Search Results

Deposits formed on the plungers, barrels and delivery valves of some in-line injection pumps in diesel engines. The deposits formed during 5,000 - 20,000 km of driving and caused sticking of plungers. Normally the plungers, barrels and delivery valves keep clean. Deposits formed if kerosene based arctic diesel fuel containing lubricity additive was used. Small amounts of engine oil mix with diesel fuel in the pump. A chemical reaction between the fuel lubricity additive and the engine oil, which lubricates the camshaft of the pump, caused the deposits. The problem was avoided by changing the type and dosage of the fuel lubricity additive.

Oxidation stability tests have been developed for estimation of the long term storage stability of diesel fuels. Currently, several oxidation stability test methods (eg. ENISO12205, Rancimat (EN15751), PetroOXY (EN16091)) are used for this purpose. It is common for these tests to have an elevated temperature and to add oxygen or air to accelerate the oxidation of the test fuel, and hence accelerate conduction of the test. It has been under discussion whether these tests actually represent real-life conditions. Also, it has been proposed that these oxidation stability tests could be used to estimate the thermal stability of the diesel fuels. In many cases the correlation to real-life is unclear. Stability of EN590 B0 (winter and summer grade) and B7, B30, EN590 with 30% HVO, 100% HVO, WWFC category 4 diesel, Swedish class 1 as well as the effect of cetane improver was evaluated with different oxidation stability methods.

Cold operability is estimated by fuel's cold filter plugging point (CFPP). However, correlation of CFPP with diesel vehicle performance originates from a period when simple in-line or distributor fuel injection systems were applied and fuels did not contain biocomponents. Today, common rail fuel injection systems are used and there seem to be remarkable differences in their design between vehicle models. Seven cars were tested in a climate chamber. The best cars operated down to 8°C below fuel's CFPP but the worst get into problems 5°C above CFPP with the same fuel. It is challenging to define what CFPP is needed in order to guarantee trouble-free winter performance because there are big differences between car models. It is fundamental to get the fuel temperature of a vehicle's fuel filter above the fuel's cloud point during driving, and this depends on fuel system design factors, such as location and size of fuel filter and fuel heater if it is used.

Diesel fork-lifts are often preferred over LPG due to lower costs and superior fire safety in in-door use but exhaust causes problems. Air quality was measured with standard and reformulated diesel fuel in a warehouse where diesel fork-lifts operated. Sulphur was 605 ppm for the standard and 7 ppm for the reformulated fuel. Aromatics were respectively 31 vol-% and 12 vol-% and 95-% distillation points 352 °C and 286 °C. Fuel reformulation reduced particulates in the ware-house air by 40 %, particulate SOF by 50 % and mutagenicity of SOF by 80 %. NO, NO2, SO2 and PAH concentrations were low. Irritation and the possibility of long-term health problems reduced.

Emissions of heavy duty engines using hydrocarbon fuels and rape seed methyl ester (RME) were measured according to the ECE R49 test procedure. The effect of fuel density on engine power was taken into account in the ECE R49 tests. The two reformulated fuels tested had sulphur below 50 ppm, aromatics below 20 vol-%, cetane number over 49 and reduced triaromatic content. Particulates were measured in a AVL Mini Dilution Tunnel 474 and gaseous unregulated hydrocarbons by Siemens FTIR. Reformulation reduced NOx by 5 to 12 %, particulates by 10 to 25 % and Ames mutagenicity by 56 to 74 %. RME increased NOx by 4 to 9 %, reduced particulates by 0 to 33 % and the mutagenicity by 17 %. Cetane number was found to be not important in reducing emissions. Low fuel triaromatic and low particulate PAH content reduced the mutagenicity of particulates.

When a new type of fuel is introduced, it is necessary to ensure that exhaust gas aftertreatment systems work properly with these fuels. Today diesel particulate filter (DPF) is an inherent part of current diesel engine's exhaust gas aftertreatment system due to stringent exhaust emission limits. The functioning of DPF depends on the composition of soot particulates of exhaust gas, whereas the type of soot depends on the fuel used. To avoid clogging, DPF has to be regenerated regularly. This regeneration is usually increasing fuel consumption, so the longer the regeneration interval is, the better is fuel economy. Fuel quality and engine-out particulate emissions are important factors affecting to the need of regeneration. Renewable fuels burn cleanly and produce less particulate emissions than ordinary diesel fuel. Therefore, the increase of exhaust backpressure is slower enabling longer regeneration frequency.

Unregulated emissions of reformulated diesel fuels (sulfur < 50 ppm, aromatics < 20 vol-%) were compared to the European EN590 specification fuel (sulfur < 500 ppm, aromatics < 35 vol-%) in three IDI passenger cars and one DI van using FTP and/or ECE/EUDC emission test procedures. The effect of reformulated diesel fuels on the mutagenicity of particulate soluble organic fraction (SOF) was studied. Fuel reformulation reduced particulate emissions in IDI cars. Reformulating fuel by decreasing heavier aromatics - without decreasing final boiling point - reduced particulate mutagenicity on emission basis. At low ambient temperature (-7°C) particulate PAH and mutagenic emissions increased compared to the standard ambient temperature (+22°C) with all fuels.

In a diesel engine, both physical and chemical properties of the fuel affect exhaust emissions. This study focused on the separation of some physical and chemical effects of the fuel on the NOx emission. The tests were conducted with a bus engine using four diesel fuels with different density and aromatics levels. The measurements were performed using five injection timing settings to screen the effects of changes in actual injection timing. When conventional diesel fuel was replaced by reformulated diesel, NOx was reduced 7-13 %. Changes in the injection timing due to differences in the physical properties accounted only for a minor part (10-25 % relative) of the total reduction of NOx, whereas the greater part of the reduction (75-90 % relative) was due to other reasons, mainly fuel chemical properties.

When switching from regular diesel fuel (sulfur free) to paraffinic hydrotreated vegetable oil (HVO), the changes in fuel chemistry and physical properties will affect emission characteristics in a very positive way. The effects also depend on the technology, after-treatment and sophistication of the engine. To determine the real effects in the case of city buses, 17 typical buses, representing emission classes from Euro II to EEV, were measured with HVO, regular diesel and several blended fuels. The average reduction was 10% for nitrogen oxides (NOx) and 30% for particulate matter (PM). Also some engine tests were performed to demonstrate the potential for additional performance benefits when fuel injection timing was optimized for HVO.

Diesel fuels must have good flow properties at low ambient temperatures. These fuels have lower densities than normal fuels. Fuel-injection pumps work on the basis of volume, and thus the fuel mass flow is reduced by density decrease. This leads to lower engine power. In Finland, for instance, the engine power reduction is about 10% when the fuel is changed from summer grade to arctic winter grade. The problem could be solved in future by using fuel density sensors in electronically governed injection pumps or by using fuel heaters so that vehicles could run on high density fuels also in winter.

Hydrotreating of vegetable oils or animal fats is an alternative process to esterification for producing biobased diesel fuels. Hydrotreated products are also called renewable diesel fuels. Hydrotreated vegetable oils (HVO) do not have the detrimental effects of ester-type biodiesel fuels, like increased NOx emission, deposit formation, storage stability problems, more rapid aging of engine oil or poor cold properties. HVOs are straight chain paraffinic hydrocarbons that are free of aromatics, oxygen and sulfur and have high cetane numbers. In this paper, NOx - particulate emission trade-off and NOx - fuel consumption trade-off are studied using different fuel injection timings in a turbocharged charge air cooled common rail heavy duty diesel engine. Tested fuels were sulfur free diesel fuel, neat HVO, and a 30% HVO + 70% diesel fuel blend. The study shows that there is potential for optimizing engine settings together with enhanced fuel composition.

Hydrotreated vegetable oil (HVO) named NExBTL is a 2nd generation renewable diesel fuel made by a refinery-based process converting vegetable oils to paraffins. Also animal fats are suitable for feedstocks. Properties of this non-ester type biobased fuel are very similar to GTL. It contains no sulfur, oxygen, nitrogen or aromatics. Cetane number is very high (∼90). Cloud point can be adjusted by severity of the process from -5 to -30°C, heating value is similar to diesel fuel, storage stability is good, and water solubility is low. Emissions of two heavy duty engines and two city buses are presented with HVO and sulfur free EN 590 diesel fuel. The effect of HVO on regulated emissions compared to EN 590 fuel was: NOx -7 % … -14 % PM -28 % … -46 % CO -5 % … -78 % HC 0 % … -48 % Aldehydes, PAHs, mutagenicity and particulate size were also measured.

Lubricity testing of reformulated diesel fuels (sulfur <0 005 w-%, aromatics <20 vol-%) was started in 1990. A 1000 hour in-house test rig with distributor pumps was used for testing fuels and additives. When lubricity is not adequate, excessive wear is seen in the pump. A field test on 140 buses each accumulating 150 000 - 250 000 km with reformulated diesel was carried out. Reformulated diesel has been on the market since 1993 without problems. Lubricity was evaluated with HFRR test and compared to the pump rig results. HFRR overestimated the need for lubricity additives. Fuel sulfur was found to be not the only indicator of lubricity and lubricity of low sulfur diesel was as good as high sulfur when other fuel parameters were kept constant.

Diesel cars are sometimes refueled with gasoline by mistake. Already small amounts of gasoline are harmful for diesel fuel's lubricity, cetane number, viscosity and flash point, and may cause vapor bubbles. Cases are laborious to fix. Repair costs may be thousands of euros if fuel injection system break down has taken place. Misfueling of diesel fuel into gasoline is not common in cars but may take place in non-road engines refueled from canisters. This will cause engine oil dilution, reduced octane number and running problems. Adding of SCR-urea into fuels causes serious problems. Coolant and windshield washing concentrate may be added thinking that they help to dissolve water into fuel; only additives indented for fuels shall be used. Practice has shown that even automotive professionals may not know which misfuelings are serious and which are harmless. Some misleading advice has also been distributed by the media.

Diesel fuel was reformulated by reducing sulfur to < 0.005 wt-%, aromatics to < 20 vol-% and by limiting heavy polyaromatics. This reduced NOx, particulate, PAH and mutagenic emissions plus exhaust odor. Oxidation catalysts operated well. Less deposits formed in the EGR system. Fuel lubricity was enhanced by additives evaluated by injection pump tests and HFRR. Three years of field testing with 140 buses showed no fuel related problems. Oil change period could be lengthened and fuel consumption was unchanged. Demand for reformulated fuel was triggered by differentiating taxation based on quality. Fuels have been used since 1993 without problems. Life cycle analysis showed no increase of CO2.