Power-producing units of modern ships are difficult machines, which consist of a set of nodes, aggregates and parts. Unfortunately, it does not mean they are perfect. For a long time engineers tried to develop efficiency of units. Nowadays it is not the only question, which is important to solve. We have to follow ecological rules and standards, they are becoming tougher every year. The basis for such things is the harmful emissions occurring because of the work of engines. The air of ports is polluted, water also becomes a source of pollution of flora and fauna. Ecologists raise the alarm. And today their voices are heard. There are reasonable arguments and objective reasons for looking for more risk-free engine types or improving ones.
Nowadays Europe countries use different acts established by International Maritime Organization (IMO). It was organized by United Nations Organization in 1948. Activity of IMO began in 1958. International Maritime Organization is engaged at the protection of water areas and monitoring the ecological situation. One of the most perspective variants matching environmental requirements is the modification of the classic four-stroke marine diesel engine or diesel generator to a two-fuel gas-diesel engine. Using of natural gas at certain modes could be a cause of significant improvement of the ecology of water areas.
To preserve the stability of operation, economy of exploitation and efficient distribution of fuel at ship, it is possible to use gas at partial modes only. Nominal mode could be carried out when diesel fuel is used. They say that the gas-diesel engine is capable to produce only 80% of power given by the diesel engine. This difference cannot be significant and noticeable at the partial modes. Newspaper “Maritime News of Russia” No. 13, 2017 (458)  – The Federal Water Transport newspaper presented an article about the acceptance by the Yamal LNG Company the world’s first icebreaker gas carrier Christophe de Margerie (deadweight 172,600 m3).
The world is gradually choosing gas. At the magazine “Engine Designing” (No. 3, 2011) published an article “Buses used with biogas.” At the article described that the company “Volvo” received an order to design a batch of gas-diesel buses working on biogas. Their engines should be more economical (about 30-40%) than conventional gas engines. At the gas engines with spark ignition the Otto cycle is used, it is worse than diesel cycle in terms of efficiency. They used diesel engines for the project, which function with fuel consisting about 70% of gas. The basis of idea is a diesel bus with cylinders of gas installed on the roof. The gas is not liquefied. The engines are equipped with a gas supply system, where a prepared active mix with an optimal air-fuel proportion is used. The main fuel is gas, and liquid fuel should ensure its ignition.
Nowadays you can also see buses with gas-cylinders equipment at St. Petersburg and Leningrad region. According to the article of the Internet magazine “Wheels”, there is a factor of greater economy benefit of such buses. We have an example of using “NEFAZ” buses (130 units with equipment for NG). They were working for 16 hours a day for a month. At the same time, the cost of fueling them with methane was 1,68 million rubles, while the cost of fueling buses with diesel fuel would be up to 3,34 million rubles.
There are also problems at the designing and using of gas-diesel. The operation of a diesel engine using gas with an ignition portion of diesel fuel contributes to the formation of coke in the nozzle openings of the atomizer. When the pressure is lowered, the needle may hang, have poor mobility, the stroke will increase. All these factors lead to the penetration of gases into the atomizer. That is why it is necessary the design and adjustment parameters of the fuel equipment ensure the needle and the discharge valve fit on the seat up to the point of intersection of the fuel pressure in the atomizer chamber and the pressure of the gases in the cylinder.
The optimization of the operation of internal combustion engines, as well as of any other types of engines, is based on such components as:
The principle of operation of a successfully designed gas-diesel engine guarantees not only the improvement of environmental indexes, but also good economic prospects. The qualitative process of fuel injection and spraying guarantees its greatest useful implementation at the engine using.
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