Application of high-power plasma gun for thermal cycle testing of refractory foams

Abstract

A high-power hollow-cathode plasma-gun was utilized to perform durability tests of advanced silicon carbide (SiC) foam materials under extreme thermal cyclic loading conditions. SiC-foam is a primary candidate for in-cylinder thermal regenerators in diesel engines. The SiC regenerator would be exposed to rapid thermal cycling by alternating hot (∼700°C) and cold (∼50°C) gases with cycling rates ranging between 3 and 50 Hz and with flow rates of 0.1–0.3 l/cycle at gas pressures between 1 and 2 atm. Simulation of these conditions outside a combustion engine would require an elaborate experimental setup capable of alternating flow between hot and cold gas reservoirs. Furthermore, a high-temperature rapid gas flow switching system would have to be developed. Instead, a high power plasma gun was used to deliver the required hot working gas at a flow rate of 60 l/min and at a pressure of ∼2 atm. Instead of an elaborate gas flow switching system an electrically driven open flathead engine was used to alternate between the cold and hot gases at frequencies of up to 5 Hz. The plasma gun was found to be a highly economical system for delivering hot argon gases at necessary flow rates of 0.25 l/cycle. A description of the experimental setup using the high-power plasma gun is given and representative results of the SiC-foam thermal cycling performance are reported.