Published 18 issues per year
ISSN Print: 1064-2285
ISSN Online: 2162-6561
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A Modified Thermal Mixing Efficiency and its Application to Lobed Mixer Nozzle for Aero-Engines
ABSTRACT
A newly modified thermal mixing efficiency, based on the definition suggested by T. H. Frost, is proposed for a lobed mixing exhaust system, using the principles of conservation of energy, variance concept, and dimensionless analysis. Then, the modified thermal mixing efficiency is applied to two cases of the lobed mixer nozzles with different lobe shapes and boundary conditions, and the results are compared with the ones calculated by the original thermal mixing efficiency. According to the analysis, the mixing process of the lobed mixer nozzle described by the original thermal mixing efficiency is not consistent with the laws of physics. However, the modified thermal mixing efficiency formula can correctly describe the mixing process between the core and fan flows in the lobed mixer nozzle. In addition, the relationship for mixing between the core and fan flows and the ratio of the lobe height to the lobe width are investigated and the conclusion is drawn in this paper. When the core and fan flow area at the lobe exit respectively remains the same as the corresponding one at the nozzle inlet, the modified thermal mixing efficiency at the nozzle exit experiences a process of increase, declination, and augmentation, as h/blobe increases. When the lobe width is constant, the modified thermal mixing efficiency at the nozzle exit is proportional to h/blobe.
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