Analysis of Noise Generated by Low Solidity Cascade Diffuser in a Centrifugal Blower

2008 ◽  
Author(s):  
Daisaku Sakaguchi ◽  
Masahiro Ishida ◽  
Hironobu Ueki ◽  
Hiroshi Hayami ◽  
Yasutoshi Senoo
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Centrifugal Blower ◽  
Discrete Frequency ◽  
Edge Location ◽  
Rotating Impeller ◽  
Low Solidity Cascade Diffuser ◽  
Blade Leading Edge

This paper deals with the effect of the blade leading edge location (RLSD) of a low solidity cascade diffuser (LSD) on noise and diffuser performance in a centrifugal blower. The noise of the LSD was measured and analyzed comparing with that of vaneless diffuser (VLD) in view points of overall noise, discrete frequency noise and broadband noise. The numerical flow analysis was conducted in the impeller and the diffuser by using a Navier-Stokes solver. The noise of the VLD varied little in a wide flow rate range, on the other hand, that of the LSD increased remarkably in the small flow rate by about 7 dB. The noise of the LSD did not increase near the design flow and was almost equal to that of the VLD. It was found that the increase in noise due to LSD is dependent mainly on the broadband noise between 600∼1000Hz, which was closely correlated to the lift force of the LSD blade. The two kinds of discrete frequency noise appeared due to an interaction between the rotating impeller and the LSD blade and another interaction between the rotating impeller blades and the reverse flow toward the impeller exit, but their influence on the overall noise were relatively small. By shifting the LSD blade leading edge location downstream from RLSD = 1.1 to 1.2, the noise was reduced by about 3 dB at the maximum without deterioration of the diffuser performance. The maximum lift coefficient of the LSD blade was achieved as high as 1.5 at the high attack angle of 17 degrees even in the case of RLSD = 1.2, resulting in improvement of the diffuser performance by about 40% and in reduction of the unstable flow range by about 11%.

Improvements in Aerodynamic Performance and Noise Due to Low Solidity Cascade Diffuser in a Centrifugal Blower

2007 ◽  
Author(s):  
Daisaku Sakaguchi ◽  
Masahiro Ishida ◽  
Tengen Murakami ◽  
Hiroshi Hayami ◽  
Yasutoshi Senoo ◽  
...  
Keyword(s):  
Leading Edge ◽  
Aerodynamic Performance ◽  
Broadband Noise ◽  
Wake Flow ◽  
Frequency Noise ◽  
Vaneless Diffuser ◽  
Centrifugal Blower ◽  
Flow Rates ◽  
Small Flow ◽  
Large Flow

A high efficiency and a wide operating range are required in recent centrifugal compressors and blowers. Low solidity circular cascade diffuser (LSD) was proposed in place of vaned diffuser and channel diffuser for achieving both higher pressure ratio and wider operating range. In the present study, aerodynamic performance and noise characteristics of LSD were investigated changing a radial location of LSD leading-edge. It is known that an interaction occurs between jet-wake flow discharged from the rotating impeller and the LSD leading edge, however jet-wake flow pattern is almost uniformalized until the radial position of R = 1.20 in the vaneless diffuser. Aiming at reducing the noise generated by the interaction mentioned above, the LSD leading edge was moved from RLSD = 1.10 to 1.15 and 1.20 in a centrifugal blower with low specific speed. The frequency spectra of noise were analyzed and the noise due to LSD were discussed from the view point of overall noise, discrete frequency noise and broadband noise. In order to clarify the relationship between the flow field and the noise, flow behavior in the impeller as well as in the diffuser was simulated using a Navier-Stokes solver ANSYS-CFX. According to the present experimental results, about 40% improvement in diffuser performance and about 11% improvement in unstable flow range were achieved in small flow rates by the LSD compared with the vaneless diffuser except for a small deterioration in diffuser performance at the large flow rate. On the other hand, the noise increased clearly in the case of RLSD = 1.10 at the large flow rate and the small flow rates as well. By locating the LSD blade leading edge downstream farther from the impeller exit, a remarkable reduction in overall noise was achieved without deterioration of diffuser performance. It is found that the noise increase due to LSD is mainly dependent on the broadband noise based on the jet-wake flow, the interaction between the reverse flow and the impeller blades results in the discrete frequency noise defined by the frequency of cross product of the rotational speed of the impeller and the number of LSD blade, and a significant reduction in noise is achieved by uniformalization of the jet-wake flow.

Effects of Diffuser Vane Geometries on Compressor Performance and Noise Characteristics in a Centrifugal Compressor

2013 ◽  
Author(s):  
Yohei Morita ◽  
Nobumichi Fujisawa ◽  
Takashi Goto ◽  
Yutaka Ohta
Keyword(s):  
Centrifugal Compressor ◽  
Noise Level ◽  
Leading Edge ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Numerical Techniques ◽  
Vaned Diffuser ◽  
Noise Characteristics ◽  
Edge Vortex ◽  
Compressor Performance

The effects of the diffuser vane geometries on the compressor performance and noise characteristics of a centrifugal compressor equipped with vaned diffusers were investigated by experiments and numerical techniques. Because we were focusing attention on the geometries of the diffuser vane’s leading edge, diffuser vanes with various leading edge geometries were installed in a vaned diffuser. A tapered diffuser vane with the tapered portion near the leading edge of the diffuser’s hub-side could remarkably reduce both the discrete frequency noise level and broadband noise level. In particular, a hub-side tapered diffuser vane with a taper on only the hub-side could suppress the development of the leading edge vortex (LEV) near the shroud side of the diffuser vane and effectively enhanced the compressor performance.

scholarly journals A new design way for cylindrical blades with adjustable inlet blade angles

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401983017
Author(s):  
Jing Yan ◽  
Xiaobing Liu ◽  
Li Peng ◽  
Jianan Li
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Design Flow ◽  
Improve Performance ◽  
Plan View ◽  
Pump Design ◽  
New Approach ◽  
Traditional Design ◽  
Inlet Angle ◽  
Blade Leading Edge

A new approach for cylindrical blade design is presented in this article. Authors of this article analyzed the main reasons which are responsible for the low efficiency of untwisted blades and found out that the shock losses along the blade leading edge are much higher than those of twisted blades. Furthermore, based on the analysis, this article proposed a new design approach that is different from the traditional one. This new approach can reduce hydraulic losses at blade leading edge and improve performance and efficiency of cylindrical blades. In the traditional design process, to draw blade projection in plan view, an incidence at intersection of blade leading edge and inner streamline on the meridional section is selected for calculating blade inlet angle accurately. Because the incidence and the blade inlet angle at the intersection of blade leading edge and outer streamline are formed automatically, the blade inlet angles at this point are not suitable for oncoming flow direction, generating noticeable shock losses at this place. In the new design program, blade inlet angles at both intersection points formed by blade leading edge and the outer, inner streamlines are accurately calculated. This makes the shock losses generated by blade leading edge be minimized. Moreover, in conventional design, the projection of blade pressure side into plan view consists of only one plane curve. In the new design way, projection of blade surface in plan view is composed of two curves joined smoothly and continuously. Two impellers with fundamentally identical geometrical parameters were designed and manufactured, and the only difference is that their cylindrical blades were calculated and configured by applying a traditional design method or a the new approach. Test findings from an open loop indicate that in a wide load range from 0.8 to 1.2 times design flow rate, both head and efficiency of the new pump were raised. Over the operating range, efficiency of the new pump increased by 0.5% to 2.7%. Particularly, for higher flow rate, pump performance was improved significantly, and the increase of efficiency at pump design point arrived at 2.7%. The results suggest that the new approach presented in this article offers an effective and useful means to improve performance of low specific speed pumps.

Effect of Inducer Leading-edge Configuration on Unstable Flow at Low Flow Rate in a Centrifugal Blower

2002 ◽  
Vol 2002.55 (0) ◽  
pp. 129-130
Author(s):  
Masahiro ISHIDA ◽  
Taufan SURANA ◽  
Tetsuhiro FUKUNAGA ◽  
Daisaku SAKAGUCHI ◽  
Zi xiang SUN
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Low Flow ◽  
Centrifugal Blower ◽  
Unstable Flow ◽  
Low Flow Rate

C13 Noise Characteristics of Centrifugal Blower with Low Solidity Cascade Diffuser : Mechanism of Broadband Noise

2008 ◽  
Vol 2008.61 (0) ◽  
pp. 79-80
Author(s):  
Yu KOBA ◽  
Tengen MURAKAMI ◽  
Daisaku SAKAGUCHI ◽  
Masahiro ISHIDA ◽  
Hironobu UEKI
Keyword(s):  
Broadband Noise ◽  
Centrifugal Blower ◽  
Noise Characteristics ◽  
Low Solidity Cascade Diffuser

Analysis of Secondary Flow Behavior in Low Solidity Cascade Diffuser of a Centrifugal Blower

2010 ◽  
Author(s):  
Masahiro Ishida ◽  
Tengen Murakami ◽  
Daisaku Sakaguchi ◽  
Hironobu Ueki ◽  
Hiroshi Hayami ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Flow Behavior ◽  
Vortex Formation ◽  
Leading Edge ◽  
Centrifugal Blower ◽  
Flow Rates ◽  
Noise Characteristics ◽  
Small Flow ◽  
Blade Tip ◽  
Low Solidity Cascade Diffuser

Aiming at reducing noise without deterioration of diffuser performance in a low solidity cascade diffuser (LSD) of a centrifugal blower, the authors have proposed to locate a shallow and short groove or a slot between the diffuser wall and the LSD blade tip limiting to near the blade leading edge. The effect of the LSD blade tip-groove on the blower characteristics and the noise characteristics were investigated experimentally as well as numerically. The mechanism being able to maintain the high LSD blade loading even at small flow rates was pursued in view points of the vortex formation and the induced secondary flow. In addition, the effect of the tip-groove length on the vortex formation in the shroud tip-groove and the secondary flow behavior in the LSD were analyzed numerically and an optimum tip-groove configuration was proposed. It is concluded that formations of the stable and intense vortex in the shroud tip-groove and the recirculating secondary flow along the shroud wall toward the impeller exit are the key factors for achieving a high LSD performance and reducing noise simultaneously at small flow rates.

Sign in / Sign up

Export Citation Format

Share Document