Purpose of this study is to demonstrate the new application for obtaining the detail information about the secondary atomization processes of a burning emulsion droplet. Secondary atomization was caused by vigorous boiling of superheated water during the fuel droplet burning. The AE (i.e. acoustic emission) measurement, which is commonly used for measuring the fracture processes in the materials, was newly applied to measure the occurrence of bubble phenomena in a burning droplet. n-Hexadecane in water emulsion droplet, which was suspended at the tip of a quartz filament, was burned in a quiescent air environment. The filament was mounted at the center of cylindrical block. AE sensor was mounted on the opposite side of the block. The AE signals of the internal bubble phenomena was successfully measured thorough the quartz filament as an acoustic probe. It is observed that the internal boiling of emulsified water occurs prior to the occurrence of micro-explosion. It is concluded that the distribution function of the waiting time for the onset of micro-explosion and internal boiling are correlated to the Weibull distribution, classified to the wear-out type. It is also concluded that intensity distribution of disruptive events of micro-explosion or internal boiling is successfully evaluated relatively using the AE measurement.
In this study, applicability of the gas fuel generated from wood biomass by thermal chemical processes to an homogenous charge compression ignition engine is investigated in experiment. In particular, the availability of inhomogeneity of both fuel concentration and temperature is evaluated to control the combustion against the variation of fuel composition. Inhomogeneity of premixture is varied by changing the ratio of fuel injected to two points, one far from the intake valve and another near the intake valve. In this system, both local fuel concentration and local temperature of premixture vary; the lower fuel concentration point has higher initial temperature. Two test fuels with difference in H2 concentration are used. The influence of the inhomogeneity on both ignition timing and combustion duration was found. Higher inhomogeneity retards ignition timing for its lower temperature and prolong combustion duration for its distributed combustion in the cylinder. Furthermore, the effect of inhomogeneity and the acceptable inhomogeneity depended on fuel composition. Higher H2 content fuel can use higher inhomogeneity and receive much favors for decreasing maximum in-cylinder gas pressure rising rate.
Three asphaltenes recovered from the vacuum residue of Middle East crude oil mixture (ME), the atmospheric residues of Minas crude oil (MI) and Cold lake oil sand bitumen (CL), were separated into 5 fractions (Fr1-Fr5) according to average molecular weight (Mn) and a fraction from effluent (Fr6) by preparative gel permeation chromatography (GPC), with >95 wt% of the total recovery. The original asphaltene and the fractions were analysed by elemental analysis, 1H-NMR and analytical GPC to obtain the input data for an average molecular structural analysis (H/C, N/C, S/C atomic ratios, and atomic ratios of hydrogen types). The dependencies of those parameters on Mn were represented using 1 or 2 linear fitting equations, respectively. Using the equations, the parameters were calculated followed by the estimation of carbon aromaticity (fa) from those parameters. An average molecular structural analysis was applied to Fr1-Fr5 fractions at several Mns to estimate the numbers of units (condensed aromatic ring systems) and aromatic rings per molecule (M and Ra). M was 1.0 at low Mn range, then increased with increasing Mn. Ra increased linearly with increasing Mn. The numbers of aromatic rings per unit (Ra/M) were about 8-10 at M=1.0 in every original asphaltene, and then increased up to 13-15 for ME and MI, but kept about 9 for CL. An average molecular structural analysis was also performed for every original asphaltene and Fr6 fraction. In the case of ME and MI, Ra/M for Fr6 was larger than that for original asphaltene, and MI had larger unit size than ME. On the other hand, Fr6 fractions for CL had almost the same Ra/M as original asphaltene, while Fr6 fraction contained more hetero atoms.