JBMS-72-1:2010(2020 identification)

This translated document is provided for convenience only;
any references to JBMIA on this Standard must be based on
the Japanese version.

Annex A(normative)
Micro-fan p-q curve measurement method
A.1 Scope
In this standard, it is prerequisite for airborne noise measurement to get the p-q curve of fan under test.
Generally, for this purpose, various methods in ISO 5801 based on measurement using an air chamber arequoted.
As set forth in ISO 5801 itself, the lower limit of application of those methods is 12 000 in Reynolds number(See Table 5 in ISO 5801:1997 or Table 4 in 22.4.2, ISO 5801:2007). In this case, Reynolds number 12 000,in terms of lower limit of air flow rate, corresponds to about 0.001 m3/s (See Figure A.1).
This Annex specifies the method to find micro air flow-static pressure fan’s static pressure-air flow ratecharacteristics (p-q curve) which cannot actually be measured by the methods specified in ISO 5801.
音響パワーレベルA-weighted soundpower level
LWA (dB, reference to dB
1pW)
8060
工業用ファンRegion
intended forindustrial
fansの分野

現行規格でパワーレベル計測に対する
40
Lower limit of measuring計測下限
sound power

事務用ファン

Region intended forの分野
business fanslevel specified by existing(マイクロホンstandardsの性能限界)(microphone’s performancelimit)

20

Range in which new measurement
騒音計測距離等
method is requiredの再検討が必要

マイクロファン
Region ofの分野
low noisefans

超低騒音ファン
Extremely
low noise fans

風量Ｑm3/s
0.0001

New air flow rate measurement
新しい流量測定
method is required 方式が必要

0.001

0.01
0.1
1 qV (m3/s)
Lower
limitofmeasurement
bythrottle
ＪＩＳやＩＳＯで規定する、絞り機構
mechanisms
flowmeter specified by JIS and ISO
流量計の計測下限

Figure A.1 — Schematic correlation of applicability of this annex and corresponding noise emissions(not to scale)

A.2 Limit of application of ISO 5801 and the solution method
A.2.1 Air flow rate measurement limit
For computing air flow rate, in ISO 5801, differential pressure type flowmeters such as nozzles, orifices, andpitot tubes are used. Among them, the nozzle is able to measure relatively small air flow rate; however, thelower limit of application of Reynolds number （Re ≥ 12 000）is specified in it. Practically, the lower limit ofair flow rate measurement range is about 0.01 m3/s. Fan’s static pressure-air flow rate characteristics (p-q1

JBMS-72-1:2010(2020 identification)
characteristics) are measured from the maximum air flow rate to the closing point; practically, the fan having
maximum air flow rate, 0.001 - 0.01 m3/s（0.06 - 0.6 m3/min）is the limit of application.
This limit is determined simply by the flowmeter; the part of differential pressure type flowmeter can bereplaced by the flowmeter which is able to resolve the problem. However, it is desirable that the flowmeter tobe used can be calibrated and traceable to domestic standards.

A.2.2 Static pressure measurement accuracy
ISO 5801 specifies that “a manometer used to measure pressure difference has inaccuracy under steadypressure and after making corrections by calibration (temperature difference from the calibration temperature,G-forces, etc.), it should not exceed either ±1 % of significant pressure or 1.5 Pa whichever is larger”. For
example, in the case of a micro fan having maximum static pressure about 10 Pa, if manometer’s accuracy
stays 1.5 Pa, inevitably it becomes 15 % of static pressure measurement range, so it is impractical to set
corresponding air flow rate point.
For this reason, in terms of accuracy of manometer for static pressure measurement, in measuring fan’s staticpressure-air flow rate characteristics, it follows ISO 5801, however, in actual operations, due attentions mustbe paid to the followings.
a) In the case where accuracy of ±1 % of significant static pressure is not secured, accuracy of the manometerused is to be recorded.
b) The manometer to use shall have ±1 % degradation ability of cutoff static pressure of the fan under test.
c) Reproducibility (including hysteresis) of zero point (0 point of static pressure) also should be within ±1 % ofcutoff static pressure of the fan under test.

A.3 Configuration of micro air flow rate measuring equipment and the scope of applicationa) Range of air flow rateb) Flowmeterc) Size of wind tunnel

0.015 m3/s or less
It is able to measure the maximum air flow rate of the fan under test with accuracyof ±3 %.
See Figure A.2.
＞Ｄ0.5Ｄ

Flowmeter
流量 計＞0.5Ｄ

Variable
可 変給charging
気シ ステsystem
ムＤ

Fan供試
undertestン
ファ

温度 計
差圧 計
Differential
manometer

Buffering
緩衝板 plate

整Rectifier
流装 置Thermometer

Figure A.2 — Configuration of micro air flow rate measuring equipmentd) Flow direction of this equipment can be either push or suck against the wind tunnel.
e) Configuration of the wind tunnel shall be square or round shape of section size D.
f) Within the scope covered by Annex A, section size D is to be 300 mm or more. However, when crosssection surface of blowing/sucking comes close to the wind tunnel wall, it should be expanded. Also when
air flow rate is small, section area can be reduced down to 200 mm at minimum proportional to themaximum air flow rate in use.
g) Two metal meshes should be installed at the fan side of the rectifier as specified in ISO 5801. At the otherside, punched metal plate with opening ratio 20 % - 30 % is to be used.
h) At the hookup of the wind tunnel and the flowmeter, a buffering plate should be installed.

2JBMS-72-1:2010(2020 identification)i) As for a flowmeter and variable charging system, the flow direction of air supply/discharge can be changed
and flow rate range can be expanded depending on combinations.
j) In order to measure by expanding air flow rate range, plural flowmeters can be arranged by connecting inparallel. However, leak from any unused flowmeter is not allowed.

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