Flow coupling effects in jet-in-crossflow flowfields

The combustor designer is typically required to design liner orifices that effectively mix airjets with crossflow effluent. Computational fluid dynamics (CFD) combustor analysis is typically used in the design process; however, the jets are usually assumed to enter the combustor with a uniform velocity and turbulence profile. The jet-mainstream flow coupling is usually neglected because of the computational expense. This study was performed to understand the effect of jet and mainstream how coupling, and to investigate jet boundary conditions that are commonly used in combustor internal calculations. A case representative of a plenum-fed quick-mix section of a rich burn/quick mix/lean burn combustor, i.e,, a jet to mainstream mass-how ratio of about 3 and a jet to mainstream momentum-flux ratio of about 30, was investigated. This case showed that the jet velocity entering the combustor nas very nonuniform, with a low normal velocity at the leading edge of the orifice and a high normal velocity at the trailing edge of the orifice, Three different combustor-only cases were analyzed, each with a uniform inlet jet profile. None of the cases matched the plenum-fed calculations. To assess liner thickness effects, a thin-walled case was also analyzed. The CFD analysis shelved the thin-walled jets had more penetration than the thick-walled jets.