Equilibrium Properties of High-Temperature Air for aNumber of Pressures

Abstract

This paper presents compositions and thermodynamic properties for air in chemical equilibrium for a number of pressures and a range of temperatures. The temperature range of interest is from 300 to 30,000 K and the pressures covered are 1 x 10 -6 , 1 x 10 -4 , 1 x 10 -2 , 1, and 100 atm. Twenty-two species that can result from an original mixture of 21% O 2 ,78% N 2 , and 1% Ar are included in the analysis. The equilibrium composition is presented in terms of mole fractions. The thermodynamic properties presented are the constant-pressure specific heat, specific enthalpy, specific entropy, molecular-weight ratio, ratio of specific enthalpy to specific internal energy, ratio of frozen specific heats, ratio of equilibrium specific heats, and the isentropic index. Because a number of other investigators have obtained equilibrium-air properties over the years, another objective of this work is to make comparisons with these results. These comparisons are important so that the reader can see where the results agree and where they differ. The results presented here cover a wider range of conditions than those presented elsewhere for properties that are important for analyzing high-speed flight conditions.