1847.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



m 



off in density. In the first six experiments no discharge of air takes place, 

 the velocity of the fan merely keeping the air at a fixed den&ity or pressure 

 per square inch due to that velocity. The remaining 20 cxperinients show 

 the fan discharsing air. An inspection of the table will show that, under 

 various conditions of velocity of the tips of the fan, that density of the 

 air, and theoretical quantity of the air discharged, varies, but not in a direct 

 ratio. The best results are obtained when the velocity of the tips of vanes 

 coincide with the velocity, and 9-IOths of the velocity a body would ac- 

 quire by falling freely the height of a homogenous column of air due to its 

 density. This is what we have called the theoretical velocity ; or, mother 

 ■words, the greatest quantity of air is discharged by the fan with the least 

 expenditureof power when' the tips of the vanes move at these velocities. 



In a recent set of experiments, the inlet openings in the sides of the fan- 

 chest were coolri.cted to 12 inches, anil 6 inches diameter— the original 

 diameter being I'J inches. The results obtained were, that with the 12 

 inch openings, the power expended was 2J to 1 compared to the openings 

 of 17.J inches, the velocity of fan, the density of air, and the cubic discharge 

 being' the same. AVith the inch opening the same results followed as 

 ■with the 12 inch, only the density of air decreased one-quarter. These 

 experiments show that the inlet openings must be of sufficient size, that the 

 air msy have a free and uninterrupted action in its passage to the blades ; 

 for if we at all impede this action, we do so at the expense of power. Here 

 follows a copy of the tables of 32 experiments, after which the paper gives 

 the dimensions of fan employed in these experiments— namely, 3 ft. lOi in. 

 diameter; width of the vane, lOf inches; and the length, 14 inches. 

 The fan is eccentric U-ieth inches; the vanes are five in number, and are 

 placed at an angle of 6° to the plane of the diameter. The inlet openings 

 on the side of the fan-chest are lij inches diameter. The outlet opening 

 or discharge passage is 12 inches wide and 12 inches deep ; the space be- 

 tween the tips of tlie blades and the chest increasing from two eighths of 

 an inch on the exit pipe, to 3^ inches at the bottom, in a perpendicular line 

 with the centre. 



Mr. Buckle said, that he had found that the area of the discharge and 

 the density of the air corresponded very nearly. His object had been lo 

 show the quantity of the air discharged at a certain density, and the power 

 it required to eliect that result. 



2. -Another paper on the same subject, from Mr. Jones, of the Bridge- 

 water Foundy, Bridgewater, was also read. 



Mr. Jones observes—'- There is, perhaps, no point upon which mechan- 

 ics have had a greater variety of opinion than that of the application of 

 the fan for manufacturing and other purposes ; nor is there any other sub- 

 ject which has caused more disappointment; and I am decidedly of opinion 

 that this has been principally occasioned by constructing the air passages 

 too small in the fans, as well as the passages leading to the tuyeres. Facts 

 are always better than opinions ; and in offering the following statement, I 

 merely give the result of six months' constant work. Two points of im- 

 portance in the construction of fans are, an exact balance of the fan upon 

 the axle, and a careful and judicious arrangement for getting up the speed 

 so as to avoid either tight straps, or any slipping up on the pulleys. With 

 this I forward you a drawing of the fans I have constructed. Yoii will 

 perceive that I have the openings unusually large, but the results have 

 fully justified the proportions. With these two fans we have been melting 

 50 to GO tons of iron per day, at the rate of a to tons per hour, with a 

 consumption of coke of 2u8 lb. lo the ton of irou ; in addition to which 

 there are upwards of 50 smiths' fires blown at the same time. The power 

 required is about eight horses, the motion being taken from a 12 horse 

 power engine by means of a Tin. gutta percha belt, the shaft running at 

 73 revolutions per minute ; the speed of the fan is about 750. They are 

 driven by a pulley on each end of the spindle. This I think much better 

 than a single strap. The openings at the side of the fans are 2 ft. 4 in. in 

 diameter, and the outlets are 24 inches by 12 inches. The passage from 

 the fan is 2' 9" by 1' 9'', leading to a reservoir under the cupola 18' 0" by 

 7' 0" by 4' 0" deep, from which we have two tuyeres G indies in diameter. 

 The pressure of blast is about 5J oz. per inch. The only thing to which I 

 wish to call your attention is the increased size of the air passages ; and 

 when we consider the large quantity of iron melted, and the small propor- 

 tion of coke used, the result is very satisfactory." 



Mr. Buckle remarked, that his paper had been drawn up for the pur- 

 pose of recording a course of experiments made during a series of years 

 at his leisure, and which had been executed with the utmost care. The 

 results were important to those who were about to adopt the fan, as teach- 

 ing them that its size must not be a matter of guess-work. Wlien he him- 

 self had a fan made, all the advice he could obtain was, " Make it big 

 enough." The parties who said so knew nothing about it. Had he been 

 then in possession of the results of his subsequent experiments, he should 

 have had his fan made only half its present size. He now found that all 

 required was, that the tips of the fan should revolve with 9I0ths of the 

 theoretical velocity, lu driving the fan at that speed they would obtain 

 the largest portion of blast at the least expenditure of power. By driving 

 them at a greater velocity, the power was absorbed without producing a 

 greater quantity of blast. 



Mr. CowpiiB wished to know if the horse-power mentioned by Mr. 

 Jones was indicated or commercial horse power ? Was it the same as 

 that meant by Mr. Buckle?— Mr. Buckle said, he had ascertained the 

 power by a dynanometer, having a spiral spring and a piston attached. 

 Having ascertained the amount indicated by the engine wlieu disconnected 

 with the fan, he had deducted that amount from the amount shown in 



every experiment The engine was nominally a H-horse power engine. 

 He had found that by a succession of fans, the first transmitting the blast 

 to the second, and so on, he obtained by the third or fourth a pressure of 

 2jjlbs. on the square inch. 



Alderman Geach remarked, that this plan was in use at a furnace fitted 

 up some three or four months since in Derbyshire, where they proved that 

 they could obtain a pressure of 2jlbs. on the square inch, and that (hey 

 could make better irou, and in a larger quantity, than by the old plan. — 

 Mr. Buckle had not been previously aware that the plan had been tried, 

 but he had ascertained that uniformity of the discharge wa> greater thau 

 that of the blowing cylinder, and the quality of the iron would be better. 



Mr. Henderson said, that in the works in Scotland with which he was 

 connected, they had a fan so badly constructed that they were about to 

 have it altered, which, nevertheless, turned out 220 to 230 tons of casting 

 per week. They had found that they could get something like double in- 

 dicated power out of the ordinary Fairbairn's engine, compared with what 

 it was sold for. He should like to know the proper form of the fan, the 

 proper length of pipe, and the size of the pipe which conducted the blast 

 from the fan to the place where they wished to use it. In Scotland they 

 were working a shaft 200 feet long ; -anil he should like to know whether 

 they could effect their object by laying down underground piping, instead 

 of having a shaft to conduct the power to near the place where they wished 

 to use it. They had enlarged the tuyere pipe, having ascertained that, in 

 melting iron, the density of the air was not so important as the quantity, 

 and that it was necessary that the air should be admitted in large quanti- 

 ties. — Alderman Geach knew of one furnace where the cupola was 150 

 feet from the blast. — Mr. H. Smith stated some experiments, which went 

 to show, as the Chairman remarked, that, putting the case in an extreme 

 point of view, the further the blast was from the fire the better. The 

 discussion was then adjourned, to afford an opportunity for further experi- 

 ments. 



3. " Heated Air." The next paper was from Mr. Wilkinson, who, the 

 Chairman observed, had been so bold as to try a totally new plan for 

 economising fuel, by introducing heated air into the boiler of a steam-engine, 

 among the steam, by which the inventor estimated that he effected a saving 

 of 20 to 25 per cent, in fuel. They had had steam and healed air sepa- 

 rately, but this was the first attempt to combine them. The following are 

 extracts from the paper : — 



" It is an unalterable law of Nature that to produce a given quantity of 

 steam, a given quantity of heat must be imparted to the water, and that in 

 proportion to the steam required. Therefore, under the most advantageous 

 circumstances, to produce an effect, a certain amount of combustion must 

 necessarily be expended. Now I find, from repeated experiments, that 

 water alone is not the most economic agent to work with ; and, by way 

 of elucidating this fact, I will explain one, and only one, though not the 

 most successful of my experiments, and this was made on a six-horse power 

 high-pressure engine, working in the manufactory of Mr. J. Burman, 

 Cumberland-street, Curtain-road, London. The principle consists in the 

 injection of a stream of air, heated to the high temperature of 800, into the 

 steam in the boiler — by which means the temperature, and consequently, 

 the expansive force of the steam, was increased. To effect this object, an 

 iron pipe or tube was bent in a serpentine form, so as to prtsent a great 

 extent of surface, and placed under the boiler, there to receive a red heat 

 from the glowing part of the fire, after it had passed the bridge on its course 

 to the flue. One end of this rarefying chamber was connected with an in- 

 jecting airpunip, proportioned lo the size of the cylinder of the eugine. 

 The other end was inserted by a continuation of the tube above the surface 

 of the water into the steam in the boiler. The whole capacity of the tube 

 was greater than the volume of compressed air which it received from each 

 stroke of the piston of the pump, so that theair did not enter tiie boiler until 

 it had acquired the full heat or nearly so of the red-hot tube through which 

 it passed. At every stroke of the piston the same quantity of cold air was 

 injected into the tube. That part of the air which was next to the pomp 

 was forced into a hotter place, and the air, which previously occupied that 

 hLitter place, was forced on to a still hotter one, and so on, until the fur- 

 thermost and hottest of all was discharged into the steam in the boiler. 

 The pressure of air iu the tube, strictly speaking, exceeded that of the 

 steam in the boiler, for it was an excessive pressure that overcame the re- 

 sistance in the boiler. That, at the commencement of each stroke the air 

 in the cylinder of the pump was in equilibrium wiihthe external air, and 

 only opposed a resistance as it became compressed, and gradually increased 

 its compressed force until it arrived at its maximum, which was the point 

 of equilibrium with the compressed air in the hot tube and the resistance of 

 the steam. Taking all things into account, the whole amount of power 

 expended in working the pump was about a per cent., or 120th of the force 

 which acted on the steam cylinder of the engine, and the result of the ex- 

 periment showed that the application of the healed air caused a reduction 

 in the quantity of coal consumed of from 25 to 30 per cent., and this was 

 continued for several weeks, the engine of course working at its usual 

 pressure." 



The Chairman had had his attention called to the subject by Mr. R. 

 Stephenson, who wished him to try it in the locomotives on the line, but 

 he had preferred lo wail till he had ascertained whether the principle was 

 economical, and whether the results could be depended on with a station* 

 ary engine. — Mr. CowPER had seen the invention tried, and observed that 

 the engine worked slower with than without it ; but, as the inventor coa- 



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