• Journal of the Korean Society for Precision Engineering
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• v.32 no.4
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• pp.369-375
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• 2015

This paper presents ejection of high viscosity fluids with magnetostrictive inkjet printhead(Magjet), which is not common with any other printhead. The MagJet uses a magnetostrictive material, Terfenol-D rod with 10-mm in diameter and 50-mm in length, as an actuation mechanism. It has been known that high viscosity is often an obstacle in ejecting small and mono-disperse droplets. We calculated required pressure with fluidic inertia (Bernoulli equation) and viscous loss (Hagen Poiseuille equation). The required pressure for ejecting a droplet is 1300kPa. The generated force and displacement with Terfenol-D rod are estimated to be 480N (2600kPa) and $28{\mu}m$, respectively. It was enough that Magjet eject high viscosity fluid (Max 1000cP). The experiments are performed to eject the high viscosity fluid with Magjet. The ejection of high viscosity fluids is successful with the aid of Terfenol-D's high performance.

• The KSFM Journal of Fluid Machinery
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• v.7 no.2 s.23
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• pp.21-26
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• 2004

In this study the effects of fluid viscosity on the pump performances for a conventional centrifugal pump were experimentally investigated. The study aimed to compare the pump characteristics between water and viscosity fluids. In order to measure the flow rate and pressure, v-notch welt and bourdon pressure gauges were used for the codes of KS B6301 and KS B6302. The working fluids were water, aqueous sugar and glycerin solutions. The results were summarized as follows : The experimental results were summarized as follows : the pump characteristics of the total head, shaft power, and efficiency with high viscosity fluids were different from those of water. When the viscosity of the applied fluid was increased, the total head and efficiency were more decreased than those of water. The decreasing gradients of the total head and the efficiency were larger than water due to the increased disk friction losses at the duty operation point. However, the shut-off head was almost constant regardless the viscosity of applied fluids. Each efficiency curves for the sugar $20w\%$ and glycerin $20w\%$ solutions was decreased up to $15.1\%$ and $34.4\%$ than that of water, respectively.

• Tribology and Lubricants
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• v.15 no.4
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• pp.343-353
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• 1999

The role of viscosity index improver's(Ⅶ) additives for modem engine lubrication is complex. Under the condition of atmosphere or low shear rate, the characteristics of Ⅶ added lubricant is verified and quoted frequently for mathematical model of lubricant behavior. However, recent research shows that added lubricant has the characteristics of shear thinning at high shear rate condition although it performs well enough over the whole range of working temperature. At high shear rate, they show significant decrease of apparent viscosity irrespective of temperature. Many experimental researches verify that Ⅶ added lubricant shows boundary film layer formation on the solid surface as well as shear thinning effect by its polymeric molecular characteristics. The intend of our research is to verify the effects of Ⅶ from the viewpoint of continuum mechanics, because conventional Reynolds'equation with only pressure-viscosity relation cannot fully predict the lubricant behavior under the Ⅶ added condition. In these aspects, Reynolds'equation of Newtonian fluid model lacks the reflection of real fluid behavior and there is no way to explain the non-linear characteristics of Ⅶ added lubricant. In this research, we mathematically modeled the Ⅶ added lubricant behaviors which are the characteristics of non-Newtonian fluid behavior at high shear rate and boundary film formation on the solid surface. The consideration of elastic deformation in the contact region is also included in our computation and finally the converged film pressure and the film thickness with elastic deformation are obtained. The results are compared with those of Newtonian fluid model.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.367-370
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• 2003

In this study the effects of fluid viscosity on the pump performances of a conventional centrifugal pump were experimentally studied. The study aimed to compare the pump characteristics for water and high viscosity fluids. The Working fluids are water, aqueous sugar solution and glycerin solution. The pump characteristics of total head and efficiency with high viscosity fluids were different. The performance curves of efficiency for the sugar and glycerin solutions were decreased up to 8.1% and 12.9% than that of water.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.192-198
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• 1999

The present study proposes modified temperature-dependent non-Newtonian viscosity model and investigates flow characters and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The proposed modified temperature dependent viscosity model has non-zero value near the high temperature and high shear rate region while on the existing viscosity models have zero value. Two versions of thermal boundary conditions involving difference combination of heated walls and adiabatic walls are analyzed in this study. The combined effect of temperature dependent viscosity, buoyancy, and secondary flow caused by second normal stress difference are ail considered. The Reiner-Rivlin model is adopted as a viscoelastic fluid model to simulate the secondary flow caused by second normal stress difference. Calculated Nusselt numbers by the modified temperature-dependent viscosity model gives under prediction than the existing temperature-dependent viscosity model in the regions of thermally developed with same secondary normal stress difference coefficients with experimental results in the regions of thermally developed. The heat transfer enhancement of the viscoelastic fluid in a 2:1 rectangular duct is highly dependent on the secondary flow caused by the magnitude of second normal stress difference.

• Tribology and Lubricants
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• v.20 no.1
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• pp.33-40
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• 2004

This study represents the newly advanced formulation of hydraulic fluids for extended drain interval and introduces the performance results of used oil samples from various excavators. The used oil samples, in this paper, show that there is a sharp change in viscosity drop and moderate additive depletion when viscosity index of hydraulic oil is very high. For the extension of hydraulic fluid life, it is necessary to improve the stability of viscosity and oxidation. New target properties from the used oil analysis were proposed for extended life. Performance of newly developed hydraulic oil based on used oil analysis is compared with previously used one. The properties of new formulation are the viscosity index of 140 and improved thermal stability consists of VHVI base oil. Field test results showed the possibility of extension of fluid life. Additionally, for development of high performance product, new required propertied and performances were discussed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.29-36
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• 2002

High fluid concrete unlike OPC concrete is made with various material, and the phase of fresh concrete is considerably different. In order to understand fluidity phase and mix properties of high fluid concrete, concrete is required to access as suspension structure which consists of aggregate and paste. The focus of this paper is to analyze the test results and quantify the effect of mix proportions of molar and fineness modulus of ,and on the properties of fresh mortar. The effect of water-binder ratio, sand-binder ration, content; of ggbs (by mass of total cementitious materials), and various contents of water reducing agent on the yield stress and plastic viscosity of the mix is studied. Based on the experimental results, the following conclusion; can be drawn: (1) The mixing time needed (or high fluid mortar was approximately two times more than that of ordinary portland mortar. (2) The fluidity phase of mortar could be explained by yield stress of mix and the fluidity of mortar. (3) As the content of ggbs increased, yield stress of mortar was decreased and plastic viscosity of it was increased. (4) For the high fluid mortar, it was appeared that sand-binder ratio should be below 1.5.

• Tribology and Lubricants
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• v.15 no.3
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• pp.248-256
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• 1999

Many tribological components in automobile engine undergo high load and sliding speed with thin film thickness. The lubrication characteristics of the components are regarded as ether hydrodynamic lubrication or boundary lubrication, whereas in a working cycle they actually have both characteristics. Many modem engine lubricants have various additives for better performance which make boundary film formation even under hydrodynamic lubrication regime. Conventional Reynolds equation with the viewpoints of continuum mechanics concerns only bulk viscosity of lubricant, which means that its simulation does not give insights on boundary lubrication characteristics. However, many additives of modern engine lubricant provide mixed modes of boundary lubrication characteristics and hydrodynamic lubrication. Especially, high molecular weight polymeric viscosity index improvers form boundary film on the solid surface and cause non-Newtonian fluid effect of shear thinning. This study has performed the investigation about journal bearing system with the mixed concepts of boundary lubrication and hydrodynamic lubrication which happen concurrently in many engine components under the condition of viscosity index improver added.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.453-464
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• 2002

The electrorheological(ER) fluid is a new material and is used for the mechanical motion devices such as semi-active suspensions, high speed clutches, and vibration isolators. The ER fluid applications need high voltage power supplies having special requirements to control the viscosity of the ER fluid. This paper deals with the development of the high voltage power supply for the semi-active suspension system using the ER fluid. The characteristics of the ER fluid are analyzed, and the design and implementation of the high voltage power supply are presented. It is well demonstrated through the experiment that the developed high voltage power supply shows a good performance suitable for the ER fluid application.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.61-64
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• 2000

In order to analyse the effect of the fluid viscosity changes on the centrifugal pump, the computer simulation method and the performance correction chart are used. The centrifugal pump is designed using the traditional method, and the 3D computational grid is generated for the impeller and casing. Working fluids are water, high viscous oil and muddy water. The viscosity of muddy water is measured by the unsteady capillary tube viscometer. The pump performances are predicted well through the computer simulation. The performance curves of head and efficiency for oil and muddy water are decreased. The torques of oil and muddy water, which is calculated by performance correction chart are predicted at a lower value than the computer simulation.