Transportation of people and goods largely relies on the use of fossil hydrocarbons, contributing to global warming and problems with local air quality. There are a number of alternatives to fossil fuels that can avoid a net carbon emission and can also decrease pollutant emissions. However, many have significant difficulty in competing with fossil fuels due to either limited availability, limited energy density, high cost, or a combination of these. Methanol (CH 3 OH) is one of these alternatives, which was demonstrated in large fleet trials during the 1980s and 1990s, and is currently again being introduced in various places and applications. It can be produced from fossil fuels, but also from biomass and from renewable energy sources in carbon capture and utilization schemes. It can be used in pure form or as a blend component, in internal combustion engines (ICEs) or in direct methanol fuel cells (DMFCs). These features added to the fact it is a liquid fuel, making it an efficient way of storing and distributing energy, make it stand out as one of the most attractive scalable alternatives. This review focuses on the use of methanol as a pure fuel or blend component for ICEs. First, we introduce methanol historically, briefly introduce the various methods for its production, and summarize health and safety of using methanol as a fuel. Then, we focus on its use as a fuel for ICEs. The current data on the physical and chemical properties relevant for ICEs are reviewed, highlighting the differences with fuels such as ethanol and gasoline. These are then related to the research reported on the behaviour of methanol and methanol blends in spark ignition and compression ignition engines. Many of the properties of methanol that are significantly different from those of for example gasoline (such as its high heat of vaporization) lead to advantages as well as challenges. Both are extensively discussed. Methanol's performance, in terms of power output, peak and part load efficiency, and emissions formation is summarized, for so-called flex-fuel engines

-Removing the biomass limit is one of the great challenges to further enlarge the share of renewable ethanol as alternative for fossil fuels. One of the possible solutions for this constraint are the ternary GEM (Gasoline-Ethanol-Methanol) blends. The air-to-fuel ratio of these blends is hereby chosen at the value of an E85-blend (9.75 kg air/ kg fuel) while the ethanol is replaced by methanol/gasoline and therefore these blends are called 'isostoichiometric'. If the methanol is produced out of renewable sources, these blends can help extend the part of clean fuels on the market. The ternary blends show few differences in physical properties for the total range of possible blends and are considered as drop-in alternatives to the original E85-blend for a flex fuel engine. In this paper the performance and engine-out emissions of four of these GEM-blends were examined on a 4 cylinder 1.8 l PFI production engine. A single cylinder engine with high compression ratio was used for a preliminary study of the knock behavior of these blends. The measurement results are compared with those on neat gasoline, methanol and ethanol to demonstrate the potential of these ternary blends as a fossil fuel alternative. All the GEM fuels which were tested gave very similar results to E85 and can therefore indeed be used as 'drop-in' fuels for flex-fuel vehicles.

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To better understand and predict the combustion behavior of methanol in engines, sound knowledge of the effect of the pressure, unburned mixture temperature, and composition on the laminar burning velocity is required. Because many of the existing experimental data for this property are compromised by the effects of flame stretch and instabilities, this study was aimed at obtaining new, accurate data for the laminar burning velocity of methanol−air mixtures. Non-stretched flames were stabilized on a perforated plate burner at 1 atm. The heat flux method was used to determine burning velocities under conditions when the net heat loss from the flame to the burner is zero. Equivalence ratios and initial temperatures of the unburned mixture ranged from 0.7 to 1.5 and from 298 to 358 K, respectively. Uncertainties of the measurements were analyzed and assessed experimentally. The overall accuracy of the burning velocities was estimated to be better than ±1 cm/s. In lean conditions, the correspondence with recent literature data was very good, whereas for rich mixtures, the deviation was larger. The present study supports the higher burning velocities at rich conditions, as predicted by several chemical kinetic mechanisms. The effects of the unburned mixture temperature on the laminar burning velocity of methanol were analyzed using the correlation u L = u L0 (T u /T u0 ) α . Several published expressions for the variation of the power exponent α with the equivalence ratio were compared against the present experimental results and calculations using a detailed oxidation kinetic model. Whereas most existing expressions assume a linear decrease of α with an increasing equivalence ratio, the modeling results produce a minimum in α for slightly rich mixtures. Experimental determination of α was only possible for lean to stoichiometric mixtures and a single data point at ϕ = 1.5. For these conditions, the measurement data agree with the modeling results.

On the applicability of empirical heat transfer models for hydrogen combustion engines AbstractHydrogen-fuelled internal combustion engines are being investigated as an alternative for current drive trains because they have a high efficiency, near-zero noxious and zero tailpipe greenhouse gas emissions. A thermodynamic model of the engine cycle would enable a cheap and fast optimization of engine settings for operation on 10 hydrogen, facilitating the development of these engines. The accuracy of the heat transfer submodel within the thermodynamic model is important to simulate accurately the emissions of oxides of nitrogen which are influenced by the maximum gas temperature. These emissions can occur in hydrogen internal combustion engines at high loads and they are an important constraint for power and efficiency optimization. The most 15 common heat transfer models in engine research are those from Annand and Woschni. These models are developed for fossil fuels, which have different combustion properties. Therefore, they need to be evaluated for hydrogen. We have measured the heat flux and the wall temperature in an engine that can run on hydrogen and methane. This paper describes an evaluation of the models of Annand and Woschni, using those heat 20 flux measurements and assesses if the models capture the effect of changing combustion and fuel properties. The models fail on all the tests, so they need to be improved to accurately model the heat transfer generated by hydrogen combustion.Keywords: hydrogen, methane, internal combustion engine, experimental, heat transfer, model

Experimental measurements of the laminar burning velocity are mostly limited in pressure and temperature and can be compromised by the effects of flame stretch and instabilities. Computationally, these effects can be avoided by calculating one-dimensional, planar adiabatic flames using chemical oxidation mechanisms. Chemical kinetic models are often large, complex and take a lot of computation time, and few models exist for multi-component fuels. The aim of the present study is to investigate if simple mixing rules are able to predict the laminar burning velocity of fuel blends with a good accuracy. An overview of different mixing rules to predict the laminar burning is given and these mixing rules are tested for blends of hydrocarbons and ethanol. Experimental data of ethanol/n-heptane and ethanol/n-heptane/iso-octane mixtures and modeling data of an ethanol/nheptane blend and blends of ethanol and a toluene reference fuel are used to test the different mixing rules. Effects of higher temperature and pressure on the performance of the mixing rules are investigated. It was found that simple mixing rules that consider only the change in composition are accurate enough to predict the laminar burning velocity of ethanol/hydrocarbon blends. For the blends used in this study, a Le Chatelier's rule based on energy fractions is preferable because of the similar accuracy in comparison to other mixing rules while being more simple to use.