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Aviation History
1942
1942 - 0197.PDF
JANUARY 22ND, 1942 FLIGHT 7~> *bi H„,( at tjmax was found to be the same as for the original area F0; at F« = o.4F0, a slight decrease was observed", doubtless due to the above-mentioned factor limiting the validity of comparison. In the second series of experiments, a separate entry impeller was provided for each reduced intake diameter, the blade-setting angles being increased to furnish a theo retically constant suction volume.' However, instead of a ratio of 1:1:1, the suction volumes V, were found to be in the ratio 1: 0.82: 0.50. Thus, if all other blower dimensions remain constant, it is impossible to obtain an increase in the intake velocity despite the fact that the dimensions of the volute are now correct for each case. The observed variation of the head was almost the same as in the preceding case. To complete the investigation, characteristic curves were also plotted for a cross-sectional area F<j = o.4 F<>, with an entry impeller blade angle of ^x= const. = 90 deg. on all diameters (see Fig. 38). As the pumping limit was reached it was impossible to determine if the maximum efficiency had been attained or not. In all experiments with entry impellers of different diameters the main rotor itself re mained unchanged. Although this simplified the arrange ment of the experiment, it probably had an unfavourable effect owing to the double transformation of velocity, j^^ivrther experiments will be needed, gradually eliminating these drawbacks, which impair the validity of the result. The blades of the Szydlowski-Planiol supercharger, a French design for the Hispano-Suiza engine, are of an exceptional type. Fig. 39 shows the rotor, and Fig. 40" the diffusor vanes of this blower, of which, presumably, a number of experimental units are in existence. The blade form appears to be based on the principle of removal and renewal of the boundary layer based on the theory of the slotted wing. A special claim, as yet untested, is made that this blade-form assures constant rate of increase of the adiabatic efficiency factor q<„i, and the indicated adia- batic efficiency i),u(j. The available published results show no distinguishable advantage. By DVL tests, the adia batic efficiency factor at a tip speed of about 300 m/sec is of the order of qaa ~ 0.67, and the internal efficiency therefore tjtad 0.79. In application to the Hispano-Suiza engine, however, the new blower probably represents a considerable advance, since the standard blower provided for that engine had an unsatisfactory performance. Clever but Impractical The designers of this blower, in recapitulating its advan tages, lay particular stress on the indifference of the " fish profile" (by which the particular blade-shape of the entry impeller is meant) to appreciable fluctuations in direction of the incident flow, produced by the special method of regu lation. The Szydlowski-Planiol supercharger is particu larly carefully designed. Even if this blade form should offer some advantages, it is hardly suitable for general adoption on account of difficulty of manufacture, first cost and maintenance. Furthermore, this type oi blade will be particularly liable to damage; if the engine backfires, the diffuser vanes will assuredly be fractured. The sub divided blades of the entry-impeller also produce an increase in the axial length of the blower. The overall dimensions of the blower, however, are not unfavourable. POST-WAR AIR LINES Capt. H. Balfour's Views on VTp] the Future of Civil Policy Essential Flying : A Bold Government (HE biggest job of post-war world reconstruction will be building up air communications," said Capt. Harold Balfour, Under Secretary of State for Air, when addressing the Overseas League at a recent lunch. "The greatest opportunity for adventure and achievement on the part of young men of the world," he added, "will lie in this field." The British Commonwealth of Nations depended for its strength on unity, and unity on ability to meet, talk and trade with each other. The strength of the British Isles, as the ceutre of the Commonwealth, rested only upon the fact that it was the capital. We must link up the centre to the outlying nations; the outlying nations must link ^ach to the other. Then, alongside and co-operating with 1 the other free- nations of the world, we could girdle the globe with a ring of civil air fleets, flying tor peace but protected by strength. Saying that war had not killed civil air communications but had only diverted them from peacetime commercial aims to service in the war effort. Capt. Balfour pointed out that our civil communications linked up to America, Africa, Egypt, India, Australia and New Zealand, and were all kept going regularly ; they also extended to Scandinavia, and now to Teheran and Russia " Open Sky " for Democracy Their peacetime future depended r.pon a Government policy of bold, swift decisions. We shall have to be big and bold in our thinking and planning and in our spending," he said, "if the post-war world of air communications, as of other things, is to be built on the philosophy of plenty." We needed an Imperial policy which would dovetail 'into a world policy. British air routes should run in co operation and partnership with he air-lines of the other free peoples who had been allies in war and would still be allies in peace. One thing was certain. The day of " back-yard " flying rights had gone and must give place to a policy of the " open sky " for those who had fought with us. This was the spirit of the Atlantic Charter. "I foresee three types of route," Capt. Balfour con tinued. '' There will be the ' greyhound ' route of strato sphere lines, flying stages of probably never less than 1,000 miles and carrying urgent, passengers, freight and mails. There will be the maijpk' uiifc' squtes connecting the capitals and other important centres. J; And there will be the ' feeder' services spreading out from these capitals and centres to the outlying distriare of each territory. "Each route will need 'Cdifferertt sort of equipment. Government money will be required lor design and re search. It is no good thinking we can catch up the years lost in warfare or satisfy thfaeeds of an educated public without expenditure of great sums of money, "I believe we must accept improvisation with war equipment lor a two- to three-year interim period. The day fighting ends we should start to keep open our routes with military equipment, converting it as best we can to civil needs. Thus we should use redundant equipment, train commercial crews, develop our ground organisation, gain general experience, and build up a goodwill ready fot when we can swing into use our proper civil aircraft. "As we start to operate on the interim period, the Government of the day must take courage in both hands and tell our aircraft industry to build, say, three types of overseas aircraft, one of which ought to be a giant flying boat. The Government must gamble a great sum of money—but, after all, little compared with one week's cost of the war—in ordering perhaps 500. Soo or 1,000 of these aircraft, with guarantees that they will be operating within two years from the time the order is placed. "It is the duty of every citizen in this country, and throughout the British Commonwealth, to concern himself with the future." Capt. Balfour concluded.
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