Abstract
It is known that the transonic resonance takes place, in divergent section of supersonic nozzle, similarly to the longitudinal acoustic resonance of a conical section with one end closed and the other end open. And the “conical section” is similar to the separation zone between shock wave and nozzle exit in divergent part of supersonic nozzle. The present paper describes an experimental work to investigate a reduction of transonic resonance by change the lip length of 2-Dimensional converging-diverging nozzle. In this study, the nozzle pressure ratio varied in the range between 1.4 and 2.2 as shock-containing flow conditions. And a Schlieren optical system was used to visualize the flow fields. Especially, by using a high-speed video camera, we obtained the shock position at that moment. And acoustic measurements were employed to compare the sound spectra level of each experimental case. And it was found that the transonic resonance was decreased when a large separation zone located at the side, where a nozzle-lip attached to nozzle exit additionally. In this case, the amplitude of shock oscillation and wall static pressure oscillation were also decreased.
Highlights
Supersonic jet noise is frequently encountered in many diverse engineering applications such as supersonic aircraft engine, jet propulsion thrust vectoring, fuel injection for supersonic combustion, soot blower devices, thermal spray devices, etc
It is known that the transonic resonance takes place, in divergent section of supersonic nozzle, to the longitudinal acoustic resonance of a conical section with one end closed and the other end open
It is called “transonic tone” or “transonic resonance”. It is poorly known under what process the transonic tone can occur and how to reduce the transonic resonance in actual flow complicated by shock oscillation and shock wave/boundary layer interaction phenomenon
Summary
Supersonic jet noise is frequently encountered in many diverse engineering applications such as supersonic aircraft engine, jet propulsion thrust vectoring, fuel injection for supersonic combustion, soot blower devices, thermal spray devices, etc. Zaman et al investigated the characteristics of the transonic tone in various nozzle conditions [2], and provided correlation equations to predict the transonic tone frequency from a collection of data for single round nozzles. They showed that transonic tone takes place to the (no-flow) longitudinal acoustic resonance of a conical section with one end closed and the other end open. It is called “transonic tone” or “transonic resonance”. It takes account of nozzle-lip length and the location of large separation zone in parallel
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