Date of Award

Fall 1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical Engineering

First Advisor

Mohamed E. Labib

Second Advisor

Rong-Yaw Chen

Third Advisor

John Vincent Droughton

Fourth Advisor

Pasquale J. Florio

Fifth Advisor

Ralph Hensler

Abstract

Current automobile air bag inflator technology is complex, expensive and environmentally unsafe. A new and novel air bag inflator based on fast combustion reactions of methane-oxygen mixtures has been developed and studied. The thermodynamics and mass flow parameters of this new inflator have been modeled and found to be in agreement with experimental results.

The performance of the fast combustion inflator was evaluated in terms of pressure-time relationships inside the inflator and in a receiving tank simulating an air bag as well as the temperature-time relationship in the tank.

In order to develop this fast combustion inflator, several critical issues were studied and evaluated. These included the effects of stoichiometry, initial mixture pressure and extreme hot and cold conditions. Other design and practical parameters, such as burst disk thickness and type, ignition device, tank purging gas, concentration of carbon monoxide produced and severity of temperature in the tank were also studied and optimized. Several inflator sizes were investigated and found to meet most of the requirements for a successful air bag inflator.

A theoretical and integrated model has been developed to simulate the transient pressure and temperature as well as the mass flow rate from the inflator to the tank. The model is based on the change in the internal energy inside the inflator and the receiving tank as the mass flows from the inflator to the tank. The model utilizes the Chemical Equilibrium Compositions and Applications code developed by NASA to estimate the equilibrium conditions in the inflator. A large volume of experimental results made at different conditions were found to be in agreement with the integrated model.

The fast combustion inflator developed during this research is simple in principle and construction and is environmentally attractive.

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