The Modeling of Fuel Auto-Ignition Delay and Its Verification Using Diesel Engines Fueled with Oils with Standard or Increased Cetane Numbers

Abstract

This article contains the results of mathematical modeling of the self-ignition delay (τc sum) of a single droplet for various fuels, and the results of measurement verification (τc) of this modeling in diesel engines. The result of modeling the τc sum (as a function of the diameter and ambient temperature of the fuel droplet) revealed two physical and two chemical stages that had different values of the weighting factor (WFi) in relation to the total delay of self-ignition. It was also found that the WFi values of individual phases of the self-ignition delay differed for different fuels (conventional and alternative), and in the total value of τc sum. The measured value of the self-ignition delay (τc) was determined in tests using two diesel engines (older—up to EURO II and newer generation—from EURO IV). The percentage difference in the Δτc sum value obtained from modeling two fuels with different cetane number values was compared with the percentage difference in the Δτc value for the same fuels obtained during the engine measurements. Based on this analysis, it was found that the applied calculation model of the self-ignition delay for a single fuel droplet can be used for a comparative analysis of the suitability of different fuels in the real conditions of the cylinder of a diesel engine. This publication relates to the field of mechanical engineering.