FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1945
1945 - 2113.PDF
448 FLIGHT OCTOBER 25TH. 1945 ROLLS-ROYCE DERWENT This view shows the engine mounting by means of trunnions and a torsion - free linkage. The Rolls-Royce organisation was able to employ flight facilities which had hitherto been lacking. Actually, it had the first flying test bed for jet engines at its disposal. This was a Wellington bomber which early in 1942 had been con- verted by Vickers to carry a, jet engine in place of the normal tail turret. A.complete set of testing and recording instruments was provided in a special compartment in the fuselage. This machine was capable of flight at altitudes up to 25,000ft., and the first series of tests extended over 25 hours running. *The unit was then re- moved for examination, and a second series of tests was undertaken, involving a running time of 100 hours. A second Wellington, equipped with Merlin two-stage super- charged engines was subsequently converted for tests at altitudes up to 35,000ft., and in this form is still in use. First 100-hour Test Engines of the W2B/23 type, built by Rolls-Royce and named the Welland, were supplied for installation in the Gloster experimental E/28 single-engined aircraft and in April, 1943, a Welland made the first observed 100-hour run under type-test conditions. In June, 1943, two Welland units were installed in the Gloster F9/40, prototype of the Meteor aircraft. The engine had a maximum diameter of 43m. and weighed 850 lb. For the F9/40 it was rated for a thrust of 1,450 lb., although on test it gave 1,600 lb., and was later developed to 1,700 lb. thrust. Since that time there has never been less than six Meteor aircraft undergoing test. The design was stabilised and production facilities were organised. By May, 1944, the engine was approved as possessing a reliability suitable for R.A.F. operations, and regular deliveries were commenced. It was at this time that the Welland established the first 500-hour run under type-test conditions. Actually, the engine was set up for a 100-hour test; and on its con- clusion was continued for a further 400 hours under similar conditions. Prior to this the Air Ministry had rated the engine in service for a maximum of 80 hours running between overhauls. As a result of the 500-hour test the period between overhauls was stepped up to 180 hours. Series I Derwent Designed Whilst all these activities were proceeding Rolls-Royce decided to embark on a new design to embody the fruits of their development work. This new project was to be of the same maximum diameter for installation in the standard Meteor engine nacelles but to develop a static thrust 0* 2,000 lb. W7ork was commenced in the drawing office in April, 1943. By July it had been built and was placed on test, and in November, 1943, it passed »s 1 >o-hour type-test at 2,000 lb. thrust. In *5SgriL of4the next year it completed its first flight test in thevMeteor with a service rating of 1,800 lb. thrust and weight of 920 lb. In view of'the satisfactory performance a programme of continuous development work was undertaken involv- ing many 100-hour tests culminating in a successful 500- hour type-test. The new engine was known as the B37, R-R Derwent, Series I. The Series II engine gave an increased thrust of 2,200 lb. Series III was a special unit for experiments to provide suction on aircraft wing sur- faces for boundary layer removal. Series IV gave a further increase in thrust to 2,400 lb. This was not the only activity, however. New designs were being prepared, and much had been learnt from the continuous testing programme. The -Dement Series V, whilst retaining the maximum diameter of 43m., was an entirely new unit developing twice the thrust of the original Derwent I. It is this engine which enabled the Gloster Meteor to achieve its amazing speed. This history of the Derwent engine to date demon- strates the phenomenally rapid development of turbine jet units. Turbine engines can be designed, built, brought to rated performance, and put into production with a speed and facility utterly impossible for a piston- type engine. Furthermore, the working components/of a turbine engine each perform a single function con- tinuously. In a piston engine, by contrast, some parts have to perform several different duties intermittently. It follows that a successful turbine engine can be fairly easily scaled up or down in*a manner quite impracticable for a piston engine in which divergent operational characteristics are compromised in a specific design. Only Two Rotating Components A turbine jet engine has two main rotating components, the compressor and the turbine, and a combustion syste All three must be of high individual efficiency to produce a successful propulsion unit. In the Derwent Series I, to which these notes refer, a centrifugal compressor is em- ployed not solely because this type had been developed so intensively in, the past as a supercharger but because it has wider operating characteristics than the axial type favoured by the Germans. It is cheaper to produce, more robust, of lighter weight, can be run at higher speeds and is not prone to icing. The choice of a double-sided impeller was made in order to obtain the maximum intake area for a given tip diameter. It must be realised that more than 40 lb. of air (that is more than 500 cu. ft. per second) must flow through the engine and that the compressor determines the necessary diameter of the nacelle on the aircraft. A minor advantage] is that forces on each side of the impeller balance out ana consequently no special provision for axial thrust is required. To reach the rear intake the air flows past the diffuser necks and the ends of the combustion chambers. It might be imagined that warming would occur sufficient to impair the efficiency of the compressor- Actually, careful measure- ment has shown a difference of only 3-4 deg. C. between intake air temperatures at front and rear. The impeller is a single forging of High Duty Alloy, RR56, with twenty-nine vanes each side. Entry vanes are
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
