Hence,  L  =  total  losses  of  head,

100  H      14-67x100      ^^^
=  100  ,,  =  jj^  =  j^:g.^^:3^  =  57-7  per  cent.
We  also  find  that  the  rev.  per  min.  N,  H  the  head  in
ft.,  and  G  the  gallons  per  min.  are  connected  by  the
relation

N2  +  0-02225  G  N  -  9850  H  -  001285  G2  =  0,

which  can  readily  be  thrown  into  the  form  of  equation  (22).
The  following  table  gives  the  results  of  calculaticn  from
the  above  equation : —


TABLE  27.— THEORETICAL  AND  ACTUAL  HEAD.
—

No.  of
experiment.
Actual  head.  -

Calculated
headi

Diflerence.
1

14-67

15-1

-  0-43

4

14-7

15-05

-0-35

6

14-75

14-86

..     -O.-ll

8

14-75

14-71

+  0-04

10

14-75

14-4

+  0-35.
12

17-4

17-85

-  0-45     •

15

17-3

17-66

-0-3

.     17

17-4

17-45

-0-05

19

17-4

17-35

+  0-05

21

17-6

17-05

+  0-55

22

17-6

17-16

+  0-46

Open-rvnning  Fan  Experiments. — A   paper  i®  by  Walton
Brown  contains  several  experiments  with  a  Waddle  fan


138


CENTRIFUGAL  FANS


haying  an  expanding  rim  (fig.  61).  In  other  respects  it  is
a  simple  open-running  fan,  with  the  vanes  curved  so  as  to
be  convex  to  the  outlet.  The  following  are  the  principal
dimensions  of  the  fan  : —

Diameter  to  periphery  of  divergent  outlet  36  ft.  4  in.
Diameter  to  the  extremities  of  the  blades  35  ft.
Diameter  of  inlet  ring        ...         ...         ...   1 3  ft.  6  in.
Width  at  outlet       1ft.  l^in.
Width  at  periphery  of  fan 2  ft.  2|  in.
Capacity  of  fan        2,583  cu.  ft.
The  experiments  in  Table  28  have  been  selected  from
those  given.
TABLE  28.— TESTS  RESULTS :  WADDLE  FAN.
No.  of  experiment.
1

2

4*

6

V.
Rev.  per  min.  of  fan  ...
