Specifics of pyrotechnic actuators simulation

Аuthors

Bykov L. V.^*, Yanyshev D. S.^**

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

*e-mail: bykovlv@mai.ru
**e-mail: dyanishev@gmail.com

Abstract

Mathematical modeling of pyrotechnic drives gas dynamics is associated with the conjugate multifactor problem solution. Extraction of basic parameters, determining the ongoing proces­ses character, is necessary while solving this problem. Computational model should account for mathematical models of the combustion products and the rod movement of the pyrotechnic drive. The rod movement is determined from the balance equation of the forces acting on it. The conducted studies revealed that accounting for the thermal-physical properties variability of the working fluid plays one of the key roles while dynamics computing of the compressible flows. Evaluation of viscosity impact of the friction factor value at various Reynolds numbers for the cases of steady-state flows was performed. The error in viscosity factor determining in the case, when the temperature dependence was not accounted for, was of 300%-500% order for the temperature range under consideration, and the error in linear friction pressure loss determining decreased from 32% to 17% with Reynolds number within the range of laminar to fully turbu­lent flow. In real flow in the pyrotechnic drive, besides linear friction losses, active vortex, forming in the places of drastic flow changes, and transients are involved. Thus, the error in vis­cosity factor determining and, hence, not only mass-average, but also local Reynolds number, by which local turbulent characteristics are determined, may lead to the error in rod movement speed of the pyrotechnic actuator determining of 50%-100% order. The performed calculations of the pyrotechnic actuator rod dynamics yielded the results similar to the data obtained experi­mentally. Accounting for variable viscosity allowed obtaining the calculation results conformity with the experimental data within the 25%-30% range.

Keywords:

flow dynamics; numerical simulation; pyrotechnic actuator; dynamic charac¬teristics.

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