Experimental and theoretical determination of the admittances of a family of nozzles subjected to axial instabilities

✍ Scribed by W.A. Bell; B.R. Daniel; B.T. Zinn

• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 605 KB
• Volume: 30
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1016/s0022-460x(73)80112-9

✦ Synopsis

In combustion instability analyses of rocket engines, it is necessary to determine the interaction between the oscillations in the combustor and the wave system in the nozzle. This interaction can be specified once the nozzle admittance is known. The present paper is concerned with the experimental and theoretical determination of the admittances of practical nozzles that are subjected to axial oscillations. The impedance tube technique, modified to account for thepresence of a mean flow, was used to experimentally measure the one-dimensional nozzle admittances. The modified impedance tube theory and experimental facility used to evaluate the nozzle admittance are briefly discussed in this paper. Crocco's nozzle admittance theory is used to predict the admittances of the tested nozzles for comparison with the experimental data. The theoretical and experimental nozzle admittances are obtained for a family of nozzles having Mach numbers from 0.08 to 0-28, different angles of convergence, and different radii of curvature at the throat and entrance sections. The analytical and experimental results are presented as curves showing the frequency dependence of the real and imaginary parts of the nozzle admittances. Examination of these data shows that the theoretical and experimental admittance values are in good agreement with one another which indicates that existing nozzle admittance theories may be used in practice to predict one-dimensional nozzle admittances.