Effect of magnetized ethanol-gasoline blends on vibration and sound emissions of a single cylinder SI engine

The purpose of the present study was to investigate the effects of magnetized ethanol-gasoline fuel blends on the vibration and sound status of a single-cylinder gasoline engine. Totally 36 tests were conducted including two factors: ethanol (with share of 0, 5, 10 and 20% blended with gasoline) and magnetic eld intensity (0, 5300 and 7000 G) at three replications as factorial experiment based on completely randomized design. The sound signals of the engine at 10 cm distance from the driver's ear were recorded and its vibration was measured in Z direction. The results of statistical analysis of engine vibration and sound data showed a signicant difference at 1% probability level between various fuel blends in all studied magnetic levels. The maximum sound pressure level with averages of 88.41 was belonged to pure gasoline and magnetic intensity of 7000 G and minimum value (78.94 dB) was belonged to 10% ethanol-gasoline blend and magnetic intensity of 5300 G. The driver can operate the engine for both 10–20% ethanol shares with all studied magnetic intensities without use of any ear protector. In the presence of magnetic eld, vibration decreased by increasing ethanol up to 10%. The maximum amount of vibration in frequency domain obtained without using magnetic eld. For 5300 G magnetic intensity, the least amount of vibration was observed at all frequencies.


Introduction
The motorized machines that are used in the eld of transportation, industry and agriculture along with high advantages, have some disadvantages such as noise, vibration, and environmental pollutions.
Today, reducing the emissions of internal combustion engines is one of the most important environmental concerns. Decrease of fossil fuel sources and increase of environmental pollutions of these fuels encouraged the researchers to conduct more investigations on renewable fuels (Iliev, 2019).
Several techniques have been applied to reduce engine emissions such as improving the engine design and enhancement of fuel characteristics adding biofuels to fossil fuels (Mwangi et al., 2015;Chang et al., 2014a). One of the prerequisites for using a fuel is how it affects the engine. Biofuels will reduce the use of fossil fuels and consequently emissions of greenhouse gases (Gobadian et al, 2009).
Bioethanol, biodiesel and pure vegetable oils have recently been considered as reasonable and promising biofuels. One of the most important of these fuels as alternative fuel is bioethanol which forms a proper fuel when it is blended in gasoline (Zoldy, 2011). Ethanol is a plant-based and renewable fuel with high oxygen content in its molecular structure. Therefore, it requires less oxygen than diesel and gasoline for combustion and therefore has fewer pollutants (Iodice et al, 2017). Also, it has a low octane number and is therefore used as an octane number augmenter in spark ignition engines (Saxena and Williams, 2007).
The other technique which recently used to reduce emissions and fuel consumption is magnetizing the inlet fuel to engines using an external magnetic eld (Govindasamy and Dhanapani, 2007;Hricak, 1994).
Intermolecular bond lengths and angles in liquid fuels play important roles in determining surface tension. By applying the magnetic eld to the fuel stream, as the bond angle increases, the surface tension decreases, which improves fuel evaporation resulting in more complete combustion. Also, internal energy of the fuel molecules increases and they are more easily separated and their tendency to react with oxygen cause to have better combustion process (Chen et al, 2017;Pramodkumar et al, 2017).
Investigating the sound emission and vibration resulting from the combustion process in internal combustion engines has always been of interest to researchers. The vibration directly has a destructive effect on the engine parts and operators as well as the noise that causes an adverse impact on the While most studies report engine performance under ethanol-gasoline blends or operate magnetic eld on the fuel separately, an analytical experiment is required to explore effect of these conditions simultaneously on vibration and sound emission of engine. Therefore, this work focuses on the blending ethanol with gasoline in proportions ranging from 0 to 20% (V/V) and then a magnetic eld applied on the fueling system line to assess the impact of magnetic eld on vibration and noise emissions of singlecylinder four-stroke SI engine.

Experimental equipment and data acquisition
In this work, the vibration and noise pollution of a single-cylinder direct-injection gasoline engine of a lawnmower (Model 53 PO, Italy) with maximum power output of 2.6 kW and a constant speed of 2850 rpm were studied.
To magnetize the fuel blends, six neodymium magnet blocks with 50 × 40 × 20 dimensions were used.
This magnet is one of the strongest and most popular types of magnets and is known as a mineral magnet because of its elements such as neodymium.
The two boxes with inner diameters of 40 × 150 mm were provided to mount the magnets in the fueling line systems. The intensity of magnetic eld has a reverse relation with the distance of the magnets from each other. So, to provide the magnetic intensities of 5300 and 7000 G, two intervals were considered as 10 and 5 cm, respectively.
The magnet was installed between the fuel tank and engine. A non-magnet fuel line were provided and implemented on the studied engine ( Fig. 1).
In order to reach steady state during the tests, the engine warmed up for 10 min with pure gasoline and there were about 10 min intervals between two consecutive experiments. Then the different prepared of ethanol-gasoline blends were poured into the fuel tank. To create the magnetized blend, the magnet blocks put on both sides of the fuel pipe line to create the desired magnetic eld. Then sound and vibration of the engine were measured.
To measure the vibration of the lawnmower engine according to IEC 1010, CE and ISO 9001 standards, a accelerometer (VB-8203, Lutron, Taiwan) with accuracy of 0.1 m.s − 2 and the frequency range of 0.01-10 kHz was used. This accelerometer has a magnetic base to enables fast and constant connection to the surface of the object that was positioned perpendicular to the engine body (Z direction).
A sound level meter (SL 4013, Lutron, Taiwan) with accuracy of 0.1 dB and frequency range of 31.5-8000 dB was applied. The device has two outputs, AC Voltage Output and RS232 Computer Interface Output. The microphone connected to the sound level meter senses sound pressure changes and converts them to voltage changes. To record the vibration and acoustic data, the device software, Lutron 801 model SW-U801-WIN, was used.
The characteristics of the test site for measuring the noise of the lawnmower engine selected in according with the standards of the International Organization and the Society of Automotive Engineers (ISO 5131, 1996;ISO 7216, 1992), so that the measurement area should be a at and open land without cover and large re ective surfaces at a distance of at least 50 meters from the test site.
Measurements were carried out under ambient conditions with no precipitation and wind speeds lower than 5 m.s − 1 . Therefore, the conditions of the test site environment such as background noise level, wind speed and ambient air temperature were measured during the tests.
In this study, the sound level was measured in the driver's ear position so that the microphone was located 10 cm away from the driver's ear. The test was carried out with an ambient temperature of 12 °C and a wind speed of 1.8 m.s − 1 .

Analysis Of Engine Vibro-acoustic Emissions
In this study, statistical analysis of data in time domain was performed as factorial experiment based completely randomized design using SAS 9.1 Software. The main factors in this study included fuel (four levels) and magnetic eld intensity (three levels). The measured attributes were vibration and sound signals. Experiments were performed at constant engine speed and in three replications (Table 1). Table 1 Experimental conditions to measure engine sound and vibration.   According to the signi cant effects of the main factors and their interaction, Duncan's multiple range test was performed to compare the vibration (in the Z direction) and sound averages of the engine for different eld intensities and fuel combinations (Tables 4 and 5). There was a signi cant difference among E0, E5, E10 and E20 blended fuels in three magnetic intensities (0, 5300 and 7000 Gauss) in vibration and sound levels. But there was no signi cant difference between E5 and E10 in all magnetic intensities and between E0 and E5 at 5300 G on engine vibration. There was a signi cant difference between the mean noise for E0 and E5 blended fuels when using magnetic eld with intensities of 5300 and 7000 G but no signi cant difference was observed between E10 and E20 blends.    As shown in Fig. 2(A), with increasing ethanol, the engine vibration decreased and the lowest vibration released by the E5 mixture with mean value of 8.37 m.s − 2 . But with increasing ethanol content, E5-20, due to the high viscosity and density and low thermal value of ethanol compared to gasoline (Rakopoloulos et al., 2008;Li et al., 2007), the engine vibration increased, and the highest vibration was related to the E20 blend with mean value of 14.68 m.s − 2 .

Variables
Similarly, the results showed that by exerting magnetic eld on the fuel compounds, the vibration value in all fuel blends decreased and the lowest vibration was observed as 6.71 m.s − 2 for E10 with magnetic eld of 5300 G.
Also, the values of the sound pressure level at the driver's ear position, Fig. 2(B), showed that the highest sound pressure level occurred in pure gasoline (E0) and 7000 G of magnetic eld intensity with average of 8.41dB. The lowest noise level was observed for E10 blend with a magnetic eld intensity of 5300G with average of 78.94 dB. In the case of E10 and E20 blends in both non-magnetized and magnetized fuels, the mean sound pressure level was below the standard limit of 85dB(A).

The 1/3 octave band analysis
The 1/3 octave band spectrum of the engine vibration and sound pressure level were obtained. For example, Fig. 3 showed the effect of the magnetic eld on E20 blend fuel in frequency domain using 1/3 octave band spectrum. The 1/3 octave band analysis for all treatments showed that the vibration increased at frequencies between 31.5 and 100 Hz and the maximum vibration was reached at frequency 100 Hz and then declined steeply. At higher frequencies, the vibration decreased with greater slope, which may be due to the absence of acceleration components at higher engine frequencies (Salokhe et al. 1995).
Generally, the one-third octave band of the engine vibration showed that the vibration in all blended fuels had decreasing trend with increasing the magnetic eld intensities. The 5300 G of eld has the lowest vibration.
The vibration values corresponding to 5300 G magnetic eld intensity was lowest for all the studied fuel blends and the highest amount of vibration released to pure gasoline fuel and it decreased by increasing ethanol percentage.
By investigation the 1/3 octave diagrams, it was observed that the highest sound pressure level for all blended fuel samples and in all magnetic eld intensities were in the frequency range of 31.5 to 200 Hz.
The frequencies corresponding to the maximum sound levels also changed by alteration the percentage of fuel blends and using the magnetic eld and these variations were mostly between the frequencies of 250 to 800 Hz.
The results showed that the maximum amount of SPL was related to pure gasoline for all studied magnetic intensities and the magnetic intensity of the 5300 G had the greatest effect on decreasing of engine sound level. Also, by increasing ethanol percentage up to 10% in the studied fuel blends, the SPL values decreased for all magnetic intensities.

Conclusion
In the present study the effect of two essential variables, namely ethanol-gasoline blends and magnetic eld on vibration and acoustic emission of gasoline engine were analyzed.
With analysis of the obtained data, it was revealed that adding ethanol into gasoline from 0 to 20% (v/v ethanol content) causes to reduce vibration and acoustic emissions, so that the E5 and E10 blends had greatest decrementing impact on vibration and sound emissions, respectively. Such test fuels, by applying the magnetic eld with 0, 5300 and 7000 G intensities, would lead to a signi cant reduction in vibro-acoustic emissions in comparison with commercial gasoline (E0), and 5300 G intensity revealed the greatest effect on the emissions decreasing among the other intensities.
It can be concluded that by creating a magnetic eld, the required force is gradually provided to overcome the hydrocarbon clusters of the fuel structure and the breakdown of these clusters allows more oxygen to bond to the intermediate carbons. Also, the decreasing of vibro-acoustic emissions is related to the high oxygen content in the ethanol molecules which enhances fuel oxidation. Therefore, the combustion process becomes uniform and eventually produces less vibration and noise pollution. But it is noticeable that the effect of ethanol percentage on the emission reduction was higher than that of magnetic intensity.

Declarations
Availability of data and materials: Not applicable Competing interests: The authors have declared no con ict of interest.
Funding: Not applicable.

Figure 1
Implementing magnetic block on the fueling system line.

Figure 2
Procedure of sound and vibration signals analysis.  The 1/3 octave spectrum of A) vibration and B) sound level of engine at E20 fuel blend with different magnetic elds.