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Alcohol fuels, primarily ethanol and methanol, have emerged as one of the important alternatives for sustainable transportation and power generation applications, due to the overall lower carbon dioxide (CO2) emissions. The higher octane number of alcohol makes it suitable for spark ignition (SI) engines while lower blend ratios can be used for compression ignition (CI) engines as well. Since significant work and exploration have already been performed for the application of alcohol in SI engines, the present study is primarily focused on alcohol utilization in CI engines. This review majorly consists of three parts: first, a discussion on the physical and chemical properties of ethanol and methanol from the fuel perspective, second, combustion, and engine performance of CI engines fueled with alcohol and lastly, emissions characterization of alcohol as fuel. A summary of this review is provided which highlights the potential of alcohol utilization in the form of blend or under dual-fuel combustion modes, as well as neat alcohol fueled CI engine. Alcohol-fueled CI engine improves the soot-NOx trade-off characteristic in comparison to conventional diesel combustion, this fuel could be an enabler to meet future emissions regulations. Overall lower CO2 emissions (up to 15% lower compared to diesel) by utilizing alcohol as fuel make it suitable for sustainable transportation. [ABSTRACT FROM AUTHOR]

In present study, the effect of fuel premixing ratio, direct fuel injection timings and engine compression ratio on the soot particle emissions in nano-size range from a non-road compression ignition engine is investigated. Experiments are conducted on modified dual fuel single cylinder engine at 1500 rpm. To run the engine in dual fuel mode, port fuel injection (PFI) system is installed by modifying intake manifold of the engine and developing a PFI controller. Experiments are conducted for various fuel premixing ratio of gasoline/methanol-diesel at different engine load, diesel fuel injection timing and compression ratios. Differential mobility spectrometer based particle sizer is used for investigation of the soot particle number-size distribution, surface area-size distribution, particle mass-size distribution and total particle number concentration from the engine exhaust at various test conditions. Results revealed that total particle number concentration is higher at full engine load and increases with fuel premixing ratio (especially in case of methanol-diesel dual fuel operation). Additionally, the peak particle number and mass concentration reduces with an increase in compression ratio of the engine. [ABSTRACT FROM AUTHOR]

Alcohols (ethanol and methanol) are being widely considered as alternative fuels for automotive applications. At the same time, homogeneous charge compression ignition (HCCI) engine has attracted global attention due to its potential of providing high engine efficiency and ultralow exhaust emissions. Environmental legislation is becoming increasingly stringent, sharply focusing on particulate matter (PM) emissions. Recent emission norms consider limiting PM number concentrations in addition to PM mass. Therefore, present study is conducted to experimentally investigate the effects of engine operating parameters on the PM size-number distribution in a HCCI engine fueled with gasoline, ethanol, and methanol. The experiments were conducted on a modified four-cylinder diesel engine, with one cylinder modified to operate in HCCI mode. Port fuel injection was used for preparing homogeneous charge in the HCCI cylinder. Intake air preheating was used to enable auto-ignition of fuel-air mixture. Engine exhaust particle sizer (EEPS) was used for measuring size-number distribution of soot particles emitted by the HCCI engine cylinder under varying engine operating conditions. Experiments were conducted at 1200 and 2400 rpm by varying intake air temperature and air-fuel ratio for gasoline, ethanol, and methanol. In this paper, the effect of engine operating parameters on PM size-number distribution, count mean diameter (CMD), and total PM numbers is investigated. The experimental data show that the PM number emissions from gasoline, ethanol, and methanol in HCCI cannot be neglected and particle numbers increase for relatively richer mixtures and higher intake air temperatures. [ABSTRACT FROM AUTHOR]

Homogeneous charge compression ignition (HCCI) engines have potential to provide both diesel like efficiencies and very low NOx and particulate matter (PM) emissions. There is growing global interest in using alternative biofuels in order to reduce the reliance on conventional fossil fuels. Therefore this experimental study was carried out to investigate performance, combustion and emission characteristics of HCCI engine fueled with ethanol and methanol and compare it with baseline gasoline fuel. The experiments were conducted on a modified four-cylinder four-stroke engine at different engine speeds using port fuel injection technique for preparing homogeneous charge. To achieve auto-ignition of air-fuel mixture in the combustion chamber, intake air pre-heater was used. In-cylinder pressure data acquisition with subsequent heat release analysis and exhaust emission measurements were done for combustion and emission diagnostics. In this paper, effect of intake air temperature and air-fuel ratio on combustion parameters, thermal efficiency, combustion efficiency, ringing intensity and emissions in HCCI engine is analyzed and discussed. Results show that methanol and ethanol are good replacements to gasoline in HCCI combustion mode. [ABSTRACT FROM AUTHOR]

Highlights: [•] Combustion phasing is analyzed by fitting probability density functions. [•] Combustion stability improves on increasing intake air temperature. [•] Test conditions with late start of combustion have larger cyclic variations. [•] Large deviations from normal distribution in combustion duration for knocking/misfire. [•] GEV distribution covers full range of distribution shapes for combustion duration/phasing. [Copyright &y& Elsevier]

Abstract: Combustion instability and cyclic variations lead to the requirement of closed loop control for use of homogeneous charge compression ignition (HCCI) engine technology for automotive applications. The closed loop control of HCCI combustion requires robust combustion timing parameters with a systematic and detailed study of its variations vis-à-vis engine operating conditions. An experimental study is conducted to provide insight into cyclic variations of HCCI combustion phasing for two fuels (gasoline and methanol) using statistical techniques. In this study, cycle-to-cycle variations of heat release parameters such as Maximum Rate of Heat Release (ROHRmax), 10% Mass Burn Fraction (MBF), 50% MBF, 90% MBF and Indicated Mean Effective Pressure (IMEP) of HCCI combustion engine fueled with methanol and gasoline were investigated using a modified two-cylinder, four-stroke engine. The experiments were conducted with different engine operating conditions at constant intake air temperature (140°C) and different air–fuel ratios at constant engine speed (1500rpm). To evaluate the cycle-to-cycle variations of combustion parameters at different test conditions, coefficient of variation (COV) and standard deviation of parameters were used. The results showed that CA50 (crank angle position of 50% MBF) is a robust parameter for the closed loop control of HCCI combustion. [Copyright &y& Elsevier]

[Display omitted] • Nanoparticle and carbonyl emission from methanol-diesel dual fuel was investigated. • Health risk assessment for nanoparticle and carbonyl emissions was conducted. • Methanol-diesel engines carbonyl emission has a higher cancer risk potential. • Diesel engine nanoparticles showed higher lung load and longer retention period. • At high loads, Methanol in diesel engines can reduce health risks significantly. Engine-emitted nanoparticles pose a threat to respiratory health, prompting the exploration of solutions like low carbon alternative fuels (methanol) and reactivity-controlled compression ignition (RCCI) engines. However, employing methanol in RCCI engines releases carcinogenic carbonyl compounds. The present study aims to experimentally investigate nanoparticle and carbonyl emissions from conventional diesel (CDC), gasoline-diesel RCCI (GD-RCCI) and methanol-diesel RCCI (MD-RCCI) engines. This study focuses on predicting lung loading caused by emitted nanoparticles and the potential cancer risk associated with carbonyl compounds. The investigation explores the impact of engine load (lower and medium) and fuel premixing ratio (r p) on particle and carbonyl emissions in RCCI engines. Findings reveal that MD-RCCI reduces total particle number (TPN) emissions by 60% compared to CDC. Results indicate that the concentration of nucleation mode particles (NMPs) decreases as engine load increases, while accumulation mode particles (AMPs) increase for both CDC and MD-RCCI combustion modes. With an increase in r p , the NMPs in the MD-RCCI and GD-RCCI engines are increased. Furthermore, the emission of HCHO and CH 3 CHO decreases with an increase in engine load. As the r p increases, HCHO and CH 3 CHO increase significantly. The forecast for lung loading reveals that nanoparticles emitted by CDC show a 30 % higher lung load compared to MD-RCCI. Additionally, as engine load increases, lung loading due to particles increases in CDC and decreases in MD-RCCI. In all test conditions, RCCI combustion demonstrates lower lung retention compared to CDC engine. The lung loading of particles of MD-RCCI decreases significantly with an increase in premixing ratio for a constant load as compared to GD-RCCI. The MD-RCCI engine shows higher cancer risk potential as compared to CDC and GD-RCCI engines. Operating the MD-RCCI engine at medium loads is advantageous for environmental and human health considerations. [ABSTRACT FROM AUTHOR]