Cycle Resolved LDV Measurements in a Motored IC Engine

Abstract

LDV measurements have been made in an IC engine motored at 1200 rpm. The data rates were sufficiently high to allow the bulk velocity to be characterized in individual cycles. The relative cyclic fluctuation of the bulk velocity was found to be as large as 200 percent. The turbulence intensity was calculated using both the velocity fluctuation with respect to the ensemble average velocity and the velocity fluctuation with respect to the cycle resolved bulk velocity. The former includes both the cyclic fluctuation of the bulk velocity and the turbulence, and therefore gave estimates of the ensemble averaged turbulence intensity which were from 50 to 100 percent greater than that obtained using the in-cycle fluctuation with respect to the bulk velocity. The relative cyclic fluctuation of the time averaged turbulence intensity, calculated over a 64-degree interval in each cycle, was found to be small, i.e., less than 20 percent. The high data rates also made it possible to determine the ensemble averaged temporal autocorrelation function from which the spectral energy distribution and the integral time scale were calculated.

Topological flow evolutions in cylinder of a motored engine during intake and compression strokes

“…Obviously, the cycle-averaged tumble ratio in the diametral plane is large at Fo401; at which the inlet stream is drastically deflected. When the swirl and/or the tumble ratios are promoted, the mixing induced by the large-scale rotating flow motions and the small-scale turbulent eddy convection are expected to be significant (Ekchian and Hoult, 1979;Hirotomi et al, 1981;Arcoumanis et al, 1982;Liou and Santavicca, 1985;Nadarajah et al, 1998).…”

Integral Length Scales and Time Scales of Turbulence in an Optical Spark-Ignition Engine

“…Possible ways to achieve this can be found in [71] who discussed using a moving average of the in-cycle velocity with a window-size selected between a turbulent microscale and the characteristic period of the piston motion, e.g. 10 °CA by [72] via polynomial curve fitting, or frequency domain filtering by [73] …”

Eulerian and Lagrangian description of a pulsatile, partially turbulent flow

“…Values of u i and uj correspond to data already converted to true turbulence. The integral scale is defined according to Liou and Santavicca (1985).…”

“…Several methods have been proposed to solve this problem; some from internal combustion engine researchers (Liou and Santavicca 1985;Obokata et al 1987) and also in the biomedical engineering literature (Tiederman et al 1988). Even though the philosophy underlying these works is partially useful, the specificity of each situation obliges to look for particular procedures giving a good discrimination among different sources of velocity variance.…”