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Aviation History
1947
1947 - 0614.PDF
' Z-* FLIGHT APRIL 24TH, 1947 Thornton Engine Laboratory Research on Rich and Weak Mix- ture Performance, Direct Injection, Fuel Boiling and Turbine Lubrication The imposingentrance of the engine researchlaboratory at Thornton, themotif of which was : " Secondto None." IN the early years of the war constructionwork began on an aircraft engine research •laboratory at Thomton-le-Moors, Cheshire. By the middle of 1943 it was apparent that theaccommodation available was no longer ade- quate, and so additions were put in hand.These were completed in July, 1945. the final installations of engines and equipment beingrecently accomplished. In the spring of 1942 the services of the laboratory were offered toM.A.P. for the duration of the war; this offer was accepted, and Thornton became theM.A.P. Fuel and Oil Research and Develop ment Laboratory. The establishment has now returned to thecontrol of Shell-Mex, Ltd., and is directing its energies to civil aviation problems. The generalidea behind the design of the building and its equipment was to produce a laboratory secondto none of its kind. To-day some 300 staff are employed with about sixty scientists under the Director of Research,Brigadier R. A. Bagnold, O.B.E., F.R.S. The Aero Engine Laboratory is directed by Dr. C. G. Williams, the engineerin charge is J. G. Dawson, chief chemist Dr. T. P. Hughes and Technical Editor Dr. C. B. Davies. The facilitiesavailable in this magnificently equipped laboratory which we were invited to inspect include: Nine full-scale single-cylinder test cells; five test roomscapable of housing up to twelve small-scale engines; cold rooms to accommodate a main engine and reach —40 deg C;two rig rooms; two main engines installed in a Halifax air- craft ; analytical laboratory ; fuel laboratory ; oil laboratory ;photographic department; electronics department; metal- lurgical laboratory with heat treatment room; instrumentshop; microscope and balance room : machine shop; general fitting shop; engine fitting shop; electricians' shop; tin-smiths' and welding shop; fuel blending facilities; fuel stores; engine and materials stores; conference room andlibrary; drawing office; report duplicating section; general administration offices. Resistance to Detonation The wartime research programme was necessarily deter-mined to a large extent by war needs primarily related to improving aircraft power and range, altitude perform-ance, and reliability. The main factor limiting the power output from a givenengine on a given fuel is detonation, and the problem of the detonation resistance of a given fuel in a givenengine has to be considered under two main heads, (i) rich- mixture or take-off performance, and-(ii) weak-mixture orcruising performance. During the early years of the war most emphasis was placed on rich-mixture performance,since the greatest need was for ever higher maximum speeds from fighters. There was abundant evidence thatthe octane number was not a reliable indication of rich- mixture performance, and the first problem studied atThornton was the development of an improved test which would indicate most correctly the rich-mixture qualitiesof a fuel in order that adequate control might be main- tained over this characteristic. Late in 1943 it was indicated that, if a fuel could be madeavailable having a rich-mixture performance 20 per cent better than that of the obtaining grade, certain engines could be up-graded to take advantage of the improvedquality. Most of the initial experimental production blends were made up and tested at Thornton, and in the summerof 1944 the so-called " 150 grade" was brought into use during the invasion of the Continent and was also used togive the extra speed required for countering flying bombs. As the war progressed and it was realized that rich-mixture performance could be fairly readily obtained and controlled, greater attention was given to the weak-mixtureperformance because of its greater importance in relation to cruising range and load. A programme of study was also undertaken in relationto direct fuel injection in German engines. The investi- gation showed that certain German engines required theuse of a fuel superior to the current B 4, but it was evident that the highly aromatic C 3 fuel provided a very largemargin of power which, incidentally, the Germans would not be in a position to use unless they improved theirpiston design. A great deal of interesting information was also obtainedregarding the characteristics of fuel injection used on Ger- man engines. This indicated that one of the importantadvantages of direct injection was the superior weak- mixture anti-knock performance. This would imply that,to obtain the given cruising output, a fuel of lower anti«-< knock value could be used with direct injection than with acarburettor. It was established that the reasons for this fa-?t were the cooling effect due to the evaporation obtained bythe injection of fuel direct into the combustion chamber, ' and the fact that direct injection permitted an increased,;valve overlap which, in turn, resulted in improved scaveng- ing and internal cooling. Further development of this workis now proceeding at Thornton, and the work on direct injection has included a study of low-volatility so-called"safety fuels" and some of the problems involved iu' their use. At the beginning of the war, altitudes of 20,000ft wereconsidered high, whilst at the end of the war heights of 40,000ft were commonly reached. This necessitated con-stant attention to problems of vapour lock or fuel boiling. A great deal of fundamental work on this subject has beendone at Thornton and, in one case, information supplied to the manufacturers enabled an increase in ceiling ofabout 10,000ft to be achieved. One of the factors which
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