Technical Field of the Invention

The present invention relates to coal nanoparticles developed to be used as a fuel additive in order to improve the thermo-physical fuel properties of the diesel, biodiesel, or diesel-biodiesel fuel mixtures that are used in diesel engines, to increase the performance of the engine, and to reduce exhaust emissions.

State of the Art

In the state of the art, there are many various metal-based nano fuel additives in order to reduce fuel consumption, increase performance, and reduce exhaust emissions. These studies are grouped in two different categories as liquid and solid (nano fuel additives) fuel additives. In recent years, the research and use of nano fuel additives with the development of nanotechnology has drawn attention. It has been observed that in general, the fuel properties are improved, the fuel consumption is reduced, the engine performance is increased, and the exhaust emissions is reduced in the experimental studies carried out by means of adding different nanoparticles to the fuel. Mirzajanzadeh et al. [1 ] have determined that the fuel consumption of the engine is reduced, and the exhaust emissions are reduced in case cerium oxide (CeC ) nanoparticles and multi-walled carbon nanotubes (MWCNT) in different concentrations are added to diesel-biodiesel fuel mixtures. Mehregan and Moghiman [2], on the other hand, have indicated that the fuel consumption of the engine is reduced, the thermal efficiency of the engine is increased, and nitrogen oxide (NOx) emissions are reduced by 40% with the study they were conducted by means of adding manganese oxide and cobalt oxide nanoparticles to diesel-biodiesel fuel at the concentration of 25 ppm and 50 ppm.

In the state of the art, the patent application numbered EP 1 587 898 A1 discloses the use of carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxide (NOx), sulfur oxide (SO2), and cerium oxide nanoparticles, which have the potential to reduce soot emissions, as fuel additives. Here, the catalyst effect of cerium oxide is utilized. In addition, it is stated that detergent or other fuel additives may also be present in this fuel additive. In the state of the art, another patent document numbered US 8,163,044 B2 discloses a method for combustion improvement and emission reduction with a fuel additive comprising a suspension of nanoparticle oxides in a fuel miscible liquid carrier. Here, the fuel additive that is used in order to increase combustion efficiency, improve fuel economy, and reduce exhaust emissions comprises zinc oxide nanoparticles in an amount of 70-80% by mass, magnesium oxide nanoparticles in an amount of 10-23% by mass, cerium oxide nanoparticles in an amount of 1 -5% by mass, copper oxide nanoparticles in an amount of 1 -5% mass, and ferric oxide nanoparticles in an amount of 1 -5% by mass. The patent document numbered WO 2008/147076 A1 , on the other hand, discloses a fuel additive containing magnesium nanoparticles. This nano-fuel additive, which contains a magnesium salt complex and an organic acid complexing agent, can be added to fossil fuels previously, or it can be injected into a combustion chamber immediately after the combustion starts in boiler systems. It has been stated that millions of magnesium oxide particles are generated with the synergistic effect of magnesium nanoparticles in a combustion environment, and these emissions will be reduced by means of that said particles absorb sulfur emissions (compounds) in various forms at the immediate end of the first formation process thereof.

In the state of the art, another patent document numbered US 8,182,555 B2 relates to the use of nano-sized zinc oxide as a fuel additive. Here; it has been stated that the fuel additive accelerates the combustion by means of creating a catalytic effect during combustion and increases the combustion efficiency, and also that the oxygen in the nano-fuel composition accelerates the oxidation of the hydrocarbon fuel. Patent application numbered US 2019/0276760 A1 discloses the use of nano-sized Perovskite type of materials as fuel additives in order to increase the combustion efficiency or combustion temperature of gaseous and liquid fuels. In the state of the art, another patent document numbered CN101684419 B protects the nano-nickel fuel additive that allows for increasing the heating value of the fuel, improving the combustion efficiency, reducing carbon deposits -on the vital engine parts and reducing engine noise, and saving energy. Nano-nickel fuel additive can be added to gasoline, diesel, fuel-oil, biofuel and similar fuels; therefore, it has been stated that it has a very wide application area such as automobiles, trains, ships, and boilers.

A great majority of the products that are commercially available and called nano fuel additive contains metal or metal oxide-based nanoparticles. In case metal-based nanoparticles are used as fuel additives, engine performance is increased, fuel consumption is reduced, and exhaust emissions are reduced in a certain amount. However, metal-based nano fuel additives have significant disadvantages despite these advantages it offers. Although these nanoparticles have a role in cleaning the engine and improving combustion, their effects on increasing engine performance are limited. The most important disadvantage thereof is that metal or metal oxide-based nanoparticles spread to the atmosphere together with the exhaust gases at the end of combustion, thereby, causing metal emissions, and these metal emissions accumulate in biological structures directly or indirectly, thereby, causing toxic effects. Metal nanoparticles cannot be kept by means of any available filtration system to be placed on the exhaust system and are released directly into the atmosphere due to extremely small diameters thereof. Nanoparticles released into the atmosphere with exhaust gases mix in air, soil and water, reach living life indirectly or directly, and accumulate in biological structures, thereby creating a toxic effect. Diesel particle filters are utilized in order to keep the particles in the exhaust gases in available emission control systems. However, these filters can efficiently keep only the micron-sized particles. There are certain studies to control the metal emissions in the state of the art. For example, the release of iron-based nanoparticles into the atmosphere may be limited by means of magnets placed in the exhaust system in case iron-based nanoparticles are utilized as a fuel additive. However, this application is only applicable for limited types of metal nanoparticles with magnetic properties. Problems regarding the control of metal emissions still continue since no control system has been developed for other metal emissions. It is also known that metal-based nanoparticles have a carcinogenic effect. Metal-based fuel additives have been utilized for a very long time, from 1923 to the 1990s. For example, leaded compounds and iron-based compounds were added to gasoline in order to increase the octane number of gasoline. However, after it was determined that these metal-based substances are carcinogenic and cause neurological diseases, especially in infants, their use was prohibited. Due to these reasons mentioned here, the use of metal or metal oxide-based nanoparticles as a fuel additive poses a great risk for human and environmental health. Metal-based nano fuel additives have no commercial applications except very special applications such as rocket and missile fuels due to the aforementioned risks. In addition to these, production costs thereof are quite high since the production of metal or metal oxidebased nanoparticles as fuel additives can be carried out with multi-staged and complex chemical and physical methods and requires advanced technology. In addition, metal nanoparticles have a low oxidation resistance. This situation creates difficulties in terms of application, metal nanoparticles are coated with another material by means of using very complex and costly electrochemical methods in order to increase the oxidation resistance of nanoparticles. However, all these processes greatly increase the cost of the end product. This situation also causes an increase in fuel prices, and therefore, it is necessary to develop new fuel additives that are more environmentally friendly, have minimal harm to health, and are economic instead of metal-based nanoparticles.

Coal, which is one of the fossil fuels containing hydrocarbons and high levels of carbon, is utilized in coal combustion systems with different methods in addition to being utilized directly as a fuel. One of said methods disclosed in the invention subjected to the patent application numbered US 4,722,740 A is the use of fuel, which is obtained by mixing coal with 50-70% of water, and/or different liquids, and which is called aqueous coal slurry fuel, as the main fuel or a secondary fuel in combustion systems. On the other hand, the patent document numbered US 8,500,827 B2 relates to the method of using the coal water slurry that is obtained by means of adding micronized and nano-sized coal dust to the water as main fuel and intermediate fuel in combustion systems, or fuel cells. Here, it is indicated that alcohol fuels such as ethanol, methanol, propanol, and butanol in addition to water, or fuels such as diesel, biodiesel, engine lubrication oil, fuel oil may be added to the coal water slurry in order to increase the heat of combustion. The main object of these coal related patent applications is not to utilize micron/nano coal particles as a fuel additive, but to use coal as a main fuel. In these coal-related fuel studies and the like, coal particles are mixed with water at a rate of 50-70%, or other liquids and used as fuel directly. The viscosity of the fuels is also high due to the high amount of coal dust added, and therefore, technical problems may arise, and some engines also necessitate a modification in case these fuels are used in diesel engines. In the state of the art, the fuel additives used in order to reduce fuel consumption, increase performance and reduce exhaust emissions for diesel, biodiesel, or dieselbiodiesel fuels have problems such as the difficulty of production of fuel additives, high costs, and the harmful/toxic effects of exhaust emissions on human health and the environment, and due to the limitations and inadequacy of the developments regarding these problems, it is necessitated making an improvement in the relevant technical field.

Brief Description and Objects of the Invention

The present invention discloses a fuel additive that reduces the fuel consumption, increases the performance thereof, reduces harmful exhaust gas emissions, is environmentally friendly, and is economic for use in diesel, biodiesel, or dieselbiodiesel fuels. Said fuel additive is the coal nanoparticles.

The main object of the present invention is to provide an environmentally friendly and economic fuel additive in order to increase the performance of diesel-biodiesel fuels, reduce fuel consumption, and reduce harmful exhaust gas emissions. Coal nanoparticles do not cause metal emissions since they are obtained from coal and are organic/hydrocarbon-based substances. Harmful exhaust emissions are reduced by means of the coal nanoparticle fuel additive according to the present invention since it is hydrocarbon-based and does not contain extra contaminants (especially metallic substances) as other nano fuel additives. The coal nanoparticles in the fuel bum by being included in the combustion of the fuel since coal contains a large amount of carbon atoms (60-90%), and in such a case, the heat of combustion increases. Thus, lower exhaust gas emissions and also better fuel performance are obtained since it provides more efficient combustion. In the laboratory studies relevant to the present invention, it was determined that the thermal efficiency of the engine is increased while the specific fuel consumption, nitrogen oxides (NOx), and carbon monoxide (CO) emissions are reduced by means of adding coal nanoparticles to diesel and biodieseldiesel fuels. Thus, air pollution caused by exhaust gases is reduced by means of the present invention. Another object of the present invention is to reduce the diesel-biodiesel fuel consumption and to increase the performance thereof. Coal nanoparticles have direct effects on the air-fuel mixture formation process and combustion. Coal nanoparticles in the fuel generate a large surface area for the fuel in order to contact with air. This allows the fuel to evaporate quickly and mix with the air by means of improving the heat transfer property of the fuel. The homogeneous air-fuel mixture generates more efficient combustion and also produces lower exhaust gas emissions. In addition, coal nanoparticles accelerate the combustion by creating a catalytic effect during the combustion and increase the heat of combustion. -Coal nanoparticles create a catalyst effect during the combustion, thereby accelerating the combustion and increasing the heat of combustion due to the positive effects thereof such as increasing the turbulence intensity in the cylinder during combustion, mixing, evaporation, heat transfer mechanisms, and increasing the combustion rates. Thus, improvements are provided also in engine performance and exhaust emissions.

Yet another object of the present invention is to obtain a fuel additive that can be a commercialized, that does not have a carcinogenic effect, produces low exhaust gas emissions, and does not require an extra emission control system in practice. Coal nanoparticles do not have carcinogenic exhaust emissions or toxic effects.

Yet another object of the present invention is to obtain an effective fuel additive to be used in diesel, biodiesel, or diesel-biodiesel fuels with simpler methods and low cost. Coal nanoparticles can be produced in a short time by simple physical methods (grinding, filtering, etc.) contrary to metal-based nanoparticles. Therefore, the difficulty of producing nano fuel additives with coal nanoparticles is eliminated. In addition, the present invention enables a fuel additive that increases the performance of diesel and diesel-biodiesel fuels, reduces fuel consumption, and generates low exhaust gas emissions with low cost and simple processes, since it is originated from coal and is a material that is cheap and easily accessible, thereby not requiring high technology for the production of coal nanoparticles.

Yet another object of the present invention is to produce a fuel additive that does not cause changes in fuel standards and is suitable for available engine/combustion systems. In the present invention, since the coal particles are nano-sized and added to the fuel in very low concentrations (5-2000 ppm, in other words, 0.0005-0.2% by mass), the increase in the viscosity of the fuel is limited, the properties of the fuels do not change beyond the standard limits, and the fuel standards are fulfilled, and it complies with the technology of current engine/combustion systems since it does not cause any technical problems in the engine. Therefore, there is no need for any structural changes in available diesel engines or boiler systems to use coal nanoparticles as a fuel additive.

In summary, by means of the present invention;

- thermophysical properties of diesel or diesel-biodiesel fuels are improved,

- fuel additives that can be obtained from abundant and easily accessible sources with simple methods are provided, and thus, the cost is reduced,

- low fuel consumption is ensured,

- combustion efficiency and engine performance of diesel or diesel-biodiesel fuels are increased,

- there is no need for any modification in the diesel engine since the fuel standards are fulfilled and it does not cause any technical problems in the engine,

- the emission of harmful exhaust gases of diesel or diesel-biodiesel fuels is reduced, thereby minimizing harmful effects to human health and the environment.

- Coal nanoparticle fuel additives can be utilized in a safe manner in commercial applications by means of the aforementioned advantages.

Description of the Figures Illustrating the Invention

Figure 1 : illustrates the view of SEM image of coal nanoparticles.

Figure 2: illustrates the average particle diameter distribution of coal nanoparticles.

Figure 3: illustrates the schematic view of the nano fuel containing coal nanoparticles.

Figure 4: illustrates the effect of coal nanoparticles on engine specific fuel consumption.

Figure 5: illustrates the effect of coal nanoparticles on the thermal efficiency of the engine. Figure 6: illustrates the effect of coal nanoparticles on exhaust gas temperature.

Figure 7: illustrates the effect of coal nanoparticles on NOx emission.

Figure 8: illustrates the effect of coal nanoparticles on HC emission.

Figure 9: illustrates the effect of coal nanoparticles on CO emission.

Description of Elements/Parts/Components of the Invention

Parts shown in the figures are enumerated and numbers corresponding the respective parts are provided below in order to provide a better understanding for the fuel with coal nanoparticles additive developed according to the present invention.

1 . Bottle

2. Liquid Fuel

3. Coal Nanoparticles

Detailed Description of the Invention

The present invention relates to the coal nanoparticles, a fuel with coal nanoparticles additive, and a method for producing it in order to be utilized as a fuel additive for the diesel, biodiesel, or diesel-biodiesel fuel used in diesel engines or boilers. A fuel additive, which is environmentally friendly, does not have a harmful effect on human health, and does not have a carcinogenic effect is provided, and the exhaust gas emissions are reduced by means of the hydrocarbon-based nature of coal nanoparticles. In addition, since it contains carbon atoms at a high rate (60-90%), the heat of combustion is increased due to the combustion of coal nanoparticles in the fuel by including in the combustion of the fuel, and lower exhaust gas emissions, and also better engine performance are provided since more efficient combustion is ensured, and the fuel consumption is reduced.

The fuel additive of the present invention consists of coal nanoparticles. Coal nanoparticles to be used as fuel additives are obtained by means of turning the coal samples with low ash and sulfur content, and also with high grindability into nano-sizes at 600-1200 rpm rotation speed, and at the end of 45-480 minutes of grinding time in a high energy-vibrating ball grinding mill. In the present invention, coal nanoparticles at a size of 1 -500 nm are utilized. Grinding is performed for 45 minutes at a speed of 1200 rpm in case grinding is performed in a wet environment. When grinding is performed in a dry environment, this time is 480 minutes. The grindability of coal is explained by the Hardgrave Index. In case said values are high, the coal sample is more easily ground to nano sizes, i.e., grinding time, speed, etc. parameters are decreased. The Hardgrave index of the coal samples used in the present invention is greater than 90. Coal samples with a value lower than the above-mentioned value may also be used, however, such samples require longer grinding time and higher grinding speed to obtain nano-sizes.

The coal nanoparticles obtained are characterized in order to determine morphological properties thereof after the grinding process. In an embodiment of the present invention, coal nanoparticles that can be used as fuel additives were obtained by means of grinding at a grinding speed of 1200 rpm and for 45 minutes in wet environment. The Scanning Electron Microscope (SEM) image of coal nanoparticles is illustrated in Figure 1. It was determined that the coal nanoparticles are nano-sized and have approximately a spherical form according to the SEM analysis. From this analysis, it is understood that coal particles clump together after the grinding process due to cold welding or electrostatic forces. However, the coal nanoparticles that are clumped are distributed as nanoparticles during the ultrasonic mixing process applied in the nano fuel preparation stage. Figure 2 illustrates the average diameter distribution of coal nanoparticles. As can be seen from this figure, a major part of the coal nanoparticles has diameters less than 50 nm. The diameter value of the coal nanoparticles can be further reduced by changing the grinding parameters.

Characterized coal nanoparticles are added to the fuel at a rate of 5-2000 ppm (i.e., 0.0005-0.2% by mass). In a preferred embodiment of the present invention, maximum 300 ppm coal nanoparticles (for example, 300 mg coal nanoparticles per 1 kg of fuel) are added to the fuel. First, a mechanical/magnetic mixing process is applied for 5-30 minutes, preferably 15 minutes, and then ultrasonic mixing process is applied at 40 Hz of operating frequency for 5-90 minutes, preferably 45 minutes, in order to ensure the homogeneous distribution of the coal nanoparticles in the fuel and to increase the stabilization of the coal nanoparticles in the fuel. In case the fuel is kept in tanks for a long time, surfactant at a rate of 0.05-3% by mass of the fuel, preferably 1 %, is added to the fuel in order to prevent/decelerate coal nanoparticles to deposit the bottom of the fuel tank over time. In addition, in case a surfactant is desired to be added, first, a certain amount of coal nanoparticles and surfactant are added in a container and mixed with a spatula (scoop). Subsequently, this mixture is added to the fuel, and mechanical and ultrasonic mixing processes are performed. Namely, the surfactant is added to the fuel before the mechanical and ultrasonic mixing process is carried out. Coal nanoparticles may also be used by directly being added to the fuel (without using surfactant) after being obtained via the grinding process. At the end of these process steps, fuel with coal nanoparticles additive is obtained. Fuel with coal nanoparticles additive can be used directly in diesel engines/boilers, or in diesel/biodiesel fueled boiler systems. The blending of prepared coal nanoparticles may also be easily performed in daily practice at refineries or fuel distribution stations since adding coal nanoparticles to the fuel is carried out by means of simple, physical methods.

It should be noted that the ash and sulfur content of the coal should be low while selecting the coal sample. As lower the sulfur content of the selected coal, so higher the amount of coal nanoparticles that can be added to the fuel. It is also important not to exceed the maximum amount of sulfur specified in the fuel standards. In addition, the lower the ash content of the coal, the minimum carbon deposits and wear on engine parts. Available hard coals that are analysis-certified and commercially available can be used in the production of coal nanoparticles. In an embodiment of the present invention, the total ash and maximum sulfur content by mass of the coal samples used is 9±1 % and 0.8%, respectively, and these values and coal samples under these values are usable in the production of coal nanoparticles.

Fuel with coal nanoparticles additive can be used directly without requiring any modification in all vehicles/systems (automobile, bus, construction equipment, ship, diesel electric generator, boiler, etc.) with diesel motor/diesel fuel. Fuel standards are not changed and there is no need for any modification in the engines/systems in which the fuel is used due to the reasons such as that the coal particles are nano-sized and added to the fuel in very low concentrations (max 2000 ppm), and therefore, the increase in the viscosity of the fuel is limited, and it is not required to additional filtering due to low exhaust emissions thereof.

In an embodiment of the present invention, coal nanoparticles at a rate of 300 ppm (300 mg) were added to 1 kg (1.2 L) of diesel fuel or diesel-biodiesel fuel, and it was determined that nitrogen oxide (NOx) emissions are decreased by 11.8%, while the thermal efficiency of the engine is increased by 6.3%. It was determined that while the thermal efficiency is increased by 3.4%, the specific fuel consumption, nitrogen oxide (NOx), and carbon monoxide (CO) emissions are decreased by 2.4%, 3.4% and 15.63%, respectively, in case coal nanoparticles are added to a biodiesel-diesel fuel mixture containing biodiesel at a rate of 20% by volume.

In an embodiment of the present invention, coal nanoparticles can be mixed with the fuels in the tanks in the amounts specified at the refineries/fuel distribution stations and the fuel can be sold in this way. However, not all fuel distribution stations/companies may use this fuel additive. Therefore, coal nanoparticles can be blended with small volumes of fuel such as 0.5 L or 1 L at high concentrations, thereby, obtaining ready- to-use fuel with coal nanoparticles additive. Readily-prepared fuel with coal nanoparticles additive with high concentrations can be purchased by individual users and discharged into a vehicle fuel tank. Considering that the fuel tank volume of a light commercial vehicle is approximately 60 L, 1 L of fuel with coal nanoparticles additive, which will be sold for the use of coal nanoparticles at a rate of 300 ppm, contains approximately 15 g of coal nanoparticles. The coal nanoparticle concentration of the fuel in the tank will be 300 ppm when said 1 L of fuel with coal nanoparticles additive is discharged into a 60 L tank. Similarly, 0.5 L of fuel with coal nanoparticles additive contains 30 g of coal nanoparticles, and the coal nanoparticle concentration of the fuel in the tank will be 300 ppm when an individual user discharges it into a 60 L tank.

The produced coal nanoparticles at a rate of 300 ppm (300 mg coal nanoparticles per 1 kg of fuel) were added into the diesel fuel and diesel-biodiesel fuel mixture (B20: fuel mixture containing biodiesel at a rate of 20% + diesel at a rate of 80%) by means of mechanical and ultrasonic processes. Due to the natural black color of coal nanoparticles, the color of fuels with coal nanoparticle additive is also black. Engine performance and emission tests were carried out after the test fuels were prepared. Engine tests were carried out on a 4-stroke, water-cooled diesel engine. The tests were carried out at constant speed (1500 rpm) and at different loads (25%, 50%, 75%, and 100%) (where the load is the power capacity of the motor, i.e., the 100% load state is the operating state of the motor at the maximum power output thereof).

Figure 4 illustrates the effect of test fuels on the specific fuel consumption of the engine. Specific fuel consumption is the amount of fuel consumed per unit of power produced by the engine and allows for comparing the performance of the engines with different sizes. Here, coal nanoparticles added diesel fuel and diesel-biodiesel fuel mixture are labeled as D+C and B20+C, respectively. The biodiesel fuel used in the experiments was produced from corn oil. When Figure 4 is examined, coal nanoparticles reduced the specific fuel consumption of the engine, especially at high engine loads. The reason for this is that coal nanoparticles have a high surface area/volume rate and increase the heat of combustion by including in combustion during the combustion. This effect is reduced since the amount of fuel injected into the cylinder at low loads is less. By means of adding coal nanoparticles at a rate of 300 ppm to diesel (D) and dieselbiodiesel (B20) fuel, the specific fuel consumption is reduced by 1.5%, and 2.4% on average (average of values at all engine loads), respectively.

Figure 5 illustrates the effect of test fuels on the thermal efficiency of the engine. Thermal efficiency is a performance parameter used for thermal machines (machines where combustion is performed) and is implied as the ratio of the power produced by the engine to the fuel power included in the combustion. The specific fuel consumption of the engine is low in case the thermal efficiency of the engine is high. This relationship is clearly seen in Figure 5, wherein the thermal efficiency is increased since the fuel additive coal nanoparticles decrease the specific fuel consumption of the engine. By means of adding coal nanoparticles at a rate of 300 ppm to diesel and B20 fuel, the thermal efficiency is increased by 1 .6% and 3.4% on average (average of values at all engine loads), respectively. The performance increase in B20 fuel was higher than in the diesel fuel with the addition of coal nanoparticles. The reason that the coal nanoparticles improve the heat conduction properties of the fuel. Coal nanoparticles ensured that B20 fuel, which demonstrates poor evaporation characteristics compared to diesel, has evaporated more easily and thereby, forming a better air-fuel mixture. Increasing the homogeneity (quality) of the air-fuel mixture increases the performance thereof and reduces the exhaust emissions. Therefore, from this, it is understood that coal nanoparticles are suitable fuel additives to increase the engine performance of biofuels.

Figure 6 illustrates the effect of test fuels on the exhaust gas temperature. By means of adding coal nanoparticles at a rate of 300 ppm to diesel and B20 fuel, the exhaust gas temperature is decreased by 2.84% and 1.8% on average (average of values at all engine loads), respectively. The exhaust gas temperature relates to the calorific value of the fuels. However, low exhaust gas temperature is an indicator indicating that a larger portion of the heat energy generated by combustion is converted into effective engine power.

Nitrogen oxide (NOx) emissions have the highest share among the pollutant emissions in the exhaust of diesel engine vehicles. Controlling/reducing NOx emissions is more difficult and costly than other emissions. However, reducing NOx emissions with fuel additives may be performed in a more easy and affordable manner. Figure 7 illustrates the effect of coal nanoparticles on NOx emission. By means of adding coal nanoparticles at a rate of 300 ppm to diesel and B20 fuel, NOx emissions are decreased by 11.8% and 3.4% on average (average of values at all engine loads), respectively. In addition, the physical ignition delay is reduced due to the fact that the coal nanoparticles improve the thermophysical properties of the fuel. Here, the ignition delay indicates the time from when the fuel starts to be injected into the cylinder until the combustion starts. Ignition delay directly affects the performance and emission generation thereof. Therefore, it is desired that the ignition delay is short in order to obtain high performance and low emission. Less fuel is included in the uncontrolled combustion in case the ignition delay is shortened, and in this case, the formation of thermal NOx decelerates. It is thought that coal nanoparticles reduce NOx emissions as a result of the above-mentioned effect.

Figure 8 illustrates the effect of coal nanoparticles on hydrocarbon (HC) emissions. HC emission is a product of incomplete combustion, and in case the combustion efficiency of the fuel increases, HC emission reduces. As illustrated in the figure, coal nanoparticles have reduced HC emissions by 75% on average. The reason is that coal nanoparticles improve the properties of the fuel and provide a more homogeneous airfuel mixture formation. In addition, it is understood that the disadvantages, which is caused by the high density and viscosity of biodiesel compared to diesel fuel, are partially reduced by coal nanoparticles.

The CO emission is a product of incomplete combustion and is an extremely toxic gas. Figure 9 illustrates the effect of coal nanoparticles on CO (carbon monoxide) emission. As illustrated in the figure, CO emission has reduced by 15.6% on average when coal nanoparticles are added to the B20 fuel. However, CO emission has increased by 12.8% since the carbon ratio of the fuel is increased when coal nanoparticles are added to diesel fuel. The increased carbon ratio of the fuel due to the addition of coal nanoparticles has not caused an increase in CO emissions since biodiesel contains oxygen in its composition.

According to the data obtained from the preliminary engine tests related to the present invention, coal nanoparticles increase the performance of the engine and reduce exhaust emissions. No structural changes were carried out in order to use the fuels with coal nanoparticle additive in the engine, and no technical problems were encountered during the experiments. This indicates that coal nanoparticles can be used directly in available engines.

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