Abstract
Several classical and non-classical reduced-order nucleation rate models are presented and compared to experimental values for the homogeneous nucleation rate of CO2 in supersonic nozzles. The most accurate models are identified and are used in simulations of a condensing supersonic expansion flow. Experimental results for the condensation onset point of CO2 in a variety of expansion facilities are presented and compared to simulations and to new data acquired at the SBR-50 facility at the University of Notre Dame.
Highlights
The maximum Reynolds number achievable by ground test facilities is often limited by liquefaction of the working fluid at low static temperatures and/or high static pressures
This is corrected in self-consistent classical nucleation theory (SCCNT) [58,59] by modification of the Classical nucleation theory (CNT) free energy barrier, resulting in
The extended modified liquid drop dynamical nucleation theory (EMLDDNT) [61,68,69] considers a small canonical system of M molecules constrained inside a spherical container of volume V at constant temperature
Summary
The maximum Reynolds number achievable by ground test facilities is often limited by liquefaction of the working fluid at low static temperatures and/or high static pressures. The concentration of carbon dioxide in dried air remains near atmospheric levels, which are currently 415 ppm and increasing at about 2.5 ppm per year [5] This vapor condenses within the nozzle of hypersonic expansion facilities, providing condensation nuclei for the later heterogeneous condensation of oxygen and nitrogen. Accurate modeling of the carbon dioxide nucleation process is required as a prerequisite for reliable estimates for heterogeneous condensation, and the minimum achievable stagnation temperature and maximum Reynolds number in a hypersonic expansion facility. The failure of CNT to accurately predict the nucleation rate of many fluids is fundamentally due to the fact that macroscopic approximations can not be applied to nucleating clusters composed of small numbers of discrete molecules without significant error [23]. The objective of this work is a review and comparison of reduced order models available in the literature to the experimental results of CO2 condensation onset
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