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One-sixth scale model airbag modules have been used to investigate flow aspiration effects in passenger-side airbag modules. A similarity analysis between flows in the model and the prototype unit assures reasonable approximation of the actual flows. In the controlled flow environment of the model, flow visualization suggests that the underexpanded jet structure follows the universal relationship based on experimental data and shows that aspiration occurs through the aspiration holes. Detailed velocity measurements provide the ratio of the mass added to the discharged gas for a single firing. The same approaches can be applied in the design of full-scale airbag systems.

Two mathematical models for the catalyst layer of a PEMFC, i.e. the macro-homogenous model and the agglomerate model are evaluated in this paper. The characteristics of both models and the application of both models to optimal design of catalyst layer are discussed. The one-dimensional governing equations of both models are solved analytically or numerically using the finite difference method. A simplified, analytic solution of the macro-homogenous model under ideal conditions is derived. Parametric study and sensitivity analyses are performed for the agglomerate model to identify the parameters that have significant influences on the performance of a PEMFC. Several parameters including the electrolyte thickness, porosity, oxygen permeability, and layer thickness are found to affect the limiting current significantly. A solid model is developed to visualize the structure of a catalyst layer. This solid model is used to estimate effective transport properties.