Influence of H₂ enrichment for improving low load combustion stability of a Dual Fuel lightduty Diesel engine

Abstract

Dual Fuel (DF) combustion can help to reduce the environmental impact of internal combustion engines, since it may provide excellent Brake Thermal Efficiency (BTE) combined with ultra-low emissions. This technique is particularly attractive when using biofuels, or fuels with a low Carbon content, such as Natural Gas (NG). Unfortunately, as engine load decreases and the homogeneous NG-air mixture tends to become very lean, the high chemical stability of NG can be a serious obstacle to the completion of combustion. As a result, BTE drops and UHC and CO emissions become very high. A possible way to address this problem could be the addition of hydrogen (H2) to the NG-air mixture. In this paper, a numerical study has been carried out on an automotive Diesel engine, modified by the authors in order to operate in both conventional Diesel combustion and DF NG-diesel mode. A previous experimental characterization of the engine is the basis for the CFD-3D modeling and calibration of the DF combustion process, using a commercial software. The effects on combustion stability and emissions of different NG-H2 mixtures (six blends with 5%, 10%, 15%, 20%, 25%, and 30% by volume of hydrogen) are numerically investigated at a low load (BMEP = 2 bar, engine speed 3000 rpm). The results of the CFD-3D simulations demonstrate that NG-H2 blends are able to decrease strongly CO, UHC, and CO2 emissions at low loads. Advantages are also found in terms of thermal efficiency and NOx emissions.

Introduction to the current and future use of H2 and H2-based e-fuels in combustion engines and fuel cells Special Issue

“…Life cycle analysis, including end-of-life disposal, is a critical topic that requires attention, but it is considered outside the scope of this special issue. The papers in this category include studies of: the use of anode off-gas of a methane-fueled solid oxide fuel cell system in an internal combustion engine, 7,8 the effect of compression ratio and bore/stroke ratio on methanol-fueled spark-ignition engine operation, 9,10 the role of hydrogen enrichment for diesel-pilot combustion in a high-speed compression ignition engine and in a spark-ignited large-bore engine, 11,12 the effect of oxymethylene ether on emissions and aftertreatment system design for ultra-low emission compression-ignition engine concepts, 13 the potential of Miller cycle in combination with synthetic fuels for heavy-duty engine applications 14 and the potential of hydrogen/diesel compared to gasoline/diesel reactivity-controlled compression ignition combustion utilizing a second law analysis. 15 The Editors hope you find this issue interesting and that the papers can spark a dialog on the important topic of hydrogen utilization in engines and fuel cells in the field of mobile and stationary applications.…”

“…the role of hydrogen enrichment for diesel-pilot combustion in a high-speed compression ignition engine and in a spark-ignited large-bore engine, 11,12…”

Experimental and Numerical Investigation of Methane Combustion Combined with Biodiesel in Dual Fuel Mode

“…In lean burn, the flame does not propagate properly, which would lead to the relative increase of CO and HC emissions. This phenomenon would result in lower peak pressures and temperatures in dual fuel mode and, consequently, a reduction in nitrogen oxides [1,5,6,8,9]. With regard to alternative fuels, biofuels have been explored for decades and their performance shows that they are comparable to conventional diesel from an economic point of view.…”

“…This result was observed by several other researchers in studies of biodiesels in general, which encouraged the implementation of techniques to regulate the cylinder pressure during dual fuel combustion during biofuel combustion. The aim was to increase the longevity of the biofuel engine and reduce the resulting NOx emissions [7][8][9][10][11][12]. The solutions considered were relatively related to reducing the engine load.…”

“…The solutions considered were relatively related to reducing the engine load. In addition, several authors show that the composition of diesel-biodiesel blends in appropriate proportions is one of the solutions to reduce this cylinder pressure [9][10][11][12][13]. The coupled reduction of pollutants in particular and of cylinder pressures when using biofuels remains a problem for diesel engines to this day.…”