| 摘要 |
To suppress jet noise emanating from a ducted-fan turbojet engine, an improved exhaust mixer assembly is disclosed that is mounted between the engine and the exhaust nozzle and that mixes the flow of high-velocity primary gases (turbine exhaust) with the lower-velocity air from the fan duct in a manner that achieves a significant reduction in the proportion of noise-causing high velocity gases while maintaining approximately the same thrust from the nozzle as other mixer-equipped engines. The mixer assembly includes an annular sleeve, a bulb-shaped plug disposed concentrically within the sleeve, and an annular corregugated mixer duct coaxially positioned between the plug and sleeve wherein these components are arranged so as to receive the primary and fan flows and separately redirect these flows within the assembly so that the flow of primary gases is rearwardly divergent while the flow of fan air is rearwardly convergent. As the primary and fan flows pass through a mixing plane at the aft terminus of the mixer duct, they intersect in a crossing pattern resulting from their divergent-convergent flow paths which yields faster and more complete mixing of the flows before they are discharged from the nozzle. The shaping and dimensioning of the sleeve, plug, and mixer duct are such that optimum mixing, and thus maximum suppression of noise, are achieved without introducing any excessive pressure losses in the mixer assembly and nozzle that otherwise would significantly diminish thrust. |
