Velocity measurements in particle-laden high-enthalpy flow using non-intrusive techniques

Abstract

This research aims at analysing the particle-laden flow of the hypersonic high-enthalpy wind tunnel L2K, situated in Köln at the German Aerospace Center (DLR). In the L2K wind tunnel, Martian atmosphere can be created, and the facility can simulate heat load conditions encountered during atmospheric entry of Martian missions. In the tests, a simplified Martian atmosphere (97% CO2 and 3% N2) was used. The high enthalpy flow was loaded with micrometric particles of magnesium oxide. The particles' mean velocity was measured with a 2D-2C Particle Image Velocimetry (PIV) system, in the region right downstream the nozzle expansion of the wind tunnel. The work proves the possibility of creating a high-enthalpy particle-laden flow for Thermal Protection Systems (TPS) testing with simulated Martian atmosphere. Average particle velocities of around 2000 m/s are measured and compared with the numerical simulation of the wind tunnel's particle-free flow, and with the flow velocity measured with Tunable Diode Laser Absorption Spectroscopy (TDLAS). The study also highlights some unexpected results and features of the high-enthalpy particle-laden flow and proposes some theories for the causes of such effects, which include agglomeration due to melting, and gravitational effect.