Papers by Prof. Dr. Tahsin Engin
Acta Technologica Agriculturae
This paper deals with the investigation of the performance of a nozzle used for intra-soil applic... more This paper deals with the investigation of the performance of a nozzle used for intra-soil application of liquid mineral fertilizers (LMF), determination of the range of spray angle, fall angle, droplet size, spray distribution characteristics, and substantiation of its dependence on the nozzle design parameters. The proposed nozzle has a jet-impact channel and deflector slot design with very compact overall dimensions. It can be mounted on a deep tillage knife (wing) with a height of 12–14 mm and provides flat fan spray with a high spraying angle. The following range of effective parameters has been determined: the feed channel diameter is 1–1.6 mm, the slot height is 0.35–0.7 mm, and impact surface diameter 5–8 mm. The resultant spray angle is 170–175°, and the fall angle diapason is 5–10°. These parameters contribute to determination of the tillage knife design parameters such as knife height and the height of spray window, as well as the nozzle installation parameters such as t,...
Handbook of Powder Technology, 2001
Centrifugal pumps handle fine solids in suspension in the china clay and cement industries, dredg... more Centrifugal pumps handle fine solids in suspension in the china clay and cement industries, dredging, slimes disposal and in some mineral extraction processes. To design a slurry transportation system based on centrifugal pumps, it is necessary to know the influence of solids on the performance of the pumps. It is important to realize that suspended solid particles cannot absorb, store or transmit pressure energy. Being restricted in their movement by intermolecular cohesion, molecules of solids can neither participate in maintaining or transmitting pressure energy nor increase their own kinetic energy when surrounded with liquid which carrying the pressure energy. The energy imparted to the liquid by the rotating impeller is utilized to move and support the solid particles in suspension. In this chapter, experiments are conducted to determine the individual effects of solid properties (particle size, solids specific gravity) and solids concentration by weight, as well as tip clearance effects on an open impeller centrifugal pump characteristics. Tip clearance is varied from 1.25 mm to 8 mm over the experiments and maximum particle size was approximately 2.4 mm. Test results have shown that, slurry characteristics and running tip clearance have a considerable impact on the pump performance. These effects, therefore, must be taken into account for pump design considerations and selection.
Magnetorheological (MR) shock absorber have received remarkable attention in the last decade due ... more Magnetorheological (MR) shock absorber have received remarkable attention in the last decade due to being a potential technology to conduct semi-active control in structures and mechanical systems in order to effectively suppress vibration. To develop performance of MR shock absorbers, optimal design of the dampers should be considered. The present study deals with optimal geometrical modeling of a MR shock absorber. Optimal design of the present shock absorber was carried out by using Taguchi experimental design approach.
Magnetorheological (MR) shock absorbers have received remarkable attention in the last decade due... more Magnetorheological (MR) shock absorbers have received remarkable attention in the last decade due to being a potential technology to conduct semi-active control in structures and mechanical systems in order to effectively suppress vibration. It is therefore vitally important to understand dynamic behavior of such devices whose nonlinear hysteresis is a complicated phenomenon. In the present paper, a MR shock absorbers has been designed, fabricated, tested and a fully-parametric modeling has been done using classical Bouc-Wen hysteretic model. Finally, the model has been verified against experimental data and excellent agreement has been observed between experimental and simulated data. Keyword: Magnetorhelogical shock absorbers, MR shock absorbers, MR devices, MR Fluid, Bouc-Wen model
Energy conversion applications are directly affected through the employment of turbomachines and ... more Energy conversion applications are directly affected through the employment of turbomachines and their efficiencies. Energy importance and wide-spread application of turbomachines, make it crucial to optimize their components. In order to optimizastion, the actual flow field and the interaction between the components must be revealed as 3-D studies. Although many studies have focused on the component optimization, mainly volute and impeller in water pumps, there is no systematic elaboration of the same methodology for centrifugal slurry pumps. The purpose of this paper is to improve the performance of a centrifugal slurry pump by means of Computational Fluid Dynamics (CFD). Therefore, an extensive parametric study has been carried out in order to optimize the shroud type impeller taking into account the blade discharge angle ( ), addition splitter blades and modified blade (backward long blades). Additionally, the tongue region of the original pump is re-designed. The results obtain...
Rheologica Acta, 2020
In this study, the analytical Herschel-Bulkley fluid model of a monotube mixed mode MR damper was... more In this study, the analytical Herschel-Bulkley fluid model of a monotube mixed mode MR damper was examined. The MR damper was modeled and simulated by using computational fluid dynamics (CFD) and magnetic finite elements analysis (FEA). The magnetic effects were modeled in a coupled manner with CFD. The actual rheological data was used in the CFD solver to find the cell-based viscosity by using a shear stress interpolation method. The MR damper was manufactured, and experiments were conducted to find the force-displacement and force-velocity correlations, and a good agreement was found between the numerical results and experimental data. The experimental results were also compared with analytical and numerical models under various current values. The CFD results are valuable in predicting the actual characteristics of the non-Newtonian flow inside an MR damper, and it can be used for various non-Newtonian fluid CFD models.
Thermal Science, 2020
The moisture content of oil-filled transformers insulation paper that is a cellulose-containing m... more The moisture content of oil-filled transformers insulation paper that is a cellulose-containing material comprises 8% to 10% of moisture by weight at ambient temperature and it is highly important to decrease the moisture content for effective use of a transformer. Vapor phase drying is more effective method for drying the insulation paper of the transformer as compared with other conventional methods due to less cycle time and energy consumption. The purpose of this paper is to design a solvent operated drying chamber in which drying of the insulation paper of oil filled transformer carried out. The approach of the present paper is to develop a numerical model to reduce the cycle time of the drying process. The unsteady flow, heat, and mass transfer phenomena were simulated by using CFD solver. Theoretical studies and a numerical model were conducted over thermal calculation in the drying process using solvent at different pressures. Theoretical calculations were used to validate t...
SAÜ Fen Bilimleri Enstitüsü Dergisi, 2016
Bu yayında namlulu silahların iç balistik prosesi tanımlanmıştır. İç balistik hesaplamalarına ili... more Bu yayında namlulu silahların iç balistik prosesi tanımlanmıştır. İç balistik hesaplamalarına ilişkin matematik model oluşturulmuştur. Model oluşturulurken barut tane geometrisine bağlı olarak geliştirilen biçim fonksiyonu kullanılmıştır. Modelin MATLAB ® programında kodu hazırlanmıştır. Modelin doğrulanmasında, literatürden temin edilen 40 mm silah sisteminin atış sonuçları kullanılmıştır. Söz konusu atışta kullanılan silah ve mermi parametreleri kodun çözümünde kullanılmıştır. Kodun çözümü ile atış sonuçları kıyaslanmıştır. Mermi çıkış hızı ve namlu içerisindeki maksimum basınç parametreleri açılarından yapılan kıyaslama sonucunda standart sapmanın %4 seviyesinde olduğu tespit edilmiştir. Böylelikle matematik modelin doğrulandığı sonucuna varılmıştır. Bu model kullanılarak silindirik, tek delikli silindirik ve küresel barut tanelerinin iç balistik performansına etkileri incelenmiştir.
Proceedings of the 1992 International Biomedical Engineering Days
The authors have investigated the spectral characteristics of healthy and pathological respirator... more The authors have investigated the spectral characteristics of healthy and pathological respiratory sounds. The method is based on auscultation. Respiratory sounds are recorded from both children and adults. A measurement setup is constructed and the recorded sounds are labelled as inspiration and expiration to observe the variations occurring in different phases. Power spectral densities (PSD) of the sounds are estimated
Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery, 2001
Three industrial-type centrifugal fans were designed, fabricated and tested in order to investiga... more Three industrial-type centrifugal fans were designed, fabricated and tested in order to investigate the effects of axial (tip) clearance between an unshrouded impeller and stationary casing, so that the flow field behavior may differ considerable from that of a shrouded centrifugal fan impeller. Tests were conducted under high temperatures of gas up to 1000 °C at six different values of tip clearance each. Test results showed that the tip leakage flow due to the tip clearance is an unavoidable factor, which deteriorates the fan performance, and therefore the impeller geometry should be designed considering the tip clearance losses.
Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2006
Performance of centrifugal fans with unshrouded impellers strongly depends upon complex configura... more Performance of centrifugal fans with unshrouded impellers strongly depends upon complex configuration of the asymmetrical flowfield in the axial direction, which is highly unsteady. The flowfield, in turn, is considerably affected by the design parameters of both scroll and impeller geometry, for which tip clearance is of particular interest. This article presents a three-dimensional computational fluid dynamics (CFD) simulation of the flowfield in three different unshrouded centrifugal fan impellers with varying tip clearances. A commercial CFD code, namely, Fluent V6.2.16 with a k-ɛ two-equation turbulence model was utilized in order to study the effects of tip clearance on the overall performance of each fan with the tip clearances ranging from 5 to 30 mm. The numerical results were compared with the experimental data reported previously in the literature by the present author and his colleagues, and excellent agreements were observed for each fan.
Journal of Fluids Engineering, 2004
Journal of Fluids Engineering, 2003
The feasibility of using artificial neural networks (ANN) in the prediction of head reduction of ... more The feasibility of using artificial neural networks (ANN) in the prediction of head reduction of centrifugal pumps handling slurries is examined. An ANN model is proposed and compared with the empirical correlation given by the present authors earlier. The comparison showed that the ANN could successfully be used for the prediction of head reductions of centrifugal slurry pumps. The mean deviation between predicted and experimental values is 5.86% which is reasonable for slurry handling processes.
Journal of Fluids Engineering, 2003
In order to optimally design a slurry transportation system, it is necessary to know how the pres... more In order to optimally design a slurry transportation system, it is necessary to know how the presence of solids will change the performance of the slurry pump to be installed. This paper makes the comparison of some existing correlations available in the literature to predict the head reduction factors of such centrifugal pumps handling slurries. For this purpose, a large number of published data for various centrifugal slurry pump tests in the literature have been used to develop a new correlation and then this correlation and all others have been tested against the data. For the proposed correlation, the mean and average deviations between the calculated and measured head reduction factor is 8.378 and 0.620%, respectively, for all data of mostly handling commercial slurries. It also produces 12.441% mean deviation in the prediction of efficiency ratio for 216 data points. Overall, the new correlation that can be applied to both metal and rubber lined pumps with impeller diameter u...
International Journal of Vehicle Design, 2010
Magnetorheological (MR) dampers have attracted interest from suspension designers and researchers... more Magnetorheological (MR) dampers have attracted interest from suspension designers and researchers because of their variable damping feature, mechanical simplicity, robustness, low power consumption and fast response. Therefore, optimisation of such devices is of particular interest to achieve optimal vibration control. This study deals with the geometrical optimisation of an MR shock damper using Taguchi experimental design approach. The optimal solutions of the MR damper were evaluated using analytical equations, which give the dynamic range of the damper under consideration. Optimal geometrical values obtained provided most performance in consideration of other nine alternatives of Taguchi experimental design specified for the study.
International Journal of Vehicle Design, 2012
Magnetorheological (MR) dampers have received remarkable attention due to being a potential techn... more Magnetorheological (MR) dampers have received remarkable attention due to being a potential technology to conduct semi-active control in mechanical systems in order to effectively suppress vibration. It is therefore important to understand the dynamic behaviour of such devices whose non-linear hysteresis is a complicated phenomenon. In the study, an MR damper has been designed, fabricated, tested and then its dynamic behaviour has been modelled with the classical Bouc-Wen hysteretic model. After that, the seven parameters of this model have been expressed in terms of only current excitation. By this, the total damping force has been given by a compact form in which the only independent variable is the current excitation. Finally, the model has been verified with experimental data and a good agreement has been observed.
International Journal of Thermal Sciences, 2011
Abstract The pressure drop and friction factor for the flow distilled water in microtubes with th... more Abstract The pressure drop and friction factor for the flow distilled water in microtubes with the diameters ranging from 0.20 mm to 0.589 mm were investigated experimentally. The experiments were carried out in the Reynolds number range of approximately 100–10000 and the length-to-diameter ratios (L/d) in the range of 16–265. It was observed that two different mechanisms of transition from laminar to turbulent flow occurred as smooth and abrupt. The pressure drop and friction factor values agreed with the values of classical channel flow theory. The L/d ratio had an important effect on the apparent friction factor in case of L/d
International Journal of Mechanical Sciences, 2010
In this study, an experimental and a theoretical study were carried out to predict the dynamic pe... more In this study, an experimental and a theoretical study were carried out to predict the dynamic performance of a linear magnetorheological (MR) fluid damper. After having designed and fabricated the MR damper, its dynamic testing was performed on a mechanical type shock machine under sinusoidal excitation. A theoretical flow analysis was done based on the Bingham plastic constitutive model to
International Journal of Mechanical Sciences, 2012
Magnetorheological (MR) dampers can be controlled effectively by a magnetic field and with minimu... more Magnetorheological (MR) dampers can be controlled effectively by a magnetic field and with minimum power requirement. Under the magnetic field, MR fluid behaves as a non-Newtonian fluid with controllable viscosity. Damper performance can be enhanced by getting to know better the non-Newtonian flow in the annular gap of piston head. In the study the non-Newtonian flow in the annular gap is investigated by a quasi-static analysis that enables to calculate plug thickness and damper force. Also CFD analysis of the MR damper is performed by using transient and deformed mesh to be able to simulate moving of piston head in the damper considering non-Newtonian regions. Results of the analyses have been compared to experimental data obtained from MR dampers manufactured for the study. Good agreement has been observed between experimental and analyses data. In addition, effects of stroke and velocity on the damper performance are examined in the study.
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Papers by Prof. Dr. Tahsin Engin