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Description
An ED(Expansion Deflection) nozzle, suggested by G. V. R. Rao in the 1960s, is characterized by the presence of a pintle at the center of the nozzle[1]. With this structural feature, it was anticipated that the ED nozzle could achieve a reduced length compared to the bell nozzle while maintaining the same performance. To validate this, the European Space Agency(ESA) conducted research on applying the shortened ED nozzle to the upper stage of the Ariane 5 launch vehicle and confirmed the performance benefits.
The pintle of the ED nozzle is fixed on the center of the combustion chamber's head, resembling a cantilever structure. The pintle consists of a cylindrical rod section that was extended up to the nozzle throat and a protruded pintle head section outside of the nozzle throat. This pintle is exposed to high-speed and high-pressure combustion gases in its position. Therefore, it is necessary to examine a structurally stable coupling method for the pintle to prevent its damage. Additionally, when examining the pintle design, the structural loads imposed by aerodynamic forces need to be considered. In this study, a Fluid-Structure Interaction(FSI) analysis was conducted using Computational Fluid Dynamics(CFD) to analyze the influence of aerodynamic forces on the structural integrity of the ED nozzle's pintle.
Commercial software packages, Fluent and Mechanical from ANSYS 2022 R2, were employed for 3D CFD simulations. The simulations employed the SST k-ω turbulence model, pressure inlet conditions, and atmospheric pressure as the far-field condition. The propellant used was LOx/LCH4, and the chemical composition of the combustion gas derived from NASA CEA code. The results of the fluid dynamics analysis were then incorporated into the structural analysis to perform fluid-structure interaction simulations.
Through the result of CFD analysis, the distribution of aerodynamic forces acting on the pintle was determined and compared with the results from 2D simulations. Furthermore, the structural analysis results were used to identify the stress distribution and the location of maximum stress within the pintle. In future research, the CFD will be extended to simulate the situation where combustion gases are injected from the injector hole, and the results will be compared with the findings of this study.
References
[1] Rao, G.V.R., “Analysis of a New Concept Rocket Nozzles,” Journal of Liquid Rockets and Propellants, Vol. 2, pp. 669-682, 1960.
[2] Goetz, A. et al., “Advanced Upper Stage Propulsion Concept – The Expansion-Deflection Upper Stage,” 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, A.Z., U.S.A., AIAA 2005-3752, Jul. 2005.
| Keywords | Expansion Deflection Nozzle, Fluid-Structure Interaction Analysis, Structural Load |
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