Noise Characteristics of a Reduced Blade Count Rotor with Improved Stage Efficiency

2019 ◽  
Author(s):  
Rainer Schädler ◽  
◽  
Dominic Hänni ◽  
Anestis Kalfas ◽  
Reza Abhari ◽  
...  
Keyword(s):  
Noise Characteristics ◽  
Stage Efficiency

scholarly journals Noise characteristics of a reduced blade count rotor with improved stage efficiency

2019 ◽  
Vol 3 ◽  
pp. 653-667
Author(s):  
Rainer Schädler ◽  
Dominic Hänni ◽  
Anestis Kalfas ◽  
Reza Abhari ◽  
Gregor Schmid ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Noise Level ◽  
Gas Turbines ◽  
Rotor Blade ◽  
Flow Structures ◽  
Strong Increase ◽  
Tonal Noise ◽  
Noise Characteristics ◽  
Stage Efficiency ◽  
Probe Measurements

A reduction in rotor blade count in combination with a gain in aerodynamic performance is a desirable design goal for gas turbines to reduce the overall operational costs. Reducing the number of blades provokes inherently an increase in blade loading which drives the secondary flow strength. In the presented experimental work, the results of inter-stage probe measurements in a highly loaded 1.5-stage axial turbine rig show the potential to improve the stage efficiency for a reduced blade count rotor with respect to a baseline configuration with more blades. Time-resolved probe measurements reveal the detrimental effects on the turbine tonal noise level. It is found that the periodic vorticity fluctuations induced by the interaction of the rotor passage secondary flow structures with the potential field of the downstream stator, leads at specific span positions to a strong increase in the noise level at rotor exit with respect to the baseline. Both, the downstream effect of the convected rotor flow structures as well as the periodic interaction of the second stator originated flow structures are found to drive the acoustic field of the turbine. Overall, the stage efficiency benefit achievement of 0.4% for a 22% reduction in rotor blade count is derogated by an increase in tonal noise by up to 13 dB at the second stator exit.

Noise Characteristics and Thermal Decay in Single-layer Perpendicular Recording Media

1998 ◽  
Vol 22 (S_3_PMRS_98) ◽  
pp. S3_5-8
Author(s):  
Y. Hirayama ◽  
Y. Honda ◽  
K. Ito ◽  
T. Takeuchi ◽  
M. Futamoto
Keyword(s):  
Single Layer ◽  
Recording Media ◽  
Thermal Decay ◽  
Perpendicular Recording ◽  
Noise Characteristics

Gas Discharge Noise Characteristics of the Silent Discharge Type NOx Cleaning Systems

1995 ◽  
Vol 115 (2) ◽  
pp. 99-106
Author(s):  
Keiichi Uchimura ◽  
Michiharu Shoji ◽  
Tairo Itho ◽  
Jen-Shih Chang
Keyword(s):  
Gas Discharge ◽  
Silent Discharge ◽  
Noise Characteristics ◽  
Discharge Noise

A new magnetic resonance head coil and head immobilization device for gamma knife radiosurgery: an analysis of geometric distortion and signal/noise characteristics

2002 ◽  
Vol 97 ◽  
pp. 563-568 ◽  
Author(s):  
Paul Jursinic ◽  
Robert Prost ◽  
Christopher Schultz
Keyword(s):  
Magnetic Resonance ◽  
Gamma Knife Radiosurgery ◽  
Geometric Distortion ◽  
Gradient Field ◽  
Main Magnetic Field ◽  
Content Type ◽  
Signal Noise ◽  
Noise Characteristics ◽  
Head Coil ◽  
Fine Print

Object. The authors report on a new head coil into which the Leksell aluminum localization frame can be easily and securely mounted. Mechanically, the head coil interferes little with the patient. Methods. The head coil, which is for magnetic resonance (MR) imaging, is a 12-element quadrature transmitand-receive high-pass birdcage coil with a nominal operation frequency (63.86 MHz). The coil was built into a plastic housing. This new head coil minimizes patient motion and provides a 20% increase in signal/noise ratios compared with standard head coils. An MR image test phantom was mounted in the coil and this allowed quantification of image distortion due to inhomogeneities in the main magnetic field, nonlinearity in the gradient field, and paramagnetism of the aluminum headframe. There were no significant differences in geometric distortion between the new head coil and the standard coil. Conclusions. The new head coil has advantages for reducing patient movement artifacts and has a better signal/noise ratio with no reduction in geometric accuracy.

Study on acoustic and flow-induced noise characteristics of L-shaped duct with a shallow cavity

2020 ◽  
Vol 68 (3) ◽  
pp. 209-225
Author(s):  
Masaaki Mori ◽  
Kunihiko Ishihara
Keyword(s):  
Air Conditioning ◽  
Sound Field ◽  
Frequency Range ◽  
Acoustic Characteristics ◽  
Inflow Velocity ◽  
Aerodynamic Sound ◽  
Noise Characteristics ◽  
Flow Induced Noise ◽  
Shallow Cavity ◽  
Conditioning Equipment

An aerodynamic sound generated by a flow inside a duct is one of the noise pro- blems. Flows in ducts with uneven surfaces such as grooves or cavities can be seen in various industrial devices and industrial products such as air-conditioning equipment in various plants or piping products. In this article, we have performed experiments and simulations to clarify acoustic and flow-induced sound characteris- tics of L-shaped duct with a shallow cavity installed. The experiments and simula- tions were performed under several inflow velocity conditions. The results show that the characteristics of the flow-induced sound in the duct are strongly affected by the acoustic characteristics of the duct interior sound field and the location of the shallow cavity. Especially, it was found that the acoustic characteristics were af- fected by the location of the shallow cavity in the frequency range between 1000 Hz and 1700 Hz.

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