EXPERIMENTAL AND THEORETICAL INVESTIGATION OF HIGH-PRESSURE ARCS .1. THE CYLINDRICAL ARC COLUMN (2-DIMENSIONAL MODELING)

The properties of the free-burning are column are studied for ambient pressures of 0.1 MPa (i.e., atmospheric) to 10 MPa for applications in underwater welding and cutting as well as are discharge lamps, The in fluence of transverse magnetic fields is studied in Part II. A dc curr ent of 50-100 A is applied to an argon discharge with a conical tungst en cathode and a plane water-cooled anode which are separated by sever al millimeters. The electrical properties are measured, and the temper ature distribution is determined by spectroscopic means utilizing a tw o-dimensional charge-coupled device (CCD) sensor. A self-consistent nu merical solution of the conservation equations yields the temperature, velocity, pressure, and current distributions, The predicted are temp eratures agree well with the measured temperature distributions, An an alysis of the conservation equations shows that the are column becomes radiation dominated with increasing pressures resulting in small temp erature gradients within the column and large gradients at the boundar ies, It is found that a net emission coefficient might be used to acco unt for the radiative heat transfer in the investigated parameter rang e, The are constricts due to increased convective cooling especially a t the cathode, while temperatures and velocities are decreasing, The p ower expended in the column scales approximately with the square root of the ambient pressure in line with the radiation dominance, whereas the voltage drop across the electrode sheaths exhibits no pressure dep endence for a given current.