpieces. Microstructure observation and theoretical analyses are adopted to reveal the law. The reason for that is that the roller causes greater plastic strain inhomogeneity in the smaller HCA-forming process. It is also found that the working condition with the largest HCA difference has the biggest work-hardening difference and the maximum hardness difference can be 15 %.

Keywords - non-axisymmetric spinning, work-hardening status, die-less spinning, HCA, FEM, strain


Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)2, 111-118, SI 16
DOI:10.5545/sv-jme.2016.3589

 

pdfWork Hardening of Non-Axisymmetric Die-Less Spinning (.pdf 2.8MB)




MHD Boundary Layer Behaviour over a Moving Surface in a Nanofluid under the Influence of Convective Boundary Conditions

Authors - Mohamed Abdel-wahed* – Tarek Emam

Abstract

The present work provides an analysis of the hydro-magnetic nanofluid boundary layer over a moving surface with variable thickness in the presence of nonlinear thermal radiation and convective boundary conditions. The governing partial differential equations system that describes the problem is converted to a system of ordinary differential equations by the similarity transformation method; such a system is solved numerically. The velocity, temperature, and nanoparticle concentration of the boundary layer are plotted and investigated in details. Moreover, the surface skin friction, rate of heat and mass transfer are deduced and explained in detail.

Keywords - Nanofluids, MHD flow, convective conditions, non-linear thermal radiation

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)2, 119-128, SI 17
DOI:10.5545/sv-jme.2016.4014

 

pdfMHD Boundary Layer Behaviour over a Moving Surface in a Nanofluid under the Influence of Convective Boundary Conditions (.pdf 608KB)




Comfort Improvement of a Novel Nonlinear Suspension for a Seat System Based on Field Measurements

Authors - Leilei Zhao – Changcheng Zhou* – Yuewei Yu


Abstract

This paper describes improved ride comfort of a novel nonlinear suspension for seat system based on field measurements. For the novel nonlinear suspension proposed, a rubber spring is used as its elastic element which has highly nonlinear characteristics to adapt various working conditions, and an asymmetrical damper is designed to yield asymmetric damping characteristics. Previous seat models were not very suitable for the system; thus, a nonlinear mathematical model was built to describe it better. Then, based on field measurements, the model parameters were identified, and the suspension damping coefficients were tuned under the practical constraints, to achieve satisfactory ride comfort to the greatest extent possible. Finally, the bench test was carried out, and the results show that, after the coefficients tuning, the seat vertical frequency-weighted root mean square (RMS) acceleration values are decreased by about 10 % and 8 % under the driving conditions on the highway and the gravel road, respectively, which proves the damping coefficients tuned are workable. The novel nonlinear suspension and the method of the damping coefficients tuning provide a valuable reference for further improving ride comfort to better protect the driver’s health.

Keywords - ride quality; road conditions; nonlinear suspension; coefficients tuning

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)2, 129-137, SI 18
DOI:10.5545/sv-jme.2016.3719

 

pdfComfort Improvement of a Novel Nonlinear Suspension for a Seat System Based on Field Measurements (.pdf 857KB)

 



Investigation of Mechanical Properties of Horn Powder-Filled Epoxy Composites

Authors - Duraisamy Kumar * – Sadayan Rajendra Boopathy – Dharmalingam Sangeetha – Govindarajan Bharathiraja

Abstract

Recent environmental concerns focus on the development of bio-composites, due to their low cost, and eco-friendly and bio-degradability characteristics. The aim of this work is to investigate the properties of particle-filled composites fabricated using bio-waste horn powder (HP) and epoxy resin. Composites were fabricated according to a Taguchi L9 (3×3) orthogonal array. The HP particles and matrix were mixed in an appropriate ratio, compression-moulded and cured at room temperature to produce the specimens. Properties, such as ultimate tensile strength, tensile modulus, elongation percentage at break, flexural strength, flexural modulus, impact strength and microstructure of the specimens, were investigated. Scanning electron microscopy (SEM) micrographs of tensile tested specimens show good compatibility between HP particles and resin, when the HP volume is at 10 % and increases in agglomeration with increase in the HP volume percentage. Optimization of factors was done using grey relational analysis (GRA) and analysis of variance (ANOVA). The optimum factor levels were found to be the highest NaOH concentration (con.), A3 (i.e., 0.3 N), the smallest HP size, B1 (i.e., 125 μm) and the lowest HP volume percentage, C1 (i.e., 10 %). The contribution of influencing factors in decreasing order were found to be, HP volume percentage with 90.87 %, HP size with 6.43 % and NaOH concentration with 0.78 %. From the R squared and R squared adjusted values of the properties, it is determined that most of the values are above 95 %, confirming a 95 % confidence level. Comparison between the optimum specimen and untreated HP specimens reveals that the optimum specimen has better properties. Hence, HP/epoxy composites can find application in various sectors.

Keywords - horn powder, epoxy resin, particulate composites, mechanical properties, optimization

Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 63(2017)2, 138-147, SI 19
DOI:10.5545/sv-jme.2016.3764

 

pdfInvestigation of Mechanical Properties of Horn Powder-Filled Epoxy Composites (.pdf 2.9MB)

 


 


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