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In the past we developed an injection-rate detector, however, it becomes no more applicable to modern high-pressure piezoelectric injection systems having functions of multi-stage injection due to the following problems: High-pressure injection generates shockwaves that induce pressure fluctuation, whose amplitudes of high-frequency components could be not effectively attenuated with a low-pass filter, in the detector. High-pressure injection also causes heterogeneous distribution of temperature in the detector, because the pattern of fuel flow from the injection nozzle to the discharge valve at fuel-discharging process is inappropriate. Accordingly, fuel temperature, which is necessary for identifying bulk modulus of fuel, in the detector could not be precisely obtained, thereby causing an unacceptable level of scattering for determining injection quantity. Hence, we developed a new detector in modifying its constructive design to solve the problems.

For a better understanding of soot formation and oxidation processes in conventional diesel and biodiesel spray flames, the morphology, microstructure and sizes of soot particles directly sampled in spray flames fuelled with US#2 diesel and soy-methyl ester were investigated using transmission electron microscopy (TEM). The soot samples were taken at 50mm from the injector nozzle, which corresponds to the peak soot location in the spray flames. The spray flames were generated in a constant-volume combustion chamber under a diesel-like high pressure and high temperature condition (6.7MPa, 1000K). Direct sampling permits a more direct assessment of soot as it is formed and oxidized in the flame, as opposed to exhaust PM measurements. Density of sampled soot particles, diameter of primary particles, size (gyration radius) and compactness (fractal dimension) of soot aggregates were analyzed and compared. No analysis of the soot micro-structure was made.

For better understanding of soot formation and oxidation processes in a diesel spray flame, morphology, microstructure and size of soot particles directly sampled at different locations in the spray flame (40mm to 90mm from injector nozzle tip) were investigated using a high-resolution transmission electron microscope (HRTEM). The diesel spray flame was achieved in a constant volume combustion chamber under diesel-like conditions (2.5MPa and 940K). The concentration, diameter of primary particles and the radius of gyration of soot aggregates increased in the upstream region (40 to 50mm), exhibited a peak around the mid-stream region (60 to 70mm), and then decreased in the downstream region (80 to 90mm) from the injector nozzle tip, which corresponds to formation, peak concentration and oxidation of soot particles in the spray flame, respectively.

In order for better understanding of soot formation and oxidation processes in diesel spray flame, the morphology, microstructure and sizes of soot particles directly sampled in a transient spray flame were analyzed via high-resolution transmission electron microscopy (HRTEM). The soot distribution in the spray flame was simultaneously observed by high-speed shadowgraphy. The transient spray combustion was achieved in a constant volume combustion chamber under a high pressure and high temperature condition (940 K, 2.5 MPa). The soot samples were taken at different axial locations in the spray flame, 40 - 90 mm from the injector nozzle, using an intrusive soot sampler. Pressure histories, heat release rates and laser shadowgraphs of spray combustion were compared between the cases with and without the soot sampler in order to check the intrusion effect of soot sampler on combustion.

For better understanding of soot formation and oxidation processes in a biodiesel spray flame, the morphology, microstructure and sizes of soot particles directly sampled in a spray flame fuelled with soy-methyl ester were investigated using transmission electron microscopy (TEM). The soot samples were taken at different axial locations in the spray flame, 40, 50 and 70 mm from injector nozzle, which correspond to soot formation, peak, and oxidation zones, respectively. The biodiesel spray flame was generated in a constant-volume combustion chamber under a diesel-like high pressure and temperature condition (6.7 MPa, 1000K). Density, diameter of primary particles and radius of gyration of soot aggregates reached a peak at 50 mm from the injector nozzle and was lower or smaller in the formation or oxidation zones of the spray.