OIL-REPLACEMENT ADDITIVE FOR REDUCING EMISSIONS FROM TWO-STROKE ENGINES

Abstract

An oil-replacement additive for two-stroke engine fuel capable of reducing fuel consumption, enhancing combustion and reducing emissions comprises boron and a carrier, wherein the boron concentration in said additive is in the interval of 100 to 600 ppm, the carrier comprises an alcohol, the amount of oil in the additive is less than 10% (w/w), and the balance is a fuel. Most preferably said additive is substantially oil-free. A two-stroke fuel comprising said additive, and a significantly reduced amount of oil, or substantially no oil, said fuel having a boron concentration in the interval of about 1 to 12 ppm.

Claims

1. An oil-replacement additive for two-stroke engine fuel, said additive comprising boron and a carrier, wherein the boron concentration in said additive is in the interval of 1 to 600 ppm, the carrier comprises an alcohol, the amount of oil in the additive is less than 10% (w/w), and the balance is a fuel.

2. The additive according to claim 1, wherein the amount of oil in the additive is less than 8% (w/w).

3. The additive according to claim 1, wherein the amount of oil in the additive is less than 1% (w/w).

4. The additive according to claim 1, wherein said alcohol is chosen from methanol, ethanol, propanol, and butanol, and said balance of fuel is a fuel having a flash point similar to that of the two-stroke fuel to which the additive is intended to be added.

5. The additive according to claim 1, wherein the concentration of boron is in the interval of 10 to 600 ppm.

6. The additive according to claim 1, wherein the concentration of boron is in the interval of 100 to 300 ppm.

7. The additive according to claim 1, wherein the boron is added in the form of a stable boron solution prepared by dissolving a boron compound in an alcohol, followed by vigorous mixing and exclusion of particles larger than 100 nm.

8. A two-stroke engine fuel comprising an additive according to claim 1, wherein the boron concentration in the fuel is in the interval of 1 to 12 ppm.

9. The two-stroke engine fuel according to claim 8, wherein the boron concentration is in the interval of 1 to 6 ppm.

10. The two-stroke engine fuel according to claim 8, wherein the boron concentration is about 2 to 3 ppm.

11. The two-stroke engine fuel according to claim 8, wherein the fuel contains less than 1% oil (w/w).

12. A method for reducing the emissions from a two-stroke engine, wherein an additive comprising boron dissolved in an alcohol, less than 10% oil (w/w), the balance being a fuel and the concentration of boron in said additive is the interval of 1 to 600 ppm, is added to the fuel.

13. The method according to claim 12, wherein said additive is mixed into the fuel at a proportion of about 1 part additive to 100 parts fuel.

14. The method according to claim 12, wherein said additive is injected into the cylinder together with fuel at a proportion or about 1 parts additive to 50 parts fuel.

15. The method according to claim 12, wherein the additive is added in an amount resulting in reduced emissions of total hydrocarbons, CO and CO.sub.2 with maintained lubrication of the engine.

16. The additive according to claim 1, wherein the amount of oil in the additive is less than 6%(w/w).

17. The additive according to claim 1, wherein the amount of oil in the additive is less than 2%(w/w).

18. The additive according to claim 1, wherein the additive is substantially oil-free.

19. The additive according to claim 1, wherein the concentration of boron is in the interval of 100 to 600 ppm.

20. The method of claim 12, wherein said additive is the interval of 100 to 600 ppm.

Description

EXAMPLES

Example 1

A Comparative Example

[0055] The present inventors commissioned a study to be performed at an accredited research institute (SMP, Svensk Maskinprovning AB, part of RISE). The performance of a modern, commercially available chain saw was studied in a test bench, investigating the possibility to reduce or eliminate the addition of oil to the two-stroke fuel.

Materials

[0056] Engine oil: Commercial engine oil for two-stroke engines was used (Stihl standard oil Low smoke 2 Stroke oil).

[0057] Oil replacement additive: An oil replacement additive was prepared by mixing a stable ethanol solution of boric acid, prepared according to the methods of WO 2010/134872 with an amount of the above engine oil. In the final additive, the amount of oil was 30% and the balance a mixture of kerosene and ethanol.

[0058] Fuel: Standard, commercial two-stroke fuel (unleaded 95 octane gasoline) was used. Standard oil was added to the fuel according to the engine manufacturer's instructions, i.e. 2 parts oil to 98 parts fuel (volume). In this test, the oil replacement additive was however added in a smaller amount, 1 part additive to 99 parts fuel (volume).

[0059] Two-stroke engine: A modern, commercially available chain saw (Stihl, Model MS181) was used. This chain saw has a 31.8 cc engine with a nominal effect of 1.5 kW.

Methods

[0060] The method used for differentiate the two-stroke mixtures, a standard oil and an additive according to embodiments of the present disclosure, was the G3 Standard Cycle (according to ISO standard 8178-4:2007), performed using a chain saw as defined above. The ISO 8178 is an international standard for exhaust emission measurement from a number of non-road engine applications. It is used for emission certification and/or type approval testing in many countries, including the United States, European Union and Japan. Depending on the legislation, the cycle can be defined by reference to the ISO 8178 standard, or else by specifying a test cycle equivalent to ISO 8178 in the national legislation (as it is the case with the US EPA regulations).

[0061] The ISO 8178 includes a collection of steady-state engine dynamometer test cycles (designated as type C1, C2, D1, etc.) designed for different classes of engines and equipment. Each of these cycles represents a sequence of several steady-state modes with different weighting factors.

[0062] The emissions, i.e. selected pollutants in the exhaust, were measured according to the methods disclosed in ISO 8178 and EC Directive 97/68.

[0063] Tests using the standard oil were designated A and A2, and tests using a boric acid containing additive according to the invention were designated B and B4. The test procedure was as follows: [0064] 1. A shorter warm-up run (15 min) using (A) with 2% injection, followed by [0065] 2. The actual test run with a load of 100% and 0% respectively, and simultaneous collection of data (fuel consumption, temperature, emission). [0066] 3. A shorter warm-up run (15 min) using (B) with 1% injection, followed by [0067] 4. The actual test run with a load of 100% and 0% respectively, and simultaneous collection of data (fuel consumption, temperature, emission). [0068] 5. A shorter warm-up run (15 min) using (A2) with 2% injection, followed by [0069] 6. The actual test run with a load of 100% and 0% respectively, and simultaneous collection of data (fuel consumption, temperature, emission). [0070] 7. A shorter warm-up run (15 min) using (B4) with 1% injection, followed by [0071] 8. The actual test run with a load of 100% and 0% respectively, and simultaneous collection of data (fuel consumption, temperature, emission).

[0072] It should be noted that this chain saw (Stihl MS181) has an automatic carburetor (IntelliCarb Compensating Carburetor) designed to automatically adjust the air/fuel ratio when the air filter becomes restricted or partially clogged and it thus maintains the engine's correct RPM. Therefore there was no tuning of the carburetor between test runs. It is contemplated that by tuning the carburetor, the reduction in fuel consumption and emissions would have become even more pronounced.

[0073] The fuel consumption and the specific fuel consumption are shown in Table 1 below. It is evident that replacing the standard two-stroke oil with a boric acid containing additive according to an embodiment significantly reduces fuel consumption and enhances combustion. Enhanced combustion is here evidenced as increased cylinder head temperatures.

TABLE-US-00001 TABLE 1 Fuel consumption and combustion efficiency A. HP Super A2. Syntetic B. Standard B4. C. Standard Additive oil Additive Additive oil 2% 1%. 2% 1% No oil Engine 1.2 1.3 1.4 1.2 1.3 performance [kW] [2%] RPM 10000 9981 10018 9981 10004 Specific fuel 536 480 444 501 452 consumption [g/kWh] [3%] Change: 10% 17% 7% 16% Fuel 625 613 594 584 577 consumption at rated speed [g/h] [2%] Change: 2% 5% 7% 8% Cylinder 260 265 270 268 283 head temperature [ C.] [2%]

[0074] In tests A and A2, a high performance super synthetic standard oil was added to the fuel to a concentration of 2%. In B and B4, the inventive additive was used together with 1% oil in the fuel, and in C, the additive was used without any addition of oil.

[0075] As there was no cleaning of the engine between the test runs B and A2, a remaining effect of the boric acid can be seen. Further tests investigating this phenomenon will be performed.

[0076] Without wishing to be bound by any theory, the inventors contemplate that there is a lasting effect of the boric acid, due to interactions between the boric acid and inner surfaces of the engine. Earlier research shows the existence of a thin film, confirmed by scanning electron microscope (SEM) investigations.

[0077] The results show that the boron containing additive significantly reduced both the specific fuel consumption and the fuel consumption at rated speed. The increase in cylinder head temperature indicates a more effective combustion. The reduction in fuel consumption and the increased temperature was most significant in test C, where the inventive additive was used alone, without any addition of oil.

[0078] In five test runs, the exhaust gases were collected and analyzed. The average values are presented in Table 2.

TABLE-US-00002 TABLE 2 Specific emissions (g/kWh) Specific emission (g/kWh) A2. A. B. Standard B4. C. Standard oil Additive oil Additive Additive 2% 1% 2% 1% No oil THC + Nox 47.9 41.63 42.11 44.43 39.83 13% 12% 7% 17% THC [8%] 45.4 38.56 37.46 40.44 36.96 15.07% 17.49% 10.93% 18.59% CO [8%] 264.32 203.66 152.41 194.36 212.37 23% 42% 26% 20% CO2 [8%] 1156 1095 1060 1170 996 5% 8% 1% 14% NOx [8%] 2.5 3.07 4.65 3.99 2.87 23% 86% 60% 15%

[0079] Tests A and A2, B and B4, and C represent the same conditions as above. The results show a significant reduction in exhaust emissions, seen for total hydrocarbons (THC), CO and CO.sub.2 as evident from Table 2. The increase in NOx is however an expected result from the enhanced combustion and increased temperature. This can possibly be addressed by fine-tuning the carburetor.

[0080] Further tests are necessary to obtain repeatable results, but the results so far already show that an unexpected and highly desirable reduction of the amount of oil that is added to two-stroke engine fuel can be achieved through the use of a boric acid containing additive.

Example 2

Boron Additive Reduces Wear Scar Formation

[0081] Friction reduction and wear scar formation was investigated for different two-stroke fuel mixtures, using a high-frequency reciprocating rig according to ISO standard 12156. The boron concentration was determined for each sample, Finally, a coefficient of friction (CoF) was determined for each sample. See Table 3.

TABLE-US-00003 TABLE 3 Wear scar and CoF Test 1 Elemental analysis (oil) Test 2 Boron conc. HFRR Wear Information mg/kg Scar Sample (FF5.5 w %, red ASTM EN ISO Sample ID Naphta 50%) D51185 mod 12156 CoF 1 003-39 2T Inj (B mg/kg 210 225 0.100 212) 2 003-40 2T Inj (B mg/kg 390 182 0.104 415) 3 003-41 2T Inj (B mg/kg 130 201 0.104 128)

[0082] As can be seen in Table 3, the calculated boron concentration was confirmed by the elemental analysis. All concentrations were in the interval of 100 to 600 ppm (128 (130) ppm; 212 (210) ppm; and 415 (390) ppm). Further, the determination of wear scar and coefficient of friction confirmed the usefulness of the additive.

Example 3

On-Going Multi-Variable Studies

[0083] The present inventors have commissioned a further study, based on the ISO-standard, but with the following modifications: [0084] the test engine will be operated for a longer duration when changing from an additive according to embodiments of the invention to a standard oil, in order to see how long the effect of the boric acid can be seen, or [0085] the test engine will be cleaned between test runs, in order to avoid carry over of previous test conditions [0086] different concentrations of boric acid will be tested, for example 200 mg/kg boron resulting in 2 and 4 mg/kg boron in the fuel depending on whether the boron containing oil-replacement additive is injected into the engine, or pre-mixed into the fuel [0087] different concentrations of oil in the additive will be tested, ranging from 0% to 30% per weight.

[0088] In another set-up, also commissioned by the present inventors, different compositions will be tested. The boron concentration in the additive will be in the interval of 1 to 100 ppm, resulting in a concentration of 0.01 to 1 in the fuel.

[0089] Similarly, the amount of oil will be in the interval of 0 to 30% of the additive, resulting in a concentration of 0 to 0.3 or 0.6% oil in the fuel after final mixing or injection. Compared to standard two-stroke oils and two-stroke fuels, this represents a significant reduction all the way to a total removal of the oil component.

[0090] Preliminary results indicate that already a very low boron concentration makes it possible to reduce the amount of oil. A boron concentration in the interval of 0.01 to 1 ppm in combination with a minimal addition of oil significantly reduces the emissions and improves fuel combustion and as a consequence, reduces fuel consumption.

[0091] Using a higher concentration of boric acid, but one which still is very low compared to previously disclosed concentrations, for example a concentration in the interval of 0.1 to 1 ppm, no oil needs to be added to the two-stroke fuel.

[0092] Without further elaboration, it is believed that a person skilled in the art can, using the present description, including the examples, utilize the present invention to its fullest extent. Also, although the invention has been described herein with regard to its preferred embodiments, which constitute the best mode presently known to the inventors, it should be understood that various changes and modifications as would be obvious to one having the ordinary skill in this art may be made without departing from the scope of the invention which is set forth in the claims appended hereto.

[0093] Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.