Blowdown of two-component gas mixtures in branching systems

A transient multi-volume, two-component model has been developed which is capable of describing the blowdown of gases through a piping system suddenly opened to the atmosphere. The volumes are connected through orifices or nozzles with recovery sections and in tee configurations as well as a single string. Two gas components are included in the model and exhaust into a third component such as air. Motion of a concentration front is modelled and a polytropic process represents the state of the gas in each volume. An implicit solution is required since explicit numerical solutions are unstable for these equations. The iterative method developed for the equations converges in a variety of ill-posed situations. Results compare well with data. The large difference in the critical velocities of the gases results in very unusual and difficult to model depressurization histories. A local minimum in the pressure is observed followed by a later maximum