A PC-Based Synchronous Controller for NC Gear Grinding Machines Using Multithread CBN Wheel

1999 ◽  
Vol 123 (4) ◽  
pp. 590-597 ◽  
Author(s):  
T. Emura ◽  
L. Wang ◽  
M. Yamanaka ◽  
H. Nakamura ◽  
Y. Kato ◽  
...  
Keyword(s):  
Analog Circuits ◽  
High Speed ◽  
Production Costs ◽  
Two Phase ◽  
Pitch Accuracy ◽  
High Productivity ◽  
Cbn Wheel ◽  
Gear Grinding ◽  
Phase Type ◽  
Grinding Machines

This paper describes a synchronous controller for high-productivity NC gear grinding machines that use a screw-shaped CBN wheel of multithread. The authors developed a high-precision controller for productive-type NC gear grinding machines in 1995. Because it was based on analog circuits, it required very complex electrical circuits. In this paper, we propose a PC-based synchronous controller to decrease production costs and add useful functions to it. The most useful one added this time is a function to increase pitch accuracy of gear ground with the multithread CBN wheel. Next useful one is a function to attain high-accuracy initial meshing between gear and CBN wheel. Because grinding-spindle and work spindle rotate at a high-speed, two-phase type PLL is applied to the controller. Grinding experiments showed that the newly developed controller has excellent performance.

A Study on a High-Speed NC Gear Grinding Machine Using Screw-Shaped CBN Wheel

1992 ◽  
Author(s):  
T. Emura ◽  
L. Wang ◽  
A. Arakawa
Keyword(s):  
High Speed ◽  
Reduction Gear ◽  
Grinding Wheel ◽  
Magnetic Head ◽  
Two Phase ◽  
Cbn Wheel ◽  
Gear Grinding ◽  
Phase Type ◽  
Rotary Speed ◽  
Grinding Machine

Abstract This paper describes a basic study for the development of a high-speed NC gear grinding machine using screw-shaped CBN wheel. Gear grinding machines using screw-shaped grinding wheel have already developed by Reishauer and others. However, their productivity is not high, because they use one thread type grinding wheel and the rotary speed of the workspindle is very low. The maximum rotary speed of the grinding spindle developed by the authors is 12,000 rpm and that of workspindle is 3,000 rpm. They are enough speed for gear grinding. The desired accuracy for an angle sensor of grinding spindle is more than 20 ″pp in the case of the multithread type grinding wheel. The ordinary shaft encoder cannot respond at such a high-speed. Therefore the authors used a magnetic scale of high-accuracy and an induction type magnetic head. After experiments, it became clear that two-phase type PLL proposed by T. Emura is useful for detecting low level signals obtained from the magnetic head. Since the maximum rotary speed of the workspindle is raised to 3,000 rpm, we cannot use any reduction gear. Thus a direct-drive method with an inertial damper was used. The workspindle is controlled by using the two-phase type PLL. When we grind gears, the initial setting between rotary angles of grinding wheel and work is required. The authors tried to automatically set the initial rotary angles by using a CCD camera and a microcomputer.

A Study on a High-Speed NC Gear Grinding Machine Using a Screw-Shaped CBN Wheel

1994 ◽  
Vol 116 (4) ◽  
pp. 1163-1168 ◽  
Author(s):  
T. Emura ◽  
L. Wang ◽  
A. Arakawa
Keyword(s):  
High Speed ◽  
Wave Length ◽  
Ccd Camera ◽  
Grinding Wheel ◽  
Direct Drive ◽  
Two Phase ◽  
Basic Study ◽  
Cbn Wheel ◽  
Gear Grinding ◽  
Grinding Machine

This paper describes a basic study for designing a high-speed NC gear grinding machine using a screw-shaped CBN wheel. Gear grinding machines using screw-shaped grinding wheels are quite prevalent. However, their productivity is not high, because the rotary speed of their spindles is very low. Therefore, the authors raised the maximum rotary speeds of the grinding spindle and the workspindle to 12,000 rpm and 3,000 rpm, respectively, in order to use a high-speed multithread CBN wheel. A magnetic scale whose wave length is long but pitch accuracy is high enough was used for detecting such a high-speed rotation. Since the wave length of the scale is long, a high-resolution interpolation using two-phase type PLL proposed by Emura was used. Both spindles are direct-drive type for removing backlash. When we grind gears, the initial setting between rotary angles of grinding wheel and work is required. The authors tried to automatically set the initial rotary angles by using a CCD camera.

Development of high speed servo-spindle for NC gear grinding machines

Mechatronics ◽  
1992 ◽  
Vol 2 (5) ◽  
pp. 417-432 ◽  
Author(s):  
Takashi Emura ◽  
Akira Arakawa ◽  
Michiaki Hashitani
Keyword(s):  
High Speed ◽  
Gear Grinding ◽  
Grinding Machines

Two-Phase Short Circuit in the Power Grid Powered by a Transformer with a Y/Δ-11 Winding Connection

2020 ◽  
pp. 25-30
Author(s):  
Aleksandr S. Serebryakov ◽  
Vladimir L. Osokin ◽  
Sergey A. Kapustkin
Keyword(s):  
High Speed ◽  
Short Circuit ◽  
Relay Protection ◽  
Electric Circuit ◽  
Operational Reliability ◽  
Research Purpose ◽  
Industrial Complex ◽  
Two Phase ◽  
Short Circuit Currents ◽  
Secondary Winding

The article describes main provisions and relations for calculating short-circuit currents and phase currents in a three-phase traction transformer with a star-triangle-11 connection of windings, which feeds two single-phase loads in AC traction networks with a nominal voltage of 25 kilovolts. These transformers provide power to the enterprises of the agro-industrial complex located along the railway line. (Research purpose) The research purpose is in substantiating theoretical equations for digital intelligent relay protection in two-phase short circuits. (Materials and methods) It was found that since the sum of instantaneous currents in each phase is zero, each phase of the transformer works independently. We found that this significantly simplifies the task of analyzing processes with a two-phase short circuit. In this case, the problem of calculating short-circuit currents in the traction network can be simplified by reducing it to the calculation of an ordinary electric circuit with three unknown currents. (Results and discussion) The article describes equations for calculating short-circuit resistances for one phase of the transformer when connecting the secondary winding as a star or a triangle. The currents in the phases of the transformer winding at short circuit for the star-triangle-11 and star-star-with-ground schemes are compared. It was found that when calculating short-circuit currents, there is no need to convert the secondary winding of the traction transformer from a triangle to a star. (Conclusions) It was found that the results of the research can be used in the transition of relay protection systems from electromagnetic relays to modern high-speed digital devices, which will increase the operational reliability of power supply systems for traction and non-traction power consumers.

Development and Validation of a Three-Dimensional Multiphase Flow CFD Analysis for Journal Bearings in Steam and Heavy Duty Gas Turbines

2012 ◽  
Author(s):  
Stephan Uhkoetter ◽  
Stefan aus der Wiesche ◽  
Michael Kursch ◽  
Christian Beck
Keyword(s):  
Experimental Data ◽  
Multiphase Flow ◽  
Gas Turbines ◽  
High Speed ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Journal Bearings ◽  
Heavy Duty ◽  
Present Contribution ◽  
Two Phase

The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach including cavitation and air entrainment for high-speed turbo-machinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty type gas turbine journal bearings.

Experimental Characterization of a Modified Airlift Pump

2014 ◽  
Author(s):  
Afshin Goharzadeh ◽  
Keegan Fernandes
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
High Speed ◽  
Water Flow Rate ◽  
High Speed Photography ◽  
Two Phase ◽  
Inner Diameter ◽  
Airlift Pump ◽  
Flow Map ◽  
Churn Flow

This paper presents an experimental investigation on a modified airlift pump. Experiments were undertaken as a function of air-water flow rate for two submergence ratios (ε=0.58 and 0.74), and two different riser geometries (i) straight pipe with a constant inner diameter of 19 mm and (ii) enlarged pipe with a sudden expanded diameter of 19 to 32 mm. These transparent vertical pipes, of 1 m length, were submerged in a transparent rectangular tank (0.45×0.45×1.1 m3). The compressed air was injected into the vertical pipe to lift the water from the reservoir. The flow map regime is established for both configurations and compared with previous studies. The two phase air-water flow structure at the expansion region is experimentally characterized. Pipeline geometry is found to have a significant influence on the output water flow rate. Using high speed photography and electrical conductivity probes, new flow regimes, such as “slug to churn” and “annular to churn” flow, are observed and their influence on the output water flow rate and efficiency are discussed. These experimental results provide fundamental insights into the physics of modified airlift pump.

Effect of Pressure on Bubble Growth Within Liquid Droplets at the Superheat Limit

1982 ◽  
Vol 104 (4) ◽  
pp. 750-757 ◽  
Author(s):  
C. T. Avedisian
Keyword(s):  
Vapor Bubble ◽  
Bubble Growth ◽  
High Speed ◽  
Ambient Pressure ◽  
Organic Liquid ◽  
Liquid Droplets ◽  
Growth Data ◽  
Two Phase ◽  
Photographic Evidence ◽  
Good Agreement

A study of high-pressure bubble growth within liquid droplets heated to their limits of superheat is reported. Droplets of an organic liquid (n-octane) were heated in an immiscible nonvolatile field liquid (glycerine) until they began to boil. High-speed cine photography was used for recording the qualitative aspects of boiling intensity and for obtaining some basic bubble growth data which have not been previously reported. The intensity of droplet boiling was found to be strongly dependent on ambient pressure. At atmospheric pressure the droplets boiled in a comparatively violent manner. At higher pressures photographic evidence revealed a two-phase droplet configuration consisting of an expanding vapor bubble beneath which was suspended a pool of the vaporizing liquid. A qualitative theory for growth of the two-phase droplet was based on assuming that heat for vaporizing the volatile liquid was transferred across a thin thermal boundary layer surrounding the vapor bubble. Measured droplet radii were found to be in relatively good agreement with predicted radii.

scholarly journals Bubble Dynamics in a Two-Phase Bubbly Mixture

2010 ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Discharge Voltage ◽  
Large Bubble ◽  
Water Mixture ◽  
Two Phase ◽  
Mixture Density ◽  
Bubbly Medium

The dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is investigated experimentally and the results are provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of varying intensities. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the pressure imposed in the container. The size and concentration of the fine bubbles can be controlled by the electrolysis voltage, the length, diameter, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the bubble characteristic quantities such as maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and the mixture is observed using high speed video photography. The void fraction/density of the bubbly mixture in the fluid domain is measured as a function of time and space using image analysis of the high speed movies. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to simple compressible equations employed for spherical bubbles including a modified Gilmore Equation. Suggestions for improvement of the modeling are then presented.

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