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TECHNICAL PAPERS

Prevention of Nozzle Wear in Abrasive Water Suspension Jets (AWSJ) Using Porous Lubricated Nozzles

[+] Author and Article Information
Umang Anand, Joseph Katz

The Johns Hopkins University, Department of Mechanical Engineering, Baltimore, MD 21218

J. Tribol 125(1), 168-180 (Dec 31, 2002) (13 pages) doi:10.1115/1.1491977 History: Received October 02, 2001; Revised April 16, 2002; Online December 31, 2002
Copyright © 2003 by ASME
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References

Figures

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A Sketch illustrating the principles of the method for preventing nozzle wear
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Schematic of the system supplying slurry particles and lubricant to the test chamber
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SEM images of (a) the clogged porous surface when a filter was not used, showing a coating of dirt on the surface and dirt inside the pores, and (b) the porous surface recorded after the experiments with a filter installed, free from blockage
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Components of the two-dimensional nozzle housing
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(a) The shape of the porous inserts and the slot in which they were inserted in the two-dimensional housing, and (b) geometry of the two-dimensional nozzle. All dimensions are in mm.
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(a) Components of the axisymmetric nozzle housing, and (b) cross-section of the porous axisymmetric nozzle. All dimensions are in mm.
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SEM micrograph of the top of the axisymmetric nozzle
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SEM micrograph of the cut section of the axisymmetric nozzle
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Effect of EDM machining parameters on the porous surface. SEM image: Top to bottom—improvements by decreasing the cutting speed and energy level.
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Schematic of the setup for data acquisition
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(a) The nozzle with water only, (b) with water and oil, and (c) the oil layers on the walls of the nozzle. The flow was from top to bottom. The section shown is 4.42<x<5.84 mm and 0.145 mm wide. For definition of x, see Fig. 5(b).
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(a) The nozzle with water and tracer particles, and (b) enhanced double exposure image of the tracers. The flow was from top to bottom. For location, see Fig. 11.
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The converging section of the nozzle with enhanced double exposure image of the tracers. The flow was from top to bottom. The section shown is 0.84<x<2.26 mm. For definition of x, see Fig. 5(b).
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(ac) show three samples of double exposure images of the nozzle with water and oil along with slurry (large dark objects) and tracer particles (small dark objects). The flow was from top to bottom. For location, see Fig. 11.
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The centerline liquid velocity in the two-dimensional nozzle measured using PIV, with and without injection of oil. The velocities were obtained using 135×24 measurements for each case. Every 5th data point, representing an average of 24 measurements, is shown for clarity. The error bars represent the standard deviation values at these points. For dimensions, see Fig. 5(b).
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Measured slip velocity of the slurry particles with nominal diameter of 20–45 μm close to the exit from the nozzle (4.42<x<6.35 mm) and the linear least squares fit to the data. The standard deviation for all the values is 5.2 m/s. For definition of x, see Fig. 5(b).
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(a) The 10th order curve fit to the measured liquid velocity and the computed velocity of a 25 μm spherical slurry particle based on Eq. (1); and (b) the computed slip velocities at the centerline of the nozzle for several diameters of slurry particles. For dimensions, see Fig. 5(b).
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Slurry particles impinging the nozzle walls. The flow was from top to bottom. The section shown is 4.42 mm<x<5.03 mm. For definition of x, see Fig. 5(b).
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Time taken to empty the 125 cm3 reservoir for three different oils
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The reference case: SEM images of the nozzle exit recorded (a) before and (b) after 105 minutes of test using abrasive slurry but without any oil injection
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SEM images of the nozzle exit recorded before and after 105 minutes of test with (a) oil viscosity μo=1800 mm2/s, and flow rate ratio R=0.024; (b) μo=1800 mm2/s,R=0.014; and (c) μo=460 mm2/s,R=0.041.
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SEM images of the cut section of the nozzles recorded after 105 minutes of test: (a) using abrasive slurry but without oil injection (nozzle of Fig. 20), and (b) using abrasive slurry and injection of oil with μo=1800 mm2/s and R=0.024 (nozzle of Fig. 21(a)).
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SEM images of the top of the nozzles recorded after 105 minutes of test (a) without any oil injection (nozzle of Fig. 20); and (b) μo=1800 mm2/s and R=0.024 (nozzle of Fig. 21(a)).
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The effect of oil viscosity and flow rate on the increase in effective nozzle diameter due to wear. Without oil the wear was 111 percent. Each point represents the overall wear after twenty-one identical runs, each lasting five minutes, and each performed with a fresh load of slurry and lubricant.

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