Research On Performance Of High-Speed Marine Diesel Using Heavy Fuel Oil

Since industrialization, human beings began to consume petroleum, a non-renewable resource, which is leading the shortage of light oil presently, for which more and more attention around the world have been paid on the exploitation and utilization of heavy oil. China in particular is abundant in heavy oil resources, so the development and utilization of heavy oil on the one hand can generate direct economic benefits, on the other hand can ease the problem of the supply of light oil, and reduce import of crude oil, enhancing the national energy security.Heavy oil also known as fuel oil, is a kind of internal-combustion fuel that is from the straight-run residual oil blending with the secondary processing diesel by refinery, and is the economy and desirable fuel with the high power, medium and low speed diesel engines. However, there is significant difference of the physical and chemical properties between heavy oil and light oil, so currently such small, medium and high speed diesel engines burning heavy oil is still rare.Because the viscosity, density, sulfur content and mechanical impurities of heavy oil are higher than light oil, heavy oil can not be used directly by diesel engine. It must be purified, homogenization, heat and pressure pumping and other pretreatments before use. Purification is for the purpose of removing the various impurities in the fuel and divided into two steps, gravitational sedimentation and centrifugal separation. Homogenization is achieved by grinding for the purpose of making the fuel mix and refinement. Heating reduces the viscosity of heavy oil, so that it can successfully burn in the diesel engine. Pressure pumping prevents high-temperature fuel from boiling and cavitation.In this paper, those above four pretreatments were completed by a set of pretreatment equipment. The fuel oil before and after the pretreatment test report showed that pretreatment can significantly improve the quality of heavy oil, including heavy oil viscosity reduction of 32.6%, sulfur content, carbon residue, ash, total deposits and other impurities reductions of 5.3%,15.8%,95.7%,60%, the concentration of various types of harmful metals reduction of 8.3%-72.4%. Heavy oil must be pretreated before use, making the fuel system of diesel engines burning heavy oil expands to the entire pretreatment unit. So the operation and management of the diesel engines using heavy oil are different from the normal diesel engines. The diesel engines burning heavy oil must be used light oil to start and warm up until the engine water temperature and oil temperature rose to 70℃, then they can use heavy oil, as the same time day tank and pipes should be warmed. Before engine stops, supply unit must be switch to light oil. Until it completely converts to light oil, engine could stop.In order to fully understand the performance characteristics of diesel engines burning heavy oil, a series of load performance comparison tests of burning light oil, heavy oil were carried out, In order to fully understand the performance characteristics of diesel engines burning heavy oil, a series of load performance comparison test experiments of burning light oil, heavy oil were carried out, including original machine comparison tests, different fuel supply advance angles comparison tests, different nozzles comparison tests and different supply pressure comparison tests. The results show that: after the diesel engine fueled with heavy oil the fuel consumption significantly rises, by 13.6% to 25%, the load the lower the rise greater. The exhaust temperature shows an upward trend, but the rise is modest, about 10℃of each load. The ignition delays, the load the lower the delay greater, which makes the pre-mixed combustion enhances, the peak heat release rate increases, and the maximum ratio of cylinder pressure rise increases, but the maximum combustion pressure and the crank angle corresponding to the same with light oil. Whether diesel engine uses heavy oil or light oil, the fuel consumption and exhaust gas temperature change little with different fuel supply advance angles. The variations of cylinder pressure of burning heavy oil are the same with burning light oil under different fuel supply advance angles. Ignition delays and maximum combustion pressure increases when the fuel advance angle enlarges. The ignition delays of heavy oil are basically the same with different fuel supply advance angles. Whenever engine uses heavy oil or light oil, the fuel consumption are better with 6 x 0.385 nozzle (Note:6 x 0.385,6 said holes,0.385 said aperture.), and the exhaust gas temperature are basically the same with three nozzle. The ignition delays of two oil are short with 8x0.34 nozzle. The cylinder pressure curves of heavy oil and light oil overlap with 6 x 0.385 and 6 x 0.395 nozzles. The maximum combustion pressure of different nozzles is the same. The fuel consumption, exhaust temperature and cylinder pressure do not affected by the oil supply pressure.