IMPORTANT FINDINGS AND OBSERVATIONS OF THE ROCKET NOZZLE EROSION PROCESSES AND THEORETICAL/NUMERICAL SIMULATIONS

Open Access
Author:
Lin, Chia-Yung
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Kenneth K Kuo, Thesis Advisor
Keywords:
  • rocket nozzle erosion
Abstract:
Rocket nozzle erosion has been a critical issue when rocket motor operating conditions are at high temperature and pressure. During rocket motor operation, nozzle surface are subjected to thermalchemical erosion by oxidizing gaseous species such as H2O , OH and, CO2 and/or mechanical erosion by impinging aluminum oxides when metallized propellants are used. The throat area undergoes the extreme heat transfer, thereby decreasing the thrust and causing severe performance reduction of the propulsion system. Accordingly, detailed understanding of the erosion mechanism is desirable. Shear and normal forces on the nozzle surface, temperature, pressure, heat transfer to the wall, particle impacts, chemical kinetics, and surface melting are considered primary factors of nozzle erosion. Various aspects that are closely related to the nozzle recession processes conducted by several research groups are summarized. In order to reduce the overall recession rate of the nozzle, the nozzle boundary-layer controlled system (NBLCS) has been introduced and shown the effectiveness in mitigation of the nozzle erosion. This method produces relatively low product gases to be injected into the upstream of the nozzle throat section, which not only reduces the concentration of the oxidizing species but also cools down the hot combustion product gases in the boundary layer region near the throat. Refractory materials like tungsten (W) , plays a significant role in overall nozzle erosion mechanism due to its high melting temperature. However, heterogeneous reaction kinetics must be carefully examined and modeled since tungsten oxidation by several oxidizing species such as CO2, CO and O2 could generate metal compounds with lower vaporization and/or melting temperatures. These compounds may be removed from the nozzle surface as fast as they are forms, either by vaporization or surface forces, thereby expanding the nozzle throat area and reducing overall performance. To increase the operating condition range and performance of a future rocket propulsion system, understanding the rocket nozzle erosion processes and developing methods for nozzle erosion reduction are vitally important. Thus, quantitative and qualitative experimental studies and theoretical simulations are required to be advanced due to the complexity involved in the rocket nozzle erosion characteristics.