Quantitative measurements of fuel concentrations and evaporation ratios in direct-injection methanol-n-hexane blend sprays by LIBS
Abstract
Methanol is considered to be one of promising alternative fuels. For direct-injection (DI) methanol-gasoline fueled engines, the injection of fuels into the cylinder and the subsequent evaporation and mixing processes are of great significance. So far, quantitative measurements of fuel concentrations of both liquid and vapor phases in the evaporating spray of multi-component fuels are still difficult. In this study, a novel approach based on the laser induced breakdown spectroscopy (LIBS) is developed to quantitatively measure the fuel concentrations and evaporation ratio in DI methanol-gasoline blend sprays in a constant volume vessel. Three atomic lines of H656, N746 and O777 are employed to quantify the concentrations of methanol and n-hexane. The calibrations between two peak intensity ratios and corresponding atom number ratios are established for four kinds of blend fuels (M0, M15, M50, M100). The results show a good consistency of calibration curves for different fuels, suggesting that LIBS is independent of molecular species and capable of measurements of multi-component fuels. For the measurements of evaporation ratio, the LIBS and high-speed droplet microphotography were simultaneously conducted in the droplet flow environment to determine the intensity of C2 band and liquid fuel concentration, respectively. The high fuel-specific correlations are confirmed. The estimated measurement uncertainties of total fuel concentration are <6%, and the measurement uncertainties of evaporation ratio are reduced with the increase of the radial distance. Finally, the component concentration and evaporation ratio in sprays of methanol-n-hexane are quantitatively measured, and then the evaporation processes as well as mixing characteristics of different blend sprays are compared and analyzed. The results are valuable for building the relevant numerical models and developing the combustion systems of engines fueled with methanol-gasoline blend fuels.
- Publication:
-
Spectrochimica Acta - Part B: Atomic Spectroscopy
- Pub Date:
- March 2023
- DOI:
- 10.1016/j.sab.2023.106615
- Bibcode:
- 2023AcSpB.20106615Z
- Keywords:
-
- LIBS;
- Methanol-gasoline blends;
- Fuel concentration;
- Evaporation ratio;
- Quantitative measurements