A team of researchers in Finland reports that by adjusting engine parameters for the use of hydrogenated vegetable oil (HVO) renewable diesel fuel across a range of loads (50%, 75%, and 100%), particulate matter and NOx emissions can both be reduced by more than 25% relative to the values from using HVO with standard engine conditions.
Further, the emission reduction was even higher when the target for adjusting engine parameters was exclusively to reduce either particulates or NOx.
The studied HVO fuel is fully paraffinic—it contains no aromatics, sulfur, or oxygen. The HVO fuel meets the EN590 standard in all respects except in density.
The engine used in the study was a single-cylinder research engine based on a commercial 6-cylinder off-road engine. The commercial engine fulfilled EU 97/68/EC Stage III A and EPA 40 CFR 89 Tier 3 emission standards. EGR was simulated using neat nitrogen in the charge air; the EGR percentage was defined as the percentage of added nitrogen in the total inlet air mass flow.
The team studied the results of different combinations of advanced intake valve closing (IVC); exhaust gas recirculation (EGR) percentage; injection pressure (Pinj); and start-of-injection timing (SOI) on 50%, 75%, and 100% loads. When IVC was advanced, it was accompanied with an increase in charge air pressure in order to keep the intake air mass flow constant.
Three different engine conditions were chosen for each load: low-NOx conditions (LN); low-smoke conditions (LS); and conditions where both NOx and smoke are relatively low (LNLS). The low-NOx and low-smoke conditions represent the cases where one emission can be reduced to a minimum using engine parameter adjustments, while the other emission can be reduced using suitable after-treatment techniques—i.e., selective catalytic reduction (SCR) or particulate filter (e.g., DPF). The third condition, where both NOx and smoke are rather low, shows how large emission reductions can be expected with HVO fuel by engine parameter adjustments only.
IMEP of the 50%, 75%, and 100% loads were 10.8, 16.2, and 21.4 bar, respectively. The engine speed was 1500 rpm at all the measured conditions. The researchers first established baseline emissions under standard emission conditions at all three loads.
Among the findings of the study:
- LN conditions were achieved with the use of EGR, advancing IVC by 70 degrees and delaying the start of injection from 0 to 2 degrees depending on the load. In addition, injection pressure was increased from 30 to 70%. With these adjustments, an approximately 60% decrease in NOx was achieved with the studied loads relative to the standard conditions with the HVO fuel.With the exception of increased injection pressure, all the adjustments resulted in a net increase in particulate emissions.
- To achieve LS conditions, they increased the injection pressure which enhanced combustion conditions in the cylinder. Also, on the 50% load, SOI was advanced allowing better combustion. Both of these changes thereby enhanced combustion conditions decreasing particulate emission and increasing NOx.To keep the NOx emission below the level of emission at reference conditions, a small EGR percentage and advanced IVC were used. The results show that NOx emission remained at or slightly below the reference value, but PM emission was decreased 45−68% at LS conditions depending on the load.
- LNLS conditions were achieved by reducing NOx with advanced IVC and a small percentage of EGR and by reducing particulate emission with a 30−70% increase in injection pressure depending on load. NOx emission was decreased 30−50% depending on load and PM 25−33%.
Full report by GCC Here.