Data processing: measuring – calibrating – or testing – Measurement system – Performance or efficiency evaluation
Reexamination Certificate
2000-02-16
2001-08-21
Shah, Kamini (Department: 2853)
Data processing: measuring, calibrating, or testing
Measurement system
Performance or efficiency evaluation
C381S071900, C073S649000
Reexamination Certificate
active
06278958
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for predicting a noise intensity emitted from a fan and/or a pump, more particularly, the method applied to a centrifugal fan and/or a pump.
BACKGROUND OF THE INVENTION
Though many companies are interested in noise prediction, not many studies have been performed in the area of noise prediction.
In order to control fan noise, one should be able to control performance and noise and accordingly shape of the fan needs to be modified. Low noise fan manufacturers should know how to perform experiments and how to analyze as well.
So far, any analysis method for centrifugal fan noise has not been reported because it requires not only understanding of complicated techniques but also combination of complicated techniques.
SUMMARY OF THE INVENTION
A method for fan noise prediction is provided. The method in accordance with the present invention generates performance and several noise values with fan shape and operating condition for design and manufacturing of fans.
In accordance with the present invention, the method for predicting a noise intensity emitted from a fan comprises steps for: analyzing a flow field around the fan on the basis of a fan shape and operating conditions; obtaining a noise source value of the fan from force data of blades at a given time in the analyzed flow field; and calculating a noise intensity from the noise source value.
In analyzing a flow field around the fan, data about the fan shape and the operating conditions are received, and then a flow field at every time with a vortex method in consideration of rotation of the fan analyzed.
Obtaining a noise source value of the fan comprises: reading data about the flow field along with data about the relevant fan and the relevant impeller; forming a noise source mesh over the relevant impeller or the relevant rotor, which are main sources of noise generated in the fan; calculating a sound pressure by acoustic analogy; determining whether a sound field is being analyzed in the domain of frequency or the domain of time; and calculating an observer time in consideration of a retarded time, and calculating noise source values at every time in consideration of the retarded time if the sound field is being analyzed in the domain of time, while converting the noise source values into that in the domain of frequency and obtaining a noise source value of a designated frequency from them if the sound field is being analyzed in the domain of frequency.
Calculating a sound pressure uses following Equation;
ρ
-
ρ
0
=
[
x
i
-
y
i
4
π
a
0
3
r
2
(
1
-
M
r
)
{
∂
F
i
∂
t
+
F
i
1
-
M
r
∂
M
r
∂
t
}
]
,
in which sound density related with an acoustic pressure is represented by p, speed of sound by a
0
, force data calculated from flow data, which is used as input data for noise source value calculation, by F
i
, position of a noise source mesh by x, and position of force at impeller blades by y.
Calculating a noise intensity comprises: reading data about the shape of the fan and the noise source values, and then analyzing a sound field on the basis of the data; determining whether an acoustic pressure at a point is needed, or acoustic pressures through the sound field are needed; and providing the acoustic pressure at the point if it is needed, while forming a mesh through the sound field, and then calculating the acoustic pressures at each point in the mesh if they are needed.
Analyzing a sound field after reading data about the shape of the fan and the noise source values is performed using a noise source mesh.
Analyzing a sound field after reading data about the shape of the fan and the noise source values is performed by following Equation;
C
(
P
)
φ
(
P
)
=
∫
S
[
φ
(
Q
)
∂
G
∂
n
(
P
,
Q
)
-
∂
φ
∂
n
G
(
P
,
Q
)
]
ⅆ
S
(
Q
)
+
∫
Kirchhoff
[
φ
(
K
)
∂
G
∂
n
(
P
,
K
)
-
∂
φ
∂
n
G
(
P
,
K
)
]
ⅆ
S
(
K
)
+
∫
v
Q
SC
(
X
SC
)
G
(
P
,
X
SC
)
ⅆ
v
,
in
which
∫
Kirchhoff
[
φ
(
K
)
∂
G
∂
n
(
P
,
K
)
-
∂
φ
∂
n
G
(
P
,
K
)
]
ⅆ
S
(
K
)
is a term supplied by sound mesh.
The method for predicting a noise intensity emitted from a fan in accordance with the present invention can be implemented in a computer system. Then, calculating a noise intensity from the noise source value can be performed using newly developed Kirchhoff-Helmholtz Boundary Element Method(BEM)with noise source mesh
REFERENCES:
patent: 3776363 (1973-12-01), Kuethe
patent: 5010576 (1991-04-01), Hill
patent: 5625150 (1997-04-01), Greene et al.
Seybert et al., “An Advanced Computational Method For Radiation And Scattering Of Acoustic Waves In Three Dimensions,”J. Acoust. Soc. Am.,vol. 77, No. 2, pp. 362-368, (Feb. 1985).
Jeon et al., “An Analysis Of The Flow And Sound Fields Of A Centrifugal Fan Located Near A Wedge,” 5th AIAA/CEAS Aeroacoustics Conference, pp. 1-10, (May 10-12, 1999).
Lohmann, “Prediction Of Ducted Radiator Fan Aeroacoustics With A Lifting Surface Method,” DGLR/AIAA 92 92-02-098, pp. 576-588.
“Sysnoise Rev. 5.3,”Computational Vibro-Acoustics,User's Manual vol. 2, pp. 356-365 and 396-399.
Jeon Wan Ho
Lee Duck Joo
Akin Gump Strauss Hauer & Feld L.L.P.
Korea Advanced Institute Science and Technology
Raymond Edward
Shah Kamini
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