High-spatial-resolution characterization of underexpanded hydrogen jets using spontaneous Raman scattering
Speaker
Quinn Kuijpers
About this event
The hydrogen jet lies at the foundation of H2 internal combustion engine (ICE) technology, which is why investigation of its characteristics is necessary to advance the implementation and improve the H2 ICE. In this work, spontaneous Raman scattering is used to investigate the temperature, hydrogen number density, and hydrogen mole fraction of a continuous hydrogen jet emanating into atmospheric air. Both vibrational and rotational Raman scattering methods are used to investigate the temperature field of the jet with high spatial resolution, using a spatial sampling interval of 0.1 mm in the axial direction and 0.06 mm in the radial direction. Three different pressure ratios and two different nozzle orifice diameters are studied. Schlieren imaging identifies shock structures within the jet and supports the interpretation of the Raman measurements. The jet is characterized by repetitions of low-to-high-temperature zones in the center of the jet, with increasing temperature at the edges of the jet. The hydrogen number density follows the main temperature structure of the jet, while the hydrogen mole fraction is close to one in the center of the jet, decreasing toward the jet boundary and further downstream due to mixing with the entrained air. Rotational and vibrational Raman measurements show similar overall temperature structures and values. The pressure ratio (nPr) affects both the temperature distribution and size of the jet. The temperature decreases by approximately 50–70 K between nPr = 3 and nPr = 8, while the size of the jet structures increases for nPr = 8. The nozzle diameter mainly affects the spatial dimensions of the jet and its shock structures. A comparison between nozzles shows similar quantitative temperatures along the jet axis, with the only appreciable temperature differences between the nozzles being a 10 K higher minimum temperature for the bigger nozzle size at nPr = 3.
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