Experiments and simulations on on-board oxygen generation system

The On-Board Oxygen Generation System (OBOGS) has been employed to supply oxygen-enriched air for the pilots on military aircraft for many years, which is more reliable and requires much less logistical maintenance than the stored-gas system. Moreover, its overwhelming superiority is of no capacity limitations for long time flight. A significant question in need of study is to predict the performance of OBOGS, owing to the complexity of pressure swing adsorption (PSA) progress, as well as the variety of adsorbents in use. Experimental method can be utilized but sometimes could be time-consuming and inefficient for design, evaluation and optimization. In this paper, a set of mathematical models were built in order to simulate both the two-bed and the three-bed OBOGS based on the basic theory of PSA process. Numerical method was adopted to obtain the solution. Experiments were also carried out, in which the models were validated via comparisons between the experiment results and simulation results at cyclic steady-state. Then simulation was used to predict the dynamic response of the performance of OBOGS (purity of oxygen and recovery) to the changes in product flow rate, pressure of feed and surrounding, cycle time, and orifice diameter. The cycle time and pressure of feed and surrounding were found to be the primary factors that affected the performance of OBOGS. Systems with the same molecular sieve packed in two beds and three beds were also compared. It was observed that the three-bed OBOGS showed better performance and less pressure fluctuations than the two-bed OBOGS. In addition, some design and operation parameters such as purge orifice size, cycle policy and operation pressure were optimized for a given configuration OBOGS in this paper.