Design and performance evaluation of a dual bell nozzle

• Published in: Acta astronautica Vol. 130; pp. 52 - 59
• Main Authors: Kbab, H., Sellam, M., Hamitouche, T., Bergheul, S., Lagab, L.
• Format: Journal Article
• Language: English
• Published: Elmsford Elsevier Ltd 01-01-2017; Elsevier BV; Elsevier
• Subjects: Adaptation; Aerodynamics; Bells; Boundary layers; CAD; Computational fluid dynamics; Computer aided design; Computer simulation; Conception; Constants; Design analysis; Design engineering; Dual bell nozzle; Engineering Sciences; Evolution; High altitude; Initial conditions; Mach number; Mathematical models; Mechanics; Method of characteristics; Minimum length nozzle; Nozzles; Numerical analysis; Numerical simulations; Prandtl mayer function; Studies; Supersonic aircraft; Supersonic flow; Thermodynamics; Transonic flow; Turbulence; Wall pressure; Method of characteristics; Supersonic flow; Conception; Dual bell nozzle; Prandtl mayer function; Minimum length nozzle
• DOI: 10.1016/j.actaastro.2016.10.015
• EISSN: 1879-2030
• ISSN: 0094-5765

The main objective of a dual bell nozzle is the enhancement of performances based on the principle of auto-adaptation in accordance with the altitude. Indeed, this system has as advantage the auto-adaptation of the flow for two operating modes (at low and high altitude) without mechanical activation. The principle is theoretically simple but structural forces involved can be significant. In this study, a numerical method for the design of this type of nozzle is developed. On the one hand, it is based on a transonic flow approaches to define the starting line on which the supersonic calculations will be initiated. On the other hand, the method of characteristics is used to draw the base nozzle profile. Knowing that the latter is assimilated as a polynomial of the second degree, its constants are calculated from initial conditions. In order to minimize the weight of this nozzle, its truncation proves necessary; this is performed at a point where the best compromise (weight / performances) was respected. The profile of the second curve is calculated to give a constant wall pressure. This is achieved by using the direct method of characteristics applied for a centered expansion wave that the intensity is P2/P1 at the junction. Once the profile is generated, an analysis of the thermodynamic-parameters evolution (such as: pressure, Mach number) and aerodynamic performances is conducted. For more consistency, our results are compared with numerical databases of ONERA nozzle. Simulations of flow in the nozzle with Ansys 13.0 environment for different types of meshes are presented. Also, to offset the effects of the boundary layer, the simulations were performed by using the k-ω SST turbulence model. The obtained results by the method of characteristics and numerical simulation are compared to the computed results of the literature and it was found good agreement and similarity.
•The method of characteristics is used to draw the dual bell nozzle profile.•The thermodynamic-parameters of flow are evaluated and studied.•Numerical simulations of flow in the nozzle are carried out.•The obtained results are compared to the computed results of the literature.•Boundary layer correction of the nozzle profile is performed.