Mechanisms of Metal Removal by Impacting Dust Particles

Abstract

This is a two-part paper, which stresses the materials science approach to understanding dust erosion mechanisms. The first part is an experimental phase, studying the effects upon solid-particle erosion, of such material and environmental variables as target alloy composition and heat-treat condition; dust particle velocity, size, concentration, velocity, and kinetic energy; carrier-gas true temperature and impingement angle. All test variables and their limits were chosen to simulate the range of engineering conditions and erosive environments encountered in helicopter turbine service. Actual erosion data are compared with erosion levels predicted by existing theories on particulate erosion. The second part is a diagnostic phase, programmed to detect and study visible phenomena associated with the erosion processes, using high-magnification electron microscopy. Phenomenological evidence obtained from the erosion surfaces and erosion products are used to define probable physical models of the erosion mechanisms.

Water Sand Gun as a Tool.

“…In the developed equation 3the erosion losses vary with the jet velocity to the power 2.55 at constant sand concentration. This agrees well with Finnie's indication in reference [2] that the values of velocity exponent from 2.05 to 2.44 are more realistic. c) Correlated equation (4) gives that the erosion produced by a given weight of dust is increased by decreasing concentrationaleads to more superimposed particles impacts, thus being less effective than if the same weight of dust is used with less concentration.…”

“…For either the efficiency of erosion as related to the used mass of impacting particles or to the energy consumed by the jet, it has a maximum value at an impingement angle of 33 . b) Erosion losses vary with the jet velocity to the power 1.85 for a fixed quantity of abrasives, this is expected as the erosion loss per particle is directly proportional to the incoming particle's kinetic energy as illustrated in reference [2]. In the developed equation 3the erosion losses vary with the jet velocity to the power 2.55 at constant sand concentration.…”

Aerosol particle deposition and distribution in bifurcating ventilation ducts

“…Aerosols have been identified to come from various sources: environment, equipment activities, smoking, cooking, etc. Malfunctioning of semiconductor [3], erosion in machinery [4] and health effects [5] are some of the important problems caused by deposition of particles. Inhaled particles can deposit in the respiratory tree [6] and trigger significant health problems.…”

Analysis of the high-temperature particulate collection problem

“…Following Waldmann, 1 0 0 the diffusion-imposed force for a binary medium can be expressed as (53) where a12 is the diffusion slip factor, D 1 2 is the binary gas diffusion coefficient, and 4 is the concentration of the gas component which is being collected. Equating this force with the Stokes drag yields Vn = c 12012(-V0) (54) Both theoretical and empirical expressions are available 1 0 0 for al2 and D12, This result shows that the drift velocity is independent of particulate diameter and will increase with increasing temperature because of D12,…”