Measurement of the Liquid Mass in a Diesel Spray Using Visible Light Imaging

Briggs, T. E. J. Measurement of the Liquid Mass in a Diesel Spray Using Visible Light Imaging. University of Wisconsin-Madison, 2007.

A method for measuring the liquid mass of fuel in a diesel spray using a non-intrusive imaging technique has been developed. The spray is back-illuminated using two lasers with a spectral spacing of 44nm. The two light beams are separated and simultaneously imaged with a high-speed digital camera. The resulting images are normalized, and the ratio of the two images is used to determine the liquid mass of the fuel using Beer’s Law.

The results from this measurement technique are compared with complementary measurements obtained using an x-ray absorption measurement of the same spray conditions. The present results exhibit a high level of noise in the images, which leads to a factor of two uncertainty in the mass results. The comparisons display this, with the optical measurement recording twice the fuel mass as the x-ray measurement.

Further comparisons reveal that the liquid volume fraction of fuel within the spray is similarly measured using both techniques. The optical measurements also confirm that the spray is fully atomized within the first few millimeters of the jet. This result suggests that primary breakup within the spray is at or inside the injector orifice and does not occur downstream of the nozzle.