Search

This work reports the results of X-ray μ -tomographic investigation on the inner structure of high pressure fuel sprays. X-ray imaging is widely used in industry where non-destructive and high accuracy measurements of the samples morphology are required. A high flux beam can overcome the problems related to the low absorption of hydrocarbon chains as fossil fuels, therefore synchrotron X-ray sources are generally used for fuel sprays investigation. A desktop facility has successfully been used to characterize high pressure gasoline sprays for automotive applications. A X-ray tube coupled with polycapillary optics has been used providing a high flux beam with low divergence. In this paper the last improvements concerning quantitative measurements carried out on fuel sprays are reported. [ABSTRACT FROM AUTHOR]

The effect of n-butanol on the combustion process in a DISI engine was investigated through in-cylinder pressure measurements and optical data. An optical engine was equipped with a commercial head and with high pressure wall guided injection system. 2000 rpm engine speed was chosen as representative for mid-road load automotive use. Two partially open throttle conditions were tested. All trials were performed at close to stoichiometric air–fuel ratio. Optical diagnostics based on UV–visible imaging and natural emission spectroscopy were applied to study the combustion process from spark ignition to exhaust valve opening. A custom post-detection procedure applied to digital imaging data allowed evaluating the flame area. Results were correlated with volume fraction burned obtained through thermodynamic analysis. UV–visible spectroscopy was applied to investigate formation and evolution of the main chemical compounds characterizing spark ignition and combustion processes. Pollutant measurements (HC, CO, NO x , opacity) at undiluted exhaust, for gasoline and butanol, were correlated with pressure data and in-cylinder optical results. Overall engine operation was found to be similar for both energy sources, with the alternative fuel providing a slight improvement in performance compared to gasoline, for both loads; a significant reduction of NO x and soot was also obtained for alcohol fuelling. [ABSTRACT FROM AUTHOR]

A X-ray μ -tomography technique, using a Cu K α source at 8.048 keV coupled with both polycapillary optics and CCD detector, has been developed to reconstruct the composition of a transient gasoline spray generated by a high-pressure GDI injector for automotive applications. The polycapillary elements enable shaping the divergent beams and getting high-contrast images due to the suppression of radiation multiple scattering. A pressure-tight device permits the 360 ° rotation of a six-hole nozzle, with a step of 0.1 ° , at injection pressures up to 20 MPa, while the spray plume develops in a vented Plexiglas chamber at the atmospheric backpressure. The entire system is configured as a table-top experiment. The extinction images acquired along the X-ray source-spray-detector line-of-sight have permitted the reconstruction of a 3D structure together with a morphology of the jets within a 3 mm region downstream the nozzle. The spray shape as well as the propagation direction can be clearly identified in the tomographic reconstruction for all the six jets. Quantitative measurements of the fuel mass density in the near nozzle region have been performed. Typical Gaussian-shape distribution of the intensities appears for the cross sections revealing the more dense jet regions in the core, while slight longitudinal asymmetries indicate an interaction between the jet plumes. [ABSTRACT FROM AUTHOR]

Abstract: Based on the experience in the use of polycapillary optical systems, recently XLab Frascati LNF and IM CNR have been strongly involved in studying the techniques for high resolution X-ray Imaging and micro-tomography that intends in the development of a new imaging instrument to examine low contrast samples complicated by fast developing processes. In order to get the reliable signal to noise ratio, typically available via synchrotron radiation (SR) dedicated X-ray optical devices, for the desktop solutions we have to increase the radiation fluxes from conventional sources. As known, manipulated through polycapillary optics beams result in getting higher fluxes with respect to a pin-hole (with a gain factor of 102–103). Moreover, polycapillary semi lenses can provide low divergent beams comparable by the divergence with synchrotron radiation beams (mrad order). These features make possible the realization of high resolution imaging of low contrast samples in the transmission mode without various algorithmic processes as typically done, for instance, for phase contrast imaging. This work presents the results on X-ray micro tomography for both static biological and fast dynamic samples as well as a possible future development of a polycapillary-based experimental layout for biomedical imaging diagnostics, for the studies in material and environmental sciences, for diagnostics of hi-tech samples, etc. [Copyright &y& Elsevier]

Abstract: The use of alternative fuels, as biodiesel and ethanol, for light duty CI engines to approach the target of ultra low NO x and PM emissions without fuel economy penalty has been widely investigated. Recently, it is growing the interest in the butanol as a viable alternative either single or blended with conventional based fuels both to cut the demand for fossil fuel and to reduce emissions of particulate matter without significantly increasing in NO x . In this paper, butanol effects on combustion process were investigated through conventional methods and optical diagnostics. First, blends of 80% diesel and 20% n-butanol (BU20) were used in a four cylinder, turbocharged, water cooled, DI diesel engine, equipped with a common rail injection system. Management of timing and injection pressure was carried out to achieve conditions in which the almost total amount of fuel was delivered before auto-ignition. BU20 allowed to attain almost smokeless emissions at lower injection pressure (100 MPa) than diesel fuel (120 MPa). Smokeless conditions were achieved with a slight increase in NO x emissions (around 20%) and a minor penalty for the specific fuel consumption. Afterward, the blends effects on the combustion process were studied in the combustion chamber of a single cylinder compression ignition engine equipped with the same common rail multi-jets injection system. Spray combustion and pollutant formation were investigated by UV–visible digital imaging and natural emission spectroscopy. UV–visible emission spectroscopy was used for the detection of the chemical markers of combustion process. Chemiluminescence signals, due to OH, HCO and CO2 emission bands were detected. OH emission was correlated to NO x measured at the exhaust. The soot spectral feature in the visible wavelength range was related to the engine out soot emissions. [Copyright &y& Elsevier]