Bulletin . he efficiency of the whole steam-generating apparatus which it really is, drops 14 per cent. At least10 per cent of this total drop of 14 per cent is very likely due tothe drop of furnace efficiency. ON PRESSURE DROP. The points grouped at the top of figure 9 show the relation be-tween the pressure drop through the fuel bed and the rate of com-bustion. The pressure drop through the fuel bed was obtained bysubtracting the absolute pressure over the fuel bed from the abso-lute pressure in the ash pit. Although the points do not fall alonga single curve, the indication is that the pres
Bulletin . he efficiency of the whole steam-generating apparatus which it really is, drops 14 per cent. At least10 per cent of this total drop of 14 per cent is very likely due tothe drop of furnace efficiency. ON PRESSURE DROP. The points grouped at the top of figure 9 show the relation be-tween the pressure drop through the fuel bed and the rate of com-bustion. The pressure drop through the fuel bed was obtained bysubtracting the absolute pressure over the fuel bed from the abso-lute pressure in the ash pit. Although the points do not fall alonga single curve, the indication is that the pressure drop through thefuel bed increases with the rate of combustion. With any fuel ofuniform size this relation is a necessity; to burn more fuel more airmust be passed through the fuel bed, and to pass more air throughthe fuel bed there must be a higher pressure drop. Different sizesof fuel offer different resistances to the passage of air through them DATA AND CALCULATIONS SHOWN GRAPHICALLY, 37 300 £ 200. fL, 0 10 20 30 4-0 50 60 70 80 90 Pounds of dry coal fired per hour per square foot of grate surface Figure 9.—Relation of increasing rate of combusiion to (1) pressure drop (draft) through fuel bedin inches of water; (2) pressure drop through boiler in inches of water; and (3) pounds of moist sparksejected from the stat k per hour. 38 TESTS OF COALS AND BRIQUETS ON TORPEDO BOAT. and therefore different pressure drops must be used with differentfuels to obtain the same rate of combustion. As three differentkinds of fuels are represented on the figure, the points are some-what scattered. The run-of-mine coal was a mixture of varioussizes and therefore offered higher resistance to the passage of air,and a higher pressure drop than with the briquets had to be main-tained to obtain the same rate of combustion. In the same figure the points of the middle group show the relationbetween the pressure drop through boiler and the rate of pressure drop through the boi
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
