1-Methylnaphthalene tracer planar laser-induced fluorescence thermometry study of thermal mixing and scalar statistics of jet in swirling crossflow under ambient and elevated pressure

The thermal mixing between jet and swirling crossflow is widely used in modern aero-engine and gas turbine combustors to achieve a favorable temperature distribution in the combustor outlet plane. Although practical combustors are usually operated under elevated pressure conditions, the pressure effect on thermal mixing has not been widely investigated. The present study utilized 1-methylnaphthalene single-shot dual-imaging planar laser-induced fluorescence thermometry to quantitatively measure the temperature distribution under normal (0.1 MPa, Re_j = 30 866) and elevated (0.3 MPa, Re_j = 92 070) pressure conditions within a three-dome optically accessible model combustor. A deeper penetration, a shorter deflection, and a quicker temperature evolution (indicating accelerated scalar dissipation) were observed for the 0.3 MPa condition. Through the analysis of statistical parameters including standard deviation, skewness, and excess kurtosis, a more efficient mixing region located on the windward side of the jet in swirling crossflow (JISCF) was discovered. Moreover, the regressed linear correlation between the measured skewness and the excess kurtosis achieved good agreement with literature values. In addition, the distribution of the temperature probability density function (PDF) for the current jet in swirling crossflow can be well described by the exact selection of the function form (Gaussian-based kernel density estimation or beta function), keeping the relative error of f²-property within 2%. The above analysis of statistical parameters and PDF can provide deeper insights into JISCF in aero-engine combustors, as well as a valuable reference for the combustor-relevant numerical models.