17G
PNEUMATIC AND HYDRAULIC MACHINES, PUMPS, Ac.
Class V.
Experiments on Plowing Fans,
Number
Velocity
Pressure of Air
Area of
Velocitv
Units ofWork given
Units of
Proportionper Cent, of
Area
of
of
Air-Chamber.
Opening
of the Air
Horse-power
out bv
Work
Work
of
Experi-
ment.
of Inlet
Revolu-
! ips of
from Air-
at Orifice
at which
Engine per
in efllueiit
yielded bv
Opening
tions
\ anes
Chamber
from Air-
Fngine
Minute,
stream of Air
Fan to that
in Square
made by
Inches In 11,s
of P« r
Water. Iiic1k
in
Chamber in
driving the
in pounds
measu red
given out
Inches.
Fan perMinute.
per
Second.
Square
Inches.
feet perSecond.
Fan worked.
raised
One Foothigh.
by halfits vis viva.
by Enjj'ne.Useful effectper Cent.
82-51
98+
12S-9
2-1)0 0-1040
36
112-9
1-77
53, 123
19.913
34
o
1,060
13.)-6
2-20 0*07;C
72
98-1)
3-26
107.622
26,215
24
3
1, 066
123-9
1-30 0-0470
103
7 5 • 5
2-81
1)3,847
17,901
19
4
5
1,087
1,066
142-4
139*G
0-1)0 0-0326
4*30 0*1556
144
Closed.
63*4
3-11
102,631
14,801
14
Fan Xo. 2. Common Form.—Straight vanes, inclined slightly to the radii. Diameter 30 Inches.
1
250-8
760
99*6
2-1
0-0760
36
96*4
1-22
. 40,389
12,202
30
o
722
94-6
1-5
0-0543
72
81-2
2-45
80,734
14.750
18
3
8+3
117-0
2-5
(1-0.105
104-7
4 - 55
149,928
31,780
21
. 4
912
114-5
w
0-0398
144
6J-8
3*81
: 125,GJ9
20,145
16
5
i ”
893
117-0
3*1
0-1123
Closed.
No. 830, p. 1220 (France ). Enfer, E. —, 32, Hue (leMalte, Paris . Various blowing machines. M. Enfer’sblowing machine is an improvement on the ordinaryblacksmith’s bellows, giving to it a more steady blast. Itis composed of two air-vessels, communicating by twopipes, in one of which a cylindrical bellows is worked,and the other serves as a reservoir. By simple but inge-nious contrivances the pressure of the air in the secondair-vessel or reservoir is regulated, and the bellows ismade to drive air into it, both when it ascends and de-scends. A Prize Medal is awarded.
In reporting upon the hydraulic machines exhibited, itis impossible to refrain from adverting to the generalneglect of those elementary principles of scientific know-ledge on which the perfection of such machines alwaysdepends, and, in some cases, their whole usefulness in aneconomical point of view. ' The Exhibition affords posi-tive evidence of the sacrifice of a large amount of capital,and of much mechanical ingenuity, due simply to theignorance of certain acknowledged principles of hydraulicscience. In adverting to this fact, the Jury cannot butobserve that the success with which the principles ofmechanical science,t in their application to practicalquestions, are beginning to be cultivated in France ,appeal's in the superiority of the French hydraulic ma-chines. Thus their water-wheels have attained a per-fection which is probably nowhere else to be found in theapplication of water-power. The total amount of suchpower derivable from the running waters of France , andapplicable to manufacturing purposes, has been largelyincreased, by expedients of a scientific character.}Among the most remarkable of these is the introduction,
* This is the case with the horizontal water-wheel; with-out the various scientific expedients adopted in the con-struction and working of that wheel, as the turbine, itcould not probably in any case be employed with advan-tage.
t It is but reasonable to expect that the superioritywhich the French have confessedly attained in certainbranches of industry, by cultivating the arts of design, willeventually appear—through the agency of the Ecolcs desArts et Metiers—in the scientific character of theirmachines.
+ The whole establishment of a water-wheel partakes ofthis character: the form and dimensions, for instance, ofthe sluice and coursers—the number, dimensions, and forms
of the float-boards—the dimensions of the wheel itself_
and the rate of working. It has been abundantly shown,by experiment, that by varying these conditions, the workof the same fall maybe varied by from one-half to two-thirdsof its whole amount.
now almost universal in France , of the curved float-boards of ML Poucelet in undershot and breast-wheels,and of the turbine of M. Fourneyron. It is not, how-ever, only in the adoption of new forms of water-wheelsin France , that the improvement has been apparent, butin the better establishment and more skilful working ofthe old forms; such as are in use in this country.
Of all such expedients for the economical applicationof water-power, it is a principle that, as far as it may bepossible, the water should be received on the machine,without shock, and that it should leave it without velo-city. For that there is power lost bv the shock of wateris apparent from the fact that the whole power of a fallof water may be absorbed in the reservoir into which itfalls, by the shock and commotion of its particles; and itis plain that if the water which works a machine leavesit with any velocity which might have been avoided, thenthe power which must have been expended in giving itthat velocity has been thrown away. It is another con-dition, founded on the same principle as that of avoidinga shock of the water, that there should be no suddencontractions or expansions of the influent or effluentstreams. It is, we repeat, on the scientific applicationof these principles that all expedients for the economicalworking of hydraulic machines are founded. We have,however, only to pass through the rooms of the Exhi-bition assigned to this class of machines to find themalmost universally ignored.
The record of this fact is important, as placing in ailobvious point of view the necessity of other means thanare now afforded for the scientific education of mechanicalengineers.
Pumps.
Notwithstanding the great antiquity of the pump, andits extensive use, it is one of our worst machines, con-sidered, in a mechanical sense, as a means of producing agiven result with the least possible expense of power.Simple as is its construction, it appears from the experi-ments of M. Morin,* that the amount of power lost inlifting and forcing pumps (such as fire-engines, &c.\amounts to from 55 to 80 per cent, of the whole. So thatof the work ( in pounds one foot high) done by the motivepower to drive the pump, only 45 per cent, in the best,and 18 per cent, in the worst pumps, is found to beyielded; when the weight of water actually raised inpounds is multiplied by the height to which it is raised infeet; the rest of the work being lost in the passage of the
* Papport du Jury Central, sur les produits exposes en134 ', vul. ii., p. 14. Paris , 1359.