NO330230B1 - Use of diesel fuel additives and method for operating a diesel engine. - Google Patents

Abstract

The invention provides the use, as an additive in a diesel fuel comprising a major proportion of a diesel oil, of an effective concentration of a polyether derivative of the general formula (I): R<1>-O-(R<3>-O)x-R<2>, wherein each of R<1> and R<2> independently represents a hydrogen atom, a C1-30 alkyl or alkenyl group optionally substituted by one or more amino or hydroxy groups, or a C2-7 alkanoyl group, x has an average value in the range 2 to 200, and each moiety R<3> is independently selected from C2-4 alkylene moieties, for reducing white smoke emissions under cold-running engine conditions, and a method of operating a diesel engine under cold-running conditions with reduced white smoke emissions.

Description

The present invention relates to additives for diesel fuel, more specifically the use of certain polyether derivatives in diesel fuel to provide improved properties, and a method for operating a diesel engine.

In Mech E Papers presented in London, UK, 6-7 April 1993, in the publication on pages 35 to 43, by Dr. R.E. Winsor, "Effect of fuel modifications on Detroit diesel engine exhaust emissions", describes experiments with diesel fuels including such fuel with oxygen enrichment. On page 38 of the description it is stated: "As part of the work with Allied Petro, the LE2000 fuel was added 0.5 % diglyme, and this fuel (LE2500) was tested on the 6V-92TA wagon engine along with other fuels." The addition of the diglyme was found to result in a reduced particle content of about 6% compared to the original value for LE2000. Overall, for this two-stroke wagon engine, the reformulated fuel with diglyme (LE2500) provided a significant 17% reduction in particulate matter, but no NOx improvement, compared to base #1 diesel fuel.

This interesting result with diglyme led the inventors to conduct emission tests in a Type 60 engine with 5.0% diglyme added to low sulfur (0.2%) DF-2 fuel. The base fuel met EPA specifications for 1991 certification, but detailed analysis is not available. The emissions tests consisted of two hot transient cycles with each fuel. Particulate emissions dropped from 0.169 to 0.135 g/bhp-h, a 20% reduction, while NOx showed no change. In this experiment, hydrocarbon emissions were unchanged and carbon monoxide emissions showed a significant reduction of 13%.

In a later experiment, a Type 60 engine was tested with 3.5 wt% dimethyl carbonate (DMC) added to low sulfur (0.1%) DF-2 fuel. Although this engine configuration produced relatively low particulate emissions with the base fuel, the addition of the oxygenate produced a 15% reduction in particulates and a 13% reduction in carbon monoxide.

The above engine tests were carried out under normal (hot) operating conditions.

In Canadian patent publication CA 1 273 201, and corresponding DE-A-3631225, a diesel fuel oil additive comprising

(A) an oxyalkylene derivative of an amine of the general formula:

where R<1>is an aliphatic hydrocarbon group having from 6 to 24 carbon atoms, A<1>is an alkylene group having from 2 to 4 carbon atoms, 1 and m are integers of 1 or greater, with 1 + m totaling from 2 to 10; and (B) a polyoxyalkylene glycol monoether of the general formula:

where R is a hydrocarbon group with 3-18 carbon atoms, A is an alkylene group with 3 or 4 carbon atoms and n is an integer in the range 2-60. The use and purpose described for this additive is easy cleaning of "deposits produced in the injection nozzle when the engine is operated under normal conditions, thereby preventing the nozzle from plugging with the deposits" (page 4, lines 34-37), and "the effect of improved low temperature fluidity of the diesel fuel, of water drainage, and of cleaning diesel engines and fuel systems" (page 5, lines 1-4). GB 2260337 A describes an additive concentrate for haze reduction of middle distillate fuels comprising (i) at least one alkylated amine and (ii) at least one alkylated alcohol. Preferred alkylated alcohols for use as (ii) have the formula

where R4 is an alkyl or cycloalkyl group with 2-20 carbon atoms and each of R5 and Rg are the same or different and is an alkylene or cycloalkylene group with 2-20 carbon atoms. The sum of w and z is preferably in the range 2-20. US 4623362 describes distillate fuel for indirect injection compression ignition engines containing, in an amount sufficient to minimize coke formation, in particular control nozzle coking in the pre-chambers or mixing chambers in indirect injection compression ignition engines operated with such fuel, at least the combination of (i) organic nitrate ignition accelerator and (ii) an alkoxyalkanol which when added to the fuel in combination with the organic nitrate ignition accelerator minimizes coke formation. The alkoxyalkanol is preferably according to the formula

where R' is an alkyl group with 1-12 carbon atoms, R" is a divalent aliphatic hydrocarbon group with 2-4 carbon atoms, and n is an integer from 1-4. 1 US 4,549,884 describes a liquid middle distillate fuel comprising (i) a major proportion of a liquid middle distillate hydrocarbon fuel; and (ii) an additive which provides a reduction in the proportion of visible smoke, with the formula

where

R<1> is an alkyl, aralkyl, alkaryl, cycloalkyl, alkenyl, or alkynyl hydrocarbon group; and

R<2> is hydrogen or an alkyl, aralkyl, alkaryl, cycloalkyl, alkenyl or alkynyl hydrocarbon group.

As control examples, with more visible smoke compared to ethoxylated phenol according to the above formula, nonyltetraethoxyphenol, nonyleicosa ethoxyphenol and ethyl MPA-D type of polyethoxylated alkylphenol are described. The visible smoke described in the patent document is what is often referred to as "black smoke" which occurs in engines that are operated under load at normal (warm) operating temperatures.

The present invention relates to a phenomenon which is completely different from all phenomena described in the above-mentioned prior art. This phenomenon is the problem with the emission of white smoke from diesel engines under operating conditions with the engine running cold. White smoke is usually observed from diesel engines that are started cold and before the engine has reached a fully warmed up condition.

The present invention relates to the use, as an additive in a diesel fuel comprising a major proportion of diesel oil, in an effective concentration in the range of 0.1 to 1% by weight based on the diesel fuel, of a polyether derivative with the general formula

where each R I and R 2 independently represent a hydrogen atom, a C 1.30 alkyl or alkenyl group optionally substituted with one or more amino or hydroxy groups, or a C 2.7 alkanoyl group, where x has a mean value in the range 2 - 200, and each portion R<3> is independently selected from C2-4 alkylene groups, for reducing the emissions of white smoke under cold operating conditions of an engine when the start-up temperature of the engine is 0 °C or lower.

The invention also provides a method for operating a diesel engine under cold operating conditions where the start-up temperature of the engine is 0 °C or lower, with reduced emissions of white smoke. The method is characterized in that it comprises running the engine on a diesel fuel containing a major proportion of diesel oil and an effective concentration in the range of 0.1-1% by weight, based on the diesel fuel, of a polyether derivative according to formula I as defined above.

Polyether according to formula I is present in the diesel fuel in a concentration in the range of 0.1-1% by weight, preferably 0.2-1% by weight, based on the diesel fuel. Concentrations in the range of 0.3-0.5% by weight (3000 to 5000 ppm) have been found to give very satisfactory results.

In this specification, an alkyl, alkenyl or alkylene group can be straight chain or branched, and an alkenyl group can be polyunsaturated, although it is preferably monounsaturated.

The polyether derivatives according to formula I are mainly known compounds, and they can be prepared by known methods or methods analogous to known methods, as will be readily realized by the person skilled in the art.

Preferred polyether derivatives have one or more of the following parameters:

(i) each of R<1>and R2 independently represents a hydrogen atom, a C1-20 alkyl group optionally substituted with an amino group, or a C2_

4-alkanoyl group,

(ii) x has a mean value in the range 2 to 150,

(iii) each of R<1> and R<2> independently represents a hydrogen atom or a C1-20 alkyl group optionally substituted with an amino group.

The diesel oil can be a hydrocarbon fuel (a middle distillate fuel oil), which can be a conventional fuel or preferably a low-sulphur fuel with a sulfur concentration below 500 ppm, preferably below 50 ppm, advantageously below 10 ppm (parts per million by weight of the diesel fuel). Diesel oils usually have an initial distillation temperature of approx. 160 °C and 90% point of 290-360 °C, depending on the fuel grade and application. Vegetable oils can also be used as diesel oils per se or in mixtures with hydrocarbon fuels.

Low sulfur fuels will usually require a lubricant additive to reduce fuel pump wear.

The polyether derivative according to formula I can be added directly to the fuel oil, or more appropriately as a compound in an additive concentrate.

Additive concentrates suitable for addition to diesel fuel will contain the polyether derivative according to formula 1 and a fuel-compatible diluent, which can be a non-polar solvent such as toluene, xylene, white spirit and those sold by member companies of the Royal Dutch/Shell group under the trademark "SHELLSOL" , and/or a polar solvent such as esters and especially alcohols, for example hexanol, 2-ethylhexanol, decanol, isotridecanol and alcohol mixtures such as those sold by member companies of the Royal Dutsch/Shell group under the trademark "LINEVOL", especially "LINEVOL" 79 alcohol which is a mixture of primary C7_9 alcohols, or C12-14 alcohol mixture commercially available from Sidobre Sinnova, France, under the trademark "SIPOL".

Additive concentrates and diesel fuel compositions produced therefrom may further contain additional additives such as low molecular weight amine or the hydrocarbyl substituent succinimide, e.g. a polyisobutenyl succinimide, detergents, smoke particulate removers, e.g. alkoxylated phenol formaldehyde polymers such as those commercially available as "NALCO" 7D07 (from Nalco), and "TOLAD" 2683 (from Petrolite); antifoam agents (eg, polyether-modified polysiloxanes commercially available as "TEGOPREN" 5851 from Th. Goldschmidt, Q 25907 (from Dow Corning) or "RHODORSIL" (from Rhone Poulenc)); ignition improvers (eg, 2-ethylhexyl nitrate, cyclohexyl nitrate, di-tertiary-butyl peroxide and those described in US 4,208,190, column 2, line 27 to column 3, line 21); anti-corrosion agents (e.g. those sold commercially by Rhein Chemie, Mannheim, Germany, as "RC 4801"), or polyhydric alcohol esters of a succinic acid derivative, wherein the succinic acid derivative has on at least one of its α-carbon atoms an unsubstituted or substituted aliphatic hydrocarbon group with 20-500 carbon atoms, e.g. pentaerythritol diesters of polyisobutylene-substituted succinic acid, deodorants, antiwear additives; antioxidants (eg phenols such as 2,6-di-tert-butylphenol, or phenylenediamines such as N,N'-di-sec-butyl-p-phenylenediamine), metal deactivators and lubricants (eg those which are commercially available as EC831, P631, P633 or P639 (from Paramins) or "HITEC 580 or X9429, X4848 or X4849 (from Ethyl Corporation), "Lubrizol" 539A (from Lubrizol), "VECTRON" 6010 (from Shell Additives), OLI9000 (from Associated Octel), or ADX4101B (from Adibis)).

Preferred low molecular weight amine detergents or cleaning agents are C10.20-alkylamines. Aliphatic primary monoamines, especially linear aliphatic primary monoamines, having 10-20 carbon atoms, are particularly preferred. The alkylamine preferably has 10-18, e.g. 12-18, more preferably 12-16, carbon atoms. Dodecylamine is particularly preferred.

Preferred hydrocarbyl-substituted succinimides, which include those described in EP-A-147240, are the reaction product of a polyisobutylene succinic acid or anhydride with tetraethylenepentamine, where the polyisobutylene substituent has a number-average molecular weight (Mn) in the range of 500 to 1200.

Unless otherwise mentioned, the concentration (active substance) of each additive in the diesel fuel, other than the polyether derivatives according to the general formula I, is preferably up to 1% by weight, more preferably in the range of 5 to 1000 ppm.

The concentration of active material of the haze reducer/smoke particulate remover in the diesel fuel is preferably in the range from 1-20, more preferably from 1-15, even more preferably from 1-10, and advantageously from 1-5 ppm. The concentrations of active material of other additives (with the exception of the ignition improver and the lubricant) are each preferably in the range from 0-20, more preferably from 0-10 and preferably from 0-5 ppm. The concentration of active material of the ignition improver in the diesel fuel is preferably in the range from 0-600 and more preferably from 0-500 ppm. If an ignition improver is included in the diesel fuel, this is suitably used in amounts from 300-500 ppm. If a lubricant is included in the diesel fuel, this is used appropriately in an amount from 100-500 ppm.

The diesel oil itself can be an oil containing additives or an oil without additives. If the diesel oil is an additive-containing oil, it will contain small amounts of one or more additives, for example one or more additives selected from antistatic agents, pipe flow resistance reducing agents, flow improvers (e.g. ethylene/vinyl acetate copolymers and acrylate/maleic anhydride copolymers) and antiwax agents (e.g. .eg those commercially available under the trademarks "PARAFLOW" (eg "PARAFLOW" 450; from Paramins), "OCTEL" (eg "OCTEL" W 5000; from Octel) and "DODIFLOW" (eg .eg "DOD1FLOW" V 3958; from Hoechst).

Use of the polyether derivatives according to formula I as described above can give rise to further advantages, such as cleanliness of fuel injection and reduced emissions of hydrocarbons, partially burnt hydrocarbons and particles when operating at normal (warm) operating temperatures, i.e. in addition to the advantages which achieved by cold operation of the engine.

The invention will be understood in more detail from the following illustrative examples, where temperatures are given in degrees Celsius (°C). In the examples, especially in Example 1, the various test materials are available from Aldrich, with the exception of those for which the CAS registration number is indicated, and the following polyether derivatives of general formula I:

Polveter A is a polyoxypropylene glycol hemiether (monoether) corresponding to

formula I where R<1> represents a C12-is alkyl group, R2 is hydrogen, each R<3> moiety is an isopropylene group (-CH2CH(CH3)-), and x has a mean value in the range of 17-23,

prepared using a mixture of Ci2-i5 alcohols as initiator, and with Mni in the range of 1200-1500 and a kinematic viscosity in the range of 72-82 mm<2>/s at 40 °C according to ASTM D 445, available under the trade designation "SAP 949" from the member companies of the Royal Dutch/Shell group; Acetate esters of Polyether A are produced by reaction of Polyether A with acetic acid at reflux temperature in the presence of toluene as solvent, together with acid-

catalyst, while water formed is removed by means of a Dean and Stark water trap; so that the acetate ester differs from Polyether A itself in that R is an acetyl group (-COCH3);

Polveter B is a polyoxypropylene glycol hemiether (monoether) corresponding to

formula I where R 1 , R 2 and R 3 are the same as for Polyether A, but x has a mean value in

range 3.5 to 5.5, prepared using a mixture of C12-15 alkanols as initiator, and with Mni range 435-505 and a kinematic viscosity in the range 16-21 mm/s at 40 °C according to ASTM D 445, available under the trade name "OXILUBE 500" ("OXILUBE" is a registered trademark) from members of the Royal Dutch/Shell group;

Polyether C is a polyoxypropylene glycol hemiether (monoether) corresponding to formula I where R<1>, R2 and R<3> are the same as for Polyether A, and x has a mean value of approx. 120, prepared using a mixture of C12-15 alkanols as initiator, with a hydroxyl value of 0.14 milliequivalents per grams according to ASTM D 4274-88 and Mn calculated therefrom (on the basis of one hydroxyl group per molecule) of 7150, and a kinematic viscosity in the range of 2300-2400 mm<2>/s at 40 °C according to ASTM D 445 ; and

Polveter D is a polyoxyethylene glycol hemiether (monoether) corresponding to formula I where R represents a C9.1 i-alkyl group, R is hydrogen, R is an ethylene (-CH2CH2-) group and x has an average value in the range 4.5-5, ( "DOBANOL" and "NEODOL" are registered trademarks) from member companies of the Royal Dutch/Shell group.

Example 1

The example describes tests with the above materials dissolved in automotive gas oil fuels (autodiesel) to investigate their effect in reducing the exhaust emissions of white smoke from cold starting diesel engines and before the engine reaches a fully warmed up condition.

When a diesel engine is started cold and allowed to idle, there is a tendency for incomplete combustion, leading to unwanted emissions of hydrocarbons and partially burnt hydrocarbons, with the visible symptom of white smoke during the first few minutes of engine operation. The situation is similar if the engine is allowed to run at low load and higher speed during the first few minutes after a cold start.

Common tests of the effects of fuels and additives on cold engine performance whereby a cold engine is started and allowed to run for a few minutes are considered to be rather inconsistent and with a low degree of repeatability. Test productivity is also very low as the engine or vehicle usually has to be cooled for several hours in a freezer between tests.

The test that follows was designed to reproduce in a stable and continuous manner the conditions that exist in a cold engine during the first few minutes of start-up.

The test used a Cussons/Ricardo Hydra Dl single-cylinder research engine with characteristics as listed in Table 1.

In order to achieve representative cold start conditions, the engine was operated in a test bench with a dynamometer at low engine stress and speed and with a continuously cooled coolant. The engine conditions are listed in Table 2.

During the tests, in-cylinder pressure was measured as a function of crank angle with a Kistler 6121 Al piezoelectric pressure transducer from Kistler Instrumente AG, Winterthur, Switzerland. Pressure, crank angle and dynamometer conditions were recorded and stored with an AVL 647 Indiskop high-speed analyzer with real-time data analysis, manufactured by AVL List GmbH, Graz, Austria. The AVL 647 analyzer calculated additional quantities including: IMEP (Indicated Mean Effective Pressure - a measure of the power developed in the engine cylinder); and the coefficient of variation of IMEP (COV). The COV of IMEP is a measure of the degree of irregular and poor combustion. A high value indicates very irregular combustion. During the tests, COV was calculated with the AVL 647 analyzer using in-cylinder pressure measurement equipment from a total of 500 combustion cycles.

White smoke opacity was measured with a Wager Model 650 Smoke Opacity Meter, manufactured by Robert H Wager Co., Inc., Passaic Avenue, Chatham, New Jersey, USA, located approx. 0.5 m from the outlet end of the exhaust pipe in the open air outside the test facility.

A problem with white smoke opacity measurements is that the absolute values are affected by variations in the atmospheric conditions, the conditions in the engine exhaust system and the cleanliness of the instrument's optical components, but the COV of the IMPE measurements are far more consistent both within a test and between different tests.

For these reasons, COV of IMEP measurements are advantageous over directly measured white smoke opacities to determine, for comparison, the ability of dissolved materials in the fuel to reduce white smoke emissions. To demonstrate the validity of this approach, preliminary tests were conducted to establish the relationship between measured COV by IMEP and white smoke, as follows.

Preliminary tests were done at the engine conditions in Table 2 with a coolant temperature of -6 °C. Three fuels were tested which had different cold performance in the engines. Fuel A had a natural cetane number of 41.5. Fuel B was a standard reference industrial fuel (RF73-T-90, from Halterman) with a natural cetane number equal to 50. Fuel C comprised fuel B with added 2-ethylhexyl nitrate at a concentration of 4.375 g/kg to increase the cetane number to 57.1. The fuel properties are listed in table 3.

The test results, COV of the IMEP measurements and white smoke opacities, are given in Table 4.

The results demonstrate that there is a clear connection between the COV of IMEP and the opacity of white smoke, and that a reduction in the COV of IMEP is also an indicator of a reduction in the opacity of white smoke.

Accordingly, the comparison tests that follow, to demonstrate the potential of candidate materials to reduce white smoke emissions, were based on the COV of IMEP measurements. The test procedure was as follows.

One material was tested per day by comparing the performance of material dissolved at a concentration of 4000 ppm (0.4% by weight) in a base fuel with the base fuel alone. The engine was started on a base fuel (fuel D in Table 3) with the injection timing gradually increasing. The engine coolant system was operated to maintain the coolant temperature equal to 0 °C. The dynamometer setting of speed and load in Table 2 was established and maintained. Cold operation of the engine was initially unstable, but stability gradually improved. Consistent with maintaining reasonable stability, the injection timing was gradually lowered to the test condition value of 4 °BTDC. The COV of IMEP initially had a very high value, which decreased relatively quickly until after approx. 3 hours, when the rate of lowering became slow and essentially linear. The engine was therefore operated for 3 to 4 hours to allow the COV of the IMEP to reach a reasonable plateau level before the test measurements were taken.

At this stage, the AVL 647 analyzer was used to obtain three measurements of the COV of the IMEP. The average of the three measurements was recorded.

The fuel for the engine was then changed to the additive-containing fuel (the base fuel previously used plus additive) with an arrangement of valves that allowed the fuel change to take place without interrupting the fuel flow to the engine or disrupting its operation. After the fuel change, the engine was operated for 15 to 20 minutes on the new fuel to ensure that a representative condition was achieved. A second set of COV of IMEP measurements was then taken. Three COV samples were recorded and averaged into a simple average value.

The engine fuel was then changed again, this time back to the base fuel. The engine was allowed to run for an additional 15 to 20 minutes, and a third set of base fuel COV of IMEP measurements were taken.

This procedure of measurements with the base fuel followed by measurements with additive fuel was repeated three times in a test and followed by a final set of measurements with the base fuel. In this way, four sets of measurements were taken with the base fuel and three with fuel containing additives. The latter measurements were thus always taken up between measurements with the base fuel. In subsequent analysis, operating deviations in engine performance were corrected by recording in the arithmetic mean of the surrounding base fuel measurements, to represent what the performance of the engine would be during measurements with additive fuel if it was still operated with the base fuel. These re-encapsulation and interpolation methods made possible a clear comparison between the engine behavior between the base fuel alone and the base fuel plus additive. In this way, the effects of the additive were found.

The effect of the additive material is expressed as the "COV ratio":

where COV(basisbrcnsci) is the average of the two COVs stated in parentheses for base fuel, and COV(tlisashoidigbrsensel) is the value for the base fuel with additives. An additive fuel with better performance (lower COV of IMEP and lower white smoke emissions) than the base fuel alone has a COV ratio greater than one. A ratio of 1.0 obviously indicates that the test fuel is equivalent to the base fuel.

At the conclusion of each test day, the engine was finally operated warm under moderate load for one hour to burn off any deposits formed in the previously cold combustion chamber. The warm run prepares the engine for the next day's test and was found to reduce the extent of changes in COV by IMEP that would otherwise have occurred.

Table 5 lists the results obtained by following the test procedure. For each material, the COV ratio per 4000 ppm test material dissolved in the base fuel D is stated.

Example 2

This example describes tests of the effectiveness of Polyether A dissolved in a diesel fuel to reduce the opacity of white smoke emissions from a heavy-duty commercial vehicle started at a temperature of -10 °C.

In this example, a new 1995 Mercedes-Benz L 814 D vehicle was used with a EUR02 version of the OM 364 LA turbocharged intercooled four-cylinder engine with a total displacement of 4 liters. The power rating of the engine at 2600 r/min is 103 kW and the torque rating at 1200 to 1500 r/min is 500 Nm.

Four fuels (E, F, G and H) were tested. The fuel properties are given in Table 6. Fuels F and H were typical of commercially available diesel fuels. Fuel G was a commercially available advanced test fuel with a high cetane number of 58. Fuels E and F contained a conventional amount, 300 ppm, of 2-ethylhexyl nitrate ignition improver to increase the cetane numbers. Fuels E and F also contained 10 ppm "Tegopren" 5851 antifoam from Th Goldschmidt A.G., 5 ppm "Nalco" 7D07 smoke particulate remover from Nalco, and 5 ppm RC 4801 corrosion inhibitor from Rhein Chemie. In addition, fuel E contained 4680 ppm (0.468 wt%) Polyether A to reduce the opacity of white smoke during cold engine operation. Comparing the performance of fuels E and F therefore provides direct confirmation of the effect of the polyether in reducing the opacity of white smoke.

The tests were carried out in a climate-controlled dynamometer device where the vehicle was tested under conditions that simulated a road at a constant temperature. The test simulated cold start procedures for medium-sized trucks, for example filling the pneumatic brake system or loading the vehicle at a loading ramp.

Before the start of the test series, the vehicle engine and exhaust system were pre-treated by operating for 100 km on the dynamometer under simulated road stress.

Before each individual test, the vehicle was warmed up on the dynamometer by operating for 30 minutes at 60 kg/h in the highest vehicle gear and at simulated road stress. The purpose of the heat pretreatment was to return the vehicle to the same condition before each test and to remove fuel, partially oxidized materials and deposits left in the cylinders and exhaust system from previous cold starts, thereby reducing memory effects from previous fuel. The pretreatment served to improve the repeatability of the test.

After pretreatment, the engine was switched off and the vehicle was allowed to stand in the climate-controlled device for 15 hours with the temperature controlled to -10 °C before starting the test.

The test cycle was as follows. The engine was started without the use of starting aids and idled at zero applied road load for 60 s at an engine speed of 750 r/min. Still at zero applied road load, the engine speed was increased to a fixed idle of 1200 r/min for a further 120 s using manual throttle control. Finally, the engine speed was returned to an idle speed of 750 r/min for another 60 s.

The white smoke opacity during the test cycle was measured with a Celesco optical smoke meter model 107 with a cylinder diameter of 100 mm. The use of a climate-controlled chamber improved test repeatability because the airflows are more constant and reproducible. To help make the measurements more accurate and repeatable, additional precautions were taken. All vehicle exhaust gases were collected in an open funnel (300 mm diameter, tapering to 100 mm diameter over a length of 800 mm) placed directly behind the end of the unmodified 100 mm diameter vehicle exhaust pipe, to homogenize the smoke prior to arrival at the smoke meter. The flow was induced with a constant speed fan of approx. 700 m<3>/h flow downstream of the smoke meter. The ratios of exhaust gas:induced air were approx. 1:2 at idle at 750 r/min and approx. 1:1.2 at 1200 r/min.

The engine speed, air temperature and white smoke opacity were recorded at a frequency of 10 Hz in a conventional manner with a computerized digital data logger, as will be known to those skilled in the art of climate controlled chassis dynamometers.

The measurements taken during the phase at 1200 r/min were processed to give the opacity as a function of time.

Repeated tests were conducted for each test fuel. For all fuels, the white smoke opacity during the first 60 s period of idling at 750 r/min was not significant, i.e. less than 1-2%. The white smoke opacity during idling at a higher speed of 1200 r/min was significant, with maximum opacities up to 50%.

In Table 7, the white smoke opacity for each fuel is listed against the time during the idling phase at 1200 r/min. The opacities are the arithmetic mean of two tests.

Fuel F containing added polyether A produced significantly lower white smoke opacities than fuel F (without the addition of fast idle duration). Fuel F containing added Polyether A also produced significantly lower white smoke opacities than the advanced fuel G with a much higher natural cetane number, or fuel H. The maximum smoke opacities produced with fuel F with added Polyether A were significantly lower than what was produced with all the others fuel. Polyether A reduces white smoke emissions, while changes in fuel properties, e.g. increasing the cetane number - traditionally considered to be effective - had no effect.

Example 3

This example describes tests of the effects of two polyethers, Polyether A and Polyether B, dissolved in diesel fuel with reduced hydrocarbon emissions, and the opacity of the white smoke emissions from a heavy-duty diesel engine started at a temperature of -10 °C.

The powerful EUR02-spec diesel engine was equipped with a turbocharger and intercooler and had 6 cylinders, a displacement of 7 liters and a rated output of 206 kW at 2600 r/min.

Three fuels were tested. Fuels E and F were as in Example 2. Fuel I corresponds to fuel F, with additional inclusion of 4680 ppm (0.468 wt%) Polyether B.

The tests were conducted with the engines mounted on a test bench in a climate-controlled chamber at the facilities of AVL LIST GmbH, Graz, Austria. No starting aids were used.

Before the tests with each fuel, the fuel system was thoroughly sprayed through to remove traces of previous fuel. The lubricant and the lubricating oil filter were also changed. The engine was then allowed to run warm for 20 minutes on fuel for testing at a speed of 1500 r/min and a BMEP (Brake Mean Effective Pressure) of 5 bar. The purpose of the warm pretreatment was to reset the engine to the same condition at the beginning of testing each fuel. The warm-up removed fuel, partially oxidized materials and deposits that remained in the cylinders and exhaust system after the previous cold start. This helped to reduce the after effects of previous fuel.

The engines were then allowed to stand cold for 8 hours at a temperature of -10 °C. The test cycle was carried out and controlled automatically, and consisted, after starting the engine, of operation alternatively at two idle conditions "low idle" and "fast idle", with a five second legal adjustment period between the two conditions. The first operating period lasted 180 s, immediately after engine start-up at low idle, zero applied load and 0% throttle. The resulting engine speed was 750 r/min. The engine was then operated for 25 s at "fast idle", at a throttle setting of 15% and zero applied load, to produce an engine speed of 1000 r/min gradually increasing to 1300 r/min as the test progressed and the lube oil warmed. The two conditions, 25 s slow idling followed by 25 s fast idling, were then repeated alternately a further four times. The test thus comprised an initial 180 s slow idling period followed by five periods of 25 s duration with fast idling alternating with four 24 s periods of slow idling.

The engine exhaust was 100 mm in diameter in the first length of 1250 mm from the engine, followed by a further 94 mm diameter section with a length of 485 mm. White smoke opacity was measured with a US-PHS opacity meter mounted vertically in open air above the upward open end of the exhaust pipe.

Furthermore, the exhaust hydrocarbons were measured in situ at a point 640 mm from the open end of the exhaust pipe with an AVL DP 482 dynamic particle analyzer that used infrared absorption simultaneously to monitor the hydrocarbon content, carbon content and water content of the engine exhaust gases. During the test cycle, the measurements from these instruments and the engine conditions were logged at frequencies of 2 Hz and 10 Hz, as appropriate with an AVL "Indimaster engine data recording system.

Three tests with good repeatability were carried out with each fuel. IN

Tables 8 and 9 list the average white smoke opacities and hydrocarbon concentrations in the exhaust for each fuel for each fast idling period of the cycle. The hydrocarbon concentrations in the exhaust during the first fast idle period were not measurable because the concentration was greater than 1800 ppm which is the maximum value for the range of the AVL DP 482 analyzer. The smoke capacities and hydrocarbon concentrations during the slow idling periods were very low.

Polyether A and polyether B were found to be effective in significantly reducing white smoke opacity and hydrocarbon emissions in the exhaust from a cold engine.

Claims (8)

1. Use, as an additive in a diesel fuel comprising a major proportion of diesel oil, in an effective concentration in the range of 0.1 to 1% by weight based on the diesel fuel, of a polyether derivative of general formula where each R<1> and R<2> independently represent a hydrogen atom, a C1-30 alkyl or alkenyl group optionally substituted with one or more amino or hydroxy groups, or a C2-7 alkanoyl group, where x has a mean value in the range of 2 - 200, and each part R3 is independently selected from C2.4-alkylene groups, for reducing the emissions of white smoke under cold running conditions of an engine when the start-up temperature of the engine is 0 °C or lower. 2. Use according to claim 1, where the polyether derivative according to formula I is present in a concentration in the range of 0.2-1% by weight of the diesel fuel. 3. Use according to claim 1 or 2, where the polyether derivative according to formula I is present in a concentration in the range of 0.3-0.5% by weight of the diesel fuel. 4. Use according to claims 1-3, where each of the groups R<1> and R2 independently represents a hydrogen atom, a C1.20-alkyl group which is optionally substituted with an amino group, or a C2.4-alkanoyl group. 5. Use according to claims 1-4, where each of the groups R and R independently represents a hydrogen atom or a C1.20 alkyl group which is optionally substituted with an amino group, and x has a mean value in the range 2 to 150. 6. Use according to claims 1-5, where the diesel oil has a sulfur concentration lower than 500 ppm. 7. Procedure for operating a diesel engine under cold running conditions where the starting temperature of the engine is 0 °C or lower, with reduced emissions of white smoke, characterized in that it comprises running the engine on diesel fuel containing a major proportion of diesel oil and an effective concentration in the range of 0.1-1% by weight based on the diesel fuel, of a polyether derivative according to formula I as defined in any one of claims 1, 4 or 5. 8. Method according to claim 7, where the diesel oil has a sulfur concentration below 500 ppm.