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A Waddle patent (1890) fan was erected at Craghead Collieries, and through the courtesy of Messrs. Thomas Hedley & Brothers, and their agent, Mr. James Fairley, a series of experiments were made by the writer to determine its efficiency.

This fan is delineated in Fig. 6, Plate XIX., and Fig. 7, Plate XX.; its dimensions are as follows:

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The fan is driven direct by one high pressure horizontal engine, with ordinary slide valve, and variable expansion valve, cutting off between and stroke, as required. The cylinder is 24 inches diameter, and 42 inches stroke: the piston rod (at front end only) being 3 inches diameter.

During the course of experiments 1 to 7, there were three downcast shafts, whose air was exhausted by the Waddle fan; and during experiments I to V the air was derived from two downcast shafts, instead of three as in the previous experiments.

Four seams of coal are worked at the Craghead Collieries: the Shield Row Seam at a depth of about 56 yards, the Five-Quarter Seam at 78 yards, the Main Coal Seam at 100 yards, and the Hutton Seam at a depth of about 168 yards.

Mr. A. L. STEAVENSON said he did not think they were in a position to discuss the paper at any length that day; it would be better to wait until the results of the experiments were in the hands of the members. He understood the diameter was rather more than 35 feet as given in the paper; if so it would make a difference in the results from the water-gauge, for the water-gauge varied in accordance with the square of the speed of the periphery. The results seemed to be very excellent, and fully equal to anything he had met with, and if they were correct-and no doubt they were so far as Mr. Brown was concerned-it was a very excellent fan.

Mr. HUGH WADDLE said in the old fan the blades were only a short distance within the inlet ring; consequently when the fan was of larger capacity than the mine the air was taken in close by the inlet ring all the way round, and the blades struck the air at a high velocity. Now, by bringing them towards the centre, as shown in Plate XVIII., the air struck all parts of the blades equally under the same conditions; through the blades radiating from the centre, the air was so hurried up them that the main volume would come from near the centre of the fan; but when the fan was working up to its full capacity the air was brought forward equally over

the whole inlet area. The radius of the blade was also varied to suit the watergauge and the requirements of the mine; it was altered for every water-gauge. The divergent outlet was not generally applicable to the improvement of the old type of Waddle fan, but in cases where the capacity of the fan was greater than that of the mine, he recommended the addition of his patent band shown in Fig. 3, Plate XVII.

Mr. WALLAU asked if the inventor had any exact data as to the actual gain through curving the inner ends of the blades as described?

Mr. WADDLE said he found that these curves required to be altered slightly according to the velocity of issue of air from the fan.

Mr. WALLAU asked if the blades of any fan had been altered?

Mr. WADDLE said he had tested one fan with and without the divergent outlet. After applying the divergent outlet, they found an increase in the volume produced and power utilized of about 20 per cent. When they stood opposite the outlet of the old fan, the stream of air from it could be felt at a considerable distance, but with the new fan the effects of the issue of the air were not noticeable even at a very short distance.

The CHAIRMAN asked if old fans could be altered in accordance with this principle without much trouble?

Mr. WADDLE-We cannot get good results by the addition of the divergent outlet to an old fan, as all the proportions of the fan require to be altered.

Mr. J. A. RAMSAY said if he understood the matter aright a new fan of small size would give results equal to a larger one of the old construction.

Mr. WADDLE replied that the same results could be obtained with a smaller fan of the new design; the proportion as near as possible being that a new 35-feet fan will give nearly the same volume of air as the old 42-feet pattern of fan.

Mr. C. C. LEACH asked why the blade kept was short of the periphery of the divergent outlet?

Mr. WADDLE said if the blades were carried to that periphery there would be re-entry, which it was the very means of stopping. The blades must get air from somewhere, and as the capacity of the fan at the circumference where the blades stop was so much less than at the outlet, the blades if extended as proposed would have to draw in the outside atmosphere to feed themselves.

Mr. M. WALTON BROWN said a question might be asked as to the diameter of the fan to be used in making reductions and calculations. It appeared to him that the effective diameter of the fan would be the diameter of the tips of the blades, that was 35 feet. So far as the action of the divergent outlet was concerned, it might be compared to the expanding chimney attached to the Guibal fan; and except as regards mechanical difficulties it might be a fixture and would produce the same effect with the fan running inside and just clear of it. He would like to hear the views of the members as to which diameter of the fan should be taken in reducing the results to those given at the normal velocity.

Mr. WADDLE said that no work was done beyond the tips of the blades; there was no increase of centrifugal force after the air left the blades. The divergent outlet had the effect of reducing the speed of the air rapidly as it passed into the larger area. The area being more than doubled between the inner and outer end of the divergent outlet, as a consequence the velocity of the air was reduced to at least half-speed.

Mr. R. L. WEEKS asked if an old fan had seven inches cut off the blades in the inside would there be any beneficial effect?

Mr. WADDLE replied that the results would not be improved, the water-guage at the same number of revolutions would be lowered, and the change would simply produce a fan of smaller diameter.

Mr. J. A. RAMSAY said that the alteration suggested by Mr. Weeks would not be beneficial, as the shortening of the blades of an old fan would have a deterrent effect.

Mr. LEACH asked what part of the efficiency was due to the divergent outlet? Mr. WADDLE said that point depended upon the volume of air being passed. If there was a very small quantity of air in relation to the capacity of the fan a very large proportion of the additional power utilized would be due to the alteration of the blades; if there was a very large volume of air, a much larger proportion of the efficiency would then be due to the divergent outlet.

Mr. H. AYTON enquired as to the effect that would be produced by attaching a divergent outlet to an old fan?

Mr. WADDLE said that in the trials already mentioned there was a difference under the two conditions of about 20 per cent.

Mr. T. E. FORSTER asked if better results were obtained by the divergent outlet or the band applied to an old fan?

Mr. WADDLE said if the old fan was giving a fair volume of air he would recommend the divergent outlet, but if the capacity of the mine was much less than that of the fan he would certainly recommend the band.

He understood that the end of

Mr. A. L. STEAVENSON said he had one simple little rule he always applied to fans :-D2 × R2 ÷ 800,000* which gave the theoretical water-gauge in inches, and the nearer they could approach the theoretical result the nearer they were to perfection. The Guibal fan gave as high as 67; the new Waddle fan seemed to give 60, if they took 35 feet as the outer diameter. However, if the diameter of 36 feet was taken, the results were still very good. the water-gauge when the vacuum was read was close to the inlet of the fan, which was acknowledged to be rather a strong advantage in favour of this fan. He considered, after a recent visit, that the Waddle fan at Craghead Colliery was a strong fan, very simple, and not likely to get out of order. It was an excellent fan from a mechanical point of view, and the useful effect appeared equally favourable.

*D being diameter and R revolutions of fan per minute.

Mr. M. WALTON BROWN said, with regard to the useful effect of ventilating fans, he thought that one point had frequently been overlooked; he alluded to the efficiency of the engine. A fan might be erected, for which the maker claimed 70 or 80 per cent. of useful effect, and the efficiency of the fan was entirely neutralized by attaching it to an engine and boiler consuming say 15 lbs. of coal per horsepower in the air! Another fan, of inferior design, might yield the same results from a consumption of 5 lbs. per horse-power in the air. That is to say, one fan might consume coal to the value of £400 per annum, while a more efficient fan, in consequence of the attached inferior engine and boiler, might consume £1,200 worth of coal per annum.

Mr. WADDLE said if they used an engine of too high a class they would be apt to get into difficulties; they wanted a simple engine which would utilize a good proportion of its power. They might have an engine which would use less coal, but the main saving after all was at the boilers.

Mr. BLACKETT, referring to Mr. Brown's remark on the place at which the diameter of the fan should be measured, said his conviction was certainly in favour of measuring its diameter at the tips of the blades.

The CHAIRMAN said he would propose a vote of thanks to Mr. Walton Brown. They were always glad to have new appliances brought to their notice if they showed any improvement on those at present in use; but they were also specially thankful on this occasion, as when they found that there was no business for this meeting, Mr. Brown kindly came forward at once and offered to read this interesting paper.

Mr. T. W. BENSON said he had much pleasure in seconding the vote of thanks. He was sure they must all feel obliged to Mr. Brown for supplying so interesting a paper.

The vote of thanks was cordially adopted.

NORTH OF ENGLAND INSTITUTE OF MINING AND MECHANICAL

ENGINEERS.

GENERAL MEETING,

HELD IN THE WOOD MEMORIAL HALL, NEWCASTLE-UPON-TYNE,
APRIL 11TH, 1891.

MR. W. COCHRANE, PRESIDENT, IN THE CHAIR.

The minutes of the last meeting and the proceedings of the Council were reported.

The meeting heard with very great regret of the death of Mr. John Marley, a former President of the Institute, and unanimously adopted a vote of condolence with the family.

The following gentlemen were elected, having been previously nominated:

MEMBERS

Mr. John Philip Kirkup, Singareni Collieries, Hyderabad, Deccan, India.
Mr. Seyd Ali Belgrami, A.R.S.M., Director-General of Mines to the Government
of H.H. the Nizam of Hyderabad, Deccan, India.

ASSOCIATE MEMBER

Mr. Robert Henzell, Oil Manufacturer, Close, Newcastle-upon-Tyne.

ASSOCIATES

Mr. Benjamin Mason, Burnopfield Colliery, Hobson, Lintz Green.
Mr. Thomas Macintosh, Cowpen Colliery, Blyth, Northumberland.
Mr. John Shaw, Cramlington, Northumberland.

STUDENTS

Mr. John Ritson, Marley Hill, Whickham, R.S.O.

Mr. William Mordy, Kimblesworth Colliery, Chester-le-Street.

Mr. Matthew Henry Kellett, Castle Eden Colliery.

VOL. II.-1890-91.

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