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International Journal of Energetic Materials and Chemical Propulsion

ISSN Print: 2150-766X
ISSN Online: 2150-7678

International Journal of Energetic Materials and Chemical Propulsion

DOI: 10.1615/IntJEnergeticMaterialsChemProp.v5.i1-6.960
pages 941-948

Prediction of Airbag Inflator Performance

J. C. Chastenet
S.N.P.E. - Defense-Espace, Centre de Recherches du Bouchet B.P. 2, Vert-Le-Petit, 91710, France
A. Mobuchon
SNPE Propulsion, Centre de Recherche du Bouchet, Rue Lavoisier, 91710 Vert-le-Petit, France

ABSTRACT

Airbag operating involves a great number of highly dependent components where the pyrotechnical charge used in an inflator as a gas generator is only one of the components. Moreover, specifications of these systems are more and more drastic in terms of performance, toxicity, lifetime, etc. Research and development of new gas generator compositions need to take into account all these aspects very early in the studies.
This paper describes the methodology performed by SNPE Propulsion for this purpose. This methodology is based on:

  • thermodynamic prediction of theoretical performance,
  • global modeling by means of a lumped parameter model,
  • experimental demonstrator test,
  • complete CFD simulation,
  • prototype test.
For all of these steps, except the last one, which is not under direct SNPE responsibility in the frame of an airbag industrial organization involving SNPE, examples of applications are given.
Thermodynamic prediction is a classical technical area. This point is only illustrated and identified limitations are given.
The lumped parameter model is described in regard to all of its possibilities: combustion of propellent grain or in bulk, multi-species with chemical interactions (overall reactions, chemical equilibrium or full chemical kinetics), real gas effects, thermal losses, hole erosion, and so on. This model is used for different purposes: prediction by direct simulation, experimental interpretation, determination of parameters impossible to measure, sensibility studies.
The experimental devices used to validate new composition performances are illustrated. Typical demonstrator tests in a constant volume tank allow specific phenomena identification and their introduction in the lumped parameter model.
Special analyses are done on possible interactions between pyrotechnical composition combustion and other components of the system: igniter composition, filter in combustion chamber, expansion of high-pressurized gas in hybrid generator, etc.
For a better understanding of the system operations, full CFD simulations can be performed with a model ordinarily used for rocket motor studies.