scholarly journals Influence of Nozzle Jet Flushing on Working Fluid Flow and Wire Electrode in Trim-cut WEDM

Procedia CIRP ◽  
2020 ◽  
Vol 95 ◽  
pp. 250-254
Author(s):  
Hiroki Iwai ◽  
Tomonori Ebisu ◽  
Akira Okada ◽  
Haruya Kurihara
Keyword(s):  
Fluid Flow ◽  
Working Fluid ◽  
Wire Electrode ◽  
Trim Cut

scholarly journals Improving Electrical Discharge Machining Process for Bodies of Rotation

2020 ◽  
pp. 313-324
Author(s):  
Victor Bokov ◽  
◽  
Oleh Sisa ◽  
Vasyl Yuryev ◽  
◽  
...  
Keyword(s):  
Working Conditions ◽  
Sliding Friction ◽  
Electrical Discharge Machining ◽  
Electric Arc ◽  
Working Fluid ◽  
Wire Electrode ◽  
Electrode Tool ◽  
Electrode Holder ◽  
The Wire ◽  
Machining Productivity

In modern mechanical engineering, electrical discharge machining (EDM) methods are widely used for machining bodies of rotation from difficult-to-machine materials. Those methods ensure sparing cutting and make it possible to machine any electrically conductive material irrespective of its physical and chemical properties, in particular hardness. There is a known method for dimensional machining of bodies of rotation with electric arc using a wire electrode tool that is pulled along in the machining area thus "compensating" for that tool's EDM wear and tear. The machining accuracy is therefore significantly heightened. However, when implementing this method, an effect of splashing the working fluid outside the working area of the machine and a pronounced luminous effect from the burning of the electric arc in the machining area are observed. That worsens the working conditions. In addition, when pulling the wire electrode tool along the convex surface of the electrode holder, the sliding friction arises, which eventually leads to mechanical destruction of the contact point. As a result, a deep kerf is formed on the electrode holder. When the depth of the kerf reaches the diameter of the wire electrode tool, the destruction of the electrode holder by the electric arc begins. Consequently, the durability of the electrode holder in the known method is unsatisfactory. A method of dimensional machining of bodies of rotation with electric arc using a wire electrode tool with the immersion of the machining area in the working fluid has been proposed, which makes it possible to improve the working conditions of the operator by eliminating the effect of fluid splashing and removing the luminous effect of arc burning in the machining area. In addition, it has been proposed to make the electrode holder in the form of a roller that rotates with a guide groove for the wire electrode tool, while the nozzle for creating the transverse hydrodynamic fluid flow has been proposed to be mounted in a separate fixed housing that is adjacent to the electrode holder. This technical solution replaces the sliding friction with the rolling one thus enhancing the durability of the electrode holder. Mathematical models of the process characteristics of the DMA-process (dimensional machining with electric arc) for bodies of rotation using a wire electrode tool with the immersion of the machining area in the working fluid have been obtained that make it possible to control the machining productivity, the specific machining productivity, the specific electric power consumption, and the roughness of the surface machined.

Experimental analysis on thermal and friction factor characteristics of fluid flow in tube with novel double strip helical screw tape

2019 ◽  
Vol 234 (6) ◽  
pp. 874-886
Author(s):  
Shashank R Chaurasia ◽  
RM Sarviya
Keyword(s):  
Nusselt Number ◽  
Fluid Flow ◽  
Friction Factor ◽  
Experimental Analysis ◽  
Flow Characteristics ◽  
Performance Ratio ◽  
Working Fluid ◽  
Flow Rates ◽  
Twist Ratio ◽  
Single Strip

An experimental analysis has been carried out to investigate the thermal and friction factor characteristics of fluid flow in a tube with double strip helical screw tape (DS-HST) inserts with different values of twist ratio and compared with single strip helical screw tape inserts and plain tube. Water is used as a working fluid at different flow rates with constant heat flux conditions. CFD analysis is also carried out to visualize thermal and fluid flow characteristics of fluid flow in tube with inserts. Experimental results have showed that Nusselt number and friction factor have attained excellent enhancement with double strip helical screw tape inserts in the range of flow rates than single strip helical screw tape inserts at the value of twist ratio 1.5. Correlation is also developed for Nusselt number with a range of Reynolds number, twist ratio and number of strips. Moreover, the performance ratio has attained maximum value at twist ratio of 2.5 with high values of flow rate. It is concluded that DS-HST is able to attain enhancement in the efficiency of heat exchanger, causing a reduction in size for thermal applications.

Three Dimensional Dynamic Analysis of a Piezoelectric Valveless Micropump: Effects of Working Fluid

2012 ◽  
Author(s):  
Ersin Sayar ◽  
Bakhtier Farouk
Keyword(s):  
Fluid Flow ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Piezoelectric Element ◽  
Working Fluid ◽  
Working Fluids ◽  
Valveless Micropump ◽  
Velocity Flow ◽  
Layer Membrane ◽  
Fluid Flow Analysis

Coupled structural and fluid flow analysis of a piezoelectric valveless micropump is carried out for liquid transport applications. The valveless micropump consists of trapezoidal prism inlet/outlet elements; the pump chamber, a thin structural layer (Pyrex glass) and a piezoelectric element (PZT-5A), as the actuator. Two-way coupling of forces and displacements between the solid and the liquid domains in the systems are considered where actuator deflection and motion causes fluid flow and vice-versa. Flow contraction and expansion (through the trapezoidal prism inlet and outlet respectively) generates net fluid flow. The pressure, velocity, flow rate and pump membrane deflections of the micropump are investigated for six different working fluids (acetone, methanol, ethanol, water, and two hypothetical fluids). For the compressible flow formulation, an isothermal equation of state for the working fluid is employed. Three-dimensional governing equations for the flow fields and the structural-piezoelectric bi-layer membrane motions are considered. Comparison of the pumping characteristics of the micropumps operating with different working fluids can be utilized to optimize the design of MEMS based micropumps in drug delivery and biomedical applications.

Influence of Flow Acceleration on Convection Heat Transfer of CO2 at Supercritical Pressures and Air in a Vertical Micro Tube

2010 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

The convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at relatively high Reynolds numbers (Rein = 6500), various heat fluxes and flow directions are investigated experimentally and numerically. The effects of buoyancy and flow acceleration resulting from the dramatic property variations are studied. The Results show that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference in the local wall temperature between upward and downward flow is very small when the other test conditions are held the same, which indicates that for supercritical CO2 flowing in a micro tube as employed in this study, the buoyancy effect on the convection heat transfer is insignificant and the flow acceleration induced by the axial density variation with temperature is the main factor leading to the abnormal local wall temperature distribution at high heat fluxes. The predicted temperatures using the LB low Reynolds number turbulence model correspond well with the measured data. To further study the influence of flow acceleration on the convection heat transfer, air is also used as the working fluid to numerically investigate the fluid flow and heat transfer in the vertical micro tube. The results show that the effect of compressibility on the fluid flow and heat transfer of air in the vertical micro tube is significant but that the influence of thermal flow acceleration on convection heat transfer of air in a vertical micro tube is insignificant.

Numerical Anaysis of a Thermopneumatic Micropump

2010 ◽  
Author(s):  
S. Shahsavari ◽  
M. B. Shafii ◽  
M. H. Saidi
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Working Fluid ◽  
Structure Interaction ◽  
Positive Displacement ◽  
Dimensional Simulation ◽  
Center Deflection ◽  
Bidirectional Flow ◽  
Secondary Fluid

Thermopneumatic micropump is one type of positive displacement micropump, which has many applications due to its relatively large stroke volume, low working voltage, and simple fabrication in microscale. In this paper, a numerical study of heat transfer and fluid flow in a valveless thermopneumatically driven micropump is presented. For rectifying the bidirectional flow, a nozzle and a diffuser are used as the inlet and outlet channels of the chamber. Since the fluid flow is induced by the motion of a diaphragm, the numerical simulation includes fluid structure interaction, which requires applying a dynamic mesh. The domain of solution is divided into two sections; the actuator unit, which contains the secondary fluid, and the main chamber through which the working fluid is passing. The temperature distribution, the pressure variations, and the center deflection of the diaphragm are obtained. In order to validate the model, the numerical results are compared with some experimental data, which shows fair consistency. According to the results of the three dimensional simulation, the rectification efficiency for the nozzle and diffuser channels depends on the frequency.

Fluid Flow and Boiling Heat Transfer in Mini Channels

2010 ◽  
Author(s):  
M. Venkatesan ◽  
M. Aravinthan ◽  
Sarit K. Das ◽  
A. R. Balakrishnan
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Boiling Heat Transfer ◽  
Industrial Applications ◽  
Tube Diameter ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Mini Channels ◽  
Micro Propulsion

Two phase flows in mini channels occur in many industrial applications such as electronic cooling, compact heat exchangers, compact refrigeration systems and in micro propulsion devices. Due to its significance, research on two phase flow in mini channels has become attractive. However, in recent times a controversy exists whether flow in minichannel is different from macro flow because there are still substantial disagreements among various experimental results. In the present study an experimental investigation is carried out for fluid flow and boiling heat transfer characteristics of mini channels with tube diameters ranging from 1–3mm. The tubes were made of SS with water as the working fluid. The variation in friction factor and Nusselt number with decrease in tube diameter for single phase flow was systematically studied. The point of Onset of Nucelate Boiling (ONB) was identified based on wall temperature profile. The effect of heat flux and mass flux on two phase pressure drop with three different tube diameters during sub cooled boiling were investigated. The results reveal that there is an unmistakable effect of tube diameter on fluid friction and onset of boiling during sub cooled boiling in tubes of mini channel dimensions.

Evaluation of Vibration Characteristics for Reactor Coolant Pump Considering Fluid Flow Effect

2014 ◽  
Author(s):  
Ik Joong Kim ◽  
Min Chul Kim ◽  
Gyu Ho Jang ◽  
Dae Hee Jeong ◽  
Oak Sug Kim ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fluid Flow ◽  
Response Spectrum ◽  
Vibration Characteristics ◽  
Working Fluid ◽  
Element Analysis ◽  
Coolant Pump ◽  
Flow Effect ◽  
Unbalance Response

Reactor coolant pump (RCP) is designed for the heat transfer of heat which is generated from reactor vessel to steam generators by circulating the coolant water. RCP is the only rotating equipment in the nuclear steam supply system (NSSS). Therefore, the problem of vibration has arisen caused by the hydraulic forces of the working fluid. These forces can drastically alter the critical speeds and stability characteristics and can act as significant destabilizing forces. So, vibration evaluation of RCP has been considered as a very important issue [1]. Among them, unbalance response caused by weight of unbalancing of rotating shaft could have serious effects on the entire rotor system. Thus, precise unbalance response spectrum analyses are required. In general, in order to evaluate the unbalance response characteristics for centrifugal pump, finite element analysis was performed according to the ISO 1940-1 standard. However, finite element analysis according to the ISO 1940-1 standard does not considering fluid flow effect. So, finite element analysis result and experimental results may be some differences. Vibration characteristics of RCP has affected by fluid flow effect induced from working fluid. Therefore, in order to understand vibration characteristics for the RCP shaft assembly considered in actual operating condition, rotor dynamic analysis should be performed considering the fluid flow effect. In this research, owing to accurately evaluate the vibration characteristics for the RCP considering hydro forces due to the fluid flow, we measured the bearing force and moment take into account the fluid-induced force. And then response spectrum analysis of RCP shaft assembly was performed considering fluid induced bearing radial forces which are measured values. Lastly, evaluate the vibration characteristics considering effect of fluid flow according to the number of revolution.

scholarly journals Numerical simulation of concentrating solar collector P2CC with a small concentrating ratio

2012 ◽  
Vol 16 (suppl. 2) ◽  
pp. 471-482 ◽  
Author(s):  
Velimir Stefanovic ◽  
Sasa Pavlovic ◽  
Marko Ilic ◽  
Nenad Apostolovic ◽  
Dragan Kustrimovic
Keyword(s):  
Mathematical Model ◽  
Fluid Flow ◽  
Solar Radiation ◽  
Solar Energy ◽  
Radiation Intensity ◽  
Solar Collector ◽  
Numerical Procedure ◽  
Working Fluid ◽  
Flow Rates ◽  
Solar Radiation Intensity

Solar energy may be practically utilized directly through transformation into heat, electrical or chemical energy. A physical and mathematical model is presented, as well as a numerical procedure for predicting thermal performances of the P2CC solar concentrator. The demonstrated prototype has the reception angle of 110? at concentration ratio CR = 1.38, with the significant reception of diffuse radiation. The solar collector P2CC is designed for the area of middle temperature conversion of solar radiation into heat. The working fluid is water with laminar flow through a copper pipe surrounded by an evacuated glass layer. Based on the physical model, a mathematical model is introduced, which consists of energy balance equations for four collector components. In this paper, water temperatures in flow directions are numerically predicted, as well as temperatures of relevant P2CC collector components for various values of input temperatures and mass flow rates of the working fluid, and also for various values of direct sunlight radiation and for different collector lengths. The device which is used to transform solar energy to heat is referred to as solar collector. This paper gives numerical estimated changes of temperature in the direction of fluid flow for different flow rates, different solar radiation intensity and different inlet fluid temperatures. The increase in fluid flow reduces output temperature, while the increase in solar radiation intensity and inlet water temperature increases output temperature of water. Furthermore, the dependence on fluid output temperature is determined, along with the current efficiency by the number of nodes in the numerical calculation.

Digital Control of Working Fluid Flow Rate for an OTEC Plant

1986 ◽  
Vol 108 (2) ◽  
pp. 111-116 ◽  
Author(s):  
M. Nakamura ◽  
N. Egashira ◽  
H. Uehara
Keyword(s):  
Adaptive Control ◽  
Fluid Flow ◽  
Control System ◽  
Control Theory ◽  
Digital Control ◽  
Working Fluid ◽  
Fluid Flow Rate ◽  
Control Performance ◽  
Digital Control System

The role of control in operating an OTEC plant efficiently is of great importance. This paper describes digital control of working fluid rate based on an adaptive control theory for the “Imari 2” OTEC plant at Saga University. Provisions have been made for linkage between the software of the adaptive control theory and the hardware of the OTEC plant. We can obtain satisfactory control performance using this digital control system.

Computational Fluid Dynamics Analysis of Working Fluid Flow and Machining Debris Movement in End Electrical Discharge Milling and Mechanical Grinding Compound Machining

2012 ◽  
Vol 621 ◽  
pp. 191-195 ◽  
Author(s):  
Ren Jie Ji ◽  
Yong Hong Liu ◽  
Chao Zheng ◽  
Fei Wang ◽  
Yan Zhen Zhang ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Flow Field ◽  
Electrical Discharge ◽  
Great Influence ◽  
Working Fluid ◽  
Tool Electrode ◽  
Process Performance ◽  
Mechanical Grinding ◽  
Gap Flow ◽  
Computational Fluid Dynamics Analysis

The working fluid flow and the machining debris movement in the machining gap exercise a great influence on the process performance in end electrical discharge milling and mechanical grinding compound machining. In this paper, the working fluid flow and the machining debris movement in the machining gap are modeled based on the liquid-solid two-phase flow theory. The gap flow field is calculated with the software of Fluent, and the velocity field and the pressure field are analyzed. The results show that in the gap flow field of the compound machining, the working fluid flow can be accelerated, and the machining debris can be ejected timely by the rapid rotation of the tool electrode, so the compound process performance can be enhanced.

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