A Study on Broad Band Noise Emitted from Underexpanded Radial Jet ()
ABSTRACT
This study focuses on a noise emitted from a radial underexpanded jet. The
underexpanded jet is well known as one of supersonic jets and it is formed
when the pressure ratio across a convergent nozzle is more than the critical
value. The underexpanded jet has been used in many fields, such a propulsion
of rocket, laser cutting and a glass tempering process. Such jet is exhausted
from a circular nozzle. The expansion wave, the compression wave and the
shock wave are periodically formed in the jet, which leads to quasi-periodical
shock-cell structure. On the other hand, an underexpanded jet radially issues
from intake and exhaust valves of an internal combustion engine and a pressure
control valve. The radial underexpanded jet does not have the quasi-
periodical shock-cell structure such as the jet from the circular nozzle, its
cell length decreasing along jet axis. In this study, an underexpanded jet radially
discharged from a circular slit nozzle, which consists of two circular
tubes, is experimentally examined for different nozzle pressure ratios. The jet
structure is visualized using Schlieren method and a noise emitted from the
jet is measured. Typically, the shock associated broadband noise is analyzed
and a relation between the jet structure and the radiation noise frequency is
discussed. As a result, it is found that the broadband noise lies on lower frequency
than a screech tone and that the 1st cell length plays an important role
in broadband noise radiation.
Share and Cite:
Hiramoto, Y. , Suzuki, H. , Endo, M. and Sakakibara, Y. (2019) A Study on Broad Band Noise Emitted from Underexpanded Radial Jet.
Open Journal of Fluid Dynamics,
9, 72-81. doi:
10.4236/ojfd.2019.91005.