Estimation of the accuracy to taylor length scale measurements by two-point LDV in reciprocating engines

摘要

The accuracy of the direct measurement of the Taylor length micro-scale by two-point laser Doppler velocimetry in a motored engine is analysed. The probe volume length, the portion of the correlation curve used to fit a matching parabola and the ratio between the integral and Taylor length scales of the turbulent field are the basic parameters of the present analysis. A second order model of compressed turbulence is used to predict the theoretical evolution of the integral and Taylor length scales in a reciprocating engine during the compression and expansion strokes without combustion. This prediction permits us to estimate the uncertainty on the measured length scales by simulating the finite length of the probe volumes. Finally, the application of the theoretical analysis in a real motored engine is presented and an attempt to remove bias from experimental Taylor scale has been made.