Early mine ventilation fans

After the fans employed in German metal mines, described by Agricola, their use went into decline for almost 250 years. It was not until 1827 that a mine ventilating fan was re-introduced to a colliery near Paisley, Scotland. This had a number of inclined blades fixed to a vertical shaft rotating within a circular casing. The fan was fitted over the top of the upcast shaft and air was drawn through it and discharged to atmosphere. It could be ar­gued that this was the first axial flow fan.

At the same time many mines in France and Germany experi­mented with fans working on the Archimedean screw principle, but these failed, not only from a lack of knowledge of the aero­dynamic theory, but also because the metallurgy of the time did not permit them to run at the speeds necessary for an accept­able flowrate and pressure.

Attention therefore turned again to the centrifugal fan. The im­peller of this was inherently stronger whilst the pressure devel­oped was augmented by the centrifugal force applied to the air, in addition to the blade action. Lower rotational speeds, within

Figure

This fan was old fashioned when introduced, as it was open run­ning, (Figure 1.9).

The impeller, however, had backward curved blades (Figure 1.10) and a tapered shroud so that it was extremely strong and had a non-overloading power characteristic. Fans of this type

1.8 Schiele’s improved centrifugal fan

The capacity of a typical steam engine, enabled useful duties to be performed.

In 1849 an open running 6 m diameter radial-bladed centrifugal fan with vertical shaft was installed at Geliy Gaer Colliery in South Wales. The engineer responsible for its design was Wil­liam Brunton (1777-1851) who had been trained under Boulton and James Watt at the Soho Foundry, Birmingham. Not unnatu­rally the fan was directly driven through a crank from a steam engine. A model was shown at the Great Exhibition of 1851, held in Hyde Park, London.

In 1851, James Nasmyth (1808-1890), the inventor of the steam hammer, read a paper to the British Association at its meeting in Ipswich. He described a double inlet radial-bladed centrifugal fan again directly driven by a steam engine. His the­ory was put into practice in 1854 at Abercarn Colliery, South Wales. This fan had an impeller diameter of 4.12m and ran at 60 rev/min for a duty of 21.25 m3/s against 125 Pa. Subse­quently a larger fan of 4.57m diameter running at 80 rev/min was installed at Skiar Spring Colliery, Elsecar, Yorkshire, UK.

One of the most successful centrifugal fans of the mid 19th cen­tury was that designed by Theophile Guibal (1814-1888), (Fig­ure 1.7). The fan, installed at the Jean Bart Colliery, was first de­scribed in L’histoire generate des Techniques aux P. U.F., in 1859. Guibal was born in Toulouse and educated in Paris. At the time of his invention he was Professor of the Exploitation of Mines at the University of Mons, Belgium.

Many of the early fan designers had believed that an extract fan did not require a casing, but that the air should have a free and unrestricted access to the atmosphere. Guibal was the first to show that a casing was desirable and to develop the expanding evasee to slow down the air before discharge. By 1870 nearly 150 of these fans had been installed in Belgium, France and the United Kingdom with diameters varying from 4.8m to 15.5m and flowrates from 14 m3/s to 100 m3/s at depressions of 125 Pa to 1500 Pa.

 

Early mine ventilation fans

Early mine ventilation fans

Figure 1.7 Guibal’s successful centrifugal fan

 

Early mine ventilation fans

Figure 1.9 Waddle’s open running fan

 

Early mine ventilation fans

Figure 1.10 Cross-sections of Waddle’s fan — with backward curved impeller blades

 

In 1863 Christian Schiele of Manchester, England, patented an improved fan, which was developed in small sizes for blowing cupolas and in larger sizes for the ventilation of mines. His fan had a strongly built iron impeller which could rotate at much higher speeds. The blades were backward inclined and dis­charged into a gradually increasing volute. The consequences of these improvements were a much reduced size and capital cost for a given duty, which made it popular with the accoun­tants, if no-one else (Figure 1.8).

J. R. Waddle of Llanelli, South Wales, introduced his first fan in 1864 at Bonville’s Court Colliery. It replaced a furnace at the mine which had burnt 10 tonnes of coal per week to produce a flowrateof4.72 m3/s against 48.5 Pa. The fan was 4.88m diam­eter and circulated 14.16 m3/s against 436 Pa. To some extent

 

Early mine ventilation fans Early mine ventilation fans Early mine ventilation fans

Early mine ventilation fans

Figure 1.14 Isometric view of the impeller of Rateau’s fan

подпись: figure 1.14 isometric view of the impeller of rateau’s fan

Figure 1.15 The Mortier diametral fan — perhaps the first tangential or cross-flow fan?

подпись: figure 1.15 the mortier diametral fan - perhaps the first tangential or cross-flow fan? Early mine ventilation fans

Figure 1.12 Cross-section through the Capell fan

подпись: figure 1.12 cross-section through the capell fan

Early mine ventilation fans

Figure 1.11 Cross-section through Professor Ser’s fan

Were built in diameters from 3.0 m to 15.5 m. Later examples from about 1890 were designed for higher peripheral speeds e. g. 5.5 m diameter at 300 rev/min), permitting a significant re­duction in size for a given duty. They were widely used through­out South Wales and the rest of the United Kingdom, including the mines of Cory’s Navigation Collieries, the reason for men­tioning them here!

Professor Ser of the Ecole Centrale de Paris designed his first fan in 1878, the theory being published in the Mйmoires de la Sociйtй des Ingйnieurs Civils. Usually constructed in double in­let form it had 32 forward curved blades either side of the centreplate. These were of constant width but axially inclined (Figure 1.11).

The Capell fan was designed around 1883 by the Rev George Marie Capell, a graduate of Oxford University, and an Anglican priest. He said “it is now getting known that the life of a small fan, fast running, if the fan be properly constructed and bal­anced, is longer than that of the ponderous constructions of past times”. In this he was putting into words what was being practised in France and Germany. His fan (Figure 1.12) was unique in the design of the impeller which essentially consisted of two concentric parts each having six backward curved blades either side of the centreplate. The inner and outer parts were separated by a drum having six port holes designed to have a total area equivalent to that of the impeller eyes. The in­ner part was unshrouded. As a peak efficiency of 70% was achieved, it may be deduced that the power of prayer exceeds that of the Mechanics of Fluids!

Rateau’s fan (Figures 1.13 and 1.14) of the late 1880s has sometimes been called the first mixed flow unit. In reality, how­ever, it is perhaps best described as having compound blading with a truly axial inlet and centrifugal outlet, working in a com­plex volute having a gradually increasing cross-section. The blading was carefully designed for minimum shock losses and an efficiency of 80% was claimed.

The Guibal, Ser, Capell and Rateau fans were all subject to ex­haustive practical tests. A detailed report by the Belgian Com­mission entitled Les Ventilateurs des Mines was published in the Revue Universelle des Mines, Vol.20, (1892), thus starting us along that perilous path of standardized methods of test, cer­tification of performance and contract qualification.

The Mortier diametral Fan (Figure 1.15) was perhaps the first tangential or cross-flow fan. It was manufactured by Louis Galland at Chalon-sur-Saone, France. Efficiencies in excess of 70% were indicated by Charles Innes in his book The Fan (1916), perhaps suggesting that all is not progress. Later ver-

Early mine ventilation fans

Figure 1.16 Pelzer Dortmund fan cross-sections

Early mine ventilation fans

Figure 1.17 Impeller of Pelzer Dortmund fan

Sions incorporated a movable section of scroll forflowrate con­trol.

The Pelzer Dortmund fan (Figures 1.16 and 1.17) had twelve curved vanes designed for shock-free entry and with a radial discharge. It was the first to be manufactured in varying widths according to the fan flowrate and pressure development re­quired.

Figure 1.18 Impeller of Davidson’s multivane fan 8 FANS & VENTILATION

подпись: 
figure 1.18 impeller of davidson’s multivane fan 8 fans & ventilation

Figure 1.20 Cross-section through a Keith mine fan together with impeller detail

подпись: 
figure 1.20 cross-section through a keith mine fan together with impeller detail
Sam Davidson, who had left the shores of his native Ulster for the Assam tea plantations in 1864, was perhaps the next nota­ble name in the fan industry. Dissatisfied with the crude and slow methods of withering and drying the tea leaf over open charcoal fires, he developed a cylindrical drying machine. In the development of his dryer, one feature was noted as a stumbling block to further progress. It relied on the natural draught in­duced by the furnace chimney.

Positive pressure from a fan was seen as the means of improv­ing the drying rate. By a process of trial and error, and with an absence of any scientific instrumentation, he developed the for­ward curved bladed multivane impeller (Figure 1.18) patented in 1898. Witnessing the test of a tea drying machine fitted with one of these fans, a planter friend remarked “Why it’s just like the Sirocco wind that blows off the desert”. Sir Samuel Davidson, as he later became, immediately adopted the word as his trademark, and the fan was used widely for mine ventila­tion.

In all fans of the multivane type, in which the blades are axially long compared with their radial depth, there is a tendency for the air to “fill” the blade towards the backplate and for the side closest to the shroud to actually draw in air in a recirculatory mode. This was noted by Davidson, during his experiments and many of his early units were provided with an intermediate shroud to counterbalance the effect. BF Sturtevant, in his ord­nance fan, provided the blades with cup-shaped indentations (Figure 1.19). These sought to prevent the air slipping to the back of the impeller. Perhaps more importantly, the blades were stiffer and could run at peripheral speeds approaching 503 m/s.

James Keith (1800-1843) started a fine engineering dynasty. His son George (1822-1912) was Provost, or Mayor, of his home town, the Royal Burgh of Arbroath, Scotland from 1889-1895. His grandson, also James, was renowned for the introduction to his workforce, and the world, of the eight hour working day. The resultant book, A New Chaperin the History of Labour was a best seller in 1893. To engineers, however, his important introduction was the Keith fan impeller of 1908 where

Early mine ventilation fans

Figure 1.19 Impeller of B F Sturtevant’s ordnance fan

Early mine ventilation fans

Figure 1.21 Keith mine fan during installation

Early mine ventilation fans

Rateau’s axial impeller design

подпись: rateau’s axial impeller design

Figure 1.23

подпись: figure 1.23 Early mine ventilation fans

Rateau’s horizontal cased axial flow fan

подпись: rateau’s horizontal cased axial flow fanThe external diameter was larger at the inlet or shroud side (Fig­ures 1.20 and 1.21).

Figure 1.24

подпись: figure 1.24The peripheral speed was, therefore, higher here and in conse­quence the inductive effect was greater. Amore even discharge of air across the blades was claimed whilst the nearly triangular shape gave great strength to resist centrifugal stresses and ob­viated the need for supplementary internal stays.

Early mine ventilation fans

Figure 1.25 Vertical version of Rateau’s axial flow fan

подпись: figure 1.25 vertical version of rateau’s axial flow fan Early mine ventilation fansAnother approach to the problem was in Waddle’s Turbon fan (Figure 1.22). As with his backward-bladed fan, he adopted a novel, if not idiosyncratic approach. Instead of the impeller be­ing built up from a large number of shallow blades of consider­able axial length, rings were pressed by dies and made to inter­lock with each other. The corrugated rings were secured between the backplate and holding rings by means of stay bolts. The manufacturers claimed great torsional strength, the possibility of reverse running and that the cellular construction of the air passages resulted in the air being taken hold of more effectively. As an afterthought they also claimed that it was “si­lent running”, which must have puzzled those still clinging to the belief that if it didn’t make a noise, it wasn’t doing much.

Turbon fans were made in sizes up to 2.54 m diameter which at 300 rev/min produced 1500 Pa fan static pressure and volume flowrates up to 280 m3/s in double inlet form. The width was var­ied to suit the flowrate required and peak efficiencies of 75% were claimed.

Rateau applied his mind to the design of an axial flow fan. To achieve the high pressures required he developed a high hub to

Early mine ventilation fans

Tip ratio unit (Figure 1.23) with steel vanes fixed to the rim of a slightly conical hub manufactured from cast iron. Upstream guide vanes were employed in the horizontal cased version (Figure 1.24) whilst the vertical version had a spiral admission chamber giving a contra-rotating entry (Figure 1.25). After the air left the impeller it was wholly axial and its velocity was de­creased in a diffuser section.

Whilst all this feverish activity for improving the fan was taking place, some clung to the methods of the past. Walker Brothers of Wigan, near Manchester, in the UK, sought to meet the wishes of the conservative engineers by producing the “Inde­structible” fan (Figure 1.26). A good name can sell the most out-of-date product especially when the advertisers extolled the virtues of its strong construction. Aerodynamically however, all was not well, as it came complete with an “anti-vibration shutter”, the blades discharging into a V-shaped aperture in the damper.

X

Early mine ventilation fans

Figure 1.26 Cross-sections through Walker’s so-called “Indestructible” fan

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