FIGURE 5-1. Calculated performance analysis of liquid oxygen and hydrocarbon fuel as a function of mixture ratio.
Refs. 5-7 and 5-8. The RP-1 fuel is a narrow-cut hydrocarbon similar to kerosene with an average of 1.953 mol of hydrogen for each mole of carbon; thus it has a nominal formula of CHI 953. The calculation is limited to a chamber pressure of lOOOpsia. Most of the curves are for optimum area ratio expansion to atmospheric pressure, namely, 1 atm or 14.696 psia, and a limited range of oxidizer-to-fuel mixture ratios.
For maximum specific impulse, Figs. 5-1 and 5-4 show an optimum mixture ratio of approximately 2.3 (kg/sec of oxidizer flow divided by kg/sec of fuel flow) for frozen equilibrium expansion and 2.5 for shifting equilibrium with gas expansion to sea level pressure. The maximum values of c* are at slightly different mixture ratios. This optimum mixture ratio is not the value for highest temperature, which is usually fairly close to the stoichiometric value. The stoichiometric mixture ratio is more than 3.0; much of the carbon is burned to C02 and almost all of the hydrogen to H20.
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