Prediction of the fuel regression-rate in a HDPE single port hybrid rocket fed by liquid nitrous oxide

Abstract

This paper presents a computational thermo-fluid-dynamic model of the hybrid rocket internal ballistics, which was developed with the specific aim of predicting the axial position and severity of the increased fuel-consumption spots observed in static engine firings. Numerical simulations of the internal flow field have been carried out on the configuration of the engine previously fired. The novelty of this work consists in providing a simplified methodology to calculate the regression rate measured burning liquid nitrous oxide with high-density polyethylene, which involves a series of additional complexities with respect to the case of pure gaseous oxygen (i.e., a non-decomposing oxidizer). Indeed, the typical non-premixed flame developed in the chamber is preceded by a decomposition reaction of the nitrous oxide, whose simulation implies further numerical cost. For the validation of the model, data retrieved from two firing tests are compared with the numerical results revealing good agreement of both the average regression rate and fuel consumption axial profile. A dedicated study was performed to assess the reliability of the assumptions underlying the model. Results are also compared with those obtained with either pure oxygen or 85 wt.% hydrogen peroxide. Finally, a different prechamber arrangement was suggested to address the issue deriving from excessive fuel regression.