382 



TIIK CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Dec. 



their roomentuni, nliich is counteracted only by the oilier factor, the 

 gravity. 



ll is thus readily seen that the weight of the load raised by an engine 

 working expansively, may exceed Ihe average pressure of the steam on the 

 piston, for it only requires the steam to be at a high initial pressure, so as 

 to give Ihe necessary velocity, and of course nionientuni, to the load at the 

 commencement of the stroke; it may then expand so as to brinj; clo«n the 

 average pressure and leave sufficnnt power, to be derived from the 

 momentum and the expansion, to carry forward the work. This reserved 

 power will of course be applied in a decreasing progression, while the re- 

 tarding powers would be constant. It will be a useful exercise of the 

 akill of some of your mathematical friends to calculate how far the load 

 may exceed the average pressure upon the piston. 



It appears from the table that the advantage to be derived from expan- 

 sion, increases with the expansion. It becomes tlierefore important to 

 ascertain the extent to which it may be carried. I noticed that in the Cor- 

 nish engine they use a " steam jacket" to their cylinder to prevent conden- 

 sation. This led me to inquire into the heat of the steam, and how it 

 ■would be aflected by its expansion. Mill steam expand in a cylinder from 

 any given pressure down to that of the atmosphere? Pressure or conden- 

 sation of air produces heat, and the release of it from pressure, cold. If 

 steam be aflected iu the same way, and you suffer it to expand to 100 times 

 its bulk, will not its heat be divided by 100, and be reduced below the 

 freezing point ? The cut-otV steam can take up no heat from the boiler, 

 and its inherent heat is slated to be about 1212° divided into portions, sen- 

 sible and latent, according to its pressure. As each particle of steam 

 must be supposed to contain an equal portion of heat, the heat must neces- 

 sarily be divided with the expansion of the steam. Then if it contain but 

 1212°, and this be divided by the expansion, it is evident that before the 

 steam can have expanded 40 times, its heat would be reduced below the 

 freezing point, even if the latent heat all became sensible, unless it could 

 take up heat from the cylinder, which is not of a nature to conduct it with 

 sufficient rapidity. That the heat is divided by the expansion, any one 

 may satisfy himself by placing his hand in the steam issuing from a high- 

 pressure boiler. He will in the same way be convinced that steam is not 

 frozen by expanding from 151) lb. to the pressure of the atmosphere, ^ow 

 it is impossible that in this case it should lake up from the atmosphere 

 sufficient heat to prevent freezing, if the heat, originally in it, did not ex- 

 ceed 1212°, as indicated by our books. To account for the phenomenon, 

 I suppose we may assume that the heat in atmospheric steam is correctly 

 slated at 1212°, of which 212' are sensible, and 1000° latent— a second 

 volume of water, rising in the form of steam in the boiler, takes up an 

 additional 1212° of heat; and now the steam contains twice as much 

 ■water, and twice as much heat, as atmospheric steam, shows 15 lb. pres- 

 sure by the mercurial gauge, and about 242° of heal by thermometer, the 

 remaining 2182° being latent ; and so, for each individual 15 lb. of pres- 

 sure, another volume of atmospheric steam would be compressed into the 

 original space, a less portion of its heat each time becoming latent. Ou 

 this theory, steam of 150 lb. pressure will contain 11 limes as much water 

 as atmospheric steam, and 13332° of heal, while the thermometer woulil 

 show but about 300°. And the temperature of such steam, when expanded 

 to the atmosphere, should be 8b°. It would therefore rush into the air and 

 immediately assume the form of water, which, judging merely from the 

 sensation, is near the fact. The advantage of the " steam jacket," there- 

 fore, is obvious. It is also obvious, that steam of any pressure may be 

 used, on the plan of expansion, in a condensing engine, as the heat may 

 always be reduced, by expansion, to the point at which it may be conden- 

 sed. The following calculations seem to show, that the most economical 

 engine would be built upon this plan. 



Steam at 180 lb. pressure, cut otl' at ijj of the stroke, by the table, will 

 give an average pressure of 10 lb. to ihe whole cylinder, and, by adding 

 the vacuum and air pump, 10 lb. more may readily be obtained. Such an 

 engine would therefore give a power equal to two of Bolton and Watt's, of 

 the same size, worked with atmospheric steam. Proceeding on the data, 

 that equal quantities of water are to be evaporated for each lb. pressure of 

 steam, at the same expense of fuel, on both plans, we have two cylinders- 

 full of atmospheric steam, weighing 253 grains per cubic foot on the Bol- 

 ton and Watt plan, and only t^J;, of one cylinder-full of steam at ISO lb., 

 weighing 3289 grains per cubic foot, in tlie other. The water to be evapo- 

 rated to produce the same power in both will then compare as 253 to =_?^'g', 

 or, the Bolton and Watt engine will require 15] times as much water to be 

 evaporated as the other, and fuel and boiler in the same proportion. The 

 180 lb. steam, by the theory, would contaiu 15620° of heat, which, divided 

 by the txpansion 100, would be reduced to 156°, while in the atmospheric 

 steam, there would be 1212°, or nearly 8 limes as much. Of course, the 

 condenser, air pump, and coudensing water, need only be Vj of w hat the 

 two Bolton and W alt cylinders would require for the condensing pro- 



I'f Daltou be correct in the opinion that steam, like gas, has expansive 

 power in proportion to its compression or density, we have data to calcu- 

 late the maxiujum power of steam. W ater is found to expand nearly 

 1800 times into steam of aimospheric pressure, or 15 lb. lo the inch. 

 Then, by compressing such st.aiu to ,^^ of its bulk, we should get it back 

 into water, and multiply its elastic force in the same degree, 1800 X 15 = 

 27000 1b. per square inch, the maximuiu.* In following the same law of 



* Sleam thus compressed into water, would instantly give out all its heat, and produce 

 a temperature, occoidiDB IQ Itie Uliory, of 212° X ItJOO -I- 1UU«° SB2t<l;0°, 



elastic power in proportion to density, we find, that each expansion of steam 

 to twice its volume, in a steam cylinder, gives precisely the same increment 

 of power to the piston, which must move each time double the distance. 

 Thus the distances moved by the piston foreaih expansion, form the series 

 1, 2, 4, 8, iVc, and the increment of power for each distance is -693151 of 

 the power applied before the steam is cutoB'. 



Erskine Hazard. 

 Philadelphia, July 20, 184C. 



REGISTER OF NEW PATENTS. 



If additional information be required respecting any patent, it may be obtained at tb« 

 office of this Journal. 



MANUFACTURE OF IRON. 



George Hinton Bovill, of Mill-wall, Poplar, Middlesex, engineer, 

 for " Imi>roveineuts in Ihe niativfacture of Iron." — Granted Jan. 31 ; lin- 

 rolled July 31, 1840. {With Ensruviiigs, Plate XIX) Reported in the 

 Repertory. 



The improvements relate, 1st, to an arrangement of apparatus for beat- 

 ing the blast from the flames passing off from the top or funnel head of 

 bias! furnaces ; 2nd, to an improved mode of healing the air or blast, by 

 blowing the same partly through and partly over a tire in a closed retort or 

 fire proof chamber; 3rd, to the working of blast furnaces by exhaustion 

 or suction, in contra-dislinction lo the present method of blowing air into 

 them at a greater pressure than the atmosphere : 4th, to the introduction 

 of steam above the boshes of blast furnaces; 5th, lo an improved method 

 of puddling iron by the application of the water furnace, commonly knosvn 

 as Kyiner and Leighton's furnace, the same being worked by air blown 

 into a closed ash pit, and the introduction of air over the fire lo consume 

 the gases generated ; 6th, lo a preparation to assist the working of iron io 

 the puddling furnace, and its further application lo facilitate the combina- 

 tion of steel with iron ; 7th, lo a mode of calcining iron ore by combining 

 the use of furnaces with heaps of ore ; 8lh, to a mode of construcliug 

 furnaces for heating or re heating iron. 



Plate XIX., fig. I is a side elevation, fig. 2 a section, and fig. 3 a plan of 

 apparatus placed at the top of a blast furnace, the cold air from the blast 

 main passing through the same, and being heated by the gaseous flame 

 passing oB' from the furnace top, is blown iu at the tuyeres of the furnace 

 in the ordinary manner, a is the top or stage of a blastfurnace; 4 the 

 brick tunnel head of the furnace, showing the doorway c, through vThich 

 the furnace is charged, and lo which doors are hung, confining the gaseous 

 Dame lo pass through the heating cells ; d the cold air main and branches 

 from the blowing engine connected lo the three chambers c, provided with 

 doors or bonnets/, secured by bolts and nuts, air tight: the object of these 

 doors is lo get access to the socket joints, by which the connection is made 

 with g, flat cells or chambers (shown in enlarged section, tig. 4), extending 

 across the tunnel head /», and connected, as above-iueiitiooed, to the cold 

 air chambers e on one side, and to A, three similar chambers, on the other 

 side, from which the heated air is conveyed by the three pipes i, to their 

 respective tuyeres and blown in at the bottom of the furnace, j, spaces 

 between the air-cells, ?, through which all ihe gaseous flames from Ihe 

 furnace ascend, the cold air being divided into thin currents, absorbs heat 

 in its passage through the cells §■, from the Same of ihe furnace, and ob- 

 tains sufficient temperature to be blown into the furnace. By this arrange- 

 ment the air, being divided into thin currents, is brought into contact with 

 greater heating surface, and consequently absorbs the heat therefrom more 

 rapidly than when pipes of considerable diameter are employed : it is im- 

 portant to keep the healing cells for each tuyere distinct, and by the ar- 

 rangement here shown, it is clear either of the sections may be repaired 

 without any interference or stoppage of the others; the arrons indicate 

 the direction of the currents. The great object of this part of the inven- 

 tion is to use apparatus at the tunnel head of a blast furnace of such a 

 description, that the heated compartments through which the air passes 

 shall oiler considerable depth as compared with the width, and so that the 

 air may be said to be iu a series of very thin sheets or currents of consi- 

 derable depth. 



Fig. 5 is a section of an improved hot air stove for heating the air need 

 for the blast, h a light iron case, lined with fire-brick, and provided wilh 

 a Kymer and Leighton's patent water grate, i, supplied with fuel by means 

 of a hopper, j, provided with a horizontal sliding door at the end near the 

 furnace, and at the opposite end with a piston door, I, that will move 

 freely along the hopper ; m ash pit, closed by the door n, and supplied 

 with air from llie blowing engine; o air pipe, furnished with a valve to 

 regulate the quantity of air to be admited from the cold air main p^ to 

 which also is applied the nozzles <;, to admit the cold air into the space 

 above the fire on the water grate, where it mixes with the products of com- 

 bustion and vapour of water, supplied from the water troughs of the 

 fire-bars, and passes away through the pipes r, to the tuyeres of the fur- 

 nace ; the admission of air and consequent regulation of heat of the blast 

 are governed by the slide valve s. The mode of applying the blast pos- 

 sesses a great advantage in giving a command over the working of the fur- 

 nace : when the cinder from the furnace has a glassy appearance, indicat. 

 iug the presence of unreduced oxide of iron, the admission of air over the 

 iiie shuiild be reduced or the quantity throut^h the fire iucreased ; ob the 



