Effect of Nozzle Throat Diameters on Kerosene-NOS Liquid Rocket Performance

This paper presents experimental results for the performance effects of varying converging-diverging graphite nozzle throat diameters on an in-house developed kerosene-nitrous oxide liquid rocket test stand. The project aims to enhance the performance and efficiency of small-scale liquid rocket engines by experimentally investigating the effects of nozzle throat diameter on thrust and specific impulse. By confirming the correlation between nozzle geometry and the experimental data, it provides valuable insight for improving propulsion systems and components used in experimental rocketry such as sounding rockets. This study will evaluate three different nozzle throat diameters under varying propellant pressures and mass flow rates. The liquid rocket test stand consists of an external aluminum casing with a combustion chamber measuring 20 inches in length with an outer diameter of 76 mm and an internal diameter of 1.66 inches. The nozzle throat diameters tested will be 58/64, 60/64, and 62/64 inches, each with a fixed exit diameter of 1.82 inches. Experimental results were collected over a range of total mass flow rates using complex data acquisition systems and analyzed using graphs and trend lines. The results indicate that as the throat diameter increases, the velocity of the exhaust decreases, which in turn reduces the thrust output and specific impulse. The new knowledge gained from this study can be used to verify if the trends seen will be applicable to different nozzle materials and find the optimum nozzle throat diameter.