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Aviation History
1948
1948 - 1638.PDF
414 FLIGHT SEPTEMBER 30TH, Xew Cabin Blower Des Efficiency of Roots Type Increased WADE ENGINEERING, LTD., was formed byB. H. M. Winslett and Costin Densham to studythe science ot air compression and to design and produce compressors suitable for every application. During the last nine months the company has designed and pro- duced a supercharger for use with various sizes of internal combustion engines. This design, moreover, incorporates new features which on test have been found to meet many of the problems which arise with the use of compressors for enclosed spaces, such as aircraft cabins, which require freedom from contamination. To solve so many problems at the first attempt was, perhaps, more than could be hoped for; nevertheless, the first model, a ij-litre Roots type, withstood successfully the most searching tests on the company's own test-rig, and that model is about to undergo equally severe testing at the R.A.E., Farnborough. Application of a normal supercharger to the require- ments of a large aircraft fuselage was not actually included in the original design, but since such an application shows promise of being highly satisfactory on the score of effi- ciency, silence, and also low initial cost, a new air com- pressor has now been designed specifically for aircraft pressurization. This new design, which should defeat most of the deficiencies associated with the Roots and other types of blowers, has also been submitted to the R.A.E.E. It now remains with Farnborough to approve this design, which, if satisfactory, offers great advances beneficial to military and civil pressurized aircraft. Stressed to withstand speeds up to 15,000 r.p.m., the 2-litre Roots-type blower now in production at Wade Engineering, Ltd., is capable of supplying pressures up to the equivalent of +7-10 lb/sq in with sea-lavsl intake conditions. The rotors each carry four lobes^fi lrherest- ing innovation in their design being the'inclusion of Special space-seals machined along the full lengtfr'of the tips of the lobes. Thus slip losses between J:hF"Tips of the lobes On this test-rig blowers are driven by 0 stationary engine through a step-up V-belt drive up to speeds of over 15,000 r.p.m. The blower is mounted on a cradle which is free to rock, enabling the test-rig to provide hone-power data as with a dynamometer. The Wade Roots-type blower is here shown with the end covers partially removed to show the bearings, oil seals and gears. and the supercharger casing are reduced. The outlet portof the blower is of helical form across the delivery side of the casing, designed to reduce pulsation effect. In thecase of a port running parallel with the rotor axes, which would be instantaneously uncovered along its whole lengthas each lobe reached the opening, " back-flow " takes place ; in other words, the air under outlet chamber pressure flowsmomentarily back into the blower casing. The use of a helical port, however, allows the uncovering of the outletby each rotor lobe to occur progressively, and pressure pulsations are therefore less intense. This feature con-tributes to more silent running, and an increase in overall i-50 * HORSE • MASS • R.PM. ABSOLUTE INI*KE TEMPERATUREVC DENSITTAT DELIVERY. LB.PERCU.fT. UTE INTAKE PRESSURE. LB. PER SON TE DELwEWhffESStJRE.LRPER 5O.N 4 The characteristics of the Venter (Roots-type) supercharger are here plotted in non-dimensional form, indicating mass output against H.P.
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