The turbulent structures were found to be quite comparable for both filtering methods. 3B, as the piston is driven down the cylinder, the specially shaped piston crown uncovers the exhaust port shown on the left-hand side and the hot burned gases start to escape from the combustion chamber. A comparison between spatially and temporally filtered data at the same level of fluctuation kinetic energy was performed. The difference in fluctuation kinetic energy, when normalized, between different operating conditions was found to be comparable to the difference between cycles. The mean (over the spatial domain) kinetic energy of the high-pass filtered data, and its evolution with cutoff frequency or length, was used to quantitatively compare differences between operating conditions and different cycles at the same condition.
The data were both temporally and spatially filtered to study the turbulent flowfield. Data were acquired at 1 kHz throughout the entire engine cycle, allowing the temporal and spatial evolution of the flow to be observed. FMEP = IMEP n - BMEP.High frame rate particle image velocimetry (PIV) measurements were performed in a motored engine at speeds of 6 rpm under both throttled and unthrottled conditions. Friction mean effective pressure calculation requires accurate measurement of cylinder pressure and dynamometer brake torque.
Gross indicated mean effective pressure (IMEP g) - Mean effective pressure calculated from in-cylinder pressure over compression and expansion portion of engine cycle (360° in a four-stroke, 180° in a two-stroke).Brake mean effective pressure (BMEP) - Mean effective pressure calculated from measured brake torque.Mean effective pressure (MEP) is defined by the location measurement and method of calculation, some commonly used MEPs are given here. L − 1 M T − 2 Types of mean effective pressures
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