جستجوی مقالات مرتبط با کلیدواژه « موتور دیزل دریایی » در نشریات گروه « مکانیک »

In this article, the effect of increasing turbulence intensity and changing fuel injection angle on performance and pollution of Caterpillar marine diesel engine has been investigated using computational fluid dynamics method in Fire software. To this end, two phase flow inside the diesel injector was simulated using the CFD.Solidworks software has been used for geometry creation and AVL-Fire software has been used for meshing and simulating. In order to increase the turbulence intensity, the groove inside the injector nozzle has been used and the fuel injection angle has been increased. Numerical results of injector and diesel engine simulation in operating conditions were compared with experimental data and a good agreement was observed between them. The results of diesel engine performance show that grooving, increasing turbulence intensity and fuel injection angle lead to a 75% increase in power and torque output and a 37% reduction in fuel consumption compared to the cylindrical fuel nozzle. Also, the results related to the pollution of this marine diesel engine show that in this case, the pollutants of carbon monoxide and nitrogen oxide decreasing 42.73% and 45.45%, respectively. Also, in this case, the engine has no problem in terms of producing soot pollutants and the soot produced during the combustion process is well oxidized. Then, in order to create a rotational flow and reduce the intensity of cavitation as well as the resulting erosion, the geometry of the cylindrical nozzle hole was changed to a converging cone and the groove inside it was used. The numerical results show that changing the geometry of the nozzle hole and creating a rotational flow inside it leads to reducing the severity of cavitation and thus reducing the erosion and corrosion caused by it and increasing the life of the injector nozzle. Thus the fuel spray characteristics can be controlled by creation of swirly flow and changing the nozzle geometry and needle lift profile. Numerical results and experimental data validated from previous researches.

In the present research, a novel bi-evaporator combined cooling and power cycle based on the integration of a double-stage organic Rankine cycle and an ejector refrigeration cycle is devised to recycle heat from the exhaust gas of a marine diesel engine. Instead of using conventional pure organic fluids, various appropriate zeotropic mixtures are screened for the proposed system and the results are discussed in terms of the first and second laws of thermodynamics. The results indicated that by recycling 434kW energy from the exhaust gases and using R142/Pentane with 51/49 percent a maximum thermal efficiency of 43.28% and an overall cooling load of 166.36 kW can be achieved. In this case, the net produced electricity and exergy efficiency are obtained as 21.83 kW and 20.22% which can be increased by selecting other appropriate mixtures. Additionally, using R142/Pentane with 51/49 percent as the working mixture, it is figured out that the auxiliary vapor generator contributes to the highest exergy destruction by 62.3 kW out of overall exergy destruction of 122.15 kW. Also, the energy and exergy efficiencies of the system can be increased simultaneously by increasing the evaporator bubble point temperature.

Cylinder head bolts in high-speed diesel engines must meet classical standard requirements. Moreover, they should seal cylinder head gasket due to uniform distribution of clamping forces with high durability under thermal and mechanical cyclic loads. In present study, to evaluate the performance of newly designed bolts, at first, the clamping force in cold assembly was calculated using theoretical and experimental results. Then in real engine condition, the amount of clamping force variation was derived with combustion load under hot condition. The most critical force was used to test the bolt durability in a uniaxial high cycle fatigue test. The experimental test confirmed infinite life of the bolt. Also, results show preload of used bolt could be increased about 8% that is important for maintenance and repair services. In addition, torque-angle assembly procedure precisely tightened the bolt near yield stress condition and improved sealing of the cylinder head gasket. Fuji paper test confirmed this analytical uniform clamping force results too.

In this study, in order to waste heat recovery from a marine diesel engine, a humidification – dehumidification desalination unit type of open – water and closed – air cycles with water heated is proposed for producing the consumed fresh water the crew of the ships. The energy required to produce freshwater is provided by recovered heat from exhaust gases from marine diesel engine. For this proposed system, first simulated thermodynamically and detailed energy and exergy analysis, in order to determine the main sources of irreversibility and performance characteristics of the system is conducted. Moreover, a comprehensive parametric study to find key parameters trend with system performance parameters is carried out. The study found that the system has the ability to produce 0.2746 kg.s-1 fresh water, using 432 kW of primary energy. As well as desalination efficiency and exergy efficiency were calculated to be 1.516 and 23.9%, respectively. And from an exergy analysis it can be seen that among all the components of the system, the heater has the highest exergy destruction rate, which accounts for about 73.2% of the total exergy destruction rate.