Extension of the Frozen Sonic Flow Method to Mixtures of Polyatomic Gases

Abstract

A contemporary issue of crucial importance for further developments in the field of thermal protection systems and related arc-jet-based testing activities calls for improvements in existing abilities to measure the centerline total enthalpy. Starting from the original assumptions of Vincenti and Kruger (1965) and through the elaboration of a mathematical framework relying on a specific modelling hierarchy of balance equations for the moles of different species involved, we show that the extension of the Frozen Sonic Flow Method (FSFM) to the case of polyatomic molecules can be made well posed. Dedicated experiments have been conducted using a re-entry simulation facility and varying the massaveraged enthalpy in the range between 5 and 30 [MJ/kg]. In particular, three different gas mixtures have been considered (using Nitrogen as hot feeding gas and adding cold Oxygen, Carbon Dioxide and Methane, respectively). The enthalpy ratios calculated by the FSFM, found to depend on the gas mixture, have been compared with the values determined using two alternate techniques, namely, 1) the Heating Rate Method and 2) the Calorimetric Probe Method. Given the extremely complex experimental conditions considered (high-enthalpy, low density, supersonic reactive flows), the agreement between the theoretical and experimental results can be considered very satisfactory.

A Mixed Radiative-Convective Technique for the Calibration of Heat Flux Sensors in Hypersonic Flow

“…10a, is a high enthalpy supersonic flow facility. It has enjoyed a widespread use over the last 30 years for the simulation of various planetary re-entry conditions ( [17][18][19][20][21]).…”

On the Formation and Accumulation of Solid Carbon Particles in High-Enthalpy Flows Mimicking Re-Entry in the Titan Atmosphere

“…Using the open software CEA from NASA [17], an extended version of the well-assessed Frozen Sonic Flow Method [5] and the experimental test data (mass-averaged enthalpies and pressures), an Interestingly, even though different particle dimensions were found as a result of different conditions, in no circumstances the observed samples [6] contained nitrogen (indicating the absence of tholins), regardless of their morphology.…”

“…Using the open software CEA from NASA [17], an extended version of the well-assessed Frozen Sonic Flow Method [5] and the experimental test data (mass-averaged enthalpies and pressures), an algorithm has been implemented to calculate gas thermofluid-dynamic gas properties and chemical composition at the arc-heater outlet, mixing chamber inlet (just after mixing of cold methane and hot nitrogen plasma) and finally at the nozzle outlet. The main result from this analysis is that solid carbon originates in the mixing chamber, for total enthalpy values between 10 and 15 MJ/kg.…”

“…The atmospheric entry of a spacecraft is a critical phase for the success of a planet exploration, and an efficient thermal protection system (TPS) is required to protect the probe against the energy surface flux [4]. The existing studies on this subject have essentially concentrated on the gas dissociation processes which occur when a probe enters the atmosphere of Titan at a very high temperature [5]. These studies are required to properly predict the temperature at the probe surface (in order to design relevant protection systems).…”

“…These authors found solid carbon deposited on the surfaces of an inductively coupled plasma torch operating with a Titan-like atmosphere plasma gas. In the present work, further evidence for the existence of this phenomenon is provided on the basis of a different technique, i.e., a wind tunnel driven by an industrial arc-heated facility operating with nitrogen as working gas (the methane necessary to simulate Titan's atmosphere composition has been added in a plenum-mixing chamber located upstream a supersonic nozzle, [5,7]). Conditions for the formation of such particles are also studied by means of numerical simulation.…”