Engine fuel based on a mixture of alcohol and water and containing a combustion improver additive

Abstract

A fuel for a combustion engine includes from about 95.0% to about 99.9% by weight of a liquid water/alcohol mixture, in which water makes up from about 1% to about 15% by weight of the mixture, and from about 0.01% to about 5.0% by weight of an alkyl nitrate.

Claims

1. A fuel for a combustion engine, consisting of: (a) from about 95.0% to about 99.9% by weight of a liquid water/alcohol mixture, in which water makes up from about 1% to about 15% by weight of the mixture, and (b) from about 0.01% to about 5.0% by weight of an alkyl nitrate.

2. The fuel of claim 1, consisting of from about 97.0% to about 99.9% by weight of said water/alcohol mixture, and from about 0.1% to about 3.0% by weight of said alkyl nitrate.

3. The fuel of claim 1, wherein the alkyl nitrate is selected from the group consisting of a nitrate of a linear alkyl having from 4 to 36 carbon atoms, a nitrate of a branched alkyl having from 4 to 36 carbon atoms, a nitrate of a cyclic alkyl having from 5 to 18 carbon atoms, and mixtures thereof.

4. The fuel of claim 1, wherein the alkyl nitrate is selected from the group consisting of hexyl nitrate, cyclohexyl nitrate, 2-ethylhexyl nitrate, 2-octyl nitrate, n-nonyl nitrate, isononyl nitrate, dodecyl nitrate, 2-propylheptyl nitrate, 2-tetradecyl-1-octadecyl nitrate, a mixture of C9 to C13 branched alkyl nitrates, and mixtures thereof.

5. The fuel of claim 4, wherein the alkyl nitrate is 2-ethylhexyl nitrate.

6. The fuel of claim 1, wherein the alcohol is methanol or ethanol.

7. The fuel of claim 6, wherein the alcohol is methanol.

8. A method of obtaining a fuel according to claim 1, which consists of mixing, in a liquid state, an alkyl nitrate with a water/alcohol mixture.

9. The method of claim 8, wherein the water/alcohol mixture and the alkyl nitrate are mixed in an engine tank.

10. The method of claim 8, wherein the water/alcohol mixture and the alkyl nitrate are mixed in an injector.

11. The method of claim 8, wherein the water/alcohol mixture and the alkyl nitrate are mixed in a premix chamber of an engine.

12. A method for improving the ignition, in a combustion engine, of a fuel initially consisting of a liquid water/alcohol mixture, in which water makes up from about 1% to about 15% by weight of the mixture, the method consisting of adding to the said mixture an alkyl nitrate, in an amount such as to provide a final fuel composition consisting of: (a) from about 95.0% to about 99.9% by weight of a liquid water/alcohol mixture, in which water makes up from about 1% to about 15% by weight of the mixture, and (b) from about 0.1% to about 5.0% by weight of an alkyl nitrate.

13. The method of claim 12, wherein the alkyl nitrate is selected from the group consisting of a nitrate of a linear alkyl having from 4 to 36 carbon atoms, a nitrate of a branched alkyl having from 4 to 36 carbon atoms, a nitrate of a cyclic alkyl having from 5 to 18 carbon atoms, and mixtures thereof.

14. The method of claim 12, wherein the alkyl nitrate is selected from the group consisting of hexyl nitrate, cyclohexyl nitrate, 2-ethylhexyl nitrate, 2-octyl nitrate, n-nonyl nitrate, isononyl nitrate, dodecyl nitrate, 2-propylheptyl nitrate, 2-tetradecyl-1-octadecyl nitrate, a mixture of C9 to C13 branched alkyl nitrates, and mixtures thereof.

15. The method of claim 14, wherein the alkyl nitrate is 2-ethylhexyl nitrate.

16. The method of claim 12, wherein the alcohol is methanol or ethanol.

17. The method of claim 16, wherein the alcohol is methanol.

18. The method of claim 12, wherein the water/alcohol mixture and the alkyl nitrate are mixed in a tank of the engine.

19. The method of claim 12, wherein the water/alcohol mixture and the alkyl nitrate are mixed in an injector.

20. The method of claim 12, wherein the water/alcohol mixture and the alkyl nitrate are mixed in a premix chamber of the engine.

21. An engine containing the fuel of claim 1.

22. A vehicle or vessel comprising the engine of claim 21.

23. A fuel for a combustion engine, consisting of: (a) from about 95.0% to about 99.9% by weight of a liquid water/alcohol mixture, in which water makes up from about 1% to about 15% by weight of the mixture, (b) from about 0.01% to about 5.0% by weight of an alkyl nitrate, and (c) any remaining balance to 100% by weight of at least one additive selected from the group consisting of additives with preservative functions and additives with detergent functions.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows the effect of EHN on the ignition delay of a water/methanol mixture, water making up 5 wt % of the mixture, with a single main injection (circular dots on figure) or a micro-injection followed by a main injection (square dots on figure) into the engine cylinder.

(2) FIG. 2 shows the effect of EHN on the ignition delay of a water/methanol mixture, water making up 10 wt % of the mixture, with a single main injection (circular dots on figure) or a micro-injection followed by a main injection (square dots on figure) into the engine cylinder.

(3) FIGS. 3 to 6 show the ignition delay of fuels containing methanol alone or in admixture with EHN over a range of injection temperatures.

(4) FIGS. 7 and 8 show the ignition delays of methanol-based fuels at different injection temperature as a function of the amount of EHN present in the fuels.

DESCRIPTION OF THE INVENTION

(5) As defined herein, alcohol is understood to mean an alcohol having from 1 to 4 carbon atoms. In some embodiments, the alcohol is methanol or ethanol, advantageously methanol.

(6) In one aspect, the present disclosure relates to a fuel for combustion engines which comprises about 98.0% to about 99.9% by weight of methanol and about 0.01% to about 2.0% by weight of an alkyl nitrate. In some embodiments, the fuel comprises about 0.05% to about 1.5% by weight of alkyl nitrate. In some embodiments, the fuel comprises about 0.1% to about 1.0% by weight of alkyl nitrate. In some embodiments, the fuel comprises about 0.1% to less than 1.0% (<0.1%) by weight of alkyl nitrate.

(7) In another aspect, the present disclosure relates to a fuel for combustion engines, of the compression-ignition or spark-ignition type, which comprises from about 98.0% to about 99.9% by weight of a water/alcohol mixture, wherein water makes up from about 1.0% by weight to about 15.0% by weight of the mixture, and from about 0.01% to about 5.0% by weight of an alkyl nitrate. In some embodiments, the fuel comprises about 1.0% to about 3.0% by weight of alkyl nitrate.

(8) In some embodiments, the fuel of the invention consists of the water/alcohol mixture and the alkyl nitrate (in which case the amount of alkyl nitrate in the fuel is of at least 0.1% by weight).

(9) In some embodiments, when the sum of the amount of the water/alcohol mixture and the amount of alkyl nitrate is not equal to 100% by weight, the fuel may contain one or more other additives to make the fuel 100% complete, such as additives with preservative, anti-corrosion or detergent functions.

(10) The alkyl nitrate, which is added to the water/alcohol mixture, is more particularly selected from linear alkyl nitrates having 4 to 36, advantageously 4 to 24 carbon atoms, branched alkyl nitrates having 4 to 36, advantageously 4 to 24 carbon atoms, cyclic alkyl nitrates (or cycloalkyl nitrate) having 5 to 18 carbon atoms, and mixtures thereof. In some embodiments, the alkyl nitrate is selected from hexyl nitrate, cyclohexyl nitrate, 2-ethylhexyl nitrate, 2-octyl nitrate, n-nonyl nitrate, isononyl nitrate, dodecyl nitrate, 2-propylheptyl nitrate, 2-tetradecyl-1-octadecyl nitrate, a mixture of C.sub.9 to C.sub.13 branched alkyl nitrates, and mixtures thereof. In some embodiments, the alkyl nitrate is 2-ethylhexyl nitrate alone or in admixture with one or more other alkyl nitrates as defined above, advantageously the alkyl nitrate is 2-ethylhexyl nitrate.

(11) Mixtures of C.sub.9 to C.sub.13 branched alkyl nitrates can be synthesized from the corresponding mixtures of branched C.sub.9 to C.sub.13 alcohols, for example from the alcohols available under the tradename Exxal from Exxon. As an example, a mixture of at least two branched alcohols selected from a C.sub.9 branched alcohol, a C.sub.10 branched alcohol, a C.sub.11 branched alcohol, a C.sub.12 branched alcohol and a C.sub.13 branched alcohol can be prepared and then the corresponding mixture of alkyl nitrates can be synthesized.

(12) According to some embodiments, the alkyl nitrate is mixed in the liquid state with +the water/alcohol mixture in the tank supplying the engine, to obtain the liquid fuel according to the invention.

(13) According to some embodiments, the alkyl nitrate on the one hand and methanol or the water/alcohol mixture on the other hand, are stored separately, and brought together in the liquid state in an injector, thereby forming the liquid fuel according to the invention before it is fed into the combustion chamber of the engine.

(14) According to some embodiments, the alkyl nitrate is stored separately from methanol or the water/alcohol mixture and is co-injected with methanol or the water/alcohol mixture to form the liquid fuel according to the invention in a premix chamber of the engine.

(15) The present disclosure also relates to the use of an alkyl nitrate (as defined above), in the amounts defined above, as an ignition improver for a fuel based on (or consisting of) methanol or a water/alcohol mixture.

(16) The present disclosure also relates to a method for improving the ignition of a fuel based on (or consisting of) methanol or a water/alcohol mixture in an engine, such as a combustion engine, the method comprising adding an alkyl nitrate (as defined above) to methanol or the water/alcohol mixture, in the amounts defined above. In some embodiments, the alkyl nitrate and methanol or the water/alcohol mixture are mixed in an injector. In some embodiments, the alkyl nitrate and methanol or the water/alcohol mixture are mixed in a premix chamber of the engine.

(17) The present disclosure also relates to an engine, such as a combustion engine, of a motorized vehicle (such as a car, truck, tractor, etc.), or motorized vessel (such as a tanker, container ship, etc.) containing a fuel as defined above. The present disclosure also relates to a motorized vehicle or vessel comprising an engine as defined above.

(18) The present disclosure is illustrated by the following examples given for information purposes.

EXAMPLES

(19) The performance of the fuel according to the invention compared with a fuel composed solely of methanol and water was measured using an experimental laboratory compression ignition, single-cylinder, 0.499 L direct injection engine, targeting a mean indicated pressure (MIP) of 3 Bars at 1500 rpm. After passing 100 cycles (necessary for future calculations to obtain a consistent average of values), the values of the engine's operating parameters were measured. At the same time, it was possible to record 20 pollutant measurement cycles, each 5 seconds apart, to obtain a representative average of emissions from different cycles. From the values recovered above, the following parameters characterizing fuel combustion and engine operation were extracted: dAI auto-ignition delay (ms), Mean Indicated Pressure (MIP) MIP Covariance (COVMIP), CA1 angle, CA50 angle, combustion time, pollutants (NOx, CO, H.sub.2O, HC), heat release rate.

(20) The addition of the alkyl nitrate to the water/methanol mixture improved the overall combustion and engine operating parameters, compared with a fuel consisting solely of a water/methanol mixture. The performance of the fuel of the invention could be further improved by controlling fuel injection with multiple injections at each engine cycle, for example with one or more so-called pilot micro-injections followed by a main injection.

(21) The ignition delay as a function of the fuel intake temperature is the value resulting from the tests, which is presented below to illustrate the advantages of the invention.

(22) The ignition delay dAI is defined according to the following formula in which Pc is the pressure applied to the injected fuel:

(23) $\mathrm{dAI}=t\left(\frac{\mathrm{dP}}{{\mathrm{dt}}_{\max }}\right)-t\left(P_c\right)$

Example 1

(24) This example concerns the improvement, by addition of EHN, of the combustion performance in an engine of a mixture consisting of 95% by weight of methanol and 5% by weight of water.

(25) The ignition delays were determined as a function of the intake temperature (from 313K to 473K40 C. to 200 C.), at a pressure Pc of 300 bar, of a fuel according to the invention consisting of 99.0% by weight of a water/methanol mixture, water making up 5.0% by weight of the mixture, and 1.0% by weight of EHN and for a richness of the mixture with air of 0.25. The results are shown in FIG. 1 with the ignition delay benchmarks of the water/methanol (5 wt %/95 wt %) mixture alone. It can be seen from FIG. 1 that there is a significant reduction in fuel ignition delays when the fuel contains EHN, compared to the fuel without EHN. This reduction in ignition delay is all the more important that the temperature is low.

(26) For operation with a single main injection, at an admission temperature of 403 K, the ignition delay of the fuel of the invention according to the present example was approximately 3 times less than that of the reference fuel comprising only a water/methanol mixture. The fuel of the invention ignited even at low intake temperatures below 403K, down to 373K with an ignition delay of 2 ms, for which the water/methanol mixture did not ignite.

(27) Under multiple injection conditions involving a micro-injection (lasting 400 s at a crankshaft angle of 25) followed by a main injection (lasting 1,500 s at a crankshaft angle of 15), an improvement was observed in the combustion characteristics of the methanol/water mixture, which ignited at 373 K with an ignition delay of about 1.75 ms. Combustion of the water/methanol mixture under these conditions and at this temperature was close to that of the water/methanol mixture containing 1.0 wt % of EHN, but operated with a single main injection. Below 373 K, the water/methanol mixture did not ignite. In contrast, the water/methanol mixture containing 1.0 wt % of EHN did ignite at temperatures as low as 313 K, with an ignition delay of about 1.2 ms.

Example 2

(28) This example relates to the performance improvement, by addition of EHN, of the in-engine combustion of a mixture consisting of 90% by weight of methanol and 10% by weight of water.

(29) Ignition delays were determined as a function of the intake temperature (from 313K to 463K), at a pressure Pc of 300 bar, for a fuel according to the invention consisting of 98% by weight of a water/methanol mixture, with water making up 10% by weight of the mixture, and 2% by weight EHN and for a richness of the mixture with air of 0.25. The results are shown in FIG. 2 with the ignition delay reference points for the water/methanol mixture alone. For an addition of 1% by weight of EHN, an improved fuel combustion performance was observed for intake temperatures below 433K. For an intake temperature of 413K, the fuel containing 1% by weight of EHN had an ignition delay approximately 1.5 times lower than that of the water/methanol reference fuel. At an intake temperature of 413K with 2% by weight of EHN, the ignition delay was twice lower than that of the water/methanol mixture. At an intake temperature of 403K, the water/methanol mixture did not ignite, whereas fuels containing 1% by weight of EHN and 2% by weight of EHN ignited with a delay of about 4 ms and 2.2 ms, respectively.

(30) Under multiple injection conditions, with a micro-injection (lasting 400 s at a crankshaft angle of 25) followed by a main injection (lasting 1500 s at a crankshaft angle of 15), an improvement in the combustion characteristics of the water/methanol mixture was observed, which mixture ignited at 393K with an ignition delay of around 3.5 ms. Below 393K, the water/methanol mixture did not ignite. In contrast, fuel containing 1% by weight of EHN ignited at temperatures as low as 383K with an ignition delay of around 1.5 ms. Fuel containing 2% by weight of EHN ignited up to 333K with an ignition delay of about 1.75 ms.

(31) The results of Examples 1 and 2 are summarized in Table 1.

(32) TABLE-US-00001 TABLE 1 Micro- injection Minimum Water/ followed ignition Ignition MeOH EHN Single by main temperature delay (wt %) (wt %) injection injection (K/ C.) (ms) 5%/95% 0 X 403 (130) 4 1% X 373 (100) 2 0 X 373 (100) 1.75 1% X 313 (40) 1.25 10%/90% 0 X 413 (140) 3.5 1% X 403 (130) 4 2% X 403 (130) 2.2 0 X 393 (120) 3.5 1% X 383 (110) 1.5 2% X 333 (60) 1.75

(33) These examples show that the use of alkyl nitrate in a low weight percentage can significantly improve the ignition delay of a water/alcohol-based fuel. More generally, the addition of an alkyl nitrate-type compound to a water/alcohol mixture improves overall fuel performance in a combustion engine, while maintaining limited emissions of nitrogen oxides, up to intake temperatures close to ambient temperature. There was no reason to believe that additives known to increase the cetane number of a diesel or biodiesel hydrocarbon could be used so effectively, in very small quantities, to improve the ignition of a water/alcohol mixture.

(34) In the following examples, the ignition delay improvement of methanol was measured under test conditions equivalent to those described in the scientific paper Ignition delay times of NH.sub.3/DME blends at high pressure and low DME fraction: RCM experiments and simulations (Combustion and Flame Volume 227, May 2021, Pages 120-134). The test laboratory engine is a fast compression machine equivalent to the one described in this scientific paper. This is a fast compression machine for measuring the auto-ignition time of a mixture. This machine allows compressing in a very short time the mixture in order to obtain preset pressure and temperature conditions. The liquids are admitted into the tank through a different orifice than the gas inlet. The liquid quantities are measured with a syringe and a precision balance.

Example 3

(35) The ignition delays were determined as a function of the injection temperature (between 800K and 1000K), at a pressure Pc of 30 bar, of a fuel according to the invention consisting of 99.8% by mass of methanol and 0.2% by mass of EHN and for a richness of 0.5, 1 and 1.5 of mixture with air respectively. The results are shown in FIGS. 3, 4, and 5 with the ignition delay benchmarks of methanol alone. There is a significant reduction, approximately by a factor of 5 to 10, in fuel ignition delay when the fuel contains EHN, compared to methanol alone. This reduction in ignition delay compared to methanol alone is all the more important that the temperature is low.

Example 4

(36) The ignition delays of different fuels containing either methanol alone or a mixture of methanol and EHN at 0.2%, 0.5% or 1% by weight, at different injection temperatures (temperature range 790K to 1000K), at a pressure Pc of 30 bar and a mixture richness of 1 with air, were determined. As can be seen in FIGS. 6 to 8, the addition of EHN to a methanol fuel results in a significant decrease in ignition delay compared to methanol alone.

(37) These examples show that the use of alkyl nitrate(s) in a very low weight percentage can significantly improve the ignition delay of a methanol-based fuel. There was no reason to believe that additives known to increase the cetane number of a diesel or biodiesel hydrocarbon could be used so effectively, in very small quantities, to improve the ignition of an alcohol like methanol.

(38) Although the presently disclosed subject matter and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the presently disclosed subject matter, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized according to the presently disclosed subject matter. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

(39) In addition to the various embodiments depicted and claimed, the disclosed subject matter is also directed to other embodiments having any other possible combination of the features disclosed and claimed herein. As such, the particular features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter includes any suitable combination of the features disclosed herein. Thus, the foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.

(40) It will be apparent to those skilled in the art that various modifications and variations can be made in the composition, device, and method of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.

(41) For any patents, patent applications, publications, product descriptions, and protocols are cited throughout this application, the disclosures of all of which are incorporated herein by reference in their entireties for all purposes.