A special fuel suitable for enhanced compression ignition engine

Abstract

The present invention belongs to the field of petrochemical industry, and specifically provides a special fuel suitable for strengthening compression ignition engines, wherein the special fuel is composed of coal-based diesel, tripropylene glycol methyl ether, anti-wear agent, antioxidant and metal corrosion inhibitor. Compared with traditional automotive diesel, the special fuel has a higher cetane number, better lubricity and higher oxygen content; it ensures that the power performance can still be improved at the maximum throttle opening of the strengthened engine, and also ensures that the engine does not detonate under high load; better lubricity can reduce the wear and blockage of precision parts such as diesel engine injector needle valve pairs and fuel injection nozzles, and improve the running stability of the engine. At the same time, it does not contain a cetane number improver, which avoids the disadvantages of the special fuel in a closed and poor light-shielding condition, such as the decomposition of the cetane number improver, and the increase of fuel acidity to corrode metal parts.

Description

Technical Field

[0001] The invention belongs to the field of petrochemical industry, and in particular relates to a special fuel suitable for enhancing compression ignition engines. Background Art

[0002] As the "Iron Man" of off-road racing, modified off-road diesel vehicles not only boast low-speed, high-torque characteristics conducive to off-road driving, but also boast high combustion efficiency, excellent fuel economy, and long driving range, making them a favorite among off-road competitors. Major clubs modify and strengthen their engines according to competition rules, ensuring greater impact resistance and power output.

[0003] Engine modifications also place more stringent requirements on fuel, requiring it to possess higher anti-knock properties, faster combustion rates, lower corrosiveness, and improved lubricity to accommodate such modifications. Currently, with the exception of a very small number of clubs using specialized foreign racing diesel, the vast majority of diesel vehicles use No. 0 diesel from gas stations. However, due to its relatively poor anti-knock properties, combined mixed gas calorific value, and lubricity, racing diesel engines suffer from insufficient maximum torque, severe wear on precision components like nozzles and plunger pumps, and a significant decrease in reliability, significantly impacting the normal operation of the vehicle and making it difficult to achieve faster competitive results.

[0004] Coal-to-diesel has a very high cetane number (usually no less than 65), and its combustion stability and anti-knock properties are superior to commercially available automotive diesel, making it more adaptable to the high-compression ratio operating environment of enhanced engines. However, its sole use does not achieve a further increase in power at the maximum intake volume of a modified diesel engine.

[0005] Furthermore, cetane improvers are used in the refining process to boost diesel's cetane number. While this is generally acceptable, they can decompose in the hot, humid conditions of a rally, causing diesel to oxidize and discolor, and significantly increasing its acidity, far exceeding the required upper limit of 7mg / 100ml. Therefore, specialized fuels used to enhance compression ignition engines cannot use cetane improvers, which are prone to decomposition and can affect the fuel.

[0006] Therefore, whether it is possible to combine the advantages of coal-to-diesel to provide a special fuel that is more suitable for modified enhanced compression ignition engines has become one of the urgent problems to be solved by those skilled in the art. Summary of the Invention

[0007] The present invention addresses the shortcomings of the prior art and provides a special fuel suitable for enhanced compression ignition engines. The special fuel comprises coal-based diesel, tripropylene glycol methyl ether, an anti-wear agent, an antioxidant, and a metal corrosion inhibitor. Compared to conventional automotive diesel, the special fuel has a higher cetane number, better lubricity, and a higher oxygen content. It ensures that the enhanced engine's power can still be improved at the maximum throttle opening, while also ensuring that the engine does not experience knock under high loads. The improved lubricity can reduce wear and clogging of precision parts such as diesel engine injector needle valve pairs and fuel injection nozzles, thereby improving engine operating stability. Furthermore, the fuel does not contain a cetane improver, thus avoiding the drawbacks of the special fuel, such as cetane improver decomposition and increased fuel acidity that can corrode metal parts, which can occur when the fuel is sealed or in poor light-shielding conditions.

[0008] The inventive concept of the present invention is:

[0009] In the prior art, other alcohols and ethers are used to increase the oxygen content of diesel fuel, but there are the following problems:

[0010] 1. Existing technicians increase the oxygen content by adding alcohols such as methanol. However, the cetane number of low-carbon alcohols is very low, only 3-5, making compression ignition difficult. The mixture is not conducive to engine ignition and starting.

[0011] 2. Alcohols have very strong polar bond energy and are difficult to dissolve in diesel. Although they can be made miscible with diesel by using cosolvents, their miscibility is affected by ambient temperature. At low temperatures, the solubility of methanol decreases, resulting in oil-alcohol separation, which affects the normal starting of the engine.

[0012] 3. During actual production, the inventors discovered that the acidity of PODE (polyoxymethylene dimethyl ether), commonly used in the prior art, increased after long-term storage. Data showed that after six months of storage, the acidity of PODE reached 16 mg / 100 ml, far exceeding the regulatory limit of no more than 7 mg / 100 ml for automotive diesel.

[0013] To this end, the inventors finally screened out tripropylene glycol methyl ether as a self-oxygenated component that also has a high cetane number (measured value exceeds 60), which can form a synergistic gain effect with coal-based diesel, further improving the anti-knock performance of the two after mixing. Tripropylene glycol methyl ether has better miscibility with diesel than alcohols, and can be miscible with diesel in a wide range of proportions, which can avoid the occurrence of stratification when diesel and methanol are mixed. More importantly, compared with the disadvantage of other high-carbon ethers such as PODE that cause a significant increase in acidity after long-term storage, the inventors added tripropylene glycol methyl ether to coal-based diesel and found no stratification at a ratio of less than 60%. After mixing and storing for 6 months, the acidity was also within 7mg / 100ml. It can be seen that compared with ingredients such as PODE and alcohols, tripropylene glycol methyl ether has better miscibility, acidity and other indicators with coal-based diesel when it also has a high oxygen content (oxygen content 31%). In addition, its low volatility, low toxicity and high flash point (90°C) make it an excellent component for mixing with coal-based diesel.

[0014] Enhanced diesel engines operate at higher fuel injection pressures. Under these high pressures, the lubricity of the fuel itself amplifies wear on the precision injector components, significantly shortening their lifespan. Injectors placed directly within the cylinder are subject to high temperatures, which accelerate fuel oxidation and, in particular, significantly increase the likelihood of coking of unsaturated fuel components. To address this issue, the inventors selected castor oil as an antiwear agent from a wide range of sources. Castor oil exhibits excellent high-temperature resistance and remains stable at temperatures of 500-600°C. This avoids the decomposition and acidification of traditional fatty acid-based cetane improvers under high-temperature conditions. Castor oil can be used as an antiwear agent to improve diesel lubricity, ensuring stable injector operation and extending its lifespan.

[0015] After selecting the above substances as additives, the specific technical solution adopted by the present invention is:

[0016] A special fuel suitable for enhanced compression ignition engines, the main components of which are coal-based diesel, tripropylene glycol methyl ether, an antiwear agent, an antioxidant and a metal corrosion inhibitor; the coal-based diesel comprises 50%-70% and the tripropylene glycol methyl ether comprises 30%-50% by volume, the total of which is 100%; in addition, based on the total volume of the coal-based diesel and tripropylene glycol methyl ether, the fuel further comprises 0.05%-0.1% of the antiwear agent, 0.004%-0.01% of the antioxidant and 0.001%-0.005% of the metal corrosion inhibitor.

[0017] The reason for controlling the above ratio of tripropylene glycol methyl ether to coal-to-diesel is that the inventors have found that too high or too low a content of tripropylene glycol methyl ether will affect engine commissioning or maximum horsepower.

[0018] The antioxidant is alkylated diphenylamine, the metal corrosion inhibitor is benzotriazole, and the anti-wear agent is castor oil.

[0019] Preferably, the coal-to-diesel used has a cetane number of not less than 65, a freezing point not higher than -10°C, a distillation range of 190°C-340°C, and a density not higher than 775kg / m 3 The main reason for selecting the above-mentioned coal-to-diesel standard is that coal-to-diesel used in winter requires a low pour point, otherwise the oil solidifies at low temperatures, making it difficult to pump. Therefore, the above-mentioned pour point limit is imposed. Furthermore, coal-to-diesel with a low cetane number can be excluded, ensuring that the final fuel has better combustion stability and anti-knock properties.

[0020] Preferably, the composition of the special fuel is as follows: 60% coal-based diesel and 40% tripropylene glycol methyl ether by volume; in addition, based on the total volume of coal-based diesel and tripropylene glycol methyl ether, it also contains 0.08% anti-wear agent, 0.005% antioxidant, and 0.003% metal corrosion inhibitor. Under the above ratio, the power effect and debugging requirements can reach a better level, and a balance between the two can be achieved.

[0021] Although prior art indicates that tripropylene glycol methyl ether will not oxidize under high-temperature conditions, in order to prevent extreme conditions of being placed outdoors at high temperatures, the present invention specifically adds an antioxidant to the composition to delay fuel oxidation under extreme high-temperature conditions, and uses a metal corrosion inhibitor to form a dense protective film on the surface of metal parts in the engine fuel system to prevent fuel acidity from exacerbating corrosion of precision components such as injectors.

[0022] The inventors also provide a method for preparing the above-mentioned special fuel as follows:

[0023] Add coal-based diesel, tripropylene glycol methyl ether, castor oil, antioxidant and metal corrosion inhibitor into the blending tank according to the volume ratio, fill the top of the tank with nitrogen for protection and start the pump for circulation and mixing.

[0024] In conventional preparation methods, the space above the materials stored in the blending tank is air. In order to minimize the contact between various fuel components and air and slow down the oxidation process, the inventors specially selected nitrogen protection in the tank in the above preparation method.

[0025] The properties of the special fuel obtained above are as follows: lubricity characterized by corrected wear scar diameter (60°C) / μm is 260-330 μm; cetane number is greater than 58; pour point is not higher than -10°C; sulfur content is not higher than 3 ppm; distillation range is 170°C-330°C; density is 830-865 kg / m 3 Compared with existing commonly used automotive diesel, it has significantly improved power performance and lubricity.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] The present invention utilizes high cetane number coal-based diesel as the base oil for the special fuel for the enhanced compression ignition engine, ensuring that the special fuel has high anti-knock performance, burns smoothly and not violently, and has high combustion efficiency. However, simply improving the anti-knock performance of the special fuel cannot meet the demand for further improvement of the power of such engines. Under the modification requirements of relevant competitions, such as the International Automobile Federation (FIA) Circuit Race Super Production Car Technical Rules, "only the original intake system is allowed to contain a maximum of two throttles, and the use of a variable intake system is prohibited" and "the flow rate of the injector is not limited, but its number, working principle and position must be consistent with the original." The requirements of the above rules limit the maximum intake volume of such enhanced engines. The engine intake volume cannot be further increased at the hardware level, but the provision that the injector flow rate is allowed to be changed provides a way to increase the engine intake volume from the fuel perspective.

[0028] Internal combustion engine fuel can burn more fully under the condition of approaching theoretical air-fuel ratio, and efficiency is higher.Though can realize the adjustment of fuel injection quantity by changing the fuel injector size, the air that enters engine under maximum throttle opening is fixed, the injection quantity of continuing to increase conventional vehicle diesel (oxygen-free) causes fuel to be enriched, and combustion begins to be insufficient, causes the situation that fuel sprays more power and descends on the contrary.Use oxygenated diesel oil then can well improve the problem that the actual hydrocarbon fuel that causes because of fuel injection increases is enriched, burns insufficiently, so spray more oxygenated fuel and can continue to improve engine power under maximum throttle opening situation.Find by test, increase the maximum power of engine that oxygenated fuel injection quantity can reach 5% and improve at least 2% than fuel vehicle diesel oil.And the tripropylene glycol methyl ether that adopts in this application has oxygen element in its own structure, can provide oxygen in combustion process, engine still can continue to increase fuel injection quantity by the matching debugging of ECU air-fuel ratio in throttle fully open state.

[0029] In summary, the specialized fuel provided by this application boasts a higher cetane number, improved lubricity, and a higher oxygen content. It ensures enhanced engine performance even at maximum throttle opening, while also preventing engine knock under heavy loads. Its improved lubricity reduces wear and clogging of precision components such as diesel engine injector needle valves and nozzles, improving engine operating stability. Furthermore, the fuel contains no cetane improver, thus avoiding drawbacks such as cetane improver decomposition and corrosion of metal components caused by increased fuel acidity when used in sealed, light-blocking environments. DETAILED DESCRIPTION

[0030] The following is a further detailed description of the present invention in conjunction with specific examples. However, this should not be construed as limiting the scope of the present invention to the following examples. All technologies implemented based on the above-mentioned content of the present invention fall within the scope of the present invention. Unless otherwise specified, the raw materials used in the following examples are commercially available products.

[0031] The specific embodiments of the present application and the corresponding comparative examples are shown in the following table. The compositions and contents of Examples 1-5 are as follows:

[0032] Table 1 Example scheme

[0033] Example Coal-to-diesel Tripropylene glycol methyl ether anti-wear agents antioxidants Metal corrosion inhibitors Example 1 50 50 0.05 0.01 0.001 Example 2 55 45 0.05 0.008 0.002 Example 3 60 40 0.08 0.005 0.003 Example 4 65 35 0.1 0.005 0.004 Example 5 70 30 0.15 0.004 0.005

[0034] The antioxidant used is alkylated diphenylamine, the corrosive agent is benzotriazole, and the anti-wear agent is castor oil; the coal-to-diesel used has a cetane number of 68, a freezing point not higher than -12°C, a distillation range of 190°C-340°C, and a density of 774.2 kg / m 3 , sulfur content 1.5ppm.

[0035] In addition, the inventors provide two comparative examples, as shown in Table 2:

[0036] Table 2 Comparative Example

[0037] Example sequence Coal-to-diesel Tripropylene glycol methyl ether anti-wear agents antioxidants Metal corrosion inhibitors Comparative Example 1 45 55 0 0.01 0.001 Comparative Example 2 75 25 0.05 0.008 0.002

[0038] At the same time, commercially available No. 0 diesel for automobile use is used as comparative example 3. The actual test index results of the above embodiment and comparative example samples are shown in Table 3:

[0039]

[0040] It can be seen from the above table that the cetane number and lubricity of the embodiments of the present application are better than those of comparative examples 1 and 3. A high cetane number means that the engine can increase the compression ratio, and the combustion thermal efficiency will also be improved accordingly. The same mass of fuel will ultimately output higher power.

[0041] In terms of lubricity, the wear scars in the examples are all below 300 μm, meaning the wear on precision parts is lower. Tests have shown that even with commercially available automotive diesel, the nozzles in the modified diesel engine are subject to significant wear, resulting in a reduced service life (operating time) (data shown in the table below). In Comparative Example 1, the wear scar diameter exceeds 500 μm without the use of an anti-wear agent, indicating more severe wear on the engine's precision parts. However, the technical solution of this application significantly reduces the wear scar diameter after adding a small amount of anti-wear agent, significantly improving the anti-wear effect.

[0042] Experimental example

[0043] The engine nozzle durability test was carried out using the products of this embodiment and the comparative example respectively. Table 4 shows the test results. It can be seen from the test results that the nozzle working time of Examples 1-5 is significantly better than that of Comparative Examples 1-3, indicating that the good lubricity of the embodiments is better than that of the comparative example in reducing the wear of precision parts such as diesel engine fuel injectors.

[0044] Table 4 Nozzle durability test Bench testing involved automotive diesel engines from Examples 1-4 and Comparative Examples 1-3. The test engine was a BMW 3.0L inline 6-cylinder supercharged diesel engine. External characteristics were tested at speeds commonly used in competitions, including 3500 rpm, 4000 rpm, 4500 rpm, and 5000 rpm, to compare the engine's maximum torque. The following table compares the maximum torque of the examples and comparative examples 1-3.

[0045] Table 5 Comparison of test torque

[0046]

[0047] Tests show that tripropylene glycol methyl ether exhibits a downward trend in torque when the content is above 50% or below 30%. Furthermore, excessively high content of tripropylene glycol methyl ether requires a larger nozzle, which can be inconvenient for modification and commissioning. A comprehensive comparison of the two types of tests shows that this embodiment exhibits significant advantages in lubricity and power (engine torque) over the commercially available automotive diesel in Comparative Example 3, as well as Comparative Examples 1 and 2.

[0048] For ordinary technicians in this field, the specific embodiments are only illustrative descriptions of the present invention. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concepts and technical solutions of the present invention, or the concepts and technical solutions of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A special fuel suitable for enhancing compression ignition engines, characterized in that: The fuel is composed of coal-based diesel, tripropylene glycol methyl ether, anti-wear agent, antioxidant and metal corrosion inhibitor, wherein by volume percentage, coal-based diesel is 50%-70%, tripropylene glycol methyl ether is 30%-50%, and the total of the two is 100%; based on the total volume of coal-based diesel and tripropylene glycol methyl ether, the anti-wear agent is 0.05%-0.1%, the antioxidant is 0.004%-0.01%, and the metal corrosion inhibitor is 0.001%-0.005%; The cetane number of the coal-to-diesel used is not less than 65, the freezing point is not higher than -10℃, the distillation range is 190℃-340℃, and the density is not higher than 775 kg / m 3 ; The special fuel has a corrected wear scar diameter of 260-330um at 60°C, a cetane number greater than 58, a freezing point not higher than -10°C, a sulfur content not higher than 3ppm, a distillation range of 170°C-330°C, and a density of 830-865 kg / m 3 ; The anti-wear agent is castor oil.

2. The special fuel suitable for enhanced compression ignition engine according to claim 1, characterized in that: The antioxidant is alkylated diphenylamine, and the metal corrosion inhibitor is benzotriazole.

3. The special fuel suitable for enhanced compression ignition engine according to claim 1 or 2, characterized in that: The special fuel is composed of: 60% coal-based diesel and 40% tripropylene glycol methyl ether by volume; based on the total volume of coal-based diesel and tripropylene glycol methyl ether, 0.08% anti-wear agent, 0.005% antioxidant, and 0.003% metal corrosion inhibitor.

4. The method for preparing the special fuel suitable for enhancing compression ignition engine according to claim 1, characterized in that: The specific steps are as follows: add coal-to-diesel, tripropylene glycol methyl ether, castor oil, antioxidants, and metal corrosion inhibitors into a blending tank in proportion to the volume, fill the tank with nitrogen for protection, and then start the pump for circulation and mixing.

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