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In pursuing sustainable automotive technologies, exploring alternative fuels for hybrid vehicles is crucial in reducing environmental impact and aligning with global carbon emission reduction goals. This work compares methanol and naphtha as potential suitable alternative fuels for running in a battery-driven light-duty hybrid vehicle by comparing their performance with the diesel baseline engine. This work employs a 0-D vehicle simulation model within the GT-Power suite to replicate vehicle dynamics under the Worldwide Harmonized Light Vehicles Test Cycle (WLTC). The vehicle choice enables the assessment of a delivery application scenario using distinct payload capacities: 0%, 25%, 50%, and 100%. The model is fed with engine maps derived from previous experimental work conducted in the same engine, in which a full calibration was obtained that ensures the engine's operability in a wide region of rotational speed and loads.

Ammonia has emerged as a promising carbon-free alternative fuel for internal combustion engines (ICE), particularly in large-bore engine applications. However, integrating ammonia into conventional engines presents challenges, prompting the exploration of innovative combustion strategies like dual-fuel combustion. Nitrous oxide (N2O) emissions have emerged as a significant obstacle to the widespread adoption of ammonia in ICE. Various studies suggest that combining exhaust gas recirculation (EGR) with adjustments in inlet temperature and diesel injection timing can effectively mitigate nitrogen oxides (NOx) emissions across diverse operating conditions in dual-fuel diesel engines.

Alternative fuels, such as natural and bio-gas, are attractive options for reducing greenhouse gas emissions from combustion engines. However, the naturally occurring variation in gas composition poses a challenge and may significantly impact engine performance. The gas composition affects fundamental fuel properties such as flame propagation speed and heat release rate. Deviations from the gas composition for which the engine was calibrated result in changes in the combustion phase, reducing engine efficiency and increasing fuel consumption and emissions. However, the efficiency loss can be limited by estimating the combustion phase and adapting the spark timing, which could be implemented favorably using a closed-loop control approach. In this paper, we evaluate the efficiency loss resulting from varying gas compositions and the benefits of using a closed-loop controller to adapt the spark timing to retain the nominal combustion phase.

The increasing need to reduce greenhouse gas emissions and shift away from fossil fuels has raised an interest for methanol. Methanol can be produced from renewable sources and can drastically lower soot emissions from compression ignition engines (CI). As a result, research and development efforts have intensified focusing on the use of methanol as a replacement for diesel in CI engines. The issue with methanol lies in the fact that methanol is challenging to ignite through compression alone, particularly at low-load and cold starts conditions. This challenge arises from methanol's high octane number, low heating value, and high heat of vaporization, all of which collectively demand a substantial amount of heat for methanol to ignite through compression.

The growing demand to lower greenhouse gas emissions and transition from fossil fuels, has put methanol in the spotlight. Methanol can be produced from renewable sources and has the property of burning almost soot-free in compression ignition (CI) engines. Consequently, there has been a notable increase in research and development activities directed towards exploring methanol as a viable substitute for diesel fuel in CI engines. The challenge with methanol lies in the fact that it is difficult to ignite through compression alone, particularly in low-load and cold start conditions. This difficulty arises from methanol's high octane number, relatively low heating value, and high heat of vaporization, collectively demanding a considerable amount of heat for methanol to ignite through compression. Previous studies have addressed the use of a pilot injection in conjunction with a larger main injection to lower the required intake air temperature for methanol to combust at low loads.

Mitigating human-made climate change means cutting greenhouse gas (GHG) emissions, especially carbon dioxide (CO2), which causes climate change. One approach to achieving this is to move to a carbon-free economy where carbon emissions are offset by carbon removal or sequestration. Transportation is a significant contributor to CO2 emissions, so finding renewable alternatives to fossil fuels is crucial. Green hydrogen-fueled engines can reduce the carbon footprint of transportation and help achieve a carbon-free economy. However, hydrogen combustion is challenging in an internal combustion engine due to flame instabilities, pre-ignition, and backfire. Numerical modeling of hydrogen combustion is necessary to optimize engine performance and reduce emissions. In this work, a numerical methodology is proposed to model lean hydrogen combustion in a turbocharged port fuel injection (PFI) spark-ignition (SI) engine for automotive applications.

Methanol is currently being evaluated as a promising alternative fuel for internal combustion engines, due to being attainable by carbon neutral or negative pathways (renewable energy and carbon capture technology). The low ignitability of methanol has made it attractive mostly as a fuel for spark ignition engines, however the low sooting properties of the fuel could potentially reduce the NOx-soot tradeoff present in compression ignition engines. In this work, using a 4-cylinder engine with compression ratio modified from 16:1 to 19:1, methanol combustion is evaluated under five operating conditions in terms of fuel consumption, criteria pollutants, CO2 emissions and engine efficiency in addition to the qualitative assessment of the combustion stability. It was found that combustion is stable at medium to high loads, with medium load NOx emissions levels at least 30% lower than the original diesel engine and comparable emissions at maximum load conditions.

The worldwide adoption of renewable energy mandates, together with the widespread utilization of biofuels has created a sharp increase in the production of biodiesel (fatty acid alkyl esters). As a consequence, the production of glycerol, the main by-product of the transesterification of fatty acids, has increased accordingly, which has led to an oversupply of that compound on the markets. Therefore, in order to increase the sustainability of the biodiesel industry, alternative uses for glycerol need to be explored and the production of fuel additives is a good example of the so-called glycerol valorization. The goal of this study is therefore to evaluate the suitability of a number of glycerol-derived compounds as diesel fuel additives. Moreover, this work concerns the assessment of low-concentration blends of those glycerol derivatives with diesel fuel, which are more likely to conform to the existing fuel standards and be used in unmodified engines.

The transportation industry has been scrutinized for its contribution towards the global greenhouse gas emissions over the years. While the automotive sector has been regulated by strict emission legislation globally, the emissions from marine transportation have been largely neglected. However, during the past decade, the international maritime organization focused on ways to lower the emission intensity of the marine sector by introducing several legislations. This sets limits on the emissions of different oxides of carbon, nitrogen and sulphur, which are emitted in large amounts from heavy fuel oil (HFO) combustion (the primary fuel for the marine sector). A 40% and 70% reduction per transport work compared to the levels of 2008 is set as target for CO2 emission for 2030 and 2050, respectively. To meet these targets, commonly, methanol, as a low-carbon fuel, and ammonia, as a zero-carbon fuel, are considered.

Fuel film deposits on combustion chamber walls are understood to be the main source of particle emissions in GDI engines under homogenous charge operation. More precisely, the liquid film that remains on the injector tip after the end of injection is a fuel rich zone that undergoes pyrolysis reactions leading to the formation of poly-aromatic hydrocarbons (PAH) known to be the precursors of soot. The physical phenomena accompanying the fuel film deposit, evaporation, and the chemical reactions associated to the injector film are not yet fully understood and require high fidelity CFD simulations and controlled experimental campaigns in optically accessible engines. To this end, a simplified model based on physical principles is developed in this work, which couples an analytical model for liquid film formation and evaporation on the injector tip with a stochastic particle dynamics model for particle formation.

In recent decades, the importance of emerging alternative fuels has increased significantly as a solution to the problems of global warming and air pollution from energy production. In this context, ammonia (NH3) is seen as a potential option and energy vector that may be able to overcome the technical challenges associated with the use of other carbon-free fuels such as hydrogen (H2) in internal combustion engines (ICE). In this research, a numerical methodology for evaluating the impact of using ammonia as a fuel for spark-ignition ICEs has been developed. A combination of a single-cylinder and multi-cylinder numerical experiments has been performed to identify the main challenges and determine correct engine configuration. In addition, the performance of the engine has been evaluated through standard homologation driving cycles, contrasting it with other alternative propulsion configurations.

A modern diesel engine is a reliable and efficient mean of producing power. A way to reduce harmful exhaust and greenhouse gas (GHG) emissions and secure the sources of energy is to develop technology for an efficient diesel engine operation independent of fossil fuels. Renewable diesel fuels are compatible with diesel engines without any major modifications. Rapeseed oil methyl esters (RME) and other fatty acid methyl esters (FAME) are commonly used in low level blends with diesel. Lately, hydrotreated vegetable oil (HVO) produced from vegetable oil and waste fat has found its way into the automotive market, being approved for use in diesel engines by several leading vehicle manufacturers, either in its pure form or in a mixture with the fossil diesel to improve the overall environmental footprint. There is a lack of data on how renewable fuels change the semi-volatile organic fraction of exhaust emissions.

An increasing need to lower greenhouse gas emissions, and so move away from fossil fuels like diesel and gasoline, has greatly increased the interest for methanol. Methanol can be produced from renewable sources and eliminate soot emissions from combustion engines [1]. Since compression ignition (CI) engines are used for the majority of commercial applications, research is intensifying into the use of methanol, as a replacement for diesel fuel, in CI engines. This includes work on dual-fuel set-ups, different fuel blends with methanol, ignition enhancers mixed with methanol, and partially premixed combustion (PPC) strategies with methanol. However, methanol is difficult to ignite, using compression alone, at low load conditions. The problem comes from methanol’s high octane number, low lower heating value and high heat of vaporization, which add up to a lot of heat being needed from the start to combust methanol [2].

A commercially available fuel, E85, a blend of ~85% ethanol and ~15% gasoline, can be a viable substitute for fossil fuels in internal combustion engines in order to achieve a reduction of the greenhouse gas (GHG) emissions. Ethanol is traditionally made of biomass, which makes it a part of the food-feed-fuel competition. New processes that reuse waste products from other industries have recently been developed, making ethanol a renewable and sustainable second-generation fuel. So far, work on E85 has focused on spark ignition (SI) concepts due to high octane rating of this fuel. There is very little research on its application in CI engines. Alcohols are known for low soot particle emissions, which gives them an advantage in the NOx-soot trade-off of the compression ignition (CI) concept.

De-fossilization is an increasingly important trend in the energy sector. In the transport sector the de-fossilization efforts have been centered in promoting the electrification of vehicles, nonetheless other pathways, like the use of carbon neutral or carbon-offsetting fuels under current vehicle fleets, are also worth considering. Low-carbon fuels (LCF) can be synthetized from sources that can take advantage of the carbon already present in the atmosphere (either by technologies like direct carbon capture or biological processes like photosynthesis in biofuels) and use energy from renewable sources for the necessary industrial processes. Although, LCFs can be compared to fossil fuels as energy sources for internal combustion engines, their composition is not the same and their properties can modify the engine combustion and emissions.

Focusing on the dual-mode dual-fuel (DMDF) combustion concept, a combined optimization of the piston bowl geometry with the fuel injection strategy was conducted at low, mid, and high loads. By coupling the KIVA-3V code with the enhanced genetic algorithm (GA), a total of 14 parameters including the piston bowl geometric parameters and the injection parameters were optimized with the objective of meeting Euro VI regulations while improving the fuel efficiency. The optimal piston bowl shape coupled with the corresponding injection strategy was summarized and integrated at various loads. Furthermore, the effects of the key geometric parameters were investigated in terms of organizing the in-cylinder flow, influencing the energy distribution, and affecting the emissions. The results indicate that the behavior of the DMDF combustion mode is further enhanced in the aspects of improving the fuel economy and controlling the emissions after the bowl geometry optimization.

Fleet electrification has been demonstrated as a feasible solution to decarbonize the heavy-duty transportation sector. The combination of hybridization and advanced combustion concepts may provide further advantages by also introducing reductions on criteria pollutants such as nitrogen oxides and soot. In this scenario, the interplay among the different energy paths must be understood and quantified to extract the full potential of the powertrain. One of the key devices in such powertrains is the battery, which involves different aspects regarding operation, safety, and degradation. Despite this complexity, most of the models still rely on resistance-capacity models to describe the battery operation. These models may lead to unpractical results since the current flow is governed by limiters rather than physical laws. Additionally, phenomena related with battery degradation, which decreases the nominal capacity and enhances the heat generation are also not considered in this approach.

Internal combustion engines must be individually tested at the end of the manufacturing process. In recent years classical hot test stands, where the engine is run for several minutes, are being replaced by cold test alternatives. The latter allow fast testing cycles using an external motoring device without using any fuel. The absence of fuel and combustion lowers the health and safety requirements for the plant itself and subsequent engine transport, but this comes at the cost of additional difficulties for the verification of the correct assembly and operation of the combustion system hardware. This paper presents a cold test concept, which includes dedicated measurements and algorithms for the detection of common failures in the manufacturing process, including those of the combustion hardware.

Economy decarbonization will be one of the main goals for the following years. Research efforts are being focused on reducing carbon-based emissions, by increasing the efficiency of the transport power plants while developing new fuel production methods that reduce the environmental footprint of the refinement process. Consequently, the depletion of conventional fuels derived from petroleum with high carbon content, such as gasoline and diesel, motivated the development of propulsive alternatives for the transportation sector. In this paradigm, methane (CH4) fuel appears as a mid-term solution due to its low carbon content, if compared with traditional fuels, and the low CO2 emissions during its production from renewable sources. However, the intrinsic properties of methane compromise the combustion process, subsequently increasing the emission of CO2.

The temperature of fuel injectors can affect the flow inside nozzles and the subsequent spray and liquid films on the injector tips. These processes are known to impact fuel mixing, combustion and the formation of deposits that can cause engines to go off calibration. However, there is a lack of experimental data for the transient evolution of nozzle temperature throughout engine cycles and the effect of operating conditions on injector tip temperature. Although some measurements of engine surface temperature exist, they have relatively low temporal resolutions and cannot be applied to production injectors due to the requirement for a specialist coating which can interfere with the orifice geometry. To address this knowledge gap, we have developed a high-speed infrared imaging approach to measure the temperature of the nozzle surface inside an optical diesel engine.