Quantification of the evaporative cooling in an ethanol spray created by a gasoline direct-injection system measured by multiline NO-LIF gas-temperature imaging

Two-dimensional gas-phase temperature fields were quantitatively measured in an evaporating ethanol spray with multiline excitation thermometry based on laser-induced fluorescence of nitric oxide (NO-LIF). This technique yields absolute temperature fields without calibration and simultaneously detects the spray position. The accuracy of the presented temperature measurements is ±1 K. Systematic errors of the scanned multiline thermometry approach due to time averaging in turbulent systems were investigated and found to be negligible. The pulsed spray was generated by a gasoline direct-injection nozzle with swirl injecting ethanol into air in a flow cell at room temperature and atmospheric pressure. The gas temperature inside the spray cloud was found to decrease by 10 K at ~5-10 ms after injection. Different injection pressures influence the evaporation behavior.