Laser-based measurements of surface cooling following fuel spray impingement

Paper #:
  • 2018-01-0273

  • 2018-04-03
In the following years, more stringent emission constraints for gasoline direct injection engines, in particular regarding particulate matter emissions, are to be expected. A major source for soot particle formation in these engines are fuel-rich zones near walls as a result of wall wetting during injection. In order to avoid or minimize this effect, a thorough understanding of the wall film formation and evaporation processes is necessary. The wall temperature before, during and after the film formation is an important parameter in this respect, but is not easily measured using conventional methods. In this work, we demonstrate the use of a laser-based, spatially and temporally resolved method for planar surface temperature measurements, which is not affected by the fuel film present on the wall. For the measurements, the wall is coated with a chemical binder containing thermographic phosphor particles. Following UV excitation, these particles emit luminescence with a temperature-dependent spectrum. The luminescence is captured by two cameras, equipped with different spectral filters and the ratio of the camera intensities is - after calibration - used for surface thermometry. For the investigations, the wall is homogeneously heated to a set temperature. UV-grade n-Hexane is injected using a current DI solenoid driven multi-hole injector. The surface temperature distribution is measured at different times before and after spray impingement. High spatial (pixel-to-pixel) and shot-to-shot temperature precision of 0.5 K and 0.6 K respectively, for a temperature range of 300 K to 400 K without noticeable interference from the liquid film were achieved. Following this demonstration, the technique is used to investigate the influence of the rail pressure and injection duration on the spray-induced cooling of the wall.
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