A One-Dimensional Transient Compressible Flow Model for Cooling Airflow Rate Computation 900721

Engineers have found that the one-dimensional approach to compressible flows in ducts is extremely informative and effective. This paper extends these methods to cooling airflow for engine cooling system that they may be used to understand and estimate the behavior of cooling air flow in a complex duct system. The paper contains: the underlying assumptions and resulting generalized one-dimensional compressible flow model developed primarily for numerical prediction of cooling airflow rate in the complex air circuit of engine cooling system; an inversed application of the compressible flow model to determine the flow resistances in the radiator, shutter and idling fan of a prototype engine cooling system tested by Kysor of Cadillac; a comparison of the calculated map of cooling airflow at various engine/fan and vehicle speeds to the published empirical results of a geometrical similar prototype air circuit for engine cooling system; and the ATB test results predicted by the VECSS Code with the calculated cooling airflow map.

Provisions and options for the inclusion of many practical design concerns such as the heating of air in the radiator core, fan work, wall friction forces as well as the variation of geometrical configuration along the cooling airflow passage have been built into the resulting model, so that the computational compressible flow model developed can be either for use in the preliminary design of a cooling air circuit or for use in a systematic investigation of the difficult to measure cooling airflow dynamics in actual vehicle operation.