Estimation of the volume velocity fluctuation at the tailpipe end of an I.C. engine exhaust system

In this paper, an experimental procedure for the estimation of the volume velocity fluctuation at the open end of the exhaust tailpipe of an internal combustion engine, from in-duct pressure measurements in the tailpipe, is described and discussed. In order to check the accuracy in the estimation of the fluctuating volume velocity, and to obtain an estimate of the sensitivity of the procedure to uncertainties in relevant data, a full non-linear one-dimensional flow calculation was used. The experimental set-up used and the complementary measurements performed are described, and comments on the quality of the results obtained and an evaluation of the difficulties found are given. The procedure is validated in an indirect way, checking the sensitivity of the results to a change in the geometry of the exhaust line and their correlation with tailpipe noise measurements. These comparisons show good agreement in the trends observed. However, the quality of the results is highly dependent on the emission conditions and the in-duct pressure measurement position.

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