Aerospace Propulsion Laboratory

Professor Nobuhiko YAMASAKI
Department of Aeronautics and Astronautics, Kyushu University

Missions

Education and research on aerospace propulsion systems such as aircraft gas turbine engines.

Education

Graduate School

Undergraduate School

Recent Research Themes

Flutter Analysis based on Linear Unsteady Theories

Cascade flutters for subsonic to supersonic relative flows are analyzed. The governing Euler or Navier-Stokes equations are linearlized and unsteady equations are solved in the frequency domain, to shorten the time required for aero-engine design. Developping robust and fast code and its validations are main objectives of this study.
Numerical Predictions of Fan Tone and Broadband Noises

On the subject of fan tone noise, the effects of lean and sweep of stator vanes are investigated by using the compressible unsteady RANS. With respect to the fan broadband noise, turbulent noise sources are studied by investigating the spatial distribution of the turbulent kinetic energy.

The figure shows an instantaneous pressure field caused by rotor-stator interaction. These pressure fields are passed to duct-acoustics code (linear theory) to predict sound propagation/attenuation of spinning modes.
Active and Passive Controls for Fan Tone Noise

The tone noise is actively suppressed by sound generated by loudspeakers mounted on the fan duct, or passively suppressed by sound absorbing liners on the fan duct walls. Developping active control algorithms and/or efficient passive liners are main objectives of this research.

The picture shows the fan model with a wake-generator upstream of the fan and 12 loudspeakers mounted on the duct wall.
Numerical Simulations on the Flow and Noise of a Automobile Turbocharger

The effects of mis-tuning due to manufacturing errors on the sound fields, the effects of duct curvature on the compression efficiency, and so on, are investigated by using a compressible unsteady RANS code.

The figure shows a pressure fields on the compressor rotor blades and streamlines of the flow in the volute. The color of the streamlines also indicates the pressure.
Rig Tests on the Flow and Noise of a Automobile Turbocharger

In automobile turbocharger sudden decelerator operation sometimes causes flow instability called surge. A test rig is newly made to study this transient phenomena and to find effective ways to avoid the surge. Also, noise characteristics will be measured in the near future.

The picture is a close view of the test rig. Compressed air with a 5kW electric heater is used to drive the turbine.
Numerical Prediction of Jet Noises

Compressible NS equations are solved by the compact finite difference schemes for several kinds of nozzle shapes, to study the mechanisms of jet noise generation and to find effective ways of suppressing the jet noise. The farfield acoustics are estimated by the Ffowcs Williams-Hawkings method.

In the figure, instantaneous flowfields are visualized as iso-surfaces of the second-invariant of velocity gradient tensor (gray scale) and dilatation field contours (multi-colors).
Jet Noise Suppressions Using Tab-Like Passive Control Devices

Noise spectrum and thrust are measured with various passive control devices, including tabs, chevrons, etc.

The picture shows an experimental rig of a subsonic rectangular jet, with Mach number of 0.8. Three microphones are placed with the angles of 30, 60, and 90 degrees from the jet axis in the anechoic chamber.
Large Eddy Simulations of Turbulent Non-Premixed Jet Flames

Turbulent combustion fields are modeled by the laminar flamelet model. Flowfileds are solved by an incompressible LES code that refers the flamelet database.

The figure shows instantaneous temperature field of a methane/air turbulent non-premixed flame (DLR-A flame).
Active Control of Combustion Instabilities

A model burner is used to artificially generate combustion oscillations and then the oscillations are suppressed by sound waves from a loudspeaker.

The picture shows the methane-air premixed burner model, equipped with 4 quartz glasses for observation. A microphone is mounted above the quartz glass and is water-cooled.

Past Studies

Please refer to our previous web page.

Members

Contacts

Aerospace Propulsion Laboratory
Department of Aeronautics and Astronautics, Kyushu University
#805 West Zone Building 4, 744 Motooka, Nishi-ku, Fukuoka 819-0395, JAPAN
E-mail: apl-webmaster @ aero.kyushu-u.ac.jp (Please remove white space before and after @ mark.)

Access to the Ito campus.