473 OF ENGINEERING FOKMULÆ.
Funnels of Paddle-wheel Steamers.
For marine engines, 14 square inches area per nominal horse
power is allowed.
Minimum height of water, 6 In. over flues, 8 in. over tubes.
Proportions of Locomotives, Heating and
Grate Surfaces.
H = Area of heating surface in square feet.
G = A rea of fire-grate in square feet.
W = Water evaporated in cube feet per hour.
H2
W = -0022
VT
II = 21-2 VWG.
H2
G = -0022 *s a ß°mmon proportion.
Area of grate should not be more than ^th
heating surface, or J^th w^en coal is used.
Consumption of coke about 150 lbs. per foot of
fire-grate per hour. .
Giffard’s Injector.
Q = Quantity of water injected in gallons per
hour.
P = Pressure of steam in atmospheres.
D = Diameter of throat in inches.
D = -0158 V7-^--
VP
Q = (G3 • 4 D)2 V P.
Diameter of
Throat in
decimals of
an inch.
Delivery in Gallons per hour with a Pressure per
square inch of
3011».
60 Iba.
90 lbs. I 120 lbs.
150 lbs.
56
127
226
354
505
80
ISO
321
502
122
98 113
221 255
393 455
615 ( 711
884 I 1021
127
2x5
508
793
1140