Sensitivity Analysis of Heavy Fuel Oil Spray and Combustion under Low-Speed Marine Engine-Like Conditions

Abstract

On account of their high power, thermal efficiency, good reliability, safety, and durability, low-speed two-stroke marine diesel engines are used as the main drive devices for large fuel and cargo ships. Most marine engines use heavy fuel oil (HFO) as the primary fuel, however, the physical and chemical characteristics of HFO are not clear because of its complex thermophysical properties. The present study was conducted to investigate the effects of fuel properties on the spray and combustion characteristics under two-stroke marine engine-like conditions via a sensitivity analysis. The sensitivity analysis of fuel properties for non-reacting and reacting simulations are conducted by comparing two fuels having different physical properties, such as fuel density, dynamic viscosity, critical temperature, and surface tension. The performances of the fuels are comprehensively studied under different ambient pressures, ambient temperatures, fuel temperatures, and swirl flow conditions. From the results of non-reacting simulations of HFO and diesel fuel properties in a constant volume combustion chamber, it can be found that the increase of the ambient pressure promotes fuel evaporation, resulting in a reduction in the steady liquid penetration of both diesel and HFO; however, the difference in the vapor penetrations of HFO and diesel reduces. Increasing the swirl flow significantly influences the atomization of both HFO and diesel, especially the liquid distribution of diesel. It is also found that the ambient temperature and fuel temperature have the negative effects on Sauter mean diameter (SMD) distribution. For low-speed marine engines, the combustion performance of HFO is not sensitive to activation energy in a certain range of activation energy. At higher engine speed, the difference in the effects of different activation energies on the in-cylinder pressure increases. The swirl flow in the cylinder can significantly promote fuel evaporation and reduce soot production.

Spillback nozzle characterization using pulsating LED shadowgraphy

“…To study the effect of changes in liquid viscosity on the spray characteristics the experiments were repeated with water and water-glycerol solutions [37,38]. This was done to reproduce the viscosities of some of the fuels used in the boiler [39], or achievable with a fuel preheating system [40]. The solutions were designed using the viscosity data found in literature [41].…”

2D CFD Simulation of Water Injection Strategies in a Large Marine Engine

“…Since slow-speed diesel engines are fueled with HFO (heavy fuel oil), the properties for this fuel are introduced in the model. HFO has higher density, viscosity, surface tension, and evaporation heat than automotive diesel fuel, which results in bigger droplets, longer spray penetration, and slower heat release [27,28]. The fuel properties are dependent on temperature and pressure, so the properties were introduced to the code in the form of functions.…”

Comparative Analysis of Injection of Pyrolysis Oil from Plastics and Gasoline into the Engine Cylinder and Atomization by a Direct High-Pressure Injector

“…Altaher et al observed that the higher air velocity inside the turbine chamber caused smaller SMDs, which improved the mixing and atomizing of fuel injection [22]. Other interesting works including SMD analysis were realized by Park et al [23] and Zhou et al [24]. Valuable research work on spraying and mixture formation with the aid of optical measurement instrumentation was presented by Tzanetakis et al [25] and Park et al [26].…”