A Study of the Efficacy of Flame Electrical Resistance for Standoff Measurements During the Oxyfuel Cutting Process

Abstract

This is a study of the suitability of preheat flame electrical resistance as a potential method for measuring the standoff distance an oxyfuel cutting torch and a work piece. Careful scrutiny of forty seven (47) individual experiments demonstrate that when cut quality is good, there is a linear repeatable relationship between the two with uncertainty about ± .3mm (.015in). As the cut quality degrades, the formation of top-edge dross reduces the electrical path length in the flame, and momentary reduction in the reaction rate in the kerf reduces the free electrons in the flame, causing rises in flame resistance. In these conditions, measurement uncertainty reduces to ± 1mm (.040in) or worse.

Role of Secondary Ions on the i-v Characteristics of Oxyfuel Flame Subject to an Electric Field

“…𝜌 𝑎𝑣𝑔. = ∑ 𝜒 𝑖 𝜌 𝑖 𝑁 𝑖=1 (5) where, 𝑌 𝑖 is the mass fraction, 𝜒 𝑖 is the mole fraction, 𝜇 𝑖 is the viscosity, 𝜌 𝑖 is the density of component 𝑖, respectively. 𝑁 is the mixtures' total number of components.…”

“…It has been well established that high temperature reaction zones in flames conduct electricity due to the chemi-ionization process [1,2]. Prior works in the literature [3][4][5] indicated the current-voltage (i-v) relationship with different critical parameters (such as standoff, flow rate, fuel-oxygen ratio, etc.) of oxyfuel flame to be the salient electrical characteristic under electric field in the preheating process.…”

Non-Traditional Machining Techniques in Manufacturing Industries – An Overview

“…Oxyfuel cutting utilizes the heat generated by the combustion of gases along with oxygen [46]. A cutting torch delivers a carefully controlled mixture of fuel gas and oxygen to the work surface.…”

A model for a Langmuir sheath in a stagnating dense plasma with secondary ion formation

“…This simplified model provides solutions for the current-voltage characteristics of a sheath in a dense flowing plasma when surface chemistry contributes secondary ions. The problem is motivated by the recent discovery that strong transient signals in industrial ion current sensors [1] are caused by chemical reactions with carbon in the steel being cut or welded by oxyfuel processes [2,3]. In these systems, computer controlled torches issue an oxygen-fuel-gas flame to heat a steel work piece like in Figure 1.…”

“…There are three natural length scales in these problems [8], pp.406, with a fourth unique to this particular problem: (1) the mean free path between molecular collisions, l ; (2) the Debye length, λ; (3) the integral length scale, L, representing the macro-scale physical features of the system; and (4) the length over which secondary ions are formed above the surface. In low-pressure plasmas common to gas discharge tubes, l l  , so individual charged particle trajectories may be modeled without regard for collisions.…”