Methanol-based engine fuel containing a combustion promoter
A methanol-based fuel with 0.01 to 2.0% alkyl nitrate enhances ignitability, addressing ignition issues in compression ignition engines with reduced emissions and improved engine performance.
Patent Information
- Application Number
- JP2024575688
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-06-23
- Filing Date
- 2023-06-22
- Publication Date
- 2025-07-08
AI Technical Summary
Methanol's ignition in compression ignition engines, particularly at low engine speeds, is problematic, and existing additives for improving ignitability in methanol fuels have environmental drawbacks or are not effectively quantified.
A fuel composition comprising 98.0 to 99.9% methanol and 0.01 to 2.0% alkyl nitrate, specifically 2-ethylhexyl nitrate, is used to enhance ignitability, with the alkyl nitrate being added in very small concentrations to maintain environmental friendliness and effectiveness.
The addition of alkyl nitrate significantly reduces ignition delay of methanol-based fuels by up to 1/5 to 1/10, improving engine performance without substantial environmental impact.
Smart Images
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Abstract
Description
Technical Field
[0001] The field of the present invention relates to fuels for combustion engines. The fuels of the present invention belong to new fuels with reduced environmental impact, such as those generally called "e-fuels" when produced from low-carbon electricity, low-carbon footprint hydrogen, and / or CO2. These fuels are being considered as solutions for decarbonizing transportation. The fuel of the present invention mainly (at least 98%) consists of methanol and is thus part of an environmentally friendly alternative fuel to fossil fuels. The present invention relates to an additive that can improve the ignitability of the fuel in the engine and increase the combustion rate when blended with methanol.
Background Art
[0002] "E-fuel" type methanol is a certain alternative with reduced environmental impact to replace fossil fuels and biofuels for combustion engines in the near future. When methanol produced in this way is burned, the CO2 balance becomes neutral. Methanol as a fuel has an energy density that can be used in combustion engines, while having a low cetane number. Its ignition in compression ignition engines such as diesel is problematic, especially when the engine speed is low. Various means for improving the ignitability of methanol in compression ignition engines have been disclosed.
[0003] The first means is a method of co-injecting pilot fuel or an additive into the engine together with methanol. For example, in the specification of Chinese Patent Application No. 214944586, it is described that diesel-type pilot fuel is co-injected as the primary fuel together with methanol. In the scientific paper "Effect of Cetane Improvers on Gasoline, Ethanol, and Methanol Reactivity and the Implications for RCCI Combustion" (SAE International Journal of Fuels and Lubricants Vol. 6, No. 1 (April 2013), pp. 170-187), it is described that 2-ethylhexyl nitrate (EHN) is co-injected together with a fuel mainly composed of methanol. In the combustion in a specific RCCI (Reactivity Compression Controlled Ignition) mode, a well-mixed mixture of fuel and a low-reactivity oxidant (usually using air) is compressed but does not auto-ignite. Subsequently, a high-reactivity fuel (in this case, EHN) is continuously injected during the compression cycle to form a local mixture of the low-reactivity fuel and the high-reactivity fuel. The mass ratio of the co-injected EHN is about 6%. Such a method has a major drawback that it is necessary to control the co-injection according to the engine operating conditions and the structural arrangements such as individual tanks and injection systems. Also, when using fuel oil as the pilot fuel, CO2 emissions occur, which has an adverse impact on the environment.
[0004] The second means is a blended fuel with methanol. It is known that alcohols such as methanol or ethanol can be mixed with fossil fuels, synthetic diesel fuels such as dimethyl ether (DME), or gasoline at a ratio exceeding or not exceeding half. Also in this case, the CO2 emission balance is negative for the environment.
[0005] The third means is a method of mixing an ignition promoting additive with methanol and optionally also with diesel fuel. Many patent applications such as the specification of Chinese Patent Application No. 103865592 and the specification of Chinese Patent Application No. 104232180 describe formulating a cocktail by mixing a multifunctional additive with methanol and optionally also with fuel oil. These additives have functions such as, for example, anti-corrosion, corrosion resistance, improvement of flammability, and detergency. These additives are generally at least 10% by weight of the fuel. The proportion of methanol in the fuel is 30 to 90% by weight depending on the weight percentages of the additives and diesel fuel present in the fuel. The combined effects of these additives have only been observed as a whole and the required amounts have not been accurately determined. Therefore, it is not a fuel mainly composed of methanol.
[0006] On the other hand, in the field of hydrocarbon diesel fuels and biodiesel fuels, it has been previously known that 2-ethylhexyl nitrate (EHN) is used as a cetane number improver for diesel fuels. The higher the cetane number, the lower the fuel consumption, the lower the emissions of particulate matter and NOx, the faster the cold start of the engine, the lower the engine knock and noise, and the lower the engine wear. The reaction mechanism of EHN in the presence of hydrocarbon diesel fuels has been studied in scientific literature such as "The Autoignition Behavior of Surrogate Diesel Fuel Mixtures and the Chemical Effects of 2-Ethylhexyl Nitrate (2-EHN) Cetane Improver" (vol. 108, section 4: Journal of fuels and lubricants (1999), pp. 1029-1045). However, the reaction mechanism of its diesel fuel cetane number improving effect has not yet been fully elucidated, and its use is based on empirical rules. Therefore, its effectiveness for fuels other than diesel cannot be assumed. This additive is industrially produced and widely used in commercially available diesel fuels. In Europe, more than 50,000 tons of EHN have been produced annually since the 1980s. Other alkyl nitrates can also be used as cetane number improving additives for diesel fuels. Figure 1 shows that the effects of various alkyl nitrates added to standard diesel fuel (medium paraffin-based (about 40%) with a low natural cetane number but showing a standard cetane number improving reaction) on the cetane number are similar to those of EHN. The cetane number improving effect is obtained when the blending amount of alkyl nitrate in diesel fuel is close to 0.03% by weight.
[0007] The present invention provides a solution for improving the ignitability of methanol in a combustion engine. This improvement is obtained by adding an EHN additive alone in a very small weight ratio to a mixture with methanol fuel. More generally, other alkyl nitrates known to have cetane number improving properties for diesel fuel, similar to EHN, are also recommended for improving the ignitability of methanol in the context of the present invention. It is not expected that using additives known to increase the cetane number of diesel or biodiesel hydrocarbons in very small weight percentages would be so effective in improving the ignitability of alcohols such as methanol.
Summary of the Invention
Means for Solving the Problems
[0008] The present invention relates to a fuel containing 98.0 to 99.9% by weight of methanol and 0.01 to 2.0% by weight of a compound that improves the ignition delay of methanol for a compression ignition engine or a spark ignition engine.
[0009] The above compound is an alkyl nitrate.
[0010] The above compound has the advantages of being liquid at room temperature, having low flammability, being non-toxic, and being industrially produced.
[0011] Since the above compound is present in such a low concentration in the presence of fuel methanol, it is incorporated into the fuel additive in the conventional manner.
[0012] By adding the above liquid compound to a mixture with liquid methanol, the fuel according to the present invention is formed in a tank. Alternatively, it can be separately stored, mixed with methanol to form the fuel according to the present invention, and then injected into the engine, or co-injected in a pre-mixing chamber of the engine to form the fuel according to the present invention.
[0013] Therefore, the above-mentioned alkyl nitrate type compounds, which were previously used to improve the cetane number of fossil diesel or biodiesel hydrocarbon fuels, are surprisingly effectively used as additives to improve the ignitability of methanol.
Brief Description of the Drawings
[0014]
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Best Mode for Carrying Out the Invention
[0015] The present disclosure relates to an engine fuel (especially for combustion engines) containing about 98.0 to about 99.9% by weight of methanol and about 0.01 to about 2.0% by weight of a compound composed of alkyl nitrates. In one embodiment, the fuel contains about 0.05 to about 1.5% by weight of the above compound. In another embodiment, the fuel contains about 0.1 to about 1.0% by weight of the above compound. In another embodiment, the fuel contains about 0.1 to less than 1.0% (<1.0%) by weight of the above compound.
[0016] In one embodiment, the fuel of the present invention consists of methanol and the above compound (in this case, the amount of the above compound in the fuel is at least 0.1% by weight).
[0017] In another embodiment, when the total of the amount of methanol and the amount of the above compound is not equal to 100% by weight, the fuel may contain one or more other additives such as additives having functions of anti-corrosion, corrosion resistance, or detergency so as to reach 100%.
[0018] The above compound added to methanol is selected from one or more linear, branched, or cyclic alkyl nitrates.
[0019] More specifically, the above compound is selected from linear alkyl nitrates having 4 to 36 carbon atoms, preferably 4 to 24 carbon atoms, branched alkyl nitrates having 4 to 36 carbon atoms, preferably 4 to 24 carbon atoms, cyclic alkyl nitrates (or cycloalkyl nitrates) having 5 to 18 carbon atoms, and mixtures thereof. In one embodiment, the above compound is 2-ethylhexyl nitrate, cyclohexyl nitrate, dodecyl nitrate, n-nonyl nitrate, 2-tetradecyl-1-octadecyl nitrate, hexyl nitrate, 2-octyl nitrate, isononyl nitrate, 2-propylheptyl nitrate, C9~C 13Selected from mixtures of branched-chain alkyl nitrates and these mixtures. In one embodiment, the alkyl nitrate is either 2-ethylhexyl nitrate alone or a mixture of 2-ethylhexyl nitrate and one or more other alkyl nitrates as defined above. It is advantageous for the alkyl nitrate to be 2-ethylhexyl nitrate.
[0020] C9 - C 13 The mixture of branched-chain alkyl nitrates is from the corresponding branched-chain C9 - C 13 alcohols, such as the mixture of alcohols available under the trade name Exxal manufactured by Exxon. TM As an example, after preparing a mixture of at least two branched-chain alcohols selected from C9 branched-chain alcohol, C 10 branched-chain alcohol, C 11 branched-chain alcohol, C 12 branched-chain alcohol, and C 13 branched-chain alcohol, the corresponding mixture of alkyl nitrates can be synthesized.
[0021] According to one embodiment, the above compound and methanol are stored separately and then combined in an injector to produce the fuel according to the present invention, and then supplied into the combustion chamber of the engine.
[0022] According to one embodiment, the above compound is stored separately from methanol and co-injected with methanol in the premixing chamber of the engine to form the fuel according to the present invention.
[0023] The present disclosure also relates to the use of (the above-defined) alkyl nitrates in the above-defined proportions as an ignition promoter for methanol-based (or methanol-composed) fuels.
[0024] The present disclosure also relates to a method for improving the ignitability of a methanol-based (or consisting of methanol) fuel in an engine (particularly a combustion engine), the method comprising the step of adding an alkyl nitrate (as defined above) to methanol in the proportion defined above. In one embodiment, the alkyl nitrate and methanol are mixed in an injector. In one embodiment, the alkyl nitrate and methanol are mixed in a pre-mixing chamber of the engine.
[0025] The present disclosure also relates to an engine (particularly a combustion engine) of a vehicle (automobile, truck, tractor, etc.) or a ship (tanker, container ship, etc.) containing the fuel defined above. The present disclosure also relates to a vehicle or a ship having the engine defined above.
[0026] The present invention will be described by the following examples presented for reference only.
Examples
[0027] The improvement of the ignition delay of methanol was measured under test conditions equivalent to those described in the scientific paper "Ignition delay times of NH3 / DME blends at high pressure and low DME fraction: RCM experiments and simulations" (Combustion and Flame, Volume 227, May 2021, Pages 120 - 134). The engine in the laboratory is a high-speed compressor equivalent to that described in this scientific paper, which is a high-speed compressor for measuring the auto-ignition time of the mixture. According to this machine, the mixture can be compressed in a very short time to obtain predetermined pressure and temperature conditions. The liquid is introduced into the tank through an orifice different from the gas inlet. The amount of the liquid is measured with a syringe and a precision balance.
[0028] The ignition delay dAI is defined by the following formula.
Equation
[0029] (Example 1) For the fuel according to the present invention consisting of 99.8% by weight of methanol and 0.2% by weight of EHN, the ignition delay was measured as a function of the injection temperature (800 - 1000 K) at a pressure Pc = 30 bar and an enrichment of the mixture with air of 0.5, 1, or 1.5. The results are shown in FIGS. 2, 3, and 4 together with the reference points of the ignition delay by methanol alone. When the fuel contains EHN as compared with the case of methanol alone, the ignition delay of the fuel is significantly reduced to about 1 / 5 to 1 / 10. Such a reduction in the ignition delay when compared with methanol alone becomes larger as the temperature is lower.
[0030] (Example 2) The ignition delay of each fuel containing methanol alone or a mixture of methanol and 0.2% by weight, 0.5% by weight, or 1% by weight of EHN was measured at each injection temperature (temperature range 790 K - 1000 K), a pressure Pc = 30 bar, and an enrichment of the mixture with air of 1. As can be seen from FIGS. 5 - 7, as a result of adding EHN to the methanol fuel, the ignition delay is significantly reduced as compared with the case of methanol alone.
[0031] From these examples, it was found that by using an alkyl nitrate in a very small weight percentage, the ignition delay of the methanol - based fuel can be significantly improved. There was no reason to think that the ignition performance of an alcohol such as methanol could be improved so effectively by using only a very small amount of an additive known to increase the cetane number of diesel or biodiesel hydrocarbons.
Claims
1. A compression ignition engine fuel containing 98.0 to 99.9% by weight of liquid methanol and 0.01 to 2.0% by weight of liquid alkyl nitrate.
2. The fuel according to claim 1, containing 0.05 to 1.5% by weight, particularly 0.1 to 1.0% by weight of the above alkyl nitrate.
3. The fuel according to claim 1 or 2, wherein the above alkyl nitrate is a linear alkyl nitrate having 4 to 36 carbon atoms, a branched alkyl nitrate having 4 to 36 carbon atoms, a cyclic alkyl nitrate having 5 to 18 carbon atoms, or a mixture of these nitrates.
4. The above-mentioned alkyl nitrate is 2-ethylhexyl nitrate, cyclohexyl nitrate, dodecyl nitrate, n-nonyl nitrate, 2-tetradecyl-1-octadecyl nitrate, hexyl nitrate, 2-octyl nitrate, isononyl nitrate, 2-propylheptyl nitrate, C ９ to C １３ a mixture of branched-chain alkyl nitrates, and the fuel according to any one of claims 1 to 3, selected from these mixtures.
5. The fuel according to any one of claims 1 to 4, wherein the above alkyl nitrate is 2-ethylhexyl nitrate.
6. The fuel according to any one of claims 1 to 5, consisting of 98.0 to 99.9% by weight of the above liquid methanol and 0.01 to 2.0% by weight of the above liquid alkyl nitrate.
7. A method for obtaining the fuel according to any one of claims 1 to 6, having a step of mixing the above alkyl nitrate and the above methanol in a liquid state.
8. The method according to claim 7, wherein the above methanol and the above alkyl nitrate are mixed in an engine tank.
9. The method according to claim 7, wherein the above methanol and the above alkyl nitrate are mixed in an injector.
10. The method according to claim 7, wherein the above methanol and the above alkyl nitrate are mixed in a pre-mixing chamber of the engine.
11. Use of 0.01 to 2.0% by weight of liquid alkyl nitrate in a liquid methanol-based fuel as an ignition promoter for the fuel.
12. The use according to claim 11, wherein the above alkyl nitrate is as defined in any one of claims 3 to 5.
13. A method for improving the ignitability of a fuel containing 98.0 to 99.9% by weight of liquid methanol in an engine, the method having a step of adding 0.01 to 2.0% by weight, preferably 0.05 to 1.5% by weight, more preferably 0.1 to 1.0% by weight of liquid alkyl nitrate to the methanol.
14. The method according to claim 13, wherein the above alkyl nitrate is as defined in any one of claims 3 to 5.
15. The method according to any one of claims 13 and 14, wherein the above alkyl nitrate and the above methanol are mixed in an injector.
16. The method according to any one of claims 13 and 14, wherein the alkyl nitrate and the methanol are mixed in a pre-mixing chamber of an engine.
17. An engine for a vehicle or a ship containing a fuel defined in any one of claims 1 to 6.
18. A vehicle or a ship having an engine defined in claim 17.