Abstract
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).
Highlights
This article is an open access articleIn the case of diesel engines, the emission of carbon monoxide (CO) and unburned hydrocarbons (HCs) does not pose a serious threat due to the high conversion efficiency of the commonly used oxidation reactors [1]
The principle says that if we reduce nitrogen oxides (NOx) emissions with one method, we will increase particulate matter (PM) emissions in the exhaust gas - this rule applies to fuel additives
Since the impact of engine load on the change in the Gf value is many times greater than the impact of the fuels used in the research, for this reason in the Figure 6b is shown the values of the percentage reduction in hourly consumption of test fuels in relation to the hourly consumption of base fuel
Summary
In the case of diesel engines, the emission of carbon monoxide (CO) and unburned hydrocarbons (HCs) does not pose a serious threat due to the high conversion efficiency of the commonly used oxidation reactors [1]. Multiple studies indicate increasing the RME content in fuel is associated with several negative effects related to both the combustion process and the use of these fuels This is relevant to several problems, including the stability of such fuel, the tendency to form deposits inside the engine cylinders, and increased emission of NOx in the exhaust gas. For this reason, in the presented research, an additive increasing of the cetane number of the fuel was used. Energies 2021, 14, 2784 led to the enhancement of NOx reduction to an even greater extent than for the additive itself, reducing dQk /dα while maintaining lower PM emissions in the exhaust gas compared to the base fuel by increasing dQd /dα
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