Detailed Analysis of the Effects of Biodiesel Fraction Increase on the Combustion Stability and Characteristics of a Reactivity-Controlled Compression Ignition Diesel-Biodiesel/Natural Gas Engine

Abstract

A single-cylinder marine diesel engine was modified to be operated in reactivity controlled compression ignition (RCCI) combustion mode. The engine fueling system was upgraded to a common rail fuel injection system. Natural gas (NG) was used as port fuel injection, and a diesel/sunflower methyl ester biodiesel mixture was used for direct fuel injection. The fraction of biodiesel in the direct fuel injection was changed from 0% (B0; 0% biodiesel and 100% diesel) to 5% (B5) and 20% (B20) while keeping the total energy input into the engine constant. The objective was to understand the impacts of the increased biodiesel fraction on the combustion characteristics and stability, emissions, and knocking/misfiring behavior, keeping all other influential parameters constant. The results showed that nitrogen oxides (NOx) emissions of B5 and B20 without the need for any after-treatment devices were lower than the NOx emission limit of the Euro VI stationary engine regulation. B5 and B20 NOx emissions decreased by more than 70% compared to the baseline. Significantly more unburned hydrocarbons (UHCs) and carbon monoxide (CO) emissions were produced when biodiesel was used in the direct fuel injection (DFI). The results also showed that using B5 and B20 instead of B0 led to an increase of 18% and 13.5% in UHCs and an increase of 88.5% and 97% in CO emissions, respectively. Increasing the biodiesel fraction to B5 and B20 reduced the maximum in-cylinder pressure by 3% and 10.2%, respectively, compared to B0. Combustion instability is characterized by the coefficient of variation (COV) of the indicated mean effective pressure (IMEP), which was measured as 4.2% for B5 and 4.8% for B20 compared to 1.8% for B0. Therefore, using B20 and B5 resulted in up to 34.9% combustion instabilities, and 18.5% compared to the baseline case. The tendency for knocking decreased from 13.7% for B0 to 4.3% for B20. The baseline case (B0) had no misfiring cycle. The B5 case had some misfiring cycles, but no knocking cycle was observed. Moreover, the historical cyclic analysis showed more data dispersions when the biodiesel fraction increased in DFI. This study shows the potential of biodiesel replacement in NG/diesel RCCI combustion engines. This study shows that biodiesel can be used to effectively reduce NOx emissions and the knocking intensity of RCCI combustion. However, combustion instability needs to be monitored.

Investigation of the Combined Use of Diesel and CNG Fuels on an Hcci Engine Using Response Surface Methodology (Rsm)

“…The combustion duration is expressed as the value of CA passing between CA10 and CA90 [43]. Equation 12shows the model used to estimate the combustion duration based on different input parameters.…”

A comprehensive review on the use of biodiesel for diesel engines

“…Therefore, under heavier loads, engines running on biodiesel tend to experience a slower increase in pressure rate and consequently, the peak pressure is also lower compared to when using diesel fuel (Tamilselvan et al, 2017). Figure 3 shows the difference between cylinder gas pressure and heat release rate with the crank angle of diesel fuel and different biodiesels (Ramalingam and Mahalakshmi, 2020;Seraç et al, 2020;Silitonga et al, 2017;Zarrinkolah and Hosseini, 2022). The difference is not too large to require serious modifications to the engine, however, to avoid affecting the power experience that people are used to with diesel engines, many measures are still proposed by researchers which will be clarified in the next section.…”

“…Fig.3. The different between cylinder gas pressure and heat release rate with the crank angle of diesel fuel and different biodiesels(Ramalingam and Mahalakshmi, 2020;Seraç et al, 2020;Silitonga et al, 2017;Zarrinkolah and Hosseini, 2022)(a) soybean-based biodiesel (b) Moringa oleifera biodiesel (c) Jatropha curcas biodiesel (d) sunflower methyl ester biodiesel…”

Compositional Analysis of Biodiesel Particulate Matter (BPM) from a Non-Road Diesel Generator

“…While the transportation sector is moving toward electrification to decarbonize its lightduty fleets, diesel technologies are still needed for mid-to heavy-duty and off-road applications. Interests in biodiesel have recently expanded into locomotives and ships [8][9][10]. Since Energies 2023, 16, 5010 2 of 10 biodiesel is much more carbon neutral than petrol diesel [11], its use is expected to increase in the near future due to the transition to a carbon-neutral economy.…”

“…There have been multiple reports on air pollutant emissions using biodiesel blends over the years, with the majority of studies reporting less carbon monoxide, less particulate matter, and higher NOx emissions comparing with petroleum diesel [12][13][14][15]. Only a few studies have reported opposite trends in emissions [10]. People have come to realize that emissions are dependent on many factors, such as engine and feedstock specific conditions, engine operations, sample collection methods, etc.…”