GRAPHITE COMBUSTION IN HIGH ENTHALPY SUPERSONIC FLOW

SPES (Small Planetary Entry Simulator) is an arc-heated facility in operation for a long time at the Laboratory of Aerothermodynamics of DIAS in Naples. The main components of SPES are an electric arc- heater (plasma torch Sulzer-Metco type 9MB) operating with pure nitrogen, a mixing chamber in which the plasma of nitrogen can be mixed with cold gases to simulate planetary atmospheres (eg. oxygen, carbon dioxide, methane); some conical nozzles (area ratio of 4, 20, 56, 100) for operation in supersonic/hypersonic regimes; a cylindrical chamber vacuum. For normal applications of atmospheric re-entry simulation we have the following values of the system parameters: mass flow rate: 1 g/s - average total enthalpy: 15 MJ/kg - total pressure: 0.5 x 105 Pa. Recently, we envisaged the opportunity to upgrade SPES for energy applications and qualification of high temperature materials. This upgrade results in higher mass flow rates and lower total enthalpies, in particular: mass flow rate: 10-100 g/s - average total enthalpy: 2-5 MJ/kg - total pressure: 1 to 10 x 105 Pa. The generation of these new values implies the replacement of the plasma torch with a combustion heater. Furthermore it would be necessary to strengthen the vacuum system, because of the greater mass flow, and also to provide a system to reduce pollutants. The combustor designed is driven by an industrial burner for microturbines, using methane as a fuel for its good energy properties combined with a quite safe use and availability at low cost. The combustion air is supplied from a reservoir with capacity of 4.5 m3, uploaded up to 30 bar. The preliminary tests were performed at a total pressure of 4 x 105 Pa and a total temperature of 1300 K, providing good results in terms of operative stability