Low-carbon gasoline fuels are one of the most promising approaches to reduce the carbon footprint of the transportation sector. Despite the fact that drop-in fuels can be produced by methods such as methanol-to-gasoline (MTG), ethanol-to-gasoline (ETG) or biomass hydrothermal processing, it is unclear how the composition of the fuel may affect engine performance and emissions. In fact, differences between low-carbon and petroleum gasoline have been observed experimentally and reported in the literature, including differences in deflagration speed and burning rate. However, to the best of the authors' knowledge, the chemical kinetic mechanisms responsible for these differences have not been studied with detailed chemistry before. This is in part caused by the computational cost of solving tens of thousands of conservation of species and diffusion equations in 1-D flame simulations, which prevents detailed chemical kinetic mechanisms from being used in these simulations. Thus, reduced models are used in laminar flame speed simulations, leading to chemical analyses that may be incomplete, since the chemistry in reduced mechanisms is heavily simplified.To solve this issue, a novel approach to study fuel decomposition, rate of production and chemical sensitivity at laminar flame speed like conditions with detailed chemistry was developed in this work. The approach consists of imposing the temperature profile and residence time across the flame in a plug flow reactor to simulate fuel decomposition at flame conditions (including residence time of each fuel molecule at each pressure-temperature conditions within the flame). This approach showed a very low computational cost even with highly detailed chemistry (tens of thousands of reactions), allowing in-depth analyses of the chemistry within the flame. Rate of production and sensitivity analyses were performed for multiple single-component fuels typically found in gasoline composition, for regular-grade E10 (10%vol ethanol) petroleum gasoline, MTG, ETG and biomass-derived renewable gasoline surrogates following this approach. Simulations at engine-like conditions showed that the flame accelerates instants before knock occurs due to a combination of energy and radicals released by the low-temperature chemistry of the end gas, with radical production in the reactants upstream the flame being the dominant factor. Sensitivity analyses showed that flame deflagration is controlled by reactions that generate atomic hydrogen, whereas reactions that act as a sink of atomic hydrogen (such as methyl radical recombination) are detrimental for flame speed. Species sensitivity showed that laminar flame speed is strongly sensitivity to the production of vinyl radical within the flame because vinyl radicals rapidly decompose and release atomic H and atomic O in the reaction zone of the flame. Finally, metrics to correlate the flame speed of a fuel with the formation of key species within the flame are explored.
Internal combustion engines operated in combined heat and power generation applications can achieve high overall efficiencies by utilizing both electrical output and exhaust heat, while also offering rapid load flexibility for grid support. However, engines fueled with conventional diesel or natural gas contribute significantly to greenhouse gas emissions. To mitigate CO2 emissions, engines operated with hydrogen admixture to natural gas or in pure hydrogen mode are under development. Nevertheless, the high reactivity of hydrogen and the associated risk of knocking combustion posing challenges for engine operation and can limit thermal efficiency. In addition, the low volumetric energy density of hydrogen complicates fuel transport and storage, particularly in applications lacking direct access to gas or hydrogen infrastructure. In this context, ammonia (NH3) represents a promising alternative due to its higher volumetric energy density and established transport and storage infrastructure. Direct combustion of ammonia in internal combustion engines, however, introduces several technical challenges. While ammonia combustion is CO2-free, the formation of nitrous oxide (N2O), a potent greenhouse gas, can occur. Additionally, compliance with stringent emission regulations requires effective control of nitrogen oxides (NOx) emissions and unburned ammonia (NH3 slip). Moreover, emissions of carbon monoxide (CO) and unburned hydrocarbons (HC), originating from small quantities of diesel pilot fuel used for ignition support, must also be minimized. To fully realize the greenhouse gas reduction potential of ammonia-fueled engines while meeting modern emission limits, an integrated optimization of combustion and exhaust gas aftertreatment (EAT) is essential. In this study, an ammonia-diesel dual-fuel combustion concept was investigated using a single-cylinder research engine (SCE). A coupled approach was applied, combining targeted adjustments of engine operating parameters to shape the raw exhaust gas composition with a systematic evaluation of two different exhaust aftertreatment catalyst configurations on the SCE.
This study experimentally investigates the combined effects of biodiesel-isopropanol ternary blends integrated with Diesel Oxidation Catalyst (DOC) and Selective Catalytic Reduction (SCR) emission control technologies on the combustion behavior, performance characteristics, and tailpipe emissions of a DI compression-ignition engine. The engine was run at a constant speed of 1800 rpm across four different engine loads (5.49, 10.98, 16.48, and 21.97 Nm). Test fuels included neat diesel, B20 (80% diesel + 20% biodiesel), B20P5D75 (75% diesel + 20% biodiesel + 5% isopropanol), and B20P10D70 (10% isopropanol). While peak in-cylinder pressure and heat release rate raised with engine load, the addition of 10% isopropanol (B20P10D70) extended ID and shortened the combustion duration (CD) at low and medium loads. Regarding performance, the lower calorific value of the oxygenated blends led to a slight penalty in BTE, which decreased by 4.59% for B20P10D70 at 16.48 Nm according to neat diesel. However, the integration of isopropanol blends with the DOC-SCR system yielded substantial emission mitigation. Notably, the DOC highly promoted oxidation reactions, reducing CO emissions to levels below the detection limit (zero emissions) for B20P10D70 at 10.98 Nm, and for B20P5D75 at 16.48 and 21.97 Nm loads. Furthermore, isopropanol addition resulted in lower CO 2 concentrations under the tested operating conditions, while the SCR system provided a remarkable 47.05% reduction in NO x emissions at full load with the B20P10D70 blend. These findings demonstrate that utilizing isopropanol as a biodiesel co-solvent alongside DOC-SCR systems is a highly effective strategy for suppressing diesel engine emissions.
Low load reactivity controlled compression ignition (RCCI) operation results in high engine-out total hydrocarbon (THC) emissions, and low combustion efficiency with increased fraction of the low reactivity fuel. Methods to reduce THC emissions generally lead to increased nitrogen oxides (NO x ) emissions resulting in a NO x -THC trade-off in low load RCCI operation. High THC emissions is attributed to reduced reactivity of the in-cylinder charge. Three strategies, such as: (1) increased coolant temperature, (2) use of higher reactivity (compared to diesel) paraffinic synthetic gas to liquid (GTL) fuel and (3) a small quantity of diesel injection in the intake stroke, are employed in this work to enhance the reactivity of the in-cylinder charge prior to the start of combustion and their effects on reducing THC emissions and improving combustion efficiency are investigated. With an increased coolant temperature (100°C), THC emissions reduce by ∼18% compared to baseline RCCI operation with 85°C coolant temperature. GTL, when used as an HRF at similar start of injection timing (SOI) as baseline RCCI, results in ∼34% reduction in THC emissions, albeit with an increase in NO x emissions, which, however, is reduced significantly with advancing the SOI further. A small quantity of diesel injection in the intake stroke (17% of the total diesel quantity) results in 22.5% reduction in THC emissions, and 3.2 and 4.7 percentage points increase in thermal efficiency and combustion efficiency, respectively, compared to the baseline RCCI strategy. In all these strategies, THC reduction is achieved while keeping NO x emissions below 15 ppm (<0.3 g/kWh (indicated) ).
Wide-range fuel delivery is essential for stable combustion and precise control, yet conventional injectors suffer from low resolution and strong nonlinearity at small injection quantities. This study investigates a high-linearity injector through combined experiments and multi-physics simulation to clarify full-range fuel delivery behavior and governing mechanisms. Injection-rate measurements and a validated dynamic model reveal a nonlinear injection quantity–pulse width ( Q–PW ) response at small pulse widths and a near-linear relationship after a stable high-flow stage is established. A segmented model is therefore developed for full-range fuel delivery prediction, and the critical pulse width ( PW c ) is identified as the macroscopic boundary between the two response regions. Mechanism analysis shows that the nozzle orifice diameter dominates the wide-range delivery capability, needle lift governs linear-region response and accuracy, and inlet/outlet orifice sizes jointly determine dynamic response. Larger nozzle and outlet orifices, increased needle lift, and a smaller inlet orifice expand the high-quantity regulation range, whereas opposite trends improve small-quantity control. A larger outlet throttling orifice ( DZ ), supplemented by an appropriately sized inlet orifice (DA ), provides the optimal basis for wide-condition adaptability. Comprehensive evaluation further indicates that structural parameters affect linearity, dynamic response, and modulation range in different ways, highlighting the importance of coordinated parameter matching. This work provides a basis for full-range fuel delivery prediction, structural optimization, and precision control of advanced high-pressure injection systems.
