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National Advisory Committee for Aeronautics, Technical Notes - Charts for the Computation of Equilibrium Composition of Chemical Reactions in the Carbon-Hydrogen-Oxygen-Nitrogen System at Temperatures from 2000° to 5000°K

A rapidly convergent method is described for the calculation
of the equilibrium composition of the carbonrhydrogeneoxygen-nitrogen
system in the temperature range from 2000° to 50000 K. Charts are
provided for the estimation and progressive adJuetment of two inde-
pendent variables on which the calculations are based. Additional
charts are provided for the graphical calculation of the composi-
tion. The use of the method and the charts is illustrated by an
example.

The determination of the equilibrium composition of a chemical
reaction is necessary for the solution of certain problems in chem-
istry and thermodynamics. When a reaction occurs at elevated temy
peratures, the products of reaction contain dissociated molecules
which, when present in sufficient quantity, complicate the solution
of the problem. The degree of dissociation is determined by the
temperature of the products, their partial pressures, and an equi-
librium constant for each dissociation reaction.

For reactions involving carbon, hydrogen, oxygen, and nitrogen
at temperatures between 20000 and 50000 K and at pressures below
100 atmospheres, a direct solution of the equilibrium equations is 1
impractical if not impossible. Accordingly, same method of succes-
sive approximation or trial and error is required.

If only two elements are present in the reaction the problem
is less difficult. For example, a direct method for computing the
equilibrium composition of the hydrogen-oxygen reaction is described
in reference 1.

A method of computing the equilibrium composition of a mixture
of the elements, carbon, hydrogen, oxygen, and nitrogen, by means
of a method of successive approximation is given in reference 2.

The method. was applied to combustion in the cylinder of an internal»
combustion engine. This method, although convenient for tempera-
tures up to approximately 20000 to 25000 K, becomes cumbersome for
temperatures at which a large fraction of the molecules are dis-
sociated.