India is the third-largest energy consumer in the world, behind the US and China. It is also the energy consumer that is expanding the fastest. India's energy needs are mainly met by coal, crude oil, natural gas, and renewable energy, accounting for 5.7% of the world's primary energy consumption. India were able to produce 30.49 million metric tonnes (MMT) crude oil in year 2020-21 which was 5.2% less than in year 2019-20 [1]. The consumption of petroleum products has been increased from 165.52 MMT in year 2014-15 to 214.13 MMT in year 2019-20 and it is expected to consume more in upcoming years. India had imported 254.39 MMT crude oil in year 2019-20 and 196.46 MMT in year 2020-21.This shows that the trend of import of crude oil is decreasing by almost 14%. In its National Policy on Biofuels 2018 notification, the government of India set a target of 5% biodiesel as well as 20% ethanol blend in gasoline by 2030. This goal will be achieved by adopting by the establishment of Second Generation (2G) bio refineries, the discovery of new feedstock for biofuels, the strengthening of current ethanol/biodiesel supply through increased domestic output, and the development of new technology for biofuel conversion [1][2]. Currently, more than half of the main energy used worldwide comes from the combustion of traditional fossil fuels—like diesel and gasoline. Since the price of fossil fuels is rising and global warming is still a major environmental worry, it seems inevitable that alternative fuels will be used in the future [3]. The majority of economic sectors today, including manufacturing, food production, transportation, and energy production depend heavily on fossil fuels. The world's fossil fuel supplies are rapidly running out. The components of gasoline, which is a complex mixture of C4–C12 alkanes, olefins, aromatics, etc., relies on its source and the processes used to produce it [4][5]. Since the greenhouse effect is greatly affected by the pollutant emissions produced by the burning of fossil fuels, it has become a major worry in today's world. In an effort to decrease the use of carbon-based fossil fuels and prevent the depletion of oil supplies, researchers in the automotive industry are now focusing on the use of alcohol as a an alternative fuel for internal combustion engines [6]. Alcohols have been researched, including butanol, methanol, and ethanol and are frequently used as alternative fuels to spark-ignition (SI) engines as a substitute to improve combustion efficiency and lower emissions. Even without any engine modifications, ethanol can be used in a variety of internal combustion engines. Additionally, ethanol-gasoline (gasohol) mixtures burn cleaner and produce fewer emissions than pure gasoline [7].
As focus shifts to the growing importance of PM emissions from SI engines and the increasing ethanol content in gasoline, it is important to understand, at a fundamental level, how ethanol influences the sooting tendency of gasoline. [6]. The particulate matter emissions from gasoline containing ethanol are still far less known than those from diesel or regular gasoline. To date, practically all of the ethanol in gasoline, particulate matter research and engine research has focused on low percentages of ethanol blends ( 20 vol.%) and has produced a range of outcomes [8]
According to some studies, Ethanol concentration up to 10% by volume had little to no effect on engine particulate matter emissions. This suggests that at low blend levels, engine operating circumstances are more important for determining engine PM emissions [9]. Gasoline and ethanol vary significantly in a number of important chemical and physical properties. These qualities do not always mix linearly when the fuels are combined. For instance, the enthalpy of vaporization, the distillation curve, and the Reid vapour pressure (RVP) are three crucial physical property features for gasoline-ethanol blends that affect mixture formation which all exhibit nonlinear behavior when the two fuels are combined. The measured RVP for ethanol-gasoline blends has been shown in earlier studies to considerably deviate from the predicted ideal mixture behavior[10][11]. Ethanol content is increased, the vapour pressure of ethanol-gasoline mixtures first rise, peaking between E10 and E20, then falls at greater percentages of ethanol until it reaches the value of E100 for 100% ethanol. Blends of ethanol and fuel behave very adversely. In actuality, the RVP is greater than either fundamental fuel between E0 and E50 [6]. Mužíková et al.[12] reported the effect of addition ethanol to fuel vaporisation enthalpy. According to the volume percent of ethanol in the mix, Figure. 1 illustrates the ratio of the vaporisation enthalpy for ethanol-gasoline blends to that for pure gasoline. They discovered that the rise in enthalpy with ethanol was inconsistent, in addition to being non-linear. This non-linearity makes it crucial to take into account when preparing mixtures, along with the notable rise in vaporisation enthalpy for substantial ethanol concentrations.
Internal combustion engines are manufactured to comply with regulations governing exhaust emissions, deliver performance appropriate for the vehicle class, and satisfy customer demands to cut down on daily operating expenses. Fuel costs are second only to depreciation in terms of ownership costs for newer versions[13][14]. Fuel now occupies the top spot on the list of ownership costs for older vehicles that have already undergone substantial depreciation. The majority of automobile manufacturers design nearly all of their engines to operate on Regular grade gasoline in order to help control vehicle operating expenses [15]. However, some engines need or advise using premium gas in order to accomplish the claimed power production and fuel efficiency figures. Although the extra power actually comes from engine design decisions that require high-octane Premium to avoid detonation, consumers have grown accustomed to associating Premium gasoline with better performance over time[16]. Many automobile owners today think that using Premium grade gasoline will have a number of advantages for engines made to operate on Regular, fewer emissions from the tailpipe, and better fuel efficiency[5][17][18]. Initially promoted as an improvement over Regular fuel, Ethyl gasoline ultimately became a generic term for Premium grade gasolines with superior anti-knock qualities as all gasolines adopted TEL additives. The term Ethyl, a registered trademark, was progressively replaced with "Premium" over time[19]. Leaded fuel was eventually phased out for on-road use from 1974 to 1996 due to health and emissions issues. When widespread fuel injection use led to excessive engine carbon deposits in the 1980s and 1990s, mainly as a result of insufficient fuel detergents, the superiority of premium gasoline was once more acclaimed[20][21]. New additive packets were created, and it was frequently promoted that Premium fuels contained more of the detergents required to stop deposit development. In certain operating circumstances, higher-octane fuels enable enhanced ignition timing advance because they offer greater resistance to engine detonation, or knock. A prolonged burn cycle and greater energy extraction from the air/fuel charge in the cylinder are two benefits of greater timing advance, both of which increase the torque and/or horsepower figures at the flywheel[9]. This would potentially permit smaller throttle openings and reduced fuel delivery during a specific driving cycle, with the result being improved fuel economy, under the controlled circumstances[22][23].
A higher octane number of gasoline is mainly due to aromatics present in it. The two most significant branched paraffin’s are iso-octane and toluene. Linear paraffin, which is n-heptane with an octane number of zero, is the third. [2]. To truly have gasoline with auto ignition properties, it is essential to counterbalance the aromatics and branching paraffin in the gasoline executed gas chromatography with high resolution mass spectrometry (GC-HRMS). In the Indian Institute of Technology (IIT), Bombay's Sophisticated Analytical Instrument Facility (SAIF), Patil et.al [4] conducted a test using gas chromatography with high-resolution mass spectrometry (GCHRMS) on commercially available petrol fuel as shown in Fig. 02. Authors reported that the composition of premium level gasoline, which contains different class of compounds such as Aromatics hydrocarbon compounds - (mass percentage), 36.06% 2) Ester- 3.74% 3) Hydrocarbon-8.11% 4) Diverse functional group- 10.08% 5) Ketone-1.38% 6) Nitrogen containing group-0.86%, 7) Other compounds-6.02%
McCormick et.al [24] experimentally investigated potential biofuels that allow more aggressive pursuit of sophisticated spark ignition (SI) engine efficiency techniques. By simulating gasoline as a surrogate mixture of seven components, the paraffin, isoparaffin, aromatic, naphthene, and olefin composition of regular gasoline was reproduced. This model gasoline composition contains 10% Alkanes (n-octane), 7% alkenes (1-octene), 39% isoalkane (iso-pentane), 8% cycloalkane (cyclohexane), 6% cycloalkene (cyclohexene), 15% aromatic (toluene), 15% aromatic (ethylbenzene). At the time of this investigation, there were more than 350 pure compounds and 15 mixed bioblendstocks in the database, and 117 of those satisfied the criteria for a boiling point for fuels similar to gasoline between 20°C and 165°C, and a melting or cloud point below − 10°C. [17]. They concluded that alcohols are well known as potential ingredients for SI fuel blends, particularly ethanol, which serves as a standard for the efficiency of bioblendstocks in SI engine fuel. Patil et.al [5] experimentally investigated to evaluate the effectiveness of substitute fuels when testing engines. They also determined composition of premium gasoline using chromatography test. As per PIONA compound mass comparison, aromatics compound mass % was found as 98.41% which were 82.8% in previous research studies. The paraffin mass % share was 0.656 which was 9.5% in earlier researchers report and iso-paraffin were absent. From these studies, it is decided that 10% alkanes (n-pentane, hexane etc.) will be added to premium gasohol to investigate performance, combustion and emission characteristics of premium gasohol i.e premium gasoline with 20%, 40% and 60% blending of ethanol.
Based on the idea that comparable substances will exhibit a preference for one another and are more probably to dissolve or dissipate in one another, solubility criteria are used. Significant benefits of ethanol bending include a higher octane number, fuel incorporated oxygen, and a faster flame which results in complete combustion fuel [25][26].
The focus of the current experimental investigation is to evaluate and compare the performance, combustion and emission characteristics of premium gasohol blends with partial addition of alkane’s such as n-Pentane and Hexane with different operating conditions.