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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.

Using renewable fuels is a reliable approach for decarbonization of combustion engines. iso-Butanol and n-butanol are known as longer chain alcohols and have the potential of being used as gasoline substitute or a renewable fraction of gasoline. The combustion behavior of renewable fuels in modern combustion engines and advanced combustion concepts is not well understood yet. Low-temperature combustion (LTC) is a concept that is a basis for some of the low emissions-high efficiency combustion technologies. Fuel ɸ-sensitivity is known as a key factor to be considered for tailoring fuels for these engines. The Lund ɸ-sensitivity method is an empirical test method for evaluation of the ɸ-sensitivity of liquid fuels and evaluate fuel behavior in thermal. iso-Butanol and n-butanol are two alcohols which like other alcohol exhibit nonlinear behavior when blended with (surrogate) gasoline in terms of RON and MON.

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.

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.

Low temperature combustion (LTC), is a promising alternative for combustion engines, because it combines the positive aspects of both CI and SI engines, high efficiency and low emissions. Another positive aspect of LTC is that it can operate with gasoline of different octane ratings. Still, higher octane gasolines prove to be difficult to operate at low load conditions leading to high combustion instability (COV) that leads also to high emissions. This drawback can be reduced by increasing the intake air temperature or increasing compression ratio, but it is not a viable strategy in conventional applications. For a diesel engine running under LTC conditions, a possibility is to use the existing hardware, glow plugs in this case, to increase the in-cylinder temperature at low loads and facilitate an improved combustion event.

Methanol is not a fuel typically used in compression ignition engines due to the high resistance to auto-ignition. However, conventional diesel combustion and PPC offer high engine efficiency along with low HC and CO emissions, albeit with the trade-off of increased NOx and PM emissions. This trade-off balance is mitigated in the case of methanol and other alcohol fuels, as they bring oxygen in the combustion chamber. Thus methanol compression ignition holds the potential for a clean and effective alternative fuel proposition. Most existing research on methanol is on SI engines and very little exists in the literature regarding methanol auto-ignition engine concepts. In this study, the spray characteristics of methanol inside the optically accessible cylinder of a DI-HD engine are investigated. The liquid penetration length at various injection timings is documented, ranging from typical PPC range down to conventional diesel combustion.

There is growing global interest in using renewable alcohols to reduce the greenhouse gases and the reliance on conventional fossil fuels. Recent studies show that methanol combined with partially premixed combustion provide clear performance and emission benefits compared to conventional diesel diffusion combustion. Nonetheless, high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions can be stated as the main PPC drawback in light load condition when using high octane fuel such as Methanol with single injection strategy. Thus, the present experimental study has been carried out to investigate the influence of multiple injection strategies on the performance and emissions with methanol fuel in partially premixed combustion. Specifically, the main objective is to reduce HC, CO and simultaneously increase the gross indicated efficiency compared to single injection strategy.

This study investigates particulate matter (PM) and regulated emissions from renewable rapeseed oil methyl ester (RME) biodiesel in pure and blended forms and contrasts that to conventional diesel fuel. Environmental and health concerns are the major motivation for combustion engines research, especially finding sustainable alternatives to fossil fuels and reducing diesel PM emissions. Fatty acid methyl esters (FAME), including RME, are renewable fuels commonly used from low level blends with diesel to full substitution. They strongly reduce the net carbon dioxide emissions. It is largely unknown how the emissions and characteristics of PM get altered by the combined effect of adding biodiesel to diesel and implementing modern engine concepts that reduce nitrogen oxides (NOx) emissions by exhaust gas recirculation (EGR).

Partially premixed combustion (PPC) is one of several advanced combustion concepts for the conventional diesel engine. PPC uses a separation between end of fuel injection and start of combustion, also called ignition dwell, to increase the mixing of fuel and oxidizer. This has been shown to be beneficial for simultaneously reducing harmful emissions and fuel consumption. The ignition dwell can be increased by means of exhaust gas recirculation or lower intake temperature. However, the most effective means is to use a fuel with high research octane number (RON). Methanol has a RON of 109 and a recent study found that methanol can be used effectively in PPC mode, with multiple injections, to yield high brake efficiency. However, the early start of injection (SOI) timings in this study were noted as a potential issue due to increased combustion sensitivity. Therefore, the present study attempts to quantify the changes in engine performance for different injection strategies.

Partially premixed combustion (PPC) with gasoline fuels is a new promising combustion concept for future internal combustion engines. However, many researchers have argued the capabilities of research octane number (RON) and Motor Octane Number (MON) to describe the autoignition behaviour of gasoline fuels in advanced combustion concepts like PPC. The objective of this study is to propose a new method, called PPC number, to characterize the auto ignition quality of gasoline fuels in a light-duty direct injected compression ignition engine under PPC conditions. The experimental investigations were performed on a 4-cylinder Volvo D4 2 litre engine. The ignition delay which was defined as the crank angle degrees between the start of injection (SOI) and start of combustion (SOC) was used to represent the auto ignition quality of a fuel.

The combustion process in a homogeneous charge compression ignition (HCCI) engine is mainly governed by ignition wave propagation. The in-cylinder pressure, heat release rate, and the emission characteristics are thus largely driven by the chemical kinetics of the fuel. As a result, CFD simulation of such combustion process is very sensitive to the employed reaction mechanism, which model the real chemical kinetics of the fuel. In order to perform engine simulation with a range of operating conditions and cylinder-piston geometry for the design and optimization purpose, it is essential to have a chemical kinetic mechanism that is both accurate and computational inexpensive. In this paper, we report on the evaluation of several chemical kinetic mechanisms for methanol combustion, including large mechanisms and skeletal/reduced mechanisms.

Partially premixed combustion (PPC) in internal combustion engine as a low temperature combustion strategy has shown great potential to achieve high thermodynamic efficiency. Methanol due to its unique properties is considered as a preferable PPC engine fuel. The injection timing to achieve methanol PPC conditions should be set very close to TDC, allowing to utilize spray-bowl interaction to further improve combustion process in terms of emissions and heat losses. In this study CFD simulations are performed to investigate spray-bowl interaction for a number of different piston designs and its impact on the heat transfer and the overall piston performance. The validation case is based on a single cylinder heavy-duty Scania D13 engine with a compression ratio 15. The operation point is set to low load 5.42 IMEPg bar with SOI -3 aTDC.

Diesel engines are one of the most important power generating units these days. Increasing greenhouse gas emission level and the need for energy security has prompted increasing research into alternative fuels for diesel engines. Biodiesel is the most popular among the alternatives for diesel fuel as it is biodegradable and renewable and can be produced domestically from vegetable oils. In recent years, hydrotreated vegetable oil (HVO) has also gained popularity due to some of its advantages over biodiesel such as higher cetane number, lower deposit formation, storage stability, etc. HVO is a renewable, paraffinic biobased alternative fuel for diesel engines similar to biodiesel. Unlike biodiesel, the production process for HVO involves hydrogen as catalyst instead of methanol which removes oxygen content from vegetable oil.

Heavy-duty direct injection compression ignition (DICI) engine running on methanol is studied at a high compression ratio (CR) of 27. The fuel is injected with a common-rail injector close to the top-dead-center (TDC) with two injection pressures of 800 bar and 1600 bar. Numerical simulations using Reynold Averaged Navier Stokes (RANS), Lagrangian Particle Tracking (LPT), and Well-Stirred-Reactor (WSR) models are employed to investigate local conditions of injection and combustion process to identify the mechanism behind the trend of increasing nitrogen oxides (NOx) emissions at higher injection pressures found in the experiments. It is shown that the numerical simulations successfully replicate the change of ignition delay time and capture variation of NOx emissions.

Our previous research investigated the sensitivity of combustion phasing to intake temperature and injection timing during the transition from homogeneous charge compression ignition (HCCI) to partially premixed combustion (PPC) fuelled with generic gasoline. The results directed particular attention to the relationship between intake temperature and combustion phasing which reflected the changing of stratification level with the injection timing. To confirm its applicability with the use of different fuels, and to investigate the effect of fuel properties on stratification formation, primary reference fuels (PRF) were tested using the same method: a start of injection sweep from -180° to -20° after top dead center with constant combustion phasing by tuning the intake temperature. The present results are further developed compared with those of our previous work, which were based on generic gasoline.

Methanol as an alternative fuel in internal combustion engines has an advantage in decreasing emissions of greenhouse gases and soot. Hence, developing of a high performance internal combustion engine operating with methanol has attracted the attention in industry and academic research community. This paper presents a numerical study of methanol combustion at different start-of-injection (SOI) in a direct injection compression ignition (DICI) engine supported by experimental studies. The aim is to investigate the combustion behavior of methanol with single and double injection at close to top-dead-center (TDC) conditions. The experimental engine is a modified version of a heavy duty D13 Scania engine. URANS simulations are performed for various injection timings with delayed SOI towards TDC, aiming at analyzing the characteristics of partially premixed combustion (PPC).

The focus has recently been directed towards the engine out soot from Diesel engines. Running an engine in PPC (Partially Premixed Combustion) mode has a proven tendency of reducing these emissions significantly. In addition to combustion strategy, several studies have suggested that using alcohol fuels aid in reducing soot emissions to ultra-low levels. This study analyzes and compares the characteristics of PM emissions from naphtha gasoline PPC, ethanol PPC, methanol PPC and methanol diffusion combustion in terms of soot mass concentration, number concentration and particle size distribution in a single cylinder Scania D13 engine, while varying the intake O2. Intake temperature and injection pressure sweeps were also conducted. The fuels emitting the highest mass concentration of particles (Micro Soot Sensor) were gasoline and methanol followed by ethanol. The two alcohols tested emitted nucleation mode particles only, whereas gasoline emitted accumulation mode particles as well.