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On the last experiment (19th March, 1881) with the Perkins machinery of the steam yacht “Anthracite”
260
],s,he,'woo(1---Tke t~c~';,';,+s Eoqi~e.
[Jour. Frank. Inst.
The economy to be expected from the suggested change in, methods of regulation of the ~team engine will evidently be dependent upon the manner of operati,m of the engine. Where engines have a nearly invariable ]o't(1, and when they are well adjusted to their work, the advantage would pro/)ably 1)e fi)und inappreciable; but in cases in which the engine is much to(, large fi,r its work or when the demand tbr power is very irregular, as in rolling mills or in rough weather at sea, and where (.ylinder condensation oeeurs to a great extent, the increased efficiency may be fimnd to I)e very eonsideral)le. The gain by decreased internal condensation will, perlmps, often be found to be an item of no small importance. Hobol+e,+,N..L, June, 1881.
ON T H E L A S T E X P E R I M E N T (19'tit ~IAI~ClI, 1881) W I T H TIIE PERKINS MACltINERY OF THE S T E A M Y A C I I T " ANTHt:~AC[TE." By (;hief-Engin('er lSHERW<~OIb U. S. Navy. ] n the ,lanllary~ FelJrtlal'v and March numbers (£ the present year of this journal will be found a description of the Perkins system of steam machine W in the steam yacht .bdhraeite, together with an aecount of tile two experiments which had been made with it to determine its economic ef~eiencv. The first experiment was made in England, with the vessel in fre(. route, 1)v Mr. F. d. Bramwell, an engineering expert employed fi)r that lmrpose by tile " Perkins Engine ComI)any," and the second was made 1)v a Board of ChiefEngineers of the United States Navv with the vessel secured to the dock of the New York Navy Yard. There being a wide discrepancy I)etween the results of these two experiments, the " 1)eckins Engine Company," on the return of the Anthracite to England, caused Mr. Bramwell to repeat his original experiment; and it is the object of this paper to give the data and results of the repetition--which are substantially the same as those of his original experiment--as a thrther eontribution to a knowledge of what economy may be ex.pected fr(,m the employment in a steam engine of steam of exceptionally high pressure used with a correspondingly great measure of expansiom
'J),'t., 1 8 8 1 . ]
Isherwood-- The Perkbts Engine.
261
Tile three experiments above referred to, being all that ever were made with steam of the excessive pressure employed and so enormously expandc~, have a peculiar value on account of their fewness
and of their greatly exaggerated conditions of pressure and expansion, nothing remotely approaching either bein~ t;mnd in ordinary practice. Befi)re givin~ the data and results of' the repeated experiment, it is necessary to impress the reader with the thct that the three experiments above referred to, being all made under substantially the same conditions of high pressure and great exl)ansion , have nothing with which they can be properly compared. The contention of the " P e r k i n s Engine ()ompany " is that the higher the pressure of steam and the more it is expanded, the greater will be the economy. To show this eflhct, one . r many experiments on the same maehinery~ if' all be made under the same eomlitions, are insuflldent. A series is neeessar.v, with varying eomliti.ns, begimfing with the highest pressure and greatest exl>ansion and ~radually reducing botl b ending with the least pressure and expansi,m ,~t' ordinary practice, ascertaining experimentally the results with each reduction ; thus proving or disproving, as the event amy !Je, whether or not the positloll of the " P e r k i n s Engine C o m p a n y " is well- or ill-tbmided. That Conq)any, however, has not made sm.h exl~eriments; and the two conducted by Mr. Bramwell are incoml>lete in the n.n-aseertainment of the weight of feed-water consumed per hour. h, the one conducted bv the Board of United States Naval En,_,'i,mers. h,,wever, this weight was determined. As part (,f the economic eflbet (,f "m en,.,'ine, mva,-urcd I)y the cost of the t)ower it develol)s in pounds of e,)al c()nsunw(1 p(,r hour, is due to the quality of the coal, part to the Vpe and proportions of the boiler, and the remainder t- the type "rod prop, wtions of the engine including therewith the pressure, quality and expansi,m of the steam used~ it is neressarv to separate these fiwt,,rs and ascertain what portion of the whole eflhet is due to each. Now, in the experilnents made by Mr. Bramwcll~ the finest description of hand-picked N ixon's navigation coal was burned, a coal of exceptional ,tuality for generating steam and of proportionally inere'tsed cost ; and, manifestly, whatever may be the difference in weight of wate,, vaporized in a boiler by rail D" of weight of this coal and by others of very considerably inilerior qualib~ , shouhl not he attrit)uted t . the machinery; so
262
I , herwood-- Tt : l'erki,,~ E~g&e.
[gour. Frank. Inst
that Mr. Bramwell's experiments fhil At tile outset in furnishing data with the Perkins engine ibr any proper COmlmrison with engines using steam generated 1)y inferior qualities ,)t' coal. Mr. Bramwell's last experiment shows that tile steam furnished by the Perkins boiler was riot superheated. Now, as that boiler contains 14"7227 square fleet of wAter-heating surtlwe, measured on the interior surfime of the tubes~ , r 19'6033 square feet measured on their exterior surlhee, And 15"6179 square f~et - f steam superheating surfim% measured on tire interior surfhee of" ,he tubes, , r 21"2178 square feet measured on their exterior surfiaee - all per square fbot of grate surthce-there [blh)ws th:t~, pr.mtieally, this })oiler had (14"7227 I 15"6179=) 30"3406 square feet ()f water-heating surf:we, measured on the interior surfhee of the tulles, or (19"(;0:~3-}-21"2178=) 40"8211 square feet, measured . n tire exterior surlhi.e of" the tubes; because, if water had not been (m the whole of this surfi~ee, the steam must have shown some superheating; and, had the water been on only tile normal water-heating surfim(,, the steanl would certainly have been excessively SUl)erheated with so great a l/r(,l/orti,m of steam superheating surlhee to grate surface. Thus the 1),q'kins boiler, though furnishing only saturated ste:ml, had an excepti,rnally large proportion or' water-heating to grate surthee ; in virtue of whicl b the pound of coal would vaporize in it a larger quantity of wat:er than in a b(,iler in which the ratio of' the water-heating to the grate surf'aee WAS tim nlueh less proportion eml)loyed in ordin'try prattle'(.. In this emmection, too, must be remarked that the rate of eoml)ustion in the Perkins boiler, for a full power trial, was less than half the rate of' ordinary l)r'mtiee with the eo'd used ; so that less than half tile quantity of he'll per hour was thrown UlrOn About one-third re,ire heat-absorbing surf.tee~ i)rodueing~ of course, the greater e('onomi(, vaporiz.~tiim due to these exceptionally fitvorable conditions. Before Mr. Bramwell's last experiment was made, tile pitch of the A,dhraeite's strew wqs largely increased, so that With a given weight of steam passed through the engine per hour, the steam pressures in the cylinders would all t)e higher and the piston sliced lower than in his first exi)erlment. Befbre the system according to which tile Anthraeitc's machinery was designed and is worked e:m be Accepted as experimentally proveJ~ to be economically superior to any other in use, the weight of feedwater consumed per hour, as well :~s the pawer developed~ must be
Oct., 1881.]
Isherwood-- The Perkins E~gine.
263
ascertained ibr a series of pressnres and expansions, the results of' all which shall be ibund to converge ill tile saint direction, showing an increased economy fi)r each increase in tile pressure and ill tile expansion. Until this is done, however, the experiments that have been made are o f great interest; the data and results of the last being as follows, excepting that the writer has supplied ik'om other sources an approximate estimate of the weight of feed-water consumed per hour and the deductions drawn therefrom. None of the quimtities in the ibllowing table are to be tbund it, Mr. Bramwell's report, but the writer has obtained them from the data therein given, which inchldes a reproduction of all the indicator diagrams taken, in fact, the report itself" contains but little more than the observed data of the experiment, leaving the reader t(, make his own calculations and deductions. The writer has selected from the data of the report the ten hours of the pertbrnmnee
EXPERI-
MENT MADE IN ENICLANI)~ BY ~ I l t . F . Z. t]RAM~VEI,I,, t i n TI[I,; k'~[ACIIINERY ()F 'Pile STEAM YA('IIT '~ A N T I I R A ( 3 ' r E , " '1"(, I)ETERMINE ITS E('ONOM I( ' P E I : FOILMANCE. TOTAl, 1.~.1ANTIT| l"S. Date of tile e x l ) e r i m e n t (vessel in free route), . 19th M a r c h , 1881. N u m b e r of set~ of i n d i c a t o r d i a g r m n s , t a k e n h a l f h o u r l y , 20" D u r a t i o n of t h e e x p e r i m e n t , in h o u r s a n d m i n u t e s . ('onseeutively, 10'
264
Isl~erwood-- The l)evki,,s E ~ g i , e.
T o t a l n u m b e r of p o u n d s c o n s u m e d of N i x o n ' s n a v i g a tion s t e a m coal, Total n u m b e r of p o u n d s of refuse, i n ash, etc., fi'om t h e coal, T o t a l n u m b e r of p o u n d ~ of (-on0msiilde ~gasifial)le p o f lion of t h e coal) c o n s n m e d , . P e r e e n t u m of t h e coal i n refuse of ash, T o t a l n u m b e r of d o u b l e s t r o k e s m a d e 1)y t h e p i s t o n s ol" the engine,
[Jour. Frank. Inst.
1770"86s0 88 '5434 1(182'324(~ 5" ~3650"
EN(;INE. S t e a m p r e s s u r e i n t h e boiler, in p o u n d s p e r ,~quare i n c h above the almost)here, S t e a m p r e s s u r e i n t h e receiver, iNN i)ounds p e r s q u a r e i~,ch above the at|nosphere, P o s i t i o n of t h e t h r o t t l e v a l v e , F r a c t i o n COml)leted of t h e s t r o k e of t h e p i s t o n of t h e 1st c y l i n d e r w h e n t h e s t e a m w a s e|,t of I; F r a c t i o n c o m p l e t e d of t h e s t r o k e or' t h e p i s t , n of t h e 3d c y l i n d e r w h e n t h e s t e a m w a s c u t olK N u m b e r of t i m e s t h e ~t~.,anl w a s e x l ) a n d e d , I n nolle of t h e c y l i n d e r s w a s tiN(, s t e a l n (.ushio,led, n o r w a s t h e r e e i t h e r s t e a m or e x h a u s t lc'td, V a c u u m i n t h e c o n d e n s e r , in i n c h e s of m e r c u r y B a c k p r e s s u r e i n t h e c o n d e n s e r , in p o u n d s p e r s q u a r e i n c h a b o v e zero, N u m b e r of d o u b l e s t r o k e s n m d e p,,r m i n u t e b y t h e steal,~ pistons, TEM I'I.]RATURES. P r o b a b l e t e m p e r a t u r e , i n d e g r e e s F : d l r e n h e i t , of t h e feed water, T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e boiler ,~team, c o n s i d e r e d as s a t u r a t e d , T e m p e r a t u r e , in degrees F a h r e n l w i t , of th(, s t e a m in t h e w f l v e c h e s t of t h e 1st c y l i n d e r , T e m p e r a t u r e , i n degrees F a h r e n h e i t . of t h e s t e a m in t h e 1st c y l i n d e r at t h e comnmncenle~Nt of t h e s t r o k e of t h e p i s t o n , c o n s i d e r e d as s ' t t u r a t e d , T e m p e r a t u r e , i n degrees F a h r e n h e i l , of t h e a i r i n t h e a i r space b e t w e e n t h e side of t h e ]st c y l i n d e r a n d its lagging, T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e w a t e r of cond e n s a t i o n f r o m t h e s t e a m j a c k e t ,)t" t h e 1st c y l i n d e r , T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e w a t e r of cond e n s a t i o n f r o m t h e s t e a m - j a c k e t of tb,, 2(1 c y l i n d e r , T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e w a t e r of cond e n s a t i o n f r o m t h e steam-jacket ,)f the, 3(1 c y l i n d e r ,
395"15 18"90 ~Vide o p e n . 0"6077 0"2643 22'9154 ............ 28"75 0"575 106"0833
122"0 438"0 422"5
416"3
314"6 418"5 409"8 404"0
~k't., lSS1.]
I,s'hel"wood-Tlw Perl,'i,s E~gim~.
265
t~ATI*] OF COM I~:lrSTI()N. P o n l l d s o f coal c o n s u m e d p e r h o u r , Pounds of eoml)ustible e o n s m n e d p e r h o u r , Pounds of coal e o n s u n l e d p e r h o u r per siluilre t*oo~ o f gr'tte, Po/ulds Of eoln}nlstible e o l l s u n l e d p e r h o u r p e r s q u a r e foot of grate, Potulds of coal c o n s u m e d I)er hotlr per sqtiare foot of o u t e r h e a t i n g surface, Poun(]s of coal eonsuIlled per h o u r p e r s q u a r e I'oot of iiiner h e a t i n g surface, Pounds of c o m b u s t i b l e c o n s u m e d p e r h o u r p e r ,~quare foot of o u t e r h e a t i n g surfi~ee, Poun(ls of c o m b u s t i b l e eollsunled 1)er h o u r I~Ol' s q u a r e foot of i n n e r h e a t i n g surface,
177"0868 1(;8"2325 11 '5624
10-9842 0'28:~2
0-3811 0'2691 0":~620
~T1.;AM PRESSURES :IN FIRST (~YL1 NI)ER~ PER IN I)ICAT()H.. Pressure on l)iston of 1st c y l i n d e r at c o m m e n c e m e n t of its stroke, in 1)ounds i)er s q u a r e i n c h above zero, Pressure on p i s t o n of 1st c y l i n d e r at t h e p o i n t of r u t t i n g off" t h e s t e a m , in p o u n d s per S(luare iraqi a b o v e zero, . Pressure on pistoll of lsl~ c y l i n d e r at e n d of its stroke, in p o u n d s p e r s q u a r e i n c h a b o v e zero, Mean b a c k p r e s s u r e a g a i n s t l)iston of 1st c y l i n d e r durimz its stroke, i n i)ounds p e r s q u a r e i n c h a b o v e zero, Back p r e s s u r e a g a i n s t i)istou of 1st c y l i n d e r m c o m m e n c e m e n t of its s l r o k e , ill ])Otlllds per squal'(, i n c h a b o v e zero, I n d i c a t e d p r e s s u r e on p i s t o n o f l s t e y l i m l e r , in p o u n d s per s q u a r e i n c h , Net p r e s s u r e on t)iston of 1st ~ylinder, in p o u n d s l),,r square i n e h , Total p r e s s u r e o n p i s t o n of l~t c y l i n d e r , in p o u n d s per square i n c h ,
317'69 2~il '44 175'94 79'6000
58'38 176"0625 174"0625 255*6625
~q'EAM P]¢ESSUI{ES IN ~E(!ONl) CYI.I NDI,]I{, PER [N1)I(~A'I'()]{. Pressure o n ])iston of 2d c y l i n d e r at ( . o m n m n c e m e n t of its stroke, in p o u n d s p e r s q u a r e i n c h above zero, Pressure o n i)iston of 2d c y l i n d e r at e n d of its stroke, in p o u n d s p e r s q u a r e i n e h "d)ove zero, . Mean b a c k p r e s s u r e a g a i n s t p i s t o n of 2d c y l i n d e r d u r i n g its stroke, i n p o u n d s p e r s q u a r e i n c h above zero, Back p r e s s u r e "tgainst i)iston of 211 c y l i n d e r at eomllleneeillellt of its s t r o k e , ill 1)OUlldS per S(lllare i n c h above zero, I n d i c a t e d p r e s s u r e o n l>i~ton of 211 ~.ylimhq', in l~<)unds per s q u a r e i n c h ,
103'39 44"46 :{8"6334
36"50 24"5840
266
I.~hcr~cood- TI.' l'c'kiw~ Em/i~e.
[Jom'. Frank. Inst.,
N e t p r e s s u r e o n pistmi of 2(l (.ylinde!', ill p o u n d s p e r square inch, T o t a l p r e s s u r e (m p i s l o n of 2(l cylind(,r, i n t)(mnds p e r s q u a r e i n c h , for t h e (lifli~renee b e t w e e n t h e a r e a s of t h e p i s t o n s of the, 1st "rod 2d (-ylin(Icrs,
22"5840
63"2174
STEAM I)IIESSUI:ES 1N T I I I I I D ('YIANI)ER, P E R |NI)ICAT()R.
P r e s s u r e o n p i s t o n of 34 ( ' y l i n d c r ;it (~()[nlneneelnent of its s t r o k e , ill. pOllnds l ler Sqtlal'(, i ll(~|l iil)ov() zero, P r e s s u r e o n p i s t o n of :;d eylin
33"58 27"69 10"03 3"0755
2"10 16'3612, 14"3612
19"4367
!~Ioll-; Es- PoWER. I n ( l i c a t e d h o r s e s - p o w e r d e v e l o i m d in t h e 1st ~ylillder~ I n d i c a t e d h o r s e s - p o w e r d e v e l o p e d i n tl~e 2d c y l i n d e r , I n d i c a t e d h o r s e s - p o w e r develop(.d in t i m 311 c y l i n d e r , A g g r e g a t e i n d i c a t e d lmrses-l~Ow~,r d e v .lol)ed in "all t h r e e cylinder~, . N e t h o r s e s - p o w e r d e v e l o p e d i n t l w 1st ('ylinder, N e t h o r s e s - p o w e r d e v e l o p e d in t h e 2(l ('ylinder, N e t h o r s e s - p o w e r d e v e l o p e d i n th(. :Id c y l i n d e r , A g g r e g a t e n e t horscs-l)OWer dew,h)l)ed ila all t h r e e c y l i n (lers, T o t a l h o r s e s - p o w e r d e v e l o p e d in l h e l~t cylin(ler, T o t a l h o r s e s - p o w e r d e v e l o p e d i n 1h e 2( [ c y l i n d er, T o t a l h o r s e s - p o w e r develo/)ed in 1h e 3d c y l i n d e r , A g g r e g a t e total hors(.~-p~bwcr d e v e l o p e d in all t h r e e cylinders, T o t a l h o r s e s - p o w e r (l(,velol)ed t)v th(' e x p a n d e d s t e a m "done iIl t h e 1st eylindt,r, T o t a l h o r s e s - p o w e r d~,velol)ed I)y t h e Cxl)anded ste-ml in t h e 2d c y l i n d e r , . T o t a l horses-l)owcr (l~w(qoped |,y the. e x l r m d e d s t e a m i n t h e 3d c y l i n d e r , .
33"3736 18"8080 53"3489 105"5305 32'9945 17"2777 46'8301
97'10~ 48'4821 36'3558 33'6362 118'4741 17"5092 36'3558 33"6362
0et., 1 8 8 1 . ]
[.,herwood--The Pe,'l;h~.~ TS~,.li',e.
267
WEIGIIT ()F ~TIqAM: AC(~OUNTEI) FOR lIY Tl[lq INDICATOR. Pounds of s t e a m p r e s e n t per h o u r i n t h e 1st c y l i n d e r at the p o i n t (if c u t t i n g off" t h e s t e a m , e,a l e u l a t e d from | t i e pressure t h e r e , Pounds (if s t e a m p r e s e n t pet' h o u r i n t h e 1st c y l i n d e r at the e n d of tl~e s t r o k e of its v i s t o n , calcul'~tcd l)'um 1he pressure t h e r e , Pounds of s t e ' m l c o n d e n s e d p e r h o u r in t h e ls~ c y l i n d e r to f u r n i s h t h e hea~ t r a n s m u t e d inh) t h e total horsesI)ower d e v e l o p e d in t h a t c y l i n d e r by t h e e x p a n d e d steam alone, Sum of t h e t w o i m m e d i a t e l y p r e e e d i n ~ (luantilies, . Pounds uf ste'tln | ) r e s e l l | per hotlF ill t h e 2d (.ylindev at the e n d of t h e ~troke of its piston, calculated from t h e pressure t h e r e , Pounds of s t e a m e(iudensed per h o u r in t h e 1st a n d 2(l c y l i n d e r s tu f u r n i s h t h e he~tt t r a n s m u t e d into ti~e total h o r s e s - p o w e r s d e v e l o p e d in t h o s e e y l i u d e r s hy t h e exlianded s t e a m alone, Sum of t h e t w o i m m e d i a t e l y p r e c e d i n g quantitie.~, . Pounds of s t e a m p r e s e n t p e r h o u r in t h e 3d c y l i n d e r lit the e n d of t h e s t r o k e of its p i s t o n , ('Meulated front Hm pressure there, Pounds of s t e a m c o n d e n s e d tier h o u r ill t h e lst;, 2(1 a n d 3(1 (+ylindt.rs to f u r n i s h t h e h e a t t r a n s n m t e d i n t ( i t h e totM horses-powtw devehilied i n t h o s e ~+ylindcrs tiy t h e exlIanded s t e n m alom~, Strut of t h e (wt) i m m e d i a t e l y p r e c e d i n g (it|anti||(,s, .
1043'9127
1125 2924
42"9s40 11(;8'2764:
1192"7472
14;;'4~;4:5 1336"2114
1156".53qi2
231"7801; 13S8'31(;.~
WI']IG-IIT ()l.' V~" \T[21{ ~,rAPOI¢IZI,,'lt IN TI[I.: ]{()IGI.,[{ ],'I{()M 'PHI.| FE])]I)TE.a,[ I ' E I { A T U t~ 1,].
Pounds of s t e a m e v a p o r a t e d per h o u r in t h e 1,filer, 1S30"0()q}q~, :N(iTi.z.--ln Mr. B r a m w e l l ' s p r e v i o u s e x p e r i m e n t of t h e 22d M a y , 1,~S0, tile l)OUlld o|" tn'eeisely t h e Sallle ('.oal Vttl)Ol'izt'd , fr(ull t h e t e m p e r M u r e of 122 degrees F a l n ' e n h e i t a n d u n d e r t h e tiressur~ of 371'(19 l)(iunds per s q u a r e inch above zero, 10-41S407 p o u n d s (if w a t e r ; c o n s e q u e n t l y , in ti~e p r e s e n t e x p e r i m e n t , it w i l l vat)(n'ize fr()lll t h e s a m e tellll)el'tittlre ~ I)u{ undel" the, pressure of 4(b.q'S4 p o u n d s per s q u a r e i n c h nl)ove zer% 10"3814S2 l~ounds of water. Praeti(~ally, t h i s latter v~qiorizati(in will be :~ little less, o w i n g t o the g r e a t e r ra,ldditv of t h e e u m b u s t i o n a n d to t h e h i g h e r t e l n p e r ~ t u r e of the iron heating" surt'aees of t h e boiler, aml m a y / ) e t a k e n at 10!~ 1)ounds of water per l~ound of coal, front w h i c h t h e \v~ight of s t e a m e v a l l o r a t e d 1)e~ hour ill the t)oiler, as givell u}~ove, \vtts (.:d(.ulat(,(t. ])IFFERENCE IIET~.VEEN TIlE WEI(ilIT OV ~VATEP~ VAPO]{IZED IN Tt[I,~" BOILER AND Tlll,] W E l l , l I T (hi." NTI,:.\M .\('('~[~N'I'I.]I) I,'O|'~ llY THIq INDICATOIG I)ifl~renee, in p o u n d s per hour, IJetween t h e w e i g h t of w a t e r vaporized (1S30 p o u n d s ) in t h e holler "rod t h e w e i g h t of s t e a m
268
].~herwood-- T f : l>,'~'ki~s E~gD~,'.
[aour. Frank. Inst.,
a c c o u n t e d for b y t h e i n d i c a t o r i n t h e 1st c y l i n d e r a t t h e p o i n t of c u t t i n g off t h e s t e a m , Difft+rence, ill p e r c e n t u m of t h e w e i g h t o[' w a t e r v a p o r i z e d ill tile boiler, b e t w e e n t h a t w e i g h t a n d t h e w e i g h t of s t e a m a c c o u n t e d for b y t h e indic~ltor in tht. 1st c y l i n d e r a t t h e p o i n t of c u t t i n g off t h e s t c n m , Diflierence, ill p o u n d s per h o u r , b e t w e e n t h e w e i g h t of w a t e r v a p o r i z e d i n t h e b o i h , r a n d t h e w e i g h t of s t e a m -lceounted for b y t h e i n d i c a t o r ill t h e 1st c y l i n d e r at t h e e n d of tire s t r o k e of its p i s t o n , Difference, i n p e r c e n t u m of t h e w e i g h t of w a t e r w q ) o r i z e d ill t h e boiler, b e t w e e n [h-it w e i g h t a n d t h e w e i g h t of s t e a m a c c o u n t e d for b y t h e i n d i c a t o r in t h e 1st c y l i n d e r at t h e e n d of t h e s t r o k e of its p i s t o n , Difference, in p o u n d s per h o u r , b e t w e e n t h e w e i g h t of w a t e r val)orized in tile boih,r a n d tile w e i g h t of s t e a m a c c o u n t e d for b y tile i n d i c a t o r i n t h e 2(1 c y l i n d e r at tire e n d of tlre s t r o k e of its p i s t o n , Diffi~renee, i n p e r e e n t m n of t h e w e i g h t of w a t e r v:q)orized ill t h e [)oiler, b e t w e e n t h a t w e i g h t a n d tile w e i g h t of s t e a m a c c o u n t e d for b y t h e i n d i c a t o r in t h e 2(1 v y l i n d e r at t h e e n d of tile s t r o k e of its piston, Difl~rence, ill p o u n d s p e r h o u r , b e t w e e n tile w e i g h ! of w a t e r v a p o r i z e d i n the boiler a n d t h e w e i g h t of s t e a m a c c o u n t e d for by tile i n d i c a t o r i n l h e 3d c y l i n d e r at t h e e n d of t h e s t r o k e or" its p i s t o n , Difference, i n p e r c e n t u m of t h e w e i g h t of w a t e r wq)orized ill t h c hoilcr, b e t w e e n that: w e i g h t a n d t h e w e i g h t of s t c a n l a c c o u n t e d for b y t h e indie'~tor in t h e ad c y l i n d e r at tile (~nd or' t h e s t r o k e of its p i s t o n , E('oNosi
I('
786 "0873
42"96
6(}1 "7236
36"1(;
493"7886
26"98
441'6832
24"14
I{ESI'I,TS.
P o u n d s of coal c o n s m n c d p e r h o u r per i n d i c a t e d h o r s e - p o w e r , 1"6781 P ( m n d s of coal c o n s m n e d t)er h o u r l)cr n e t h o r s e - p o w e r , 1"8237 P o u n d s of coal c o n s u m e d p e r h o u r per tot-ll horse-l)ower , 1"4947 P o u n d s of c o n l b u s t i b l e (.onsmne(t p e r h o u r p e r i n d i c a t e d horsepower, 1"5951 P o u n d s of c o m b u s t i b l e c o n s u m e d p e r h o u r p e r n e t h o r s e - p o w e r , 1"7325 P o u n d s of e o n i b u s t i b l e eonsmn(,d p e r h o u r p e r t o t a l horseBower, 1 "4200 P o u n d s of f e e d - w a t e r c o n s u m e d l)cr l m u r p e r in(iterated horsepower, 17"3410 Poun(ls of f e e d - w a t e r c o n s u n l e d l)er h e m ' p e r n e t h o r s e - p o w e r , . 18"8461 P o u n d s of f e e d - w a t e r c o l , s u l n e d p e r h o u r p e r t o t a l h o r s e - p o w e r , 15"4464 F a h r e n h e i t u n i t s of h e a t e o n s m n e d p e r It(mr per i n d i c a t e d horsepower, 19515"3167 F a h r e n h e i t u n i t s of h e a t consun,(,d l)cr h o u r p e r n e t horsepower, 21209 "1901
0ft., 1881.]
1.4,'rwood-- Tl, e l%'ki,,~ Eo.qi, e.
2~;9'
F a h r e n h e i t u n i t s of h e a t c o n s u m e d per ]tour per total horsepower, 17383"21s2 P E R ( ' F N T U M (IF " I ' o T A L PltESSURE ,bX P I S T O N S 1TTII,IZI,'I) AS I N I ) I ( ' A T E I r fl.N]) AS ~'~Wl~]'17I)I{I!]SN|TRHS.
Mean i n d i c a t e d p r e s s u r e o n t h e p i s t o n of t h e 3d e y l i m l e r , equiwtlellt to t h e s u m of t h e i n d i c a t e d p r e s s u r e on t h a t p i s t o n a n d of t h e i n d i c a t e d p r e s s u r e s on t h e p i s t o n s of t h e 2d a n d 1st cylinders, r e d u c e d respe(!tively in t h e ratios of th(. areas of tile l>ist(msof t h e 2d a n d 1st c y l i n d e r s to t h a t of t h e 3 d (.ylinder, and fl>r t h e fact of t h e 2d a n d 1st ( ' y l i n d e r s b e i n g s i n g l e a c t i n g , w h i l e t h e 3d v y l i n d e r is d o u b l e aetin~s, in t)ounds per s q u a r e inch, Mean total p r e s s u r e w h i c h a p p l i e d to t h e piston of t h e 3d c y l i n der w o u l d prodtme t h e total h o r s e s - p o w , r develol)ed hy t h e engine, Per c e n t u n t of t h e m e a n total p r e s s u r e on t h e pistotts of t h e t h r e e c y l i n d e r s , u t i l i z e d as i n d i c a t e d pressure, Mean n e t p r e s s u r e on t h e p i s t o n of t h e 3d c y l i n d e r , e~iuivalen! [o t h e Stllll o f t h e lle~ p r e s s u r e o n t h a t l d S t O l l ttlltl o f t h e l l e t pressures on t h e p i s t o n s of t h e 2(1 a n d 1st (.ylinders, re, l u t e d r e s p e c t i v e l y in t h e ratios of t h e areas of t h e p i s t o n s of t h e 2d and l s t ( : y l i n ( l e r s l o t h a t o f t h e a d c y l i n d e r , and lln" t h c l h e t o f the 2d a n d 1st (cylinders being' s i n g l e acting', w h i l e t h e "M ('ylin(ler is d o u t d e a.~:tin~', ill p o u n d s per s q u a r e ira.h, Per eellttllH of tilt! lllettn tot~tl l)ressure on t h e p i s t o n s of t h e t h r e e c y l i n d e r s utilized as m ' t pressure,
:~2-3~43
3(~'334qb 8'0"0s
'_'!)'77,S7 Sl'!)6
]:~(II I,E H ~ k l'Oll I ZA'FI()N.
Ntnnl~er of l~oumls of w a t e r t h a t w(,uhl h a v e been Val.)rizt.d ill. t h e boiler p e r h o u r h a d t h e f e e d - w a t e r been s u p p l i e d at t h e t e m l ) e r a t u r e o f 100 d e g r e e s F a h r e n h e i t aml w t p o r i z e d u n d e r the tltniosl)htq'i(_~ p r e s s u r e ()f "9"92 ili(~'hcs of lilereury, 1909"5022 Ntl/lll.)cr of 1)Oullds of Wltter t h a t w o u l d h a v e been wq~orized ill t h e boiler p e r h o u r h a d t h e f e e d - w a t e r I~een s u p p l i e d at t h e t e m p e r a t u r e of 212 d e g r e e s F a h r e n h e i t a n d v a p o r i z e d u m l e r t h e a t n i o s p h e r i e pre,ssure of 29"92 ilu:hcs of m e r c u r y , . 2132"609(i. Poul~(1.. of w a t e r v a p o r i z e d f r o m 100 (legree~ F a h r e n l w i t b y one l)ound of coal, 1(1"7823 P o u n d s ot' w a t e r v a p o r i z e d f r o m 100 degrees iCahr(nlh(,it by one p o u n d of c o m b u s t i b l e , 11"351)4 P o u n d s of w a t e r v~porizcd front 212 (legrees F a h r e n h e i t by o n e t)ound of coal, 12"0405 P o u n d s of w a t e r v a p o r i z e d froill 212 d e g r e e s Fahrenh~,it by o n e p o u n d of c o m b u s t i b l e , 12q;742
270
I.s'he~'wood--The P(~rki~nsEngine.
[Jour Frank. Inst..
(~OMPARISON OF ~ I I . BI~AMWI.:IJI.'S I~'IRSTAND LAST ~]XPERIMENTS.
As the screw of the Anthradtc had a greater pitch, and as more coal was consumed per hour, during the last experiment than during the first, the conditions of the two varied as regards the number of double strokes made by the pistons per minute, the pressure of the steam and the power developed. The steam, too, was less expanded during the last experiment and less throttled, but it was greatly throttled in both, even with the throttle valve wide open, as in the last experiment, owing to the exceedingly small diameter of the steam pipe comparably with the space displacement per minute of the pisto~ of the 1st cylinder. In the last experiment, as compared with the first, the steam pressures in boiler and cylinders were nmeh higher, the back pressure in the condenser much lower, the number of double strokes made by the pistons per minute nmeh less, and the weight of coal consumed per hour mucll greater. To what extent each of these variable conditions afflicted the final result of the cost of the power in pounds of coal consumed per hour cannot be determined; but the result of their combination, if the (,omparison be made for the cost of the total horse-power in 1)ounds of coal consumed per horn', which is the proper engineering c,)mparison under the conditions, shows that the greater pressur(~s, less expansion :tnd less piston speed , [1"4947--1"4291 )< 1(i)0 ~ 4"5903 per (the last experiment), g a v e \ ----1---t29-1 . . . . . . . . . / centum less econolnic efficiency than the lesser pressures, greater expansion and greater t)iston speed (first experiment). But as this difference may easily be within the limits of error tbr such experiments, nothing can bc tMrly concluded except tbr equality of economic performance in tim two cases. The greater economy with which, vn the contrary, the indicated horse-power was obtained during the use of the greater pressures, less expansion and less piston speed~ was due simply to the better vacuum in the condenser in that experiment, which might, except tbr accidental circumstances, have been equally good for both experiments. The h)wer the mean total pressure in the large cylinder, the more import'mr becomes the 1)ack pressure in the condenser. The still greater economy with which the net horse-t)ower was obtained during the last experiment was due to t]fe same cause, increased by the fact that the pressure required to work the engine, per se~ being the same in both cases, was a larger proportion of the
Oct., 1 8 8 1 . ]
I.qterv,ood-- The Pe,'I,'i~ts E~gb~e.
271
less total piston pressure in the first CXl)erhnenl than of the greater total 1)iston pressure in the last experiment. This realization usefully of a larger prol)ortion of the total pressure on a piston when that pressure is higher than when it is lower, owing to the thcts that the back pressure and the l)ressuve required to work the engine, per se, are constant, is an undoubted advantage tlw higher mean total pressures on the piston~ which will always (,xist, let the ett~et of other causes be what they may. The two experiments clearly show that the cylinder condensations, exclusive of' the condensation due to the deveh)pment ot' the power by the expanded steam ahme, were larger during the last experiment than during the first, a result w h M l might have been antMl)ated from the greater initial pressure in the 1st cylinder "rod less back l)rcssure in the 3d cylinder, joined with the much less speed of l)iston, notwithstanding the less expansion of the steam in the last experiment than in the first. F r o m the following table, in which will lie tbund the principal quantities that influence the comparison of the two experiments, a clear idea may be had of the extent (~t' the variations in the experimental conditions and of the resulting ett[~ets. ]~N(IINE, Mr. Bramwell's First Experiment, Last Exp~rialent.
]Date of experiment, • 22(I May, 18S0. 19th March, 1881. Steam pressure ill 1)oiler in p(mnds per square inch nbove the atmosphere , . 357'0,) 395"15 Steam pressure in boiler in 1)ounds per square i l l e h a b o v e zer()~ 371 "(;9 409'84 Position of throttle valve, ]'artly ,losed. "Wide open. [Number of times the steam was expanded, 26"S851 22"9154 V,'tcuuru ill the condenser in inches of mercury, . 26"864 2s'750 INumber of double strokes made per minute by the pistons, 130"3881 106'0833 POWER. Initial pressure on piston of 1st cylinder, in pounds per square inch above zero, B a c k pressure against piston of 3(1 cylinder, in pounds per square inch above zer%
205 '03
4"245
317"69
2"100
27 2
Ishcrv,o(~d-- The P,','l,'iJ~s E , gS~c.
[,rout. Frank. Inst.
31r. Bramwell s First Experinlent. Last ]~]xperinlent.
Aggretxate i n d i e a t e d h o r s e s - p o w e r de° v e l o p e d by t h e eIigine, Aggregate net horsesq)ower developed by the engine, A g g r e g a t e t o h d h o r s e s - p o w e r developed by t h e enffine,
80"7323
105"5305
70'3703
97"1023
96"6795
118'4741
E('ONOM 1(' ]~ESULTS. l~OIIll(lS of coal (~Oll~llllled per hOlll' p e r imlieated horse-power, P o u l H | s o f c o a l COll~ltill('(| p e r h o l l r per net horse-power, P o u n d s of coal c o n s u m e d per h o u r p e r total horse-p(~Wer, .
1 "7114
1"(;78I
1 "9(;34
1"8237
1"4291
1"4947
I ~ ( ~ [ ' I V A L E N T I)I,~,TON P R E S ~ U I I E , ~ .
M e a n indie,'~ted pressur(, on tile p i s t o n of the "M c y l i n d e r , e q u i v a l e n t to t h e s u m of t h e i n d i c a t e d p r e s s u r e (m l h a t p i s t o n a n d of t h e in(liq.ated p r e s s u r e s (m t h e p i s t o n s of t h e 2d -uld lsl ,'ylimters, r e d u c e d r e s p e c t i v e l y in t h e ratios of t h e areas of t h e p i s t o n s of t h e 2d a n d 1st c y l i n d e r s to t h a t of t h e ad c y l i n d e r , a n d for llle fact of t h e 2(l a n d 1st e y l i n d e r s b e i n g s i n g l e acting', w h i l e t h e 3(l (.ylinder is d(pulde aetim4", in l~oun(ls p e r S¢luare i n c h , ~{e~lll llet p r e s s u r e (pip tit,. p i s t o n of l l i e 3d c y l i n d e r itl 1)o1.111(].~ tPer S(]llal'e i n c h , e q u i v a l e n t to t h e Slllll Of Tile llet [)resstlre Oll tile piston a n d ol'l he net pressllres Oll | h e lPis[ons ()f | h ~ 2d a n d l~t c y l i n d e r s , re(bleed as (l(!s c r i b e d i m m e d i a t e l y ahoy(,, M e a n total p r e s s u r e on t h e piston of tile 3d c y l i n d e r in p o u n d s per S(lllare i n c h , e q u i v a l e n t to t h e .~mn of t h e totM p r e s s u r e on t l m t p i s t o n a n d of t h e total pressures on t h e p i s t o n s (~t" t h e 2d a n d 1st (.ylinders, reduced as des('ribed i m m e d i a t e l y above,
"0"14(;4
32'3643
17"560s
29"7787
24'1231
36"334(~
( %, IANI)]']I¢ (~ONDEN,~ATION.
P e r e e n t u m of t h e w e i g h t of s t e a m g e n e r a t e d in t h e boiler, e o m l e n s e d in t h e 1st c y l i n d e r at t h e p o i n t of c u t t i n g otl' t h e steam,
:~1'27
42"96
( )('t., 1,S~l.i
ib~gistcri,g App~,'(d~.s.fo," Ma~'5~c ~ "~thlc.~.
273
I~[r. I~l'allP.vcl['s ["ilsl Exl,Pl'illl~'lll. Last nxl)twilll~'lll. P.'l' ('C'lltlllll o f 1.1~,0 weight of ,5[¢'111|1 g't,ll-
(,rat,,d in tit(' hoiler, ('olldells(~d ill Ih(' 1st c y l i n d e r at l h e c u d of i h c s t r o k e o f its p i s t o n , e x t d u s i \ - c ~t' I h e ~.on,lcns;ition d u e to tile d e v e l o p m e n l . Id' l ) o w c r it|o11~,,
|~y f l i t '
cxpltlldCd
~.[(,lllIl
lN,r CclltUlll of t h e w e i g h t of s t e a m g('nc r a t e d in l h e boiler, c o n d e n s e d in l h e 2d c y l i n d e r al th(, e n d o f t i m ~troke of its l d s l o n , ~!xclusivc o f the' ~.omlensation d u e to l h e d e v c h ) l l m e n t ,.~f powcl' l~y tilt, ( , x p a m h , d sly'am
;l|Ollt~ ]N,F C t q l t U l l l Of t~|(' w e i K h t of s t e a m
21 '5:;
'2,P.~N
,~'47
2.1'14
9"q,21 :~
1 l '5~;24
~(m-
(q'atcd in th,, boiler, c ( m d c n s e d in t h e 3d (.ylindtq' :it t h e e n d (ff lh(, slr(d~e of its p i s t o n , e x c l u s i v e o f t l w c o n d e n s a t i o n d u c to l h c d c w q o p m e n t q~I tlK, p o w e r I~y t h e (,Xlmllded st(,tmt ~11()11¢'I ( !()M IH'NT ION. P o u n d s o f c o a l ¢,OllS/llll(,d ])t~l' ]lO/Ir lttq' SqLl:.ll'e fOOt Of KI;IIIt' SIII'fI/tY(~
Registering Apparatus for Marine Cables.-Th(~ most perti~et apll.tvams which has hitherto aIllacared tl)r giving graphic signals upon tile great snbnmrine lines of cable is Nil. Win. Thomson's syphon r(~eorder. There would be a gv(~'lt :Mv:mtage in :l telegraph whi(,,h would register the signals of the mirror galvanonmter. Paul Samuel proposes to use two selenium elements upon th(, s(q'ecn whcl'e lhe light from the galvanometer is rcttected: one at the right, the other at the left. Whenever om~ of them is illmninat~:d it~ ira:teased conductibility will enabl(! it to act as a relay upon :m electro-magnet, tbv marking upon a paper band the points "rod dashes tlf' the Morse alphabet. H e recommends the use of paper dipped in iodide of potassium, and of a tri:mgle which will be lnO\;ed st) that the point will be controlled hv one of th(. sclenimn elements :rod dm base by tim other; in tile fiwmer CltSC a dot will bc lWt,du~ed, in th(: latter a d a s h . - - L c s ,l[omlc,~'. W~OLF N~,. VOL. CXI I.--(THIRD SEmFS, Vol. lxxxii.)
C, lS
],s,he,'woo(1---Tke t~c~';,';,+s Eoqi~e.
[Jour. Frank. Inst.
The economy to be expected from the suggested change in, methods of regulation of the ~team engine will evidently be dependent upon the manner of operati,m of the engine. Where engines have a nearly invariable ]o't(1, and when they are well adjusted to their work, the advantage would pro/)ably 1)e fi)und inappreciable; but in cases in which the engine is much to(, large fi,r its work or when the demand tbr power is very irregular, as in rolling mills or in rough weather at sea, and where (.ylinder condensation oeeurs to a great extent, the increased efficiency may be fimnd to I)e very eonsideral)le. The gain by decreased internal condensation will, perlmps, often be found to be an item of no small importance. Hobol+e,+,N..L, June, 1881.
ON T H E L A S T E X P E R I M E N T (19'tit ~IAI~ClI, 1881) W I T H TIIE PERKINS MACltINERY OF THE S T E A M Y A C I I T " ANTHt:~AC[TE." By (;hief-Engin('er lSHERW<~OIb U. S. Navy. ] n the ,lanllary~ FelJrtlal'v and March numbers (£ the present year of this journal will be found a description of the Perkins system of steam machine W in the steam yacht .bdhraeite, together with an aecount of tile two experiments which had been made with it to determine its economic ef~eiencv. The first experiment was made in England, with the vessel in fre(. route, 1)v Mr. F. d. Bramwell, an engineering expert employed fi)r that lmrpose by tile " Perkins Engine ComI)any," and the second was made 1)v a Board of ChiefEngineers of the United States Navv with the vessel secured to the dock of the New York Navy Yard. There being a wide discrepancy I)etween the results of these two experiments, the " 1)eckins Engine Company," on the return of the Anthracite to England, caused Mr. Bramwell to repeat his original experiment; and it is the object of this paper to give the data and results of the repetition--which are substantially the same as those of his original experiment--as a thrther eontribution to a knowledge of what economy may be ex.pected fr(,m the employment in a steam engine of steam of exceptionally high pressure used with a correspondingly great measure of expansiom
'J),'t., 1 8 8 1 . ]
Isherwood-- The Perkbts Engine.
261
Tile three experiments above referred to, being all that ever were made with steam of the excessive pressure employed and so enormously expandc~, have a peculiar value on account of their fewness
and of their greatly exaggerated conditions of pressure and expansion, nothing remotely approaching either bein~ t;mnd in ordinary practice. Befi)re givin~ the data and results of' the repeated experiment, it is necessary to impress the reader with the thct that the three experiments above referred to, being all made under substantially the same conditions of high pressure and great exl)ansion , have nothing with which they can be properly compared. The contention of the " P e r k i n s Engine ()ompany " is that the higher the pressure of steam and the more it is expanded, the greater will be the economy. To show this eflhct, one . r many experiments on the same maehinery~ if' all be made under the same eomlitions, are insuflldent. A series is neeessar.v, with varying eomliti.ns, begimfing with the highest pressure and greatest exl>ansion and ~radually reducing botl b ending with the least pressure and expansi,m ,~t' ordinary practice, ascertaining experimentally the results with each reduction ; thus proving or disproving, as the event amy !Je, whether or not the positloll of the " P e r k i n s Engine C o m p a n y " is well- or ill-tbmided. That Conq)any, however, has not made sm.h exl~eriments; and the two conducted by Mr. Bramwell are incoml>lete in the n.n-aseertainment of the weight of feed-water consumed per hour. h, the one conducted bv the Board of United States Naval En,_,'i,mers. h,,wever, this weight was determined. As part (,f the economic eflbet (,f "m en,.,'ine, mva,-urcd I)y the cost of the t)ower it develol)s in pounds of e,)al c()nsunw(1 p(,r hour, is due to the quality of the coal, part to the Vpe and proportions of the boiler, and the remainder t- the type "rod prop, wtions of the engine including therewith the pressure, quality and expansi,m of the steam used~ it is neressarv to separate these fiwt,,rs and ascertain what portion of the whole eflhet is due to each. Now, in the experilnents made by Mr. Bramwcll~ the finest description of hand-picked N ixon's navigation coal was burned, a coal of exceptional ,tuality for generating steam and of proportionally inere'tsed cost ; and, manifestly, whatever may be the difference in weight of wate,, vaporized in a boiler by rail D" of weight of this coal and by others of very considerably inilerior qualib~ , shouhl not he attrit)uted t . the machinery; so
262
I , herwood-- Tt : l'erki,,~ E~g&e.
[gour. Frank. Inst
that Mr. Bramwell's experiments fhil At tile outset in furnishing data with the Perkins engine ibr any proper COmlmrison with engines using steam generated 1)y inferior qualities ,)t' coal. Mr. Bramwell's last experiment shows that tile steam furnished by the Perkins boiler was riot superheated. Now, as that boiler contains 14"7227 square fleet of wAter-heating surtlwe, measured on the interior surfime of the tubes~ , r 19'6033 square feet measured on their exterior surlhee, And 15"6179 square f~et - f steam superheating surfim% measured on tire interior surfhee of" ,he tubes, , r 21"2178 square feet measured on their exterior surfiaee - all per square fbot of grate surthce-there [blh)ws th:t~, pr.mtieally, this })oiler had (14"7227 I 15"6179=) 30"3406 square feet ()f water-heating surf:we, measured on the interior surfhee of the tulles, or (19"(;0:~3-}-21"2178=) 40"8211 square feet, measured . n tire exterior surlhi.e of" the tubes; because, if water had not been (m the whole of this surfi~ee, the steam must have shown some superheating; and, had the water been on only tile normal water-heating surfim(,, the steanl would certainly have been excessively SUl)erheated with so great a l/r(,l/orti,m of steam superheating surlhee to grate surface. Thus the 1),q'kins boiler, though furnishing only saturated ste:ml, had an excepti,rnally large proportion or' water-heating to grate surthee ; in virtue of whicl b the pound of coal would vaporize in it a larger quantity of wat:er than in a b(,iler in which the ratio of' the water-heating to the grate surf'aee WAS tim nlueh less proportion eml)loyed in ordin'try prattle'(.. In this emmection, too, must be remarked that the rate of eoml)ustion in the Perkins boiler, for a full power trial, was less than half the rate of' ordinary l)r'mtiee with the eo'd used ; so that less than half tile quantity of he'll per hour was thrown UlrOn About one-third re,ire heat-absorbing surf.tee~ i)rodueing~ of course, the greater e('onomi(, vaporiz.~tiim due to these exceptionally fitvorable conditions. Before Mr. Bramwell's last experiment was made, tile pitch of the A,dhraeite's strew wqs largely increased, so that With a given weight of steam passed through the engine per hour, the steam pressures in the cylinders would all t)e higher and the piston sliced lower than in his first exi)erlment. Befbre the system according to which tile Anthraeitc's machinery was designed and is worked e:m be Accepted as experimentally proveJ~ to be economically superior to any other in use, the weight of feedwater consumed per hour, as well :~s the pawer developed~ must be
Oct., 1881.]
Isherwood-- The Perkins E~gine.
263
ascertained ibr a series of pressnres and expansions, the results of' all which shall be ibund to converge ill tile saint direction, showing an increased economy fi)r each increase in tile pressure and ill tile expansion. Until this is done, however, the experiments that have been made are o f great interest; the data and results of the last being as follows, excepting that the writer has supplied ik'om other sources an approximate estimate of the weight of feed-water consumed per hour and the deductions drawn therefrom. None of the quimtities in the ibllowing table are to be tbund it, Mr. Bramwell's report, but the writer has obtained them from the data therein given, which inchldes a reproduction of all the indicator diagrams taken, in fact, the report itself" contains but little more than the observed data of the experiment, leaving the reader t(, make his own calculations and deductions. The writer has selected from the data of the report the ten hours of the pertbrnmnee
EXPERI-
MENT MADE IN ENICLANI)~ BY ~ I l t . F . Z. t]RAM~VEI,I,, t i n TI[I,; k'~[ACIIINERY ()F 'Pile STEAM YA('IIT '~ A N T I I R A ( 3 ' r E , " '1"(, I)ETERMINE ITS E('ONOM I( ' P E I : FOILMANCE. TOTAl, 1.~.1ANTIT| l"S. Date of tile e x l ) e r i m e n t (vessel in free route), . 19th M a r c h , 1881. N u m b e r of set~ of i n d i c a t o r d i a g r m n s , t a k e n h a l f h o u r l y , 20" D u r a t i o n of t h e e x p e r i m e n t , in h o u r s a n d m i n u t e s . ('onseeutively, 10'
264
Isl~erwood-- The l)evki,,s E ~ g i , e.
T o t a l n u m b e r of p o u n d s c o n s u m e d of N i x o n ' s n a v i g a tion s t e a m coal, Total n u m b e r of p o u n d s of refuse, i n ash, etc., fi'om t h e coal, T o t a l n u m b e r of p o u n d ~ of (-on0msiilde ~gasifial)le p o f lion of t h e coal) c o n s n m e d , . P e r e e n t u m of t h e coal i n refuse of ash, T o t a l n u m b e r of d o u b l e s t r o k e s m a d e 1)y t h e p i s t o n s ol" the engine,
[Jour. Frank. Inst.
1770"86s0 88 '5434 1(182'324(~ 5" ~3650"
EN(;INE. S t e a m p r e s s u r e i n t h e boiler, in p o u n d s p e r ,~quare i n c h above the almost)here, S t e a m p r e s s u r e i n t h e receiver, iNN i)ounds p e r s q u a r e i~,ch above the at|nosphere, P o s i t i o n of t h e t h r o t t l e v a l v e , F r a c t i o n COml)leted of t h e s t r o k e of t h e p i s t o n of t h e 1st c y l i n d e r w h e n t h e s t e a m w a s e|,t of I; F r a c t i o n c o m p l e t e d of t h e s t r o k e or' t h e p i s t , n of t h e 3d c y l i n d e r w h e n t h e s t e a m w a s c u t olK N u m b e r of t i m e s t h e ~t~.,anl w a s e x l ) a n d e d , I n nolle of t h e c y l i n d e r s w a s tiN(, s t e a l n (.ushio,led, n o r w a s t h e r e e i t h e r s t e a m or e x h a u s t lc'td, V a c u u m i n t h e c o n d e n s e r , in i n c h e s of m e r c u r y B a c k p r e s s u r e i n t h e c o n d e n s e r , in p o u n d s p e r s q u a r e i n c h a b o v e zero, N u m b e r of d o u b l e s t r o k e s n m d e p,,r m i n u t e b y t h e steal,~ pistons, TEM I'I.]RATURES. P r o b a b l e t e m p e r a t u r e , i n d e g r e e s F : d l r e n h e i t , of t h e feed water, T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e boiler ,~team, c o n s i d e r e d as s a t u r a t e d , T e m p e r a t u r e , in degrees F a h r e n l w i t , of th(, s t e a m in t h e w f l v e c h e s t of t h e 1st c y l i n d e r , T e m p e r a t u r e , i n degrees F a h r e n h e i t . of t h e s t e a m in t h e 1st c y l i n d e r at t h e comnmncenle~Nt of t h e s t r o k e of t h e p i s t o n , c o n s i d e r e d as s ' t t u r a t e d , T e m p e r a t u r e , i n degrees F a h r e n h e i l , of t h e a i r i n t h e a i r space b e t w e e n t h e side of t h e ]st c y l i n d e r a n d its lagging, T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e w a t e r of cond e n s a t i o n f r o m t h e s t e a m j a c k e t ,)t" t h e 1st c y l i n d e r , T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e w a t e r of cond e n s a t i o n f r o m t h e s t e a m - j a c k e t of tb,, 2(1 c y l i n d e r , T e m p e r a t u r e , i n d e g r e e s F a h r e n h e i t , of t h e w a t e r of cond e n s a t i o n f r o m t h e steam-jacket ,)f the, 3(1 c y l i n d e r ,
395"15 18"90 ~Vide o p e n . 0"6077 0"2643 22'9154 ............ 28"75 0"575 106"0833
122"0 438"0 422"5
416"3
314"6 418"5 409"8 404"0
~k't., lSS1.]
I,s'hel"wood-Tlw Perl,'i,s E~gim~.
265
t~ATI*] OF COM I~:lrSTI()N. P o n l l d s o f coal c o n s u m e d p e r h o u r , Pounds of eoml)ustible e o n s m n e d p e r h o u r , Pounds of coal e o n s u n l e d p e r h o u r per siluilre t*oo~ o f gr'tte, Po/ulds Of eoln}nlstible e o l l s u n l e d p e r h o u r p e r s q u a r e foot of grate, Potulds of coal c o n s u m e d I)er hotlr per sqtiare foot of o u t e r h e a t i n g surface, Poun(]s of coal eonsuIlled per h o u r p e r s q u a r e I'oot of iiiner h e a t i n g surface, Pounds of c o m b u s t i b l e c o n s u m e d p e r h o u r p e r ,~quare foot of o u t e r h e a t i n g surfi~ee, Poun(ls of c o m b u s t i b l e eollsunled 1)er h o u r I~Ol' s q u a r e foot of i n n e r h e a t i n g surface,
177"0868 1(;8"2325 11 '5624
10-9842 0'28:~2
0-3811 0'2691 0":~620
~T1.;AM PRESSURES :IN FIRST (~YL1 NI)ER~ PER IN I)ICAT()H.. Pressure on l)iston of 1st c y l i n d e r at c o m m e n c e m e n t of its stroke, in 1)ounds i)er s q u a r e i n c h above zero, Pressure on p i s t o n of 1st c y l i n d e r at t h e p o i n t of r u t t i n g off" t h e s t e a m , in p o u n d s per S(luare iraqi a b o v e zero, . Pressure on pistoll of lsl~ c y l i n d e r at e n d of its stroke, in p o u n d s p e r s q u a r e i n c h a b o v e zero, Mean b a c k p r e s s u r e a g a i n s t l)iston of 1st c y l i n d e r durimz its stroke, i n i)ounds p e r s q u a r e i n c h a b o v e zero, Back p r e s s u r e a g a i n s t i)istou of 1st c y l i n d e r m c o m m e n c e m e n t of its s l r o k e , ill ])Otlllds per squal'(, i n c h a b o v e zero, I n d i c a t e d p r e s s u r e on p i s t o n o f l s t e y l i m l e r , in p o u n d s per s q u a r e i n c h , Net p r e s s u r e on t)iston of 1st ~ylinder, in p o u n d s l),,r square i n e h , Total p r e s s u r e o n p i s t o n of l~t c y l i n d e r , in p o u n d s per square i n c h ,
317'69 2~il '44 175'94 79'6000
58'38 176"0625 174"0625 255*6625
~q'EAM P]¢ESSUI{ES IN ~E(!ONl) CYI.I NDI,]I{, PER [N1)I(~A'I'()]{. Pressure o n ])iston of 2d c y l i n d e r at ( . o m n m n c e m e n t of its stroke, in p o u n d s p e r s q u a r e i n c h above zero, Pressure o n i)iston of 2d c y l i n d e r at e n d of its stroke, in p o u n d s p e r s q u a r e i n e h "d)ove zero, . Mean b a c k p r e s s u r e a g a i n s t p i s t o n of 2d c y l i n d e r d u r i n g its stroke, i n p o u n d s p e r s q u a r e i n c h above zero, Back p r e s s u r e "tgainst i)iston of 211 c y l i n d e r at eomllleneeillellt of its s t r o k e , ill 1)OUlldS per S(lllare i n c h above zero, I n d i c a t e d p r e s s u r e o n l>i~ton of 211 ~.ylimhq', in l~<)unds per s q u a r e i n c h ,
103'39 44"46 :{8"6334
36"50 24"5840
266
I.~hcr~cood- TI.' l'c'kiw~ Em/i~e.
[Jom'. Frank. Inst.,
N e t p r e s s u r e o n pistmi of 2(l (.ylinde!', ill p o u n d s p e r square inch, T o t a l p r e s s u r e (m p i s l o n of 2(l cylind(,r, i n t)(mnds p e r s q u a r e i n c h , for t h e (lifli~renee b e t w e e n t h e a r e a s of t h e p i s t o n s of the, 1st "rod 2d (-ylin(Icrs,
22"5840
63"2174
STEAM I)IIESSUI:ES 1N T I I I I I D ('YIANI)ER, P E R |NI)ICAT()R.
P r e s s u r e o n p i s t o n of 34 ( ' y l i n d c r ;it (~()[nlneneelnent of its s t r o k e , ill. pOllnds l ler Sqtlal'(, i ll(~|l iil)ov() zero, P r e s s u r e o n p i s t o n of :;d eylin
33"58 27"69 10"03 3"0755
2"10 16'3612, 14"3612
19"4367
!~Ioll-; Es- PoWER. I n ( l i c a t e d h o r s e s - p o w e r d e v e l o i m d in t h e 1st ~ylillder~ I n d i c a t e d h o r s e s - p o w e r d e v e l o p e d i n tl~e 2d c y l i n d e r , I n d i c a t e d h o r s e s - p o w e r develop(.d in t i m 311 c y l i n d e r , A g g r e g a t e i n d i c a t e d lmrses-l~Ow~,r d e v .lol)ed in "all t h r e e cylinder~, . N e t h o r s e s - p o w e r d e v e l o p e d i n t l w 1st ('ylinder, N e t h o r s e s - p o w e r d e v e l o p e d in t h e 2(l ('ylinder, N e t h o r s e s - p o w e r d e v e l o p e d i n th(. :Id c y l i n d e r , A g g r e g a t e n e t horscs-l)OWer dew,h)l)ed ila all t h r e e c y l i n (lers, T o t a l h o r s e s - p o w e r d e v e l o p e d in l h e l~t cylin(ler, T o t a l h o r s e s - p o w e r d e v e l o p e d i n 1h e 2( [ c y l i n d er, T o t a l h o r s e s - p o w e r develo/)ed in 1h e 3d c y l i n d e r , A g g r e g a t e total hors(.~-p~bwcr d e v e l o p e d in all t h r e e cylinders, T o t a l h o r s e s - p o w e r (l(,velol)ed t)v th(' e x p a n d e d s t e a m "done iIl t h e 1st eylindt,r, T o t a l h o r s e s - p o w e r d~,velol)ed I)y t h e Cxl)anded ste-ml in t h e 2d c y l i n d e r , . T o t a l horses-l)owcr (l~w(qoped |,y the. e x l r m d e d s t e a m i n t h e 3d c y l i n d e r , .
33"3736 18"8080 53"3489 105"5305 32'9945 17"2777 46'8301
97'10~ 48'4821 36'3558 33'6362 118'4741 17"5092 36'3558 33"6362
0et., 1 8 8 1 . ]
[.,herwood--The Pe,'l;h~.~ TS~,.li',e.
267
WEIGIIT ()F ~TIqAM: AC(~OUNTEI) FOR lIY Tl[lq INDICATOR. Pounds of s t e a m p r e s e n t per h o u r i n t h e 1st c y l i n d e r at the p o i n t (if c u t t i n g off" t h e s t e a m , e,a l e u l a t e d from | t i e pressure t h e r e , Pounds (if s t e a m p r e s e n t pet' h o u r i n t h e 1st c y l i n d e r at the e n d of tl~e s t r o k e of its v i s t o n , calcul'~tcd l)'um 1he pressure t h e r e , Pounds of s t e ' m l c o n d e n s e d p e r h o u r in t h e ls~ c y l i n d e r to f u r n i s h t h e hea~ t r a n s m u t e d inh) t h e total horsesI)ower d e v e l o p e d in t h a t c y l i n d e r by t h e e x p a n d e d steam alone, Sum of t h e t w o i m m e d i a t e l y p r e e e d i n ~ (luantilies, . Pounds uf ste'tln | ) r e s e l l | per hotlF ill t h e 2d (.ylindev at the e n d of t h e ~troke of its piston, calculated from t h e pressure t h e r e , Pounds of s t e a m e(iudensed per h o u r in t h e 1st a n d 2(l c y l i n d e r s tu f u r n i s h t h e he~tt t r a n s m u t e d into ti~e total h o r s e s - p o w e r s d e v e l o p e d in t h o s e e y l i u d e r s hy t h e exlianded s t e a m alone, Sum of t h e t w o i m m e d i a t e l y p r e c e d i n g quantitie.~, . Pounds of s t e a m p r e s e n t p e r h o u r in t h e 3d c y l i n d e r lit the e n d of t h e s t r o k e of its p i s t o n , ('Meulated front Hm pressure there, Pounds of s t e a m c o n d e n s e d tier h o u r ill t h e lst;, 2(1 a n d 3(1 (+ylindt.rs to f u r n i s h t h e h e a t t r a n s n m t e d i n t ( i t h e totM horses-powtw devehilied i n t h o s e ~+ylindcrs tiy t h e exlIanded s t e n m alom~, Strut of t h e (wt) i m m e d i a t e l y p r e c e d i n g (it|anti||(,s, .
1043'9127
1125 2924
42"9s40 11(;8'2764:
1192"7472
14;;'4~;4:5 1336"2114
1156".53qi2
231"7801; 13S8'31(;.~
WI']IG-IIT ()l.' V~" \T[21{ ~,rAPOI¢IZI,,'lt IN TI[I.: ]{()IGI.,[{ ],'I{()M 'PHI.| FE])]I)TE.a,[ I ' E I { A T U t~ 1,].
Pounds of s t e a m e v a p o r a t e d per h o u r in t h e 1,filer, 1S30"0()q}q~, :N(iTi.z.--ln Mr. B r a m w e l l ' s p r e v i o u s e x p e r i m e n t of t h e 22d M a y , 1,~S0, tile l)OUlld o|" tn'eeisely t h e Sallle ('.oal Vttl)Ol'izt'd , fr(ull t h e t e m p e r M u r e of 122 degrees F a l n ' e n h e i t a n d u n d e r t h e tiressur~ of 371'(19 l)(iunds per s q u a r e inch above zero, 10-41S407 p o u n d s (if w a t e r ; c o n s e q u e n t l y , in ti~e p r e s e n t e x p e r i m e n t , it w i l l vat)(n'ize fr()lll t h e s a m e tellll)el'tittlre ~ I)u{ undel" the, pressure of 4(b.q'S4 p o u n d s per s q u a r e i n c h nl)ove zer% 10"3814S2 l~ounds of water. Praeti(~ally, t h i s latter v~qiorizati(in will be :~ little less, o w i n g t o the g r e a t e r ra,ldditv of t h e e u m b u s t i o n a n d to t h e h i g h e r t e l n p e r ~ t u r e of the iron heating" surt'aees of t h e boiler, aml m a y / ) e t a k e n at 10!~ 1)ounds of water per l~ound of coal, front w h i c h t h e \v~ight of s t e a m e v a l l o r a t e d 1)e~ hour ill the t)oiler, as givell u}~ove, \vtts (.:d(.ulat(,(t. ])IFFERENCE IIET~.VEEN TIlE WEI(ilIT OV ~VATEP~ VAPO]{IZED IN Tt[I,~" BOILER AND Tlll,] W E l l , l I T (hi." NTI,:.\M .\('('~[~N'I'I.]I) I,'O|'~ llY THIq INDICATOIG I)ifl~renee, in p o u n d s per hour, IJetween t h e w e i g h t of w a t e r vaporized (1S30 p o u n d s ) in t h e holler "rod t h e w e i g h t of s t e a m
268
].~herwood-- T f : l>,'~'ki~s E~gD~,'.
[aour. Frank. Inst.,
a c c o u n t e d for b y t h e i n d i c a t o r i n t h e 1st c y l i n d e r a t t h e p o i n t of c u t t i n g off t h e s t e a m , Difft+rence, ill p e r c e n t u m of t h e w e i g h t o[' w a t e r v a p o r i z e d ill tile boiler, b e t w e e n t h a t w e i g h t a n d t h e w e i g h t of s t e a m a c c o u n t e d for b y t h e indic~ltor in tht. 1st c y l i n d e r a t t h e p o i n t of c u t t i n g off t h e s t c n m , Diflierence, ill p o u n d s per h o u r , b e t w e e n t h e w e i g h t of w a t e r v a p o r i z e d i n t h e b o i h , r a n d t h e w e i g h t of s t e a m -lceounted for b y t h e i n d i c a t o r ill t h e 1st c y l i n d e r at t h e e n d of tire s t r o k e of its p i s t o n , Difference, i n p e r c e n t u m of t h e w e i g h t of w a t e r w q ) o r i z e d ill t h e boiler, b e t w e e n [h-it w e i g h t a n d t h e w e i g h t of s t e a m a c c o u n t e d for b y t h e i n d i c a t o r in t h e 1st c y l i n d e r at t h e e n d of t h e s t r o k e of its p i s t o n , Difference, in p o u n d s per h o u r , b e t w e e n t h e w e i g h t of w a t e r val)orized in tile boih,r a n d tile w e i g h t of s t e a m a c c o u n t e d for b y tile i n d i c a t o r i n t h e 2(1 c y l i n d e r at tire e n d of tlre s t r o k e of its p i s t o n , Diffi~renee, i n p e r e e n t m n of t h e w e i g h t of w a t e r v:q)orized ill t h e [)oiler, b e t w e e n t h a t w e i g h t a n d tile w e i g h t of s t e a m a c c o u n t e d for b y t h e i n d i c a t o r in t h e 2(1 v y l i n d e r at t h e e n d of tile s t r o k e of its piston, Difl~rence, ill p o u n d s p e r h o u r , b e t w e e n tile w e i g h ! of w a t e r v a p o r i z e d i n the boiler a n d t h e w e i g h t of s t e a m a c c o u n t e d for by tile i n d i c a t o r i n l h e 3d c y l i n d e r at t h e e n d of t h e s t r o k e or" its p i s t o n , Difference, i n p e r c e n t u m of t h e w e i g h t of w a t e r wq)orized ill t h c hoilcr, b e t w e e n that: w e i g h t a n d t h e w e i g h t of s t c a n l a c c o u n t e d for b y t h e indie'~tor in t h e ad c y l i n d e r at tile (~nd or' t h e s t r o k e of its p i s t o n , E('oNosi
I('
786 "0873
42"96
6(}1 "7236
36"1(;
493"7886
26"98
441'6832
24"14
I{ESI'I,TS.
P o u n d s of coal c o n s m n c d p e r h o u r per i n d i c a t e d h o r s e - p o w e r , 1"6781 P ( m n d s of coal c o n s m n e d t)er h o u r l)cr n e t h o r s e - p o w e r , 1"8237 P o u n d s of coal c o n s u m e d p e r h o u r per tot-ll horse-l)ower , 1"4947 P o u n d s of c o n l b u s t i b l e (.onsmne(t p e r h o u r p e r i n d i c a t e d horsepower, 1"5951 P o u n d s of c o m b u s t i b l e c o n s u m e d p e r h o u r p e r n e t h o r s e - p o w e r , 1"7325 P o u n d s of e o n i b u s t i b l e eonsmn(,d p e r h o u r p e r t o t a l horseBower, 1 "4200 P o u n d s of f e e d - w a t e r c o n s u m e d l)cr l m u r p e r in(iterated horsepower, 17"3410 Poun(ls of f e e d - w a t e r c o n s u n l e d l)er h e m ' p e r n e t h o r s e - p o w e r , . 18"8461 P o u n d s of f e e d - w a t e r c o l , s u l n e d p e r h o u r p e r t o t a l h o r s e - p o w e r , 15"4464 F a h r e n h e i t u n i t s of h e a t e o n s m n e d p e r It(mr per i n d i c a t e d horsepower, 19515"3167 F a h r e n h e i t u n i t s of h e a t consun,(,d l)cr h o u r p e r n e t horsepower, 21209 "1901
0ft., 1881.]
1.4,'rwood-- Tl, e l%'ki,,~ Eo.qi, e.
2~;9'
F a h r e n h e i t u n i t s of h e a t c o n s u m e d per ]tour per total horsepower, 17383"21s2 P E R ( ' F N T U M (IF " I ' o T A L PltESSURE ,bX P I S T O N S 1TTII,IZI,'I) AS I N I ) I ( ' A T E I r fl.N]) AS ~'~Wl~]'17I)I{I!]SN|TRHS.
Mean i n d i c a t e d p r e s s u r e o n t h e p i s t o n of t h e 3d e y l i m l e r , equiwtlellt to t h e s u m of t h e i n d i c a t e d p r e s s u r e on t h a t p i s t o n a n d of t h e i n d i c a t e d p r e s s u r e s on t h e p i s t o n s of t h e 2d a n d 1st cylinders, r e d u c e d respe(!tively in t h e ratios of th(. areas of tile l>ist(msof t h e 2d a n d 1st c y l i n d e r s to t h a t of t h e 3 d (.ylinder, and fl>r t h e fact of t h e 2d a n d 1st ( ' y l i n d e r s b e i n g s i n g l e a c t i n g , w h i l e t h e 3d v y l i n d e r is d o u b l e aetin~s, in t)ounds per s q u a r e inch, Mean total p r e s s u r e w h i c h a p p l i e d to t h e piston of t h e 3d c y l i n der w o u l d prodtme t h e total h o r s e s - p o w , r develol)ed hy t h e engine, Per c e n t u n t of t h e m e a n total p r e s s u r e on t h e pistotts of t h e t h r e e c y l i n d e r s , u t i l i z e d as i n d i c a t e d pressure, Mean n e t p r e s s u r e on t h e p i s t o n of t h e 3d c y l i n d e r , e~iuivalen! [o t h e Stllll o f t h e lle~ p r e s s u r e o n t h a t l d S t O l l ttlltl o f t h e l l e t pressures on t h e p i s t o n s of t h e 2(1 a n d 1st (.ylinders, re, l u t e d r e s p e c t i v e l y in t h e ratios of t h e areas of t h e p i s t o n s of t h e 2d and l s t ( : y l i n ( l e r s l o t h a t o f t h e a d c y l i n d e r , and lln" t h c l h e t o f the 2d a n d 1st (cylinders being' s i n g l e acting', w h i l e t h e "M ('ylin(ler is d o u t d e a.~:tin~', ill p o u n d s per s q u a r e ira.h, Per eellttllH of tilt! lllettn tot~tl l)ressure on t h e p i s t o n s of t h e t h r e e c y l i n d e r s utilized as m ' t pressure,
:~2-3~43
3(~'334qb 8'0"0s
'_'!)'77,S7 Sl'!)6
]:~(II I,E H ~ k l'Oll I ZA'FI()N.
Ntnnl~er of l~oumls of w a t e r t h a t w(,uhl h a v e been Val.)rizt.d ill. t h e boiler p e r h o u r h a d t h e f e e d - w a t e r been s u p p l i e d at t h e t e m l ) e r a t u r e o f 100 d e g r e e s F a h r e n h e i t aml w t p o r i z e d u n d e r the tltniosl)htq'i(_~ p r e s s u r e ()f "9"92 ili(~'hcs of lilereury, 1909"5022 Ntl/lll.)cr of 1)Oullds of Wltter t h a t w o u l d h a v e been wq~orized ill t h e boiler p e r h o u r h a d t h e f e e d - w a t e r I~een s u p p l i e d at t h e t e m p e r a t u r e of 212 d e g r e e s F a h r e n h e i t a n d v a p o r i z e d u m l e r t h e a t n i o s p h e r i e pre,ssure of 29"92 ilu:hcs of m e r c u r y , . 2132"609(i. Poul~(1.. of w a t e r v a p o r i z e d f r o m 100 (legree~ F a h r e n l w i t b y one l)ound of coal, 1(1"7823 P o u n d s ot' w a t e r v a p o r i z e d f r o m 100 degrees iCahr(nlh(,it by one p o u n d of c o m b u s t i b l e , 11"351)4 P o u n d s of w a t e r v~porizcd front 212 (legrees F a h r e n h e i t by o n e t)ound of coal, 12"0405 P o u n d s of w a t e r v a p o r i z e d froill 212 d e g r e e s Fahrenh~,it by o n e p o u n d of c o m b u s t i b l e , 12q;742
270
I.s'he~'wood--The P(~rki~nsEngine.
[Jour Frank. Inst..
(~OMPARISON OF ~ I I . BI~AMWI.:IJI.'S I~'IRSTAND LAST ~]XPERIMENTS.
As the screw of the Anthradtc had a greater pitch, and as more coal was consumed per hour, during the last experiment than during the first, the conditions of the two varied as regards the number of double strokes made by the pistons per minute, the pressure of the steam and the power developed. The steam, too, was less expanded during the last experiment and less throttled, but it was greatly throttled in both, even with the throttle valve wide open, as in the last experiment, owing to the exceedingly small diameter of the steam pipe comparably with the space displacement per minute of the pisto~ of the 1st cylinder. In the last experiment, as compared with the first, the steam pressures in boiler and cylinders were nmeh higher, the back pressure in the condenser much lower, the number of double strokes made by the pistons per minute nmeh less, and the weight of coal consumed per hour mucll greater. To what extent each of these variable conditions afflicted the final result of the cost of the power in pounds of coal consumed per hour cannot be determined; but the result of their combination, if the (,omparison be made for the cost of the total horse-power in 1)ounds of coal consumed per horn', which is the proper engineering c,)mparison under the conditions, shows that the greater pressur(~s, less expansion :tnd less piston speed , [1"4947--1"4291 )< 1(i)0 ~ 4"5903 per (the last experiment), g a v e \ ----1---t29-1 . . . . . . . . . / centum less econolnic efficiency than the lesser pressures, greater expansion and greater t)iston speed (first experiment). But as this difference may easily be within the limits of error tbr such experiments, nothing can bc tMrly concluded except tbr equality of economic performance in tim two cases. The greater economy with which, vn the contrary, the indicated horse-power was obtained during the use of the greater pressures, less expansion and less piston speed~ was due simply to the better vacuum in the condenser in that experiment, which might, except tbr accidental circumstances, have been equally good for both experiments. The h)wer the mean total pressure in the large cylinder, the more import'mr becomes the 1)ack pressure in the condenser. The still greater economy with which the net horse-t)ower was obtained during the last experiment was due to t]fe same cause, increased by the fact that the pressure required to work the engine, per se~ being the same in both cases, was a larger proportion of the
Oct., 1 8 8 1 . ]
I.qterv,ood-- The Pe,'I,'i~ts E~gb~e.
271
less total piston pressure in the first CXl)erhnenl than of the greater total 1)iston pressure in the last experiment. This realization usefully of a larger prol)ortion of the total pressure on a piston when that pressure is higher than when it is lower, owing to the thcts that the back pressure and the l)ressuve required to work the engine, per se, are constant, is an undoubted advantage tlw higher mean total pressures on the piston~ which will always (,xist, let the ett~et of other causes be what they may. The two experiments clearly show that the cylinder condensations, exclusive of' the condensation due to the deveh)pment ot' the power by the expanded steam ahme, were larger during the last experiment than during the first, a result w h M l might have been antMl)ated from the greater initial pressure in the 1st cylinder "rod less back l)rcssure in the 3d cylinder, joined with the much less speed of l)iston, notwithstanding the less expansion of the steam in the last experiment than in the first. F r o m the following table, in which will lie tbund the principal quantities that influence the comparison of the two experiments, a clear idea may be had of the extent (~t' the variations in the experimental conditions and of the resulting ett[~ets. ]~N(IINE, Mr. Bramwell's First Experiment, Last Exp~rialent.
]Date of experiment, • 22(I May, 18S0. 19th March, 1881. Steam pressure ill 1)oiler in p(mnds per square inch nbove the atmosphere , . 357'0,) 395"15 Steam pressure in boiler in 1)ounds per square i l l e h a b o v e zer()~ 371 "(;9 409'84 Position of throttle valve, ]'artly ,losed. "Wide open. [Number of times the steam was expanded, 26"S851 22"9154 V,'tcuuru ill the condenser in inches of mercury, . 26"864 2s'750 INumber of double strokes made per minute by the pistons, 130"3881 106'0833 POWER. Initial pressure on piston of 1st cylinder, in pounds per square inch above zero, B a c k pressure against piston of 3(1 cylinder, in pounds per square inch above zer%
205 '03
4"245
317"69
2"100
27 2
Ishcrv,o(~d-- The P,','l,'iJ~s E , gS~c.
[,rout. Frank. Inst.
31r. Bramwell s First Experinlent. Last ]~]xperinlent.
Aggretxate i n d i e a t e d h o r s e s - p o w e r de° v e l o p e d by t h e eIigine, Aggregate net horsesq)ower developed by the engine, A g g r e g a t e t o h d h o r s e s - p o w e r developed by t h e enffine,
80"7323
105"5305
70'3703
97"1023
96"6795
118'4741
E('ONOM 1(' ]~ESULTS. l~OIIll(lS of coal (~Oll~llllled per hOlll' p e r imlieated horse-power, P o u l H | s o f c o a l COll~ltill('(| p e r h o l l r per net horse-power, P o u n d s of coal c o n s u m e d per h o u r p e r total horse-p(~Wer, .
1 "7114
1"(;78I
1 "9(;34
1"8237
1"4291
1"4947
I ~ ( ~ [ ' I V A L E N T I)I,~,TON P R E S ~ U I I E , ~ .
M e a n indie,'~ted pressur(, on tile p i s t o n of the "M c y l i n d e r , e q u i v a l e n t to t h e s u m of t h e i n d i c a t e d p r e s s u r e (m l h a t p i s t o n a n d of t h e in(liq.ated p r e s s u r e s (m t h e p i s t o n s of t h e 2d -uld lsl ,'ylimters, r e d u c e d r e s p e c t i v e l y in t h e ratios of t h e areas of t h e p i s t o n s of t h e 2d a n d 1st c y l i n d e r s to t h a t of t h e ad c y l i n d e r , a n d for llle fact of t h e 2(l a n d 1st e y l i n d e r s b e i n g s i n g l e acting', w h i l e t h e 3(l (.ylinder is d(pulde aetim4", in l~oun(ls p e r S¢luare i n c h , ~{e~lll llet p r e s s u r e (pip tit,. p i s t o n of l l i e 3d c y l i n d e r itl 1)o1.111(].~ tPer S(]llal'e i n c h , e q u i v a l e n t to t h e Slllll Of Tile llet [)resstlre Oll tile piston a n d ol'l he net pressllres Oll | h e lPis[ons ()f | h ~ 2d a n d l~t c y l i n d e r s , re(bleed as (l(!s c r i b e d i m m e d i a t e l y ahoy(,, M e a n total p r e s s u r e on t h e piston of tile 3d c y l i n d e r in p o u n d s per S(lllare i n c h , e q u i v a l e n t to t h e .~mn of t h e totM p r e s s u r e on t l m t p i s t o n a n d of t h e total pressures on t h e p i s t o n s (~t" t h e 2d a n d 1st (.ylinders, reduced as des('ribed i m m e d i a t e l y above,
"0"14(;4
32'3643
17"560s
29"7787
24'1231
36"334(~
( %, IANI)]']I¢ (~ONDEN,~ATION.
P e r e e n t u m of t h e w e i g h t of s t e a m g e n e r a t e d in t h e boiler, e o m l e n s e d in t h e 1st c y l i n d e r at t h e p o i n t of c u t t i n g otl' t h e steam,
:~1'27
42"96
( )('t., 1,S~l.i
ib~gistcri,g App~,'(d~.s.fo," Ma~'5~c ~ "~thlc.~.
273
I~[r. I~l'allP.vcl['s ["ilsl Exl,Pl'illl~'lll. Last nxl)twilll~'lll. P.'l' ('C'lltlllll o f 1.1~,0 weight of ,5[¢'111|1 g't,ll-
(,rat,,d in tit(' hoiler, ('olldells(~d ill Ih(' 1st c y l i n d e r at l h e c u d of i h c s t r o k e o f its p i s t o n , e x t d u s i \ - c ~t' I h e ~.on,lcns;ition d u e to tile d e v e l o p m e n l . Id' l ) o w c r it|o11~,,
|~y f l i t '
cxpltlldCd
~.[(,lllIl
lN,r CclltUlll of t h e w e i g h t of s t e a m g('nc r a t e d in l h e boiler, c o n d e n s e d in l h e 2d c y l i n d e r al th(, e n d o f t i m ~troke of its l d s l o n , ~!xclusivc o f the' ~.omlensation d u e to l h e d e v c h ) l l m e n t ,.~f powcl' l~y tilt, ( , x p a m h , d sly'am
;l|Ollt~ ]N,F C t q l t U l l l Of t~|(' w e i K h t of s t e a m
21 '5:;
'2,P.~N
,~'47
2.1'14
9"q,21 :~
1 l '5~;24
~(m-
(q'atcd in th,, boiler, c ( m d c n s e d in t h e 3d (.ylindtq' :it t h e e n d (ff lh(, slr(d~e of its p i s t o n , e x c l u s i v e o f t l w c o n d e n s a t i o n d u c to l h c d c w q o p m e n t q~I tlK, p o w e r I~y t h e (,Xlmllded st(,tmt ~11()11¢'I ( !()M IH'NT ION. P o u n d s o f c o a l ¢,OllS/llll(,d ])t~l' ]lO/Ir lttq' SqLl:.ll'e fOOt Of KI;IIIt' SIII'fI/tY(~
Registering Apparatus for Marine Cables.-Th(~ most perti~et apll.tvams which has hitherto aIllacared tl)r giving graphic signals upon tile great snbnmrine lines of cable is Nil. Win. Thomson's syphon r(~eorder. There would be a gv(~'lt :Mv:mtage in :l telegraph whi(,,h would register the signals of the mirror galvanonmter. Paul Samuel proposes to use two selenium elements upon th(, s(q'ecn whcl'e lhe light from the galvanometer is rcttected: one at the right, the other at the left. Whenever om~ of them is illmninat~:d it~ ira:teased conductibility will enabl(! it to act as a relay upon :m electro-magnet, tbv marking upon a paper band the points "rod dashes tlf' the Morse alphabet. H e recommends the use of paper dipped in iodide of potassium, and of a tri:mgle which will be lnO\;ed st) that the point will be controlled hv one of th(. sclenimn elements :rod dm base by tim other; in tile fiwmer CltSC a dot will bc lWt,du~ed, in th(: latter a d a s h . - - L c s ,l[omlc,~'. W~OLF N~,. VOL. CXI I.--(THIRD SEmFS, Vol. lxxxii.)
C, lS