The article presents the results of research on the influence of two fuel additives that selectively affect the combustion process in a diesel engine cylinder. The addition of NitrON® reduces the concentration of nitrogen oxides (NOx), due to a reduction in the kinetic combustion rate, at the cost of a slight increase in the concentration of particulate matter (PM) in the engine exhaust gas. The Reduxco® additive reduces PM emissions by increasing the diffusion combustion rate, while slightly increasing the NOx concentration in the engine exhaust gas. Research conducted by the authors confirmed that the simultaneous use of both of these additives in the fuel not only reduced both NOx and PM emissions in the exhaust gas but additionally the reduction of NOx and PM emissions was greater than the sum of the effects of these additives—the synergy effect. Findings indicated that the waveforms of the heat release rate (dQ/dα) responsible for the emission of NOx and PM in the exhaust gas differed for the four tested fuels in relation to the maximum value (selectively and independently in the kinetic and diffusion stage), and they were also phase shifted. Due to this, the heat release process Q(α) was characterized by a lower amount of heat released in the kinetic phase compared to fuel with NitrON® only and a greater amount of heat released in the diffusion phase compared to fuel with Reduxco® alone, which explained the lowest NOx and PM emissions in the exhaust gas at that time. For example for the NOx concentration in the engine exhaust: the Nitrocet® fuel additive (in the used amount of 1500 ppm) reduces the NOx concentration in the exhaust gas by 18% compared to the base fuel. The addition of a Reduxco® catalyst to the fuel (1500 ppm) unfortunately increases the NOx concentration by up to 20%. On the other hand, the combustion of the complete tested fuel, containing both additives simultaneously, is characterized, thanks to the synergy effect, by the lowest NOx concentration (reduction by 22% in relation to the base). For example for PM emissions: the Nitrocet® fuel additive does not significantly affect the PM emissions in the engine exhaust (up to a few per cent compared to the base fuel). The addition of a Reduxco® catalyst to the fuel greatly reduces PM emissions in the engine exhaust, up to 35% compared to the base fuel. On the other hand, the combustion of the complete tested fuel containing both additives simultaneously is characterized by the synergy effect with the lowest PM emission (reduction of 39% compared to the base fuel).

No abstract

Research was conducted on fuels with additives that selectively affect the rate of kinetic (dQk/dα) and diffusion (dQd/dα) combustion in the diesel engine cylinder. In addition to the base fuel (DFB), DFKA fuel with an additive reducing dQk/dα, DFDA fuel with an additive increasing dQd/dα, and DFS fuel with both additives were tested. The main purpose of such dQ/dα course control in the engine cylinder was to simultaneously reduce the emissions of nitrogen oxides (NOx) and particulate matter (PM), and to increase the efficiency of the combustion process. Similar to the course of the dQ/dα, the course of the combustion temperature (Tc(α)) affects the NOx produced and the number of afterburned solid particles; the influence of the fuel additives on the functional curves was analysed. In addition to analysis of the temperature Tc(α) calculated from the indicator diagrams, Tc(α) analysis was conducted using the two-colour method, which allows the analysis of the isotherm distributions locally and temporarily. The two-colour method required prior endoscopic visualisation of the fast-changing processes inside the engine cylinder. Parameters defined by pressure, temperature, heat release rate, and visualisation and thermovision in the engine cylinder (as a function of the crank angle) allowed for an in-depth cause and effect analysis. It was determined why combustion of DFS fuel with both additives produced a synergy resulting in the simultaneous reduction in NOx and PM emissions in the exhaust gas and an increase in combustion efficiency. This publication relates to the field of Mechanical Engineering.

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.