1850 ] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



201 



The essential features of this invention are its comparative 

 cheapness of construction, the easy access it affords to the water- 

 channels, and reduction in the quantity of condensing-water 

 required. Its dimensions are as follows: — 



Heat-absorbing surface by the the water . 18 sq. feet per h p. 



Condensing surface 9 do. do. 



Thickness of metal through which the heat 



is conducted 1} inch. 



Weight of copper 60 lb. per h.p. 



Space occupied by plates -4 cube feet per h.p.; or 



y^th part of the space occupied by the tubes in Hall's condenser. 



Encouraged by the success of this condenser, Mr. Siemens has 

 directed his attention to the achievement of a still more important 

 object, which is to condense the steam in such a manner, that the 

 condensing water issues into the hot well at boiling heat, and yet pro- 

 duces an efficient vacuum within the working cylinder. This 

 appears paradoxical at first sight, yet it has been succesfully ac- 

 complished by a perfectly new principle, called by Mr. Siemens the 

 'Regenerative Principle of Condensation.' It consists of a rect- 

 angular trunk A, of cast-iron, the lower end of which is cylindrical, 

 and contains a working piston P, whicli performs two strokes for 

 each one of the engine. In the trunk is a set of copper plates B, 

 upright and parallel to each other, — the intervening spaces being 

 the same as the thickness of the plates, viz. — between yjth and 

 •jijth of an inch. 



The upper extremity of the condenser communicates on one side 

 to the exhaust-port of the engine, and on the other through a valve 

 V, to the hot-well H. 



The plates are fastened together by five or more thin bolts, with 

 small distance-washers between each plate. There is a lid at the 

 top of the trunk, by removing which the set of plates can be lifted 

 out. Immediately below the plates the injection-pipe enters. 



The action of the condenser is as follows: — Motion is given to 

 the piston by the engine, causing it to effect two strokes for every 

 one of the engine. At the moment that the exhaust-port of the en- 

 gine opens, the plates are completely immersed in water, a little of 

 which has entered the passage above the plates, and is, together with 

 tlie air present, carried off by the rush of steam into the hot-well, 

 the excess of steam escaping into the atmosphere. The water then, 

 in consequence of the downward motion of the piston, recedes 

 between the plates, exposing them gradually to the steam, which 

 condenses on them. Their upper edges emerging first from the 

 receding water are surrounded by steam of atmospheric pressure, 

 and become rapidly heated to about 210^. The emersion of the 

 plates still continuing, the steam is constantly brought into con- 

 tact with fresh cool surface, by which the greater portion of it is 

 condensed, until, as the piston descends, the injection enters and 

 completes the vacuum. This is done by the time the working 

 piston of the engine has accomplished |th of its stroke. The 

 upper extremities of the plates become heated to near 210°, and 

 the lower to about 160°. 



Taking the initial temperature of the condensing water at 60°, 

 the final temperature at 210°, the latent heat of steam at 212° 

 960 units, the quantity of water required is 6*6 lb. to condense 

 1 lb. of steam of atmospheric pressure. The common injection 

 condenser (supposing the temperature of the condensed steam to 

 be 110°) requires 21 '2 lb. in place of 6-6 lb. 

 The advantages of this condenser are: — 



1. Additional effective power gained on account of the vacuum 

 = 30 per cent, taking the pressure of steam at 40 lb. above the 

 atmosphere, and vacuum in the cylinder 12 lb. 



2. Heat saved in generating steam by the use of boiling feed- 

 water = 10 per cent, over the ordinary method of heating the 

 fecd-%vater to 110°, or 15 per cent, when no use is made of the con- 

 densed water for that purpose. 



3. I'he steam which escapes uncondensed may be used to cause 

 draught. 



i. The displacing cylinder takes no motive power. 



5. The condenser may be started and stopped at any time by J 

 turning the injection water on or off. If turned on, it at once form's 

 the vacuum without involving the necessity of blowing through; 

 and if turned off, it allows the engine to proceed as though it had 

 not a condenser. 



6. The air contained in the condenser is at each stroke com- 

 pletely expelled. 



r. Greater compactness, and less expense, than the injection con- 

 denser. 



Its dimensions in terms of parts of the engine are as follows: 



Area of plate-chamber = three times that of exhaust-pipe; length 



of plates = J that of stroke of engine; thickness of plates ^5 of 

 their length; spaces between plates same as thickness, but never 

 more than -J^th of an inch, as with that dimension no sediment can 

 stand against the rush of water. Capacity of displacing cylinder 

 = that of plate chamber. 



It has been attempted to adapt this condenser to the locomotive; 

 and of the advantages which would be gained if this could be done 

 there can be no doubt. In this case the two condensers were cast 

 in one piece, and placed directly in front of the cylinders. They 

 differed from that just described only in the length of the condenser 

 and stroke of the displacing piston being much shortened; so that 

 the velocity of the water between the plates may not be too great; 

 and in having a second set of discharge-valves of peculiar con- 

 struction for allowing the uncondensed steam to pass freely into 

 the funnel. The ordinary supply of feed-water not being by itself 

 sufficient to maintain the vacuum, this condenser, if applied to 

 locomotives, should only be worked at intervals, on inclines &c., 

 where its assistance would be needed. 



In its application to low-pressure engines, since the steam from 

 the cylinder has not sufficient power to force the air and heated 

 water from the condenser into the atmosphere, a communication is 

 made between the e.xhaust-valve of the condenser and the lower 

 end of the displacing cylinder, which, for convenience of arrange- 

 ment, is here reversed, and which receives the charge of water and 

 air when its piston is at the opposite end of it, and when it is there- 

 fore vacuous. 



In this case the amount of injection- water is reduced in the pro- 

 portion of three to one. Ten per cent, is saved by the feed-water 

 being made boiling hot, a great quantity of boiling water being 

 provided which cannot fail to be useful for many purposes. 



The first Regenerative Condenser was applied to a sixteen horse- 

 power high-pressure engine, at Saltby Works, near Birmingham, 

 in September lSt9, where it has been found to answer. One is 

 now being erected at the Paper Works of Messrs. Easton and 

 Amos, at Wandsworth, and will shortly be in action. 



A drawing was exhiljited, showing the condenser applied to a 

 common high-pressure engine, in connexion with a variable e.xpan- 

 sion valve, acted on by a governor, which is a modification of Mr. 

 Siemens chronometric governor, the pendulum being superseded 

 by an expanding fly-wheel. 



The principle involved in the Regenerative Condenser is applic- 

 able to many useful purposes, the most remarkable of which are 

 what Jfr. Siemens proposes to call his Regenerative Evaporator for 

 brine and other liquids, and the Regenerative Engine, which are 

 now in course of construction at the works of Messrs Fox and 

 Henderson, near Birmingham, to whose enterprise Mr. Siemens 

 expresses himself as indebted for the carrying out of his several 

 inventions. 



After the reading of the paper, a discussion took place, chiefly 

 as to the practicability of applying the condenser to locomotives, 

 in which Mr. Scott Russell, Mr. Crampton, and the author took 

 part. It was closed by the Chairman, who said that the circum- 

 stances of the locomotive were so peculiar, the requirements of 

 the most perfect simplicity, and the freedom from anv but the most 

 necessary dead weight so absolute, that he feared this could not be 

 applied to it, even if, which he doubted, the condensation could 

 take place rapidly enough where the cylinder was filled and emptied 

 four times in one second. But the principle was new to him, and 

 certainly ingenious, as were the other inventions of Mr. Siemens; 

 and in its application to stationary engines he hoped and believed 

 his ingenuity would meet its due reward. 



0-N THE CONSTRUCTION OF ARCHES WITH HOLLOW 

 CAST-IRON VOUSSOIRS. 



Lv the construction of cast-iron bridges, it has generally been 

 the practice to form a framework by means of ribs stretching 

 across the full span in one or more pieces, in the form of an arcli 

 or otherwise, which ribs are stiffened and kept steady by transverse 

 beams, diagonal struts, and ties; thus adopting to a certain extent 

 the system followed in the construction of many of the wooden 

 framed bridges, previous to the introduction of iron in being wholly 

 used for such works. This, no doubt, is a very excellent inode of 

 construction; but it is considered that by adopting the system of 

 stone bridges, and having- the voussoirs formed of cast-iron and 

 hollow, a cheaper and easier constructed bridge could be erected ; 

 while the principle is one which possesses many peculiar advantages, 

 and admits of being applied not only to arches of small, but also to 

 those of very large spans. 



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