The suitability of the analysis of the unsteady flow through the exhaust junction plays an important role in developing a computer program for matching a diesel engine to an exhaust turbocharger. This paper describes an improvement of the calculation procedure for computing the behavior of the unsteady gas flow at the exhaust junction. Measured values of pressure, temperature, and mass flow rate are compared with computer predictions using four different pipe junction computations: constant pressure model, momentum model, simplified model, and the improved exact model developed in this study. This comparison shows that the new technique gives the best agreement with the measured values, while the computer time required is twice as long. Under unsteady flow conditions the exhaust junction gives six types of flow configuration, and calculations indicate that only some of these types of flow dominate; the rest occur for only short intervals.

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