Scaling of oxygen-methane reacting coaxial jets using x-ray fluorescence to measure mixture fraction [electronic resource]

• Ngôn ngữ: eng
• Ký hiệu phân loại: 629.89 Computer control
• Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2021
• Mô tả vật lý: Size: p. 6365-6374 : , digital, PDF file.
• Bộ sưu tập: Metadata
• ID: 265705
• Chủ đề: 1. 33 advanced propulsion systems; 2. Injector scaling; 3. Liquid rocket engines; 4. Mixture fraction; 5. Reacting coaxial jets

Tóm tắt

 Stoichiometric mixing length L<
 sub>
 s<
 /sub>
  of reacting coaxial jet flames is a critical scaling parameter for liquid rocket engine combustors. Previous studies have shown that L<
 sub>
 s<
 /sub>
  for shear coaxial flames can be scaled like their non-reacting counterparts using a non-dimensional momentum flux ratio J. In addition, stoichiometric mixing lengths of reacting and nonreacting coaxial jets collapse upon a single line by altering J using an effective outer flow gas density. This effective density is calculated from a modified version of the equivalence principle, originally developed by Tacina and Dahm [1, 2] and accounts for the effects of heat release on mixing. However, previous studies also required a second nonphysical scaling constant S<
 sub>
 c<
 /sub>
  for the reacting jets, which is not predicted by the equivalence principle [3]. It was originally hypothesized that S<
 sub>
 c<
 /sub>
  is attributed to the limitation of hydroxyl (OH) planar laser-induced fluorescence, which only infers L<
 sub>
 s<
 /sub>
 . Direct quantitative measurement of conserved scalar fields using conventional optical diagnostics is difficult due to the lack of a tracer that easily fluoresces, survives high temperature oxygen flames, and is not dominated by quenching effects. To measure a conserved scalar field, this work implements x-ray fluorescence of Kr and Ar tracers to obtain quantitative mixture fraction fields. From these mixture fraction fields, stoichiometric mixing lengths for two CH<
 sub>
 4<
 /sub>
 /O<
 sub>
 2<
 /sub>
  flames are calculated and scaled against nonreacting coaxial mixing lengths using the equivalence principle. By directly measuring the stoichiometric mixing length, it is established that the additional constant is a byproduct of the OH measurement technique and the equivalence principle fully captures the scaling. Finally, comparison with high-fidelity simulation of the flame further supports this conclusion. In addition to further strengthening this scaling method, this work represents the first use of x-ray fluorescence to make quantitative conserved scalar measurements in turbulent flames.