On the smoothing explosion pressure curves using Savitzky-Golay method

Abstract

This study reports the optimal range of window width of Savitzky–Golay method for smoothing the raw oscillating explosion evolution curves obtained in methane-air mixtures. The experiments were carried out in a closed vessel of 3.375 L at various equivalence ratios (φ=0.8−1.2) and initial pressures (P0=1.0−2.5bar). All experiments were conducted at room temperature (293 K). The optimal range of window width and the corresponding explosion characteristics (the maximum explosion pressure Pmax, maximum pressure rise rate (dp/dt)max and deflagration index KG) of each initial condition were determined. The results show that (dp/dt)max is influenced markedly by the window width, and some similar behaviors (three characteristic segments) of (dp/dt)max-window width curves are found. Besides, the optimal range of window width depends not only on the equivalence ratio but also on the initial pressure, and the representative median of each range shows a downward trend with the initial pressure. And the median is stable at 1251 points when P0 is greater than 2.0 bar at φ=0.8, while it shows a linear decrease at φ=1.0 and φ=1.2, and maybe also tends to a stable value at a higher initial pressure. Furthermore, Pmax, (dp/dt)max and KG corresponding to the optimal range of window width have perfect linear correlations with P0, verifying convincingly the correctness of the range we determined.