Page:EB1922 - Volume 32.djvu/826

800 Thus with v=9-92 we note that (^)o =I -477.(^J N = '9 and

(-? ) N = i-3ii, whence = !2-6o. Proceeding in this way the dv/

figures in the last column of table 5 are obtained. In fig. 21, h is plotted against n as also is J>NP.

Stages 9-81 and 10-81 of the ideal turbine have already been dealt with so that in proceeding further with the design we start with stage 8-81 of the ideal turbine. From fig. 21, it appears that i< = 8-8l corresponds with n = 11-51 and from the curve of blade heights we get the following values for A

n = 9-51 10-51 11-51

h = 5-94 7-87 9-38

As before, an approximate value of h to replace the blades at 10-51 and 11-51 is the value of h at n = ll-oi. This value of h is 8-31 inches. Replacing the blades at the high pressure stages =o-5I and n = l'5i the same method gives us h = 1-29 inches.

If we determine the corrections for these two extremes the cor- rections for the intermediate groups can be determined with suffi- cient accuracy by linear interpolation. Equation 4 in this case becomes

h' a

W C*+D) = 7

ho*(h*+D-)>

which gives h as 8-259 ' n - ' n p'a ce of 8-31 in. as read from the curve.

At the high-pressure end of the turbine the calculated value is 1-321 in. as against 1-33 as read from the curve.

It will be seen that with the blading thus derived the pressure at the first row of guide blades is that corresponding to n = 0-49 instead of to n = o as it should be. By plotting log p against n we find that the pressure corresponding to n= 0.49 is 21.5 Ib. per sq. in. instead of 20 as assumed. This can be corrected by slightly increasing the height of the first group of blades, for which purpose we can use the approximate expression

In this expression h a denotes the corrected value of h, p, the pres- sure corresponding to n = 0-49, and pi the designed pressure in front of the first row of guide blades, whilst po denotes the pressure on discharge from the group.

We thus get & c =i-45, so that the computed blade heights are as follow:

TABLE 5.

Group No.

I.

II.

III.

IV.

V.

VI.

VII.

No. of moving rows in

I

i

I

I

i

I

I

group. . . Calculated blade height in in

1-450

1-710

2-960

3-540

5-320

8-310

9-800

Allowance for tip clear- ance ....

0-093

0-096

0-108

0-123

0-141

0-171

0-186

Net calculated blade heights

1-357

1-614

2-842

3-416

5-179

8-139

9-714

Actual blade height

if

't

2}

3J

si

8i

oj

The length of the blades in group No. VII. is for semi-wing blades as previously explained. In the above table the allowance for tip clearance is not the actual tip clearance, but the amount by which the blade heights must be reduced in order that no more steam shall pass than if there were no tip clearance whatever. This allowance has been taken as 0-002 in. per in. of drum diameter plus o-oio in. per in. of blade height, and this amount is subtracted from the com- puted blade heights.

It should, perhaps, be noted that whilst in the ideal turbine the velocity of efflux from a stage is strictly proportional to Vg this condition is only approximately fulfilled in the case of a turbine with constant drum diameter.

Had the above turbine been designed to run at 1,000 revs, per minute instead of 2,400, many more rows of blading would have been necessary, and to avoid large losses by the carrying over of kinetic energy to the exhaust a larger drum would have been advisable.

It may be mentioned that the normal blades for which the coeffi- cient in equation 5 applies are of the old type with the opening gauged to about one-third the pitch, these blades being the ones used in the turbine from the test of which the coefficient was deduced. Certain makers now use a different form of blade having a parallel tail, a departure which it is difficult to justify.

BIBLIOGRAPHY. H. L. Callendar, The Properties of Steam (1920); Steam Tables (1915); H. M. Martin, The Design and Construction of Steam Turbines (1913); A New Theory of the Steam Turbine (1918); W. J. Gondie, Steam Turbines (1917); Dr. A. Stodola, Die Dampf- 'turbine (4th ed. 1910) ; Osborne Reynolds, " On the Theory of Lubrication" Scientific Papers, vol. ii., "Lubrication," Engineering

(Dec. 9 1919) ; " The Theory of the Michell thrust bearing," Engin- eering (Feb. 20 1920) ; Gerald Stoney, " High Speed Bearings," Proc. N.E. Coast Engineers and Shipbuilders, vol. xxx. (1913-4): R. J. Walker and S. S. Cook, " Mechanical Gears of Double Reduc- tion for Merchant Ships," Trans. I.N.A. (1921); H. B. Tostevin " Experience and Practice in Mechanical Reduction Gears in \Yar- ships," Trans. I.N.A. (1920); Robert Warriner, " Reduction ( for Ship Propulsion," Trans. Amer. Soc. N.A. and M.E. (1921); " Lubrication of Gear Teeth," Engineering (Aug. II 1916); K. Bau- mann, " Some recent developments in large Steam Turbine Prac- tice," Journ. Inst. E.E. (1921). (R. H. P.; H. M. M.) ,

TURKESTAN, WEST (see 27.419). After the revolution in Russia, Western (or Russian) Turkestan became a member of the Federation of Soviet Republics. It was divided into five provinces: Semiryechia, Syr Daria, Ferghana, Samarkand 1 and Trans-Caspia. The exact position of the native states of Bukhara and Khiva, which were later occupied by the Soviet Government, remained obscure. Each of the five provinces, by the constitution of the Republic, is governed by a provincial Executive Committee or council which sends representatives to Tashkent, the. capital, where the Central Executive Committee of the Republic meets. This Committee consists of 75 members, sending representatives to Moscow to the meetings of the Central Committee of the All-Russian Federation of Soviet Republics, but the Turkestan Republic showed itself very little inclined to accept the control which the Central Committee at Moscow endeavoured to maintain. The Turkestan Committee elects a small council, forming a kind of cabinet and having control of the different branches of the administration. The right of voting being confined to members of the Communist party, the Govern- ment represented by no means one really elected by universal suffrage but rather a dictatorship of the lower classes'. The Russians in Turkestan form only about 5% of the total pop., and since most of the rural Mussulman pop. take no part in the voting, the country is governed to all intents and purposes by men elected by the very small proportion of Russians of the lower classes living in the towns. Figures for the pop. of some of the large towns in 1916 were: Khokand, 112,000; Naman- gan, 103,000; Samarkand, 89,000; Tashkent, 201,000. All trade and industry were in 1921 at an absolute standstill owing to Bolshevism.

Great success had attended the cultivation of cotton, and the high prices obtained for the Turkestan article (most of which is grown in Ferghana, where 742,000 acres were cultivated in 1915), coupled with the increase of railways, led to the abandonment of corn in favour of the cultivation of cotton, and, although W. Turkestan is a good wheat-producing country, cereals were actually imported from Russia and Siberia and cotton exported in exchange. Factories for cleaning and baling raw cotton and for extracting cotton oil were set up, and employed a large number of people, mostly in Ferghana. ; These factories were worked by crude oil from the Baku wells. The i total area under cotton in 1916, including that grown in Khiva and j Bukhara, was 1,838,215 acres, yielding about 18,000,000 poods or' 290,000 tons of raw cotton.

The cultivation of vines had also increased, and wine industries had been initiated, chiefly in Tashkent and Samarkand. A larger product of the vine was in the form of raisins and currants, of which quantities were exported to Russia.

Large quantities of fruits apples, pears, quinces, peaches, nec- tarines, apricots, grapes and melons were exported by special trains to central Europe, where the Turkestan crop was received a short time before the south European supplies ripened.

Minerals remained for the most part unworked, though the profit- able coal fields and oil wells in Ferghana were used when disturb- ances in Trans-Caspia cut Turkestan off from the Baku oil, on which it relies entirely for its industrial life. Mining is hampered by the lack of roads and by the want of machinery.

A very large industry in Bukhara is the export of Astrakhan lamb skins (called locally Karakul). Enormous flocks of these sheep are kept in the deserts around Bukhara. Attempts to breed these sheep in other countries have always resulted in a deterioration in the quality of the skins owing to some peculiarity of climate. Before the World War about ij million skins were obtained annually at a cost of 6 to 8 roubles each.

There are practically no branch roads in Turkestan, and the only means of transport in bulk is either by wagon on the few main roads, or by railway. The largest new railway project is the Semiryechenskaya railway. This line was intended to leave the Orenburg-Tashkent line at Arys (146 versts N. of Tashkent) and go to Vierni, a distance of about 900 versts. Actual construction was completed to Burnoi (220 versts) when Bolshevism came to crush all enterprise and initiative. Some work was done E. of Burnoi, but the line was