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Volume  discli.irged  in  cu.  ft.  per  niln.  per  sq.  iu.  of  centre  section.
Figs.  34  and  35.— Ch.xracteristic  Curves  :  Mine  Fans.
34. — 18'5"  Hcenan  Fan.     35. — 28"  Heeiian  Fan.
Tip  speed,  6,000  ft.  per  min.  in  each  case.
Curves  :  P  shows  brake  horse  power  ;  G,  comi)ression  ;   T,  total
gauge  ;  M,  efficiency  ;  N,  total  efficiency.
of  300  revolutions.  At  7,000  ft.  per  min.  and  318  rev,
the  water  gauge  was  3*45  and  the  discharge  23,150
cu.  ft.,  so  that  the  fan  is  amply  large  enough  for  the
work.
THEORY  OF  THE  PITOT  TUBE


81


The  types  of  gauge  tips  used  in  these  trials  are  shown
in  figs.  37-42.  A  description  of  the  method  adopted
in  testing  them  will  be  found  in  Heenan  and  Gilbert's
paper.
Thewy  of  the  Pilot  Tube. — Suppose  a  fluid  in  motion
impinges  upon  a  plane  surface  set  at  right  angles  to  it,  and
flows  away  in   a   direction  perpendicular   to  its   original


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Fio.  36.— Characteristic  Cvrves  :  Mine  Fan.
