Papers by Sebastian Verhelst
SAE technical paper series, Mar 29, 2022
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SAE Technical Paper Series, 2019
The natural gas/diesel dual-fuel engine is an interesting technique to reduce greenhouse gas emis... more The natural gas/diesel dual-fuel engine is an interesting technique to reduce greenhouse gas emission. A limitation of this concept is the emission of un-combusted methane. In this study we analyzed the influence of PFI gas-injection timing on cylinder to cylinder gas-distribution, and the resulting methane emissions. This was done on a 6 cylinder HD engine test bench and in a GT-power simulation of the same engine. The main variable in all tests was the timing of the intake port gas injection, placed either before, after, or during the intake stroke. It showed that injecting outside of the intake window resulted in significant variation of the amount of trapped gaseous fuel over the 6 cylinders, having a strong impact on methane emissions. Injecting outside of the intake stroke results in gas awaiting in the intake port. Both testing and simulation made clear that as a result of this, cylinder 1 leans out and cylinder 6 enriches. The simulation showed how this is caused by the airflow into the manifold, which enters the manifold close to cylinder 1. This flow picks up gas residing before the first cylinders, and distributes it over the cylinders further downstream. The richer cylinders have a higher absolute methane emission. By calculating the ratio between trapped and emitted methane, we found operating points where the enrichment caused by unequal gas distribution led to lower relative methane emission. This can be attributed to the better combustibility of methane under richer conditions. Although the injection timing was placed outside the intake window on purpose in our experiments, the same distribution problem occurs in situations where the gas injection is longer than the intake stroke. This is a common situation with currently available dual-fuel systems. The solution can be found in a gas injection system with significantly higher capacity. (Less)
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Energies
Isobutanol, one of the four isomers of butanol (C4H9OH), possesses some favorable properties that... more Isobutanol, one of the four isomers of butanol (C4H9OH), possesses some favorable properties that make it an attractive fuel for internal combustion engines. For instance, when compared to ethanol, isobutanol features a higher heating value and lower hygroscopicity (which prevents corrosion and enables it to be transported via pipelines). Moreover, its addition to gasoline does not distort the fuel blend’s vapor pressure to the same extent as ethanol does. All of this while having a high octane rating. Those advantages over ethanol suggest that isobutanol has the potential to be used as a gasoline oxygenate or even as a neat fuel. Furthermore, the advances made in biotechnology have enabled isobutanol to be produced from biomass more efficiently, allowing it to be used in compliance with existing renewable energy mandates. This article reviews some of the relevant literature dedicated to isobutanol as a motor fuel, covering its merits and drawbacks. Several studies on its combustion...
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SAE technical paper series, Sep 9, 2019
The present work describes the numerical modeling of medium-speed marine engines, operating in a ... more The present work describes the numerical modeling of medium-speed marine engines, operating in a fumigated dual-fuel mode, i.e. with the second fuel injected in the ports. This engine technology allows reducing engine-out emissions while maintaining the engine efficiency and can be fairly easily retrofitted from current diesel engines. The main premixed fuel that is added can be a low-carbon one and can additionally be of a renewable nature, thereby reducing or even completely removing the global warming impact. To fully optimize the operational parameters of such a large marine engine, computational fluid dynamics can be very helpful. Accurately describing the combustion process in such an engine is key, as the prediction of the heat release and the pollutant formation is crucial. Auto-ignition of the diesel fuel needs to be captured, followed by the combustion and flame propagation of the premixed fuel. In this work, an approach based on tabulated kinetics has been used, to include detailed chemistry while still maintaining acceptable computation times. To allow for the modeling of a fumigated dual-fuel engine, this approach has been extended with a Coherent Flame Model (CFM), capable of tracking the premixed flame surface. This methodology has been validated for standard diesel operation, dual-fuel diesel/natural gas and diesel/methanol operation. The model has been applied under a variety of different loads, speeds, diesel substitution ratios and equivalence ratios to capture and study a large operating range. While still observing some discrepancies between certain simulations and the corresponding experiments, already a large improvement in the prediction of fumigated dual-fuel engine operation was observed with the proposed method.
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The charge cooling effect of methanol was studied and compared to that of iso-octane. The reducti... more The charge cooling effect of methanol was studied and compared to that of iso-octane. The reduction in compression work due to fuel evaporation and the gain in expansion work were evaluated by the means of in-cylinder pressure measurements in a HD CI engine. A single injection strategy was utilized to obtain a longer premixing period to adequately capture the cooling effect. The effect was clear for both tested fuels, however, methanol generally caused the pressure to reduce more than iso-octane near TDC. It was found that the contribution of reduced compression work to the increased net indicated efficiency is negligible. Regarding the expansion work, a slower combustion with higher pressure was obtained for methanol in comparison to that of iso-octane due to the cooling effect of fuel evaporation. As a result from this, a lower heat transfer loss was obtained for methanol, in addition to the significantly lower NOx emissions.
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Fuel
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Fuel
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SAE Technical Paper Series
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The increasing greenhouse gas concentration in the atmosphere and dismissing of fossil fuels rece... more The increasing greenhouse gas concentration in the atmosphere and dismissing of fossil fuels recent decades has heightened the need for the next generation of internal combustion engines (ICE). Using alternative fuels for ICE is one of the current directions for engine development. The simplest alcohol – methanol (CH3OH) is considered as a future fuel for spark ignition (SI) engines because of its high octane number, flame speed and heat of vaporization. The engine is able to operate under high compression ratio with a cooler intake charge. Additionally, with less heat loss, the engine efficiency further improves. Thanks to its high H/C ratio, methanol is also acknowledged as a hydrogen carrier fuel. With low reaction temperature, methanol reforming technologies are widely employed in chemical industry to produce hydrogen rich gas. Currently, steam reforming is used most because this approach provides the highest yield of hydrogen. According to Peppley et al. [1], there are three ov...
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Ethanol is the most common alternative for conventi onal gasoline replacement in sparkignition en... more Ethanol is the most common alternative for conventi onal gasoline replacement in sparkignition engines. It holds multiple advantages over other renewable transportation technologies including energy density, distribution infrastructure compatibility and the possibility of efficiency improvement and pollutant emissions reduction. Most of the fuel grade ethanol is dehydrated to a minimum purity of 99,6 % before blending or direct use as fuel. As this process is the main energy consumer o f the fuel production, it is clear that a large cost reduction can be realized by dropping or decre asing this energy demand. It was investigated if hydrous ethanol is an interesting f uel for flex fuel vehicles where driving range is not of primary importance. Performance and engin e-out emissions of mixtures with 5% v/v, 10% v/v and 20% v/v water were compared to pure ethanol and gasoline on a 4 cylinder 1.8 l PFI production engine. TECHNICAL PAPER ‐
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Although waterborne transport is an energy efficient means of transport, its contribution to gree... more Although waterborne transport is an energy efficient means of transport, its contribution to greenhouse gas emissions is growing and pollutant emissions are high relative to other forms of transport. Emission legislation on the other hand is catching up by introducing strongly reduced emission limits in the upcoming years, which leads to an urgent need for alternative ways of fueling waterborne transport. In the Horizon 2020 “LeanShips” project, the use of methanol as an alternative fuel for shipping is studied in one of its demonstrators. In the demonstrator, a high speed marine diesel engine is converted for methanol use. This paper discusses the rationale for methanol as an alternative fuel for marine transportation, different possible strategies for operating vessel engines on methanol, their pros and cons, and the approach taken within LeanShips, namely dual fuel operation with methanol port injection. The potential of methanol concerning energy efficiency and pollutant emissio...
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The scope of this paper is to analyze the possibilities and feasibilities, as well as the main ex... more The scope of this paper is to analyze the possibilities and feasibilities, as well as the main experimental results reported about the emulsification method applied to waste cooking oils and fatty acid distillates as diesel engine fuels, compared with other commonly used methods. These waste products are obtained in the refining oil industry, food industry and service sector from the frying process, mainly. However, they are a little used as feedstocks to produce biofuels and constitute a potential source of contamination. From the review of the state of arts, significant decreases in exhaust emissions of nitrogen oxides, cylinder pressure, as well as increases of the ignition delay, brake specific fuel consumption, hydrocarbon, smoke opacity, carbon monoxide, particulate matters to emulsified waste cooking oils and fatty acid distillates compared with diesel fuel are reported. In some experiments the emulsified waste cooking oils achieved better performance than neat fatty acid dis...
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Flame or combustion gave humans healthy food, protection, heat, light, and so on. The combustion ... more Flame or combustion gave humans healthy food, protection, heat, light, and so on. The combustion also gave the power for a car to move from point A to point B. Most of the vehicle in the world now are powered by the internal combustion engines. The engine converts the chemical energy stored in the reactant, i.e. mixture of fuel and air, into thermal and mechanical energy. Engines and fuel technology are scalable, cheap and compact. They are also can be produced in a sustainable way or in a carbon-neutral cycle. Therefore, internal combustion engines are still the main power source for the current and for future transport systems. Renewable methanol (or synthetic methanol) is a great fuel for internal combustion engines thanks to its interesting properties and high fuel production efficiency. Methanol is also considered as a hydrogen carrier fuel, which can be easily generated on-board using engine exhaust heat. The present work focuses on the thermochemical recuperation for methanol...
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Climate change and global warming, a growing maritime sector, and the roadmap away from fossil fu... more Climate change and global warming, a growing maritime sector, and the roadmap away from fossil fuels towards a CO2 neutral economy are driving innovations and technology developments. Fuel selection criteria such as sustainability, scalability and storability, lead to the selection of methanol as a viable alternative for fossil fuels. In LeanShips, a European Horizon 2020 Innovation Project, the conversion and operation of a high speed marine diesel engine on dual fuel methanol/diesel has been demonstrated. This paper presents the applied conversion solution, its impact on combustion characteristics, and the results of dual fuel methanol/diesel operation on engine performance parameters such as brake thermal efficiency (BTE), NO and soot emissions. The results were recorded at different engine speeds ranging from 1000 to 2000 rpm and for varying loads, in total 28 load points were tested. At each load point the methanol energy fraction was increased until the boundaries for substitu...
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Fuel Communications, 2021
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Papers by Sebastian Verhelst