Alcohol as an Alternative Fuel for Internal Combustion Engines

The transportation sector is one of the main contributors to global CO₂ emissions and is expected to further increase due to the growth of population and life quality standards. Therefore, to prevent the negative impacts of climate change, the reduction of CO₂ emissions is the top priority. For these reasons, the automotive sector is facing new challenges; advanced internal combustion engines, electrification of the drive train, and replacing fossil fuels can help to meet greenhouse gas emission standards and simultaneously reduce pollutants.

The transportation sector is one of the main contributors to global CO₂ emissions and is expected to further increase due to the growth of population and life quality standards. Therefore, reduction CO₂ emissions is the top priority to prevent the negative impacts of climate change. For these reasons, the automotive sector is facing new challenges, advanced internal combustion engines, electrification of the drive train, replacing fossil fuels can help to meet greenhouse gas emission standards and simultaneously reduce pollutants. In this study, two ethanol fueling modes, dual fuel and blend, are applied in a compression ignition engine to evaluate the effect of different engine calibration parameters on the thermodynamic and emissions. A parametric analysis is conducted for the variables, fuel substitution ratio, injection pattern, fuel injection pressure, and exhaust gas recirculation. The results demonstrate ethanol being a promising alternative to fossil fuels for the globally lower emissions in compliance with the actual advanced engine technologies. Ethanol blend improves the gross-indicated efficiency compared to the dual-fuel and diesel combustion. However, the dual-fuel emitted higher THC and CO emissions than in diesel and blend cases that have comparable levels. Ethanol blends combustion with a high level of ethanol, and EGR employing a multi-injection strategy shows a positive impact on emission reduction while maintaining high efficiency compared to the dual-fuel and diesel combustion. The dual-fuel combustion employing high ethanol, rail pressure, and EGR levels leads to important benefits, minimizing the emissions and noise and maximizing the efficiency.

Particulate filter is the common technique used in the auto-industry to trap the resulted PM from the exhaust. The trapped PM should be oxidized regularly to avoid any unwanted backpressures which in turn can deteriorate the engine’s thermal efficiency and increase the fuel consumption. Soot oxidative reactivity is generally known as the ability of the PM to combust in an oxidizing environment (i.e., usually air), and it is directly linked to the physical and chemical properties of the PM—this is usually defined as the elemental composition, aggregates morphology, and carbon layer arrangement. Changing the operating fuel type results in particulates that strongly differ in their physical and chemical properties. Alcohol fuels are commonly used in spark-ignition engines, but their blends with diesel fuel have also been considered in compression ignition engines and emission benefits have been reported. However, the impact of alcohols on PM characteristics is still not widely investigated, and better understanding is required to tailor the current aftertreatment technologies to optimally operate with those fuels. This review chapter explains the PM physical and chemical properties and highlights their correlation with the oxidative reactivity toward oxygen. Special attention will be given to the role of alcohols in reducing PM emissions and changing its characteristics to better evaluate this renewable category as a potential replacement for fossil fuel application.

Maritime transportation is the most important transportation type since 90% of world trade is carried. There are 96,295 ships in operation all over the world, and more than 300 million tons of fuel is consumed annually. A significant amount of emissions are emitted when ships are in operation. There are strict emission rules and regulations that are entered into force by the International Maritime Organization. To reduce shipping emissions and comply with the emission rules and regulations, there are various technologies and methods, including engine modifications, after-treatment systems, and alternative fuels. In today’s maritime transportation, the use of alternative fuels on ships increases its popularity. Methanol is one of the promising alternative fuels for future maritime transportation. Although methanol-fueled ships are low in number now, methanol has the potential to increase in usage on ships in the future. There is a scant amount of study and a lack of knowledge about methanol usage on marine diesel engines since it is the new fuel for maritime transportation. The methanol combustion at marine diesel engines is needed to be discussed because it is a unique fuel that can provide high engine efficiency and low emissions than diesel fuel. This chapter covers information about the status of maritime transportation, international maritime emission rules and regulations, emission mitigation technologies and methods, methanol at maritime transportation, methanol properties, and combustion concepts, and the methanol partially premixed combustion strategy for maritime transportation. Lastly, the summary section comprises the chapter results. One of the main findings of the chapter is using methanol as an alternative fuel can reduce the different types of regulated emissions at maritime transportation at once without applying additional equipment while providing more efficient marine diesel engines. Another finding is the methanol partially premixed combustion (PPC) strategy showed high engine efficiency than the conventional marine gas oil-fueled diesel engine with lower CO₂ and NOX emissions. The sulfur-free structure of methanol does not emit SOX emissions and the low-carbon chain structure of the methanol molecule extremely decreases PM emission formation. This chapter confirms that the methanol PPC can be a solution for marine engines to comply with emission regulations and more efficient engine operation from low load to high load.

The internal combustion engines remain preferred prime movers for on-road and off-road applications over many decades. However, for reducing the usage of fossil fuels and the harmful pollutants emitted by the conventional engines, it has become imperative that the alternative strategies are developed. In this regard, alcohol fuels are established as one of the alternative energy resources for internal combustion engines. Alcohol fuels have many advantages such as presence of fuel-bound oxygen, higher octane number, higher volatility, etc., compared to those of gasoline. The alcohol fuels are considered as the second-generation biofuel, which is employed as alternative fuels for SI engines and the blending of alcohol fuels such as methanol, ethanol, and butanol with biodiesel, also assists in mitigating the biodiesel-NO_x penalty in diesel engines. Moreover, the alcohol fuels are effective in advanced combustion strategy like low-temperature combustion (LTC). It is opined that the alcohol fuels make use the full merits of LTC which is attributed to the increased octane number, wider equivalence ratio, broad operational range with reduction in emission, higher auto-ignition resistance, and longer ignition delay. Hence, this chapter is aimed to present significant details on combustion and emission characteristics of alcohol-fuelled engines operated on advance combustions strategy of LTC.

Alcohols are renewable in nature and are manufactured from biomass. Butanol is a higher alcohol, and previous researchers reported that it can be utilized as co-solvent to prevent the phase separation of diesel–ethanol blends. This study was conducted in various steps, viz. test of solubility of diesel–ethanol blends containing various proportions of ethanol from 0–50% in increments of 5% in a temperature range of 5–35 °C using butanol as co-solvent in the proportions from 0 to 10% in increments of 1%; test of essential properties of the fuel blends to obtain a possible diesel–ethanol for performance without modification of engine operating parameters and with modified parameters in a compression ignition engine blend under various load conditions. The optimal engine operating parameters such as intake air temperature (50, 75, and 100 °C), nozzle opening pressure (190, 200, and 210 bar), fuel injection timing (23°, 26°, and 29° before top dead center), and compression ratio (17:1, 19:1, and 20.5:1) were obtained by using L₉ orthogonal array and Taghuchi method. Result of the solubility test depicted that the blend containing 50% ethanol and 10% butanol as co-solvent was found stable up to 20 days without suffering from phase separation; results of the property testing indicated that the blend containing 45% of ethanol with 10% butanol as co-solvent possessing competent properties for diesel engine fuel with respect to the ASTM standards; results of the Taghuchi method obtained the optimal operating parameters as 19:1 compression ratio, 29° before top dead center of fuel injection timing, 190 bar of nozzle opening pressure, and 100 °C of intake air temperature. Results of the engine test depicted that the engine fueled with this fuel blend operated under optimal operating parameters produced higher brake thermal efficiency, peak in-cylinder pressure, peak heat release rate, lower oxides of nitrogen, and smoke compared to those produced by deploying the standard operating parameters. However, this fuel blend produced higher hydrocarbons and carbon monoxide emissions at all load conditions. This study replaces 55% of diesel by biofuels.

Alcohols produced from organic matter have been actively considered as a solution to energy demand and an attractive alternative to conventional fuel. These fuels are considered to be green, clean, and renewable. Alcohol-based renewable fuels are generally encouraged to be used in spark-ignition engines, and its implementation in diesel engines is overlooked, because of low cetane number and other issues with fuel injection system. This chapter is a review of recent research work available in the literature and explains about alcohol as a fuel and its utilization in diesel engine, causes of emission in diesel engine, and after-treatment devices to reduce this emission. Topics such as material compatibility and economical aspect of alcohol as a fuel in diesel engine are discussed. Toward the end, combustion characteristics with respect to addition of primary alcohol to diesel are also discussed. This study gives insight into commercial aspect of alcohols as engine fuel and encourages adoption in automobiles engines.

Low-temperature combustions strategy in internal combustion engines provides lower emissions beside high engine performance in according to chemically control combustion temperature. This strategy is divided into three engine types which are premixed charge compression ignition (PCCI), homogenous charge compression ignition (HCCI), and reactivity-controlled compression ignition (RCCI) engines. Low-temperature combustion strategies usually used two various fuels with low and high reactivity. The main purpose of LTC is to providing a lean homogenous air/fuel mixture to obtain lower emissions beside appropriate engine power. Various fuel delivery strategies and different fuels are used in LTC which can be low-reactivity fuels such as gasoline and alcohols and high-reactivity fuels such as diesel and dimethyl ether; a combination of low- and high-reactivity fuels is also in LTC strategies. Among all low-reactivity fuels, alcohol fuels were used in various researches by interested scientists. Ethanol, methanol, butanol, and n-butanol are four types of fuels which were used as low-reactivity fuels in low-temperature combustion engines. These fuels are usually used with high-reactivity fuels such as diesel (n-heptane in numerical works) or due to cooling effects employed at high engine loads as single fuels. Various properties of alcohol fuels make different influences on engine combustion and emission characteristics. This chapter categorized LTC strategies in which alcohol fuels are used as alternative fuel.

Biobutanol is a very promising renewable fuel for spark-ignition (SI) engines due to quite similar properties to conventional gasoline. This chapter discusses the possibility of usage of biobutanol in unmodified spark-ignition engines while blending them with gasoline up to 70% (v/v). Detailed characterization of combustion-related fuel properties of butanol and gasoline butanol blends has been carried out. Fuel efficiency-related performance characteristics have been investigated by comparing brake-specific fuel consumption (BSFC), maximum power, and maximum torque for various butanol blends. Cold and normal engine operation carbon monoxide (CO), hydrocarbons (HC), nitrogen oxide (NO) and carbon dioxide (CO₂₎ emissions of all the fuels have been compared along with baseline gasoline. It was observed that at most of the operating conditions, butanol blends are a better choice over gasoline in terms of emissions and performance. As butanol is an oxygenated fuel, it was observed that butanol blending resulted into improved combustion efficiency and reduced most of the emissions except for NO.

This chapter studied the effect of ethanol fumigation on engine performance using a modern compression ignition engine. Performance-related parameters were investigated at ethanol substitutions of 0, 10, 20, 30, and 40% (by energy) under 25, 50, 75, and 100% load at 1500 and 2000 rpm. Using E10 and E20 in some of the operating modes decreased FMEP and BSFC; while using E40 increased FMEP and BSFC. The mechanical efficiency improved with the use of E10 in half of the operating modes; however, in general there was a decreasing trend associated with increasing ethanol substitution. While ethanol improved the thermal efficiency, lower substitutions performed better. At lower loads, thermal efficiency decreased with higher substitutions, while at higher loads, it increased with higher substitutions. Increasing the ethanol substitution increased the maximum in-cylinder pressure. The maximum rate of pressure rise was minimally impacted at low substitutions, although it increased significantly at high substitutions (>20%). At 1500 rpm, increasing the ethanol substitution decreased the CoV of IMEP, especially with E30 and E40. However, at 2000 rpm, using higher substitutions slightly increased the CoV of IMEP (~2%) at higher loads. Under 25% load, increasing the ethanol substitution increased the maximum apparent heat release rate. Under 50 and 75% loads, by increasing the ethanol substitution there was a tendency toward having double peaks in the heat release diagram. Also, increasing the substitution rate increased the peak values. Under full load, the first peak values increased and the second peak diminished as the ethanol rate increased.

Dual-fuel operation in CI-engine is an emerging strategy to improve engine efficiency along with the simultaneous in-cylinder reduction of NO_x and PM emissions. In dual-fuel operation, low-reactivity fuel (such as methanol, ethanol) and high-reactivity fuel (such as diesel) are used in the same engine cycle. This chapter presents a detailed analysis of performance, combustion, and emission characteristics of low and medium carbon alcohol–diesel fueled dual-fuel CI-engine. This chapter also briefly explains the production of alcohol fuel and the benefits of their inimitable properties. The influence of engine operating parameters on the heat release rate, combustion duration, and cyclic combustion variations has been discussed in this chapter. Additionally, the effect of the operating parameters on CO, unburnt hydrocarbon, NO_x, soot, particle emissions, and unregulated emissions is also presented. Results depict that with an increase in engine load, the combustion characteristics changed from partial burn to misfire to proper combustion and to knocking (at full engine load). The dual-fuel operation has higher HC, CO, HCHO, CH₃OH, HCOOH, C₆H₆, 1,3-C₄H₆, and C₇H₈ emissions, whereas NO_x and soot emissions are lower than conventional diesel operation.

Diesel engines are one of the most preferred internal combustion (IC) engine for heavy-duty transport vehicles due to its higher torque characteristics and better thermal efficiency over gasoline engines. Despite of having advantages in terms of efficiency and durability, it contributes to emissions in the environment, primarily particulate matter (PM) and oxides of nitrogen (NOx). Diesel PM component is infamous for its possible carcinogenic nature. Diesel exhaust pollutants are responsible for the deterioration of air quality and harmful for human being. Formation of such air pollutants decreases significantly by blending the oxygenated fuels (such as biodiesels and alcohols) into conventional diesel. Ethanol-blended diesel fuel is a cleaner combustion choice for compression ignition (CI) engines which decreases the formation of harmful emissions in the combustion chamber. This chapter aims to review about the combustion and emission characteristics of ethanol–diesel blended fuels in CI engines. Studies show that increasing fraction of ethanol in diesel tends to reduce CO and HC emissions, while NOx emissions are reported slightly higher compare to baseline diesel. Higher ignition delay (ID) and lower combustion duration (CD) are the general characteristics for ethanol blends.