Definition and Measurement of Turbulence Parameters in Reciprocating I.C. Engines

A trend removal procedure, incorporating a distribution free trend test is employed to obtain cycle resolved turbulence data for specified crank angle intervals. Spectral analysis using Fourier transforms is then employed to investigate how the mean square value of the velocity fluctuations is distributed with respect to frequency. It is demonstrated that the spectral analysis can also be employed to estimate the contributions from cycle by cycle variations to various ensembled average turbulence parameters.

Hot wire velocity data, obtained from a Ricardo E6 engine, and from an engine model which was specifically built to investigate the mixture motion, wa used to evaluate ensembled average velocity and its standard deviation, mean velocity, turbulence intensity and the power spectrum of the mean square value of the velocity fluctuations.

It is found that:

1. (i)
   The turbulence energy is mainly contained in the low frequency velocity fluctuations.
2. (ii)
   An increase in the turbulence intensity increases the power spectral density function of the velocity fluctuations at all frequencies and thus effectively extends the power spectrum in the frequency domain.