Test drive car fuel: biodiesel PART 2

The first companies to provide warranties for their biodiesel engines were agricultural and transportation manufacturers such as Steyr, John Deere, Massey-Ferguson, Lindner and Mercedes-Benz. Subsequently, the distribution spectrum of biofuels has been significantly expanded and now includes public transport buses and taxis in some cities.

Disagreements over the grant or waiver of warranties by car manufacturers regarding the suitability of engines to run on biodiesel lead to many problems and ambiguities. An example of such a misunderstanding is the frequent cases when the manufacturer of the fuel system (there is such a precedent with Bosch) does not guarantee the safety of its components when using biodiesel, and the car manufacturer, installing the same components in its engines, gives such a guarantee ... Real problems in such controversial In some cases, they begin with the appearance of defects that have nothing to do with the type of fuel used.

As a result, he can be accused of sins in which there is no guilt, or vice versa - justified when they are. In the event of a complaint, manufacturers (of which VW is a typical example in Germany) in most cases wash their hands of poor quality fuel, and no one can prove otherwise. In principle, the manufacturer can always find the door and avoid liability for any damage that he previously claimed to be included in the company's warranty. Precisely to avoid misunderstandings and disputes of this kind in the future, VW engineers developed a fuel level sensor (which can be built into the Golf V) to assess the type and quality of fuel, which, if necessary, signals the need for correction at the moment. fuel injection electronics that control the processes in the engine.

Advantages

As already mentioned, biodiesel does not contain sulfur, as it consists entirely of natural and subsequently chemically processed fats. On the one hand, the presence of sulfur in classic diesel fuel is useful because it helps to lubricate the elements of the power system, but on the other hand, it is harmful (especially for modern precision diesel systems), since it forms sulfur oxides and acids that are harmful to their small elements. The sulfur content of diesel fuel in Europe and parts of America (California) has dropped dramatically in recent years for environmental reasons, which in turn has inevitably led to higher processing costs. Its lubricity also deteriorated with decreasing sulfur content, but this disadvantage is easily compensated for by the addition of additives and biodiesel, which in this case turns out to be a wonderful panacea.

Biodiesel is composed entirely of paraffinic hydrocarbons with straight and branched links and does not contain aromatic (mono - and polycyclic) hydrocarbons. The presence of the latter (stable and, therefore, low-cetane) compounds in petroleum diesel fuel is one of the main reasons for incomplete combustion in engines and the release of more harmful substances in emissions, and for the same reason the cetane number of biodiesel is higher than the standard. diesel fuel. Studies show that due to the specified chemical properties, as well as the presence of oxygen in the molecules of biodiesel, it burns more completely, and the harmful substances released during combustion are much less (see Table).

Biodiesel engine operation

According to a large number of studies conducted in the US and some European countries, long-term use of biodiesel reduces the wear of cylinder elements compared to cases when conventional gasoline diesel with a low sulfur content is used. Due to the presence of oxygen in its molecule, biofuel has a slightly lower energy content compared to petroleum diesel, but the same oxygen increases the efficiency of combustion processes and almost completely compensates for the reduced energy content. The amount of oxygen and the exact shape of the methyl ester molecules lead to some difference in the cetane number and energy content of biodiesel depending on the type of feedstock. In some of them, consumption does increase, but more injected fuel required to provide the same power means lower process temperatures, as well as a subsequent increase in its efficiency. The dynamic parameters of the engine operation on the most common in Europe biodiesel fuel produced from rapeseed (the so-called "technical" rapeseed, genetically modified and unsuitable for food and feed), are the same as for oil diesel. When using raw sunflower seeds or used oil from restaurant fryers (which are themselves a mixture of different fats), there is an average of 7 to 10% drop in power, but in many cases the drop can be much larger. big. It is interesting to note that biodiesel engines often avoid the increase in power at maximum load - with values ​​up to 13%. This can be explained by the fact that in these modes the ratio between free oxygen and injected fuel is significantly reduced, which, in turn, leads to a deterioration in the efficiency of the combustion process. However, biodiesel transports oxygen, which prevents these negative effects.

Problems

And yet, after so many good reviews, why isn't biodiesel becoming a mainstream product? As we have already mentioned, the reasons for this are primarily infrastructural and psychological, but some technical aspects must be added to them.

The effects of this fossil fuel on engine parts, and especially on components of the food system, have not yet been conclusively established, despite numerous studies in this area. Cases have been reported where the use of high concentrations of biodiesel in the total blend resulted in damage and slow decomposition of rubber pipes and some soft plastics, gaskets and gaskets that became sticky, softened and swollen. In principle, it is easy to solve this problem by replacing the pipelines with plastics, but it is not yet clear whether automakers will be ready for such an investment.

Different biodiesel feedstocks have different physical properties at low temperatures. Therefore, some biodiesel varieties are more suitable for use in winter than others, and biodiesel manufacturers add special additives to the fuel that lower the cloud point and help make starting easier on cold days. Another serious problem of biodiesel is the increase in the level of nitrogen oxides in the exhaust gases of engines running on this fuel.

The cost of producing biodiesel depends primarily on the type of feedstock, the efficiency of harvesting, the efficiency of the production plant and, above all, the fuel taxation scheme. For example, due to targeted tax breaks in Germany, biodiesel is slightly cheaper than conventional diesel, and the US government encourages the use of biodiesel as fuel in the military. In 2007, second-generation biofuels using plant mass as feedstock will be introduced – in this case the so-called biomass-to-liquid (BTL) process used by Choren.

Germany already has many stations where clean oil can be poured, and the filling devices are patented by the engineering company SGS in Aachen, and the conversion company Aetra from Paderborn offers them to both oil station owners and individuals. use. As for the technical adaptation of cars, significant progress has been made in this area recently. If until yesterday most of the oil consumers were prechamber diesel engines from the eighties, today mainly direct injection engines are switching to vegetable oil, even those that use sensitive unit injectors and Common Rail mechanisms. Demand is also growing, and lately the German market can offer quite suitable modifications for all cars with engines operating on the principle of self-ignition.

The scene is already dominated by serious companies that install well-functioning kits. However, the most amazing evolution takes place in the energy carrier itself. However, the price of fat is unlikely to drop below 60 cents per liter, the main reason for this threshold is that the same feedstock is used in the production of biodiesel.

Conclusions

Biodiesel is still a highly controversial and dubious fuel. Opponents have blamed it for corroded fuel lines and seals, corroded metal parts and damaged fuel pumps, and car companies have so far distanced themselves from environmental alternatives, perhaps to give themselves peace of mind. The legal regulations for the certification of this fuel, which is undoubtedly interesting for many reasons, have not yet been approved.

However, we should not forget that it appeared on the market quite recently - almost no more than ten years. This period was dominated by low prices for conventional petroleum fuels, which in no way stimulates investment in technology development and infrastructure improvements to stimulate its use. So far, no one has thought about how to design all elements of the engine fuel system so that they are completely invulnerable to the attacks of aggressive biodiesel.

However, things can change dramatically and dramatically - with the current rise in oil prices and its shortage, despite the completely open taps of OPEC countries and companies, the relevance of alternatives such as biodiesel can literally explode. Then automakers and car companies will have to provide appropriate warranties for their products when dealing with the desired alternative.

And the sooner the better, because soon there will be no other alternatives. In my humble opinion, bio and GTL diesels will soon become an integral part of the product, which will be sold at gas stations in the form of "classic diesel". And this will be just the beginning ...

Camilo Holebeck-Biodiesel Raffinerie GmbH, Austria: “All European cars built after 1996 can run smoothly on biodiesel. The standard diesel fuel that consumers fill in France contains 5% biodiesel, while in the Czech Republic the so-called “Bionafta contains 30% biodiesel”.

Terry de Vichne, USA: “Low sulfur diesel fuel has reduced lubricity and tendency to stick to rubber parts. US oil companies have begun adding biodiesel to improve lubrication. Shell adds 2% biodiesel, which carries oxygen and reduces harmful emissions. Biodiesel, as an organic substance, tends to be absorbed by natural rubber, but in recent years the latter has been replaced by other polymers. ”

Martin Styles, user England: “After driving a mine Volvo 940 (with a 2,5-liter five-cylinder VW engine) on a homemade biodiesel, the engine was disassembled for 50 km. There was no soot and soot on my head! Intake and exhaust valves were clean and the injectors worked fine on the test bench. There were no traces of corrosion or soot on them. Engine wear was within normal limits and there were no signs of additional fuel problems. ”