Lanbo Song

In this study, the spray and atomization characteristics of neat biodiesel, ethanol-biodiesel blends (BDEs), and neat diesel in a high-pressure common-rail injection system were investigated experimentally and analytically. Schlieren-type high-speed photography was utilized to capture the experimental images. The findings indicated that spray penetration and peak tip velocity decreased and the spray cone angle increased with increase in the ratio of ethanol in the blends. Two predictive models were used to generate data to compare with measurements of spray penetration and peak tip velocity. The empirical formula of equivalence ratio, Ohnesorge number, and Sauter mean diameter (SMD) were calculated to evaluate atomization levels.

This study was conducted to investigate the spray characteristics of n-butanol, using a diesel spray for comparison. Spray tip penetration and spray cone angle were tested and analyzed. A high-speed photographic system was employed to observe the spray evolution, and a common-rail system and constant-volume chamber were used to change the pressure. The results show that the n-butanol spray penetrates faster than the diesel spray while under the same conditions. The experimental trend lines support the axial development model constructed by Hiroyasu and Arai on the grounds of a similar proportional relation to time after the start of injection, and the empirical equations provide reasonable approximations to the experimental measurements of the spray tip penetration.

This article explores the effects of SiO2/Al2O3 ratios (S/A) on sintering characteristics and provides guidance for alleviating ash depositions in a large-scale circulation fluidized bed. Five synthetic coal ash (SCA) samples with different S/As were treated in a muffle furnace for 12 h at different temperatures (from 773 K to 1373 K, in 100 K intervals). The morphological and chemical results of the volume shrinkage ratio (VSR), thermal deformation analysis by dilatometer (DIL), scanning electron microscope (SEM), X-ray photoelectron spectrometer (XPS), and X-ray diffraction (XRD) were combined to describe the sintering characteristics of different samples. The results showed that the sintering procedure mainly occurred in the third sintering stage when the temperature was over 1273 K, accompanied with significant decreases in the VSR curve. Excess SiO2 (S/A = 4.5) resulted in a porous structure while excess Al2O3 (S/A = 0.5) brought out large aggregations. The other three samples (S/A = 1.5, 2.5, 3.5) are made up of an amorphous compacted structure and are composed of low fusion temperature materials (e.g., augite and wadsleysite.). Sintering temperatures first dramatically decrease to a low level and then gradually rise to a high level as S/A increases, suggesting that Al2O3-enriched additives are more effective than SiO2enriched additives in alleviating depositions.

The objective of this study was to investigate the macroscopic spray characteristics of different 0%–100% blends of biodiesel derived from drainage oil and diesel (BD0, BD20, BD50, BD80, BD100), such as spray tip penetration, average tip velocity at penetration, spray angle, average spray angle, spray evolution process, spray area and spray volume under different injection pressures (60, 70, 80, 90, 100 MPa) and ambient pressures (0.1, 0.3, 0.5, 0.7, 0.9 MPa) using a common rail system equipped with a constant volume chamber. The characteristic data was extracted from spray images grabbed by a high speed visualization system. The results showed that the ambient pressure and injection pressure had significant effects on the spray characteristics. As the ambient pressure increased, the spray angle increased, while the spray tip penetration and the peak of average tip velocity decreased. As the injection pressure increased, the spray tip penetration, spray angle, spray area and spray volume increased. The increasing blend ratio of biodiesel brought about a shorter spray tip penetration and a smaller spray angle compared with those of diesel. This is due to the comparatively higher viscosity and surface tension of biodiesel, which enhanced the friction effect between fuel and the injector nozzle surface and inhibited the breakup of the liquid jet.