Characteristics Of Combustion And Emissions Of Regenerated Fuel From Waste Lubricating Oil

The increasing of high degree of mechanization has created a huge demand for the lubricating oil, resulting in greatly increasing waste lubricating oil. Waste lubricating oil can not be directly used in diesel engines. However, it is feasible to the regenerated fuel from waste lubricating oil used in diesel engines. It is of great significance to transform the trash into treasure. A series of experiments and simulation of commonnes and individualities of the regenerated fuel from waste lubricating oil were conducted, including the physical-chemical properties, the characteristics of spray and combustion and soot formation emission of the regenerated fuel.The chemical composition, trace elements and friction characteristics of were measured by using the gas chromatography mass spectrometry, inductively coupled plasma optical emission spectrometer and high-frequency reciprocating rig. The physical-chemical properties of regenerated fuel were measured. The results show that regenerated fuel consists of straight-chain alkanes and aromatics polycyclic aromatic hydrocarbons. The sulfur content among the trace elements is the highest, followed by calcium, natrium, silicon and rubidium. The lubrication performance of the regenerated fuel is better than that of diesel. The main physical-chemical parameters of the regenerated fuel are close to those of diesel, meeting the combustion requirements in diesel engines.From the point of chemical compositions of the regenerated fuel, the premixed laminar combustion and homogeneous charge compression ignition of n-dodecane were simulated using CHEMKIN software. The premixed laminar flame speed, laminar burning flux and adiabatic flame temperature were obtained by the PLFSC model. The results show that the premixed laminar flame speed and laminar burning flux reach the peak values at the equivalence ratio of1.1. The premixed laminar flame speed decrease with the increase of initial pressure, and they increase with the increase of initial temperature. The adiabatic flame temperature reaches the maximum value between the equivalence ratios of1and1.1. The adiabatic flame temperature and laminar burning flux increase with increasing initial pressure and temperature. The chain reactions due to some radicals, such OH, O and H, are the driving force of flame spread.In the ICE model, the elementary reactions which have important effect on n-dodecane, intermediates and products, were obtained by using sensitivity analysis and rate-of-production analysis. The reaction path analysis for combustion of n-dodecane at different crank angle was performed. This reveals the evolution of combustion reaction of n-dodecane. The simulated results show that the decomposition reactions are responsible for94.6%n-dodecane consumption. The H-abstraction reactions by CH3and OH are responsible for little n-dodecane consumption, yielding smaller molecules, such as alkenes, alkanes and alkyls. As temperature and pressure increase, the decomposition reactions are responsible for less n-dodecane consumption, and the H-abstraction reactions are responsible for more n-dodecane consumption.In an atmospheric environment, the flame temperature was measured in the alcohol lamp fuelled with the regenerated fuel and diesel. The flame area of the regenerated fuel is smaller than that of diesel, but the flame temperature is higher than that of diesel. The outside flame of the regenerated fuel showed obvious yellow. The thermo-gravimetric technology was applied to study thermo-gravimetric characteristics of the two fuels and soot from them. The thermal stability of the regenerated fuel is superior than that of diesel does. The10%light-off temperature of soot from the regenerated fuel is higher than that of soot from diesel. The50%light-off temperature of soot from them is similar. Thermo-gravimetric thermal kinetics characteristics were calculated by Coats-Redfern method. The result shows that the activation energy of the regenerated fuel is larger than that of diesel.The commbustion test of186F diesel engine of fuelled with the regenerated fuel and diesel was carried out. The results show that the regenerated fuel can obtain higher peaks of in-cylinder pressure and heat release rate of diffusion combustion than diesel. The ignition time and combustion duration of the diesel engine of the regenerated fuel are almost the same as those of diesel. The distributions of the heat release rate have characters of a single peak at light loads, and dual peaks at moderate and heavy loads, regardless of the regenerated fuel or diesel. The spray and combustion models of the diesel engine fuelled with regenerated fuel were bulit by adjusting the constant of breakup model and customizing calorific value of the fuel, based on diesel in FIRE models. The indicator diagrams of the simulation and the experiment were compared to verify correctness of the simulation model. The characteristics of spray, mixture concentration, combustion and emissions of the diesel fuelled with diesel and regenerated fuel were simulated at rated condition. The simulation results show that spray penetration and spray cone angle of the regenerated fuel are basically similar to those of diesel. SMD of the regenerated fuel is greater than that of diesel, and the evaporated fuel is less than that of diesel. The equivalence ratio of the regenerated fuel is larger than that of diesel during fuel injection, but the area of rich regenerated fuel is greater that of rich diesel. The mixture of the regenerated fuel in quality is below that of diesel, resulting in lower premixed laminar flame speed of the regenerated fuel. The flame propagation start time of the regenerated fuel and diesel can be determined as the ignition timing. The higher calorific value and higher viscosity of the regenerated fuel are the main factors leading to higher NO and soot.The microstructures of soot of the regenerated fuel and diesel and were investigated by means of synchrotron small-angle X-ray scattering (SAXS). The soot microstructure information were obtained including size distribution, rotation radius, surface and interface character, and fractal by virtue of fitting the scattering intensity distribution curve base on SAXA theory. The results show that soot of the regenerated fuel has larger scattering intensity and size than that of diesel. Compared with that of diesel, the structure of soot particles of the regenerated fuel is looser and the surface of soot particles of the regenerated fuel is coarser. The Porod plots of soot of two fuels show a positive deviation, suggesting the existence of microstructure fluctuations. The study suggests that the sphere structure of soot particles the regenerated fuel is similar to that of diesel. However, the agglomeration of soot particles of the regenerated fuel strengthened and arranged more closely than that of diesel.The fuel economy and emissions of the single cylinder diesel engine fuelled with the regenerated fuel and diesel was carried out. Compared with diesel, the regenerated fuel has lower brake specific fuel consumption, higher CO emission, more NOx and HC emission at higher speeds and lightly higher soot emission at moderate loads.