THE EFFECTS OF AIR-ASSIST UPON LIQUID FUEL JET PENETRATION AND DISPERSION IN A CROSS-FLOWOF PREHEATED AIR

摘要

Modern gas turbines employ fuel-air mixers that utilize jet-in-cross-flow (JICF) fuel injection to achieve rapid fuel-air mixing. In recent years, air-assist JICF has been investigated to improve the atomization and fuel dispersion qualities provided by JICF. This article reports the results of an experimental investigation where liquid Jet-A was injected into a cross-flow at temperatures and pressures of 316 degrees-427 degrees C and 2.02-2.53 MPa, respectively, while four streams of assist air, supplied from slots in a well, impinged on the fuel jet. The effects of air-assist and fuel-to-cross-flow momentum ratio (J) upon the fuel jet's outer-edge trajectories and wake-region dispersion patterns were investigated using two shadowgraph approaches that used (1) 511 nm visible light at 21 kHz pulse rate and (2) 266/532 nm UV/visible light for multiphase detection. In the experiments, J was varied between 15 and 130, while the air-assist flow rates were varied by changing the percentage pressure drop (dP) between the assist-air supply line and the cross-flow air between 0% and 5%, corresponding to 0%-25% of fuel mass flow rate when J = 15. The measured data were used to develop correlations for the air-assist JICF's outer-edge trajectories, using an effective momentum ratio (J(eff)) that accounts for the effects of air-assist. It was observed that while air-assist had minor effects upon the spray's outer-edge trajectories, it significantly affected fuel dispersion within the spray's wake. At higher temperatures and pressures, the outer-edge trajectories were more sensitive to air-assist. Notably, there were no significant differences between the outer-edge trajectories obtained via UV and visible light shadowgraphs, indicating that the outer-edge regions of the spray largely consisted of liquid. In contrast, similar comparisons suggested high concentrations of gaseous fuel in the wake, especially at higher temperatures and pressures.