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10. Application information
16
Example 1 (mark needed):
This example shows why identifying marks are important.
Suppose you want to determine the true RPM of this fan.
The only thing you know is that its speed is less than 3,500
RPM. If you slowly decrease the flash rate starting from
3,500 FPM, the following "frozen" images appear:
Image No.:
Flash Rate:
Image No.:
Flash Rate:
What is the actual rate of the fan? Images 1, 3, 5, 6 and 8
are all "frozen," so the rate could be taken as 3,300, 1,650,
1,100, 825 and 550. Which is correct?
In order to determine the fan's actual speed, a mark is
added to one of the blades and the test is run again.
Image No.:
Flash Rate:
Image No.:
Flash Rate:
1
2
3,300
2,200
5
6
1100
825
1
2
3,300
2,200
5
6
1,100
825
3
4
1,650
1,320
7
8
733.3
550
3
4
1,650
1,320
7
8
733.3
550
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